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DarkMoe
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Question about ALG driver status
#367126 - 06/22/17 10:47 PM


Hi, first my little story of how I was complete in awe and shocked when MAME 0.62 was released in 2002 (I think that was the version), which supported for CHDs for the first time.

Now, 15 years later, and Im really curious as to what is missing to emulate the American Laser Games arcades. Is it a legal thing like Dragons Lair still being sold ? Or no one still dumped the original laser discs ? Or just the Amiga like hardware has not been emulated yet ?

Make no mistake, this is not a request, just curiosity.
Thank you !



CTOJAH
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Re: Question about ALG driver status new [Re: DarkMoe]
#367128 - 06/22/17 11:39 PM


> Hi, first my little story of how I was complete in awe and shocked when MAME 0.62 was
> released in 2002 (I think that was the version), which supported for CHDs for the
> first time.
>
> Now, 15 years later, and Im really curious as to what is missing to emulate the
> American Laser Games arcades. Is it a legal thing like Dragons Lair still being sold
> ? Or no one still dumped the original laser discs ? Or just the Amiga like hardware
> has not been emulated yet ?
>
> Make no mistake, this is not a request, just curiosity.
> Thank you !

From the official site :
Laserdisc games. They all work in theory, but are waiting for a good quality laserdisc dump.
source : http://wiki.mamedev.org/index.php/MNW



DarkMoe
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Re: Question about ALG driver status new [Re: CTOJAH]
#367129 - 06/22/17 11:42 PM


Awesome, didn't know about that page



uman
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Re: Question about ALG driver status new [Re: CTOJAH]
#367146 - 06/23/17 11:45 AM


> Laserdisc games. They all work in theory, but are waiting for a good quality laserdisc dump.

I wonder what that exactly means? I dont know what codec is used on that discs, but in a worst case wouldnt it be enough to capture them in a lossless codec format? better that then waiting the expiry date for those discs.



John Doe
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Re: Question about ALG driver status new [Re: uman]
#367152 - 06/23/17 04:56 PM


> I dont know what codec is used on that discs, but
> in a worst case wouldnt it be enough to capture them in a lossless codec format?
> better that then waiting the expiry date for those discs.

They don't use a codec, they are essentially analogue (like vhs tapes or vinyl records).

The signal doesn't just get pulled off the disc and pumped out to your tv, it's processed by the laser disc player. So the specific model of laser disc player you use is important and how well it is maintained.

Some people have been working on cutting out as much of the player as possible and doing the post processing on a PC. Although I don't think anyone involved in MAME is doing that.

I think there is also reluctance to support some laser disc games as the current rights owners are litigious.



CTOJAH
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Re: Question about ALG driver status new [Re: John Doe]
#367153 - 06/23/17 05:44 PM


...After all, (almost) all of these games are everything but playable; just interactive movie sequences and preserving them is just for history of the video games sake and perhaps some nostalgia.
For example, I've tried Space Ace on Amiga... ...ended up using cheat DoDemoDexter



John Doe
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Re: Question about ALG driver status new [Re: CTOJAH]
#367154 - 06/23/17 05:57 PM


> ...After all, (almost) all of these games are everything but playable;

Accurate emulation would be to display "out of order" 99% of the time.



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Re: Question about ALG driver status new [Re: DarkMoe]
#367155 - 06/23/17 06:13 PM


Last I remember there was no consensus on a new format to move forward with and seemingly promises of custom hardware that could help read them out in a much smarter way, then silence.

They should also be higher in resolution in my opinion, like 2X the original size or something higher and that scales better on common computer graphics cards but that's just my personal 2 cents.



DarkMoe
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Re: Question about ALG driver status new [Re: John Doe]
#367156 - 06/23/17 06:14 PM


Well, for me Crime Patrol and Drug Wars are incredible games, full of weird and funny scenes and represent part of my childhood (had the DOS ports back then).

Its weird that after all these years no one dumped the analogue laser disc (I know its impossible for it to be 100% accurate to the real one), since we have other laserdisc games like Esh Aurunmilla and Badlands.

Im thinking theres maybe some fear of legal and copyright infrigment, maybe because most of those games were released a couple of years ago for the Wii.



DarkMoe
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Re: Question about ALG driver status new [Re: Smitdogg]
#367157 - 06/23/17 06:16 PM


Fair enough, so it seems a lack of direction and interest is what's happening here.



SmitdoggAdministrator
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Re: Question about ALG driver status new [Re: DarkMoe]
#367158 - 06/23/17 06:16 PM


Because there's no way to dump them in a format that is guaranteed to still be used a year later.



SmitdoggAdministrator
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Re: Question about ALG driver status new [Re: DarkMoe]
#367159 - 06/23/17 06:19 PM


There's only like 1 person who can make the custom hardware, there were discussions here with him years ago but now I've forgotten his nickname. Might be findable in a search. There's definitely a problem with promising the world and then not delivering, making people want to "hold off for the real solution".



DarkMoe
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Re: Question about ALG driver status new [Re: Smitdogg]
#367160 - 06/23/17 06:23 PM


I understand.

Just out of curiosity, can't the same technique for the other laser disc dumps be used here ? I think it was Aaron Giles the one who developed the CHD format, and started the whole laserdisc preservation, but I may be mistaken.

Is there some sort of technical issue from the laserdisc players preventing doing the same ?

Sorry for the noob questions.



SmitdoggAdministrator
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Re: Question about ALG driver status new [Re: DarkMoe]
#367161 - 06/23/17 06:28 PM


That's the format not considered good enough. Even in Aaron's own words (paraphrasing) he said his format was not perfect but better than nothing, and at least we'd have something and not just let the discs rot away. I think it also needed a very specific setup and I don't remember if the method is even public or not. But we're probably going to have to go back to it and admit he was right all along and stop chasing the perfection dragon.



DarkMoe
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Re: Question about ALG driver status new [Re: Smitdogg]
#367162 - 06/23/17 07:01 PM


100% agreed, may not be the best method, but seeing as in the past 15 years no one came with a tangible and better method, those discs should be dumped while they still work.



uman
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Re: Question about ALG driver status new [Re: Smitdogg]
#367163 - 06/23/17 08:12 PM


also not want to be a asshole here, but that laserdisc format, what can it be in resolution terms? my guess would be max. PAL (768x576) and if that is captured in a lossless codec, what would be wrong with that? i really dont understand. Ok, it would be a collection huge in size, but other than that, fine i guess, even for the future.



SmitdoggAdministrator
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Re: Question about ALG driver status new [Re: uman]
#367164 - 06/23/17 08:22 PM


I'm not an expert on LD resolutions but (going by memory) the way Aaron described it was much lower than that and that the res they are in (something like 515 high I think) was 1.5X the original res in order to account for any loss you'd get from trying to stay at the original res. I'd personally go 2X or just captured at a common computer size like 720p and the sides in black.



R. Belmont
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Re: Question about ALG driver status new [Re: uman]
#367166 - 06/23/17 10:12 PM


> also not want to be a asshole here, but that laserdisc format, what can it be in
> resolution terms? my guess would be max. PAL (768x576) and if that is captured in a
> lossless codec, what would be wrong with that? i really dont understand. Ok, it would
> be a collection huge in size, but other than that, fine i guess, even for the future.

Arcade laserdiscs are analog video in NTSC format. That means that 480I (640x480 interlaced) is the limit of the detail you can get out of it, and in practice it was probably a bit lower.



R. Belmont
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Re: Question about ALG driver status new [Re: John Doe]
#367168 - 06/23/17 10:35 PM


> Accurate emulation would be to display "out of order" 99% of the time.

That's the truth. Even at CAX where the machines typically have been well maintained the only ones that survive both days tend to be the ones using the Daphne guys' play-the-video-off-a-SD-Card gadget in place of the laserdisc player.



uman
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Re: Question about ALG driver status new [Re: R. Belmont]
#367179 - 06/24/17 01:50 PM



> Arcade laserdiscs are analog video in NTSC format. That means that 480I (640x480 interlaced) is the limit of the detail you can get out of it, and in practice it was probably a bit lower.

Ok, i see. So the real problem are those "rare" laserdisc-players? I mean 640x480i, is 320x240 in progressive mode. I guess you dont want to keep those games interlaced.
It still would be a huge collection in terms of size, but maybe some option for users/gamers to have the possibility to convert a laserdisc game, in lets say .mp4 format but still maintaining the lossless format could help.

Would be a pity if those games will be lost. I dont know every game, but if there are any lightgun games, i would be sad .



Sune
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Re: Question about ALG driver status new [Re: uman]
#367186 - 06/24/17 07:53 PM


> It still would be a huge collection in terms of size, but maybe some option for
> users/gamers to have the possibility to convert a laserdisc game, in lets say .mp4
> format but still maintaining the lossless format could help.

They'd never do that. If such an option was available, which files do you think would end up being the only ones in circulation, the huge lossless ones or the smaller compressed ones?

S



uman
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Re: Question about ALG driver status new [Re: Sune]
#367194 - 06/24/17 09:22 PM


Dunno, but i am pretty sure, there are enough nerds outside that would keep a healthy lossless circulation, but yeah the majority would go with the compressed format, still nothing wrong in that IMHO.



taz-nz
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Finding real technical information of LaserDisc is hard work. new [Re: Smitdogg]
#367207 - 06/25/17 08:17 AM


Everybody just seems to says it's Analogue, like it's Voodoo Magic and leave it at that, like it can't possibly be understood by anyone in the Digital era.

From what I can find the encoding is fairly simple, It's just a FM modulated signal, where the length of pits and lands represent the distance between the waves in the FM signal. There are a couple of overlapping carrier waves that encode the video and the two channels of audio.

I know enough about engineering to be dangerous, so this next bit should be taken with a Cadillac sized grain of salt, and is basically me thinking out loud.

There would be a fair bit of electrical engineer involved, but capturing the output from the optical pickup (maybe using a modern Blu-ray pickup for better auto focus), would seem the logical place to do it, and then do all the post processing in the pc from there.

Presuming the disc encoding format is CAV, You could go all in and treat the laserdisc like a record, and try and isolate the disc from any drive motors stutter and eliminate disc flex, by placing it face up on a heavy belt driven platter, to gain more consistent capture results.

Making multiple captures of the same disc or more than one copy of the game, and then averaging results could help with noise reduction.

End random thoughts

Is there any information on what format of laserdisc the arcade games use? are they:
CAV (Constant angular velocity)
CLV (Constant linear velocity)
CAA (constant angular acceleration)
I'm guessing CAV and single sided, because of the way the games constantly jumping scenes.

Are they PAL or NTSC? is there a list somewhere of all the game and there disc formats ?



If all else fails, Burn the manual.



Olivier Galibert
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Re: Finding real technical information of LaserDisc is hard work. new [Re: taz-nz]
#367209 - 06/25/17 11:37 AM


> Everybody just seems to says it's Analogue, like it's Voodoo Magic and leave it at
> that, like it can't possibly be understood by anyone in the Digital era.
>
> From what I can find the encoding is fairly simple, It's just a FM modulated signal,
> where the length of pits and lands represent the distance between the waves in the FM
> signal. There are a couple of overlapping carrier waves that encode the video and the
> two channels of audio.

Simple, but fucks what little I know about signals. There's one question I'm just unable to answer: how such a signal should be digitized not to lose information? It's not just a matter of "max freq is f, db range is x, you need to sample at 2f at k*log(x) bits" since it's a binary signal where the information is encoded in high resolution timings...

OG.



taz-nz
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Re: Finding real technical information of LaserDisc is hard work. new [Re: Olivier Galibert]
#367210 - 06/25/17 12:41 PM


Yeah this is where my lack of knowledge of analogue to digital conversion and sampling rates etc, leave me scratch my head, and reading tech papers that confuse the hell out of me.



If all else fails, Burn the manual.



CTOJAH
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Re: Finding real technical information of LaserDisc is hard work. new [Re: taz-nz]
#367212 - 06/25/17 12:45 PM


> Yeah this is where my lack of knowledge of analogue to digital conversion and
> sampling rates etc, leave me scratch my head, and reading tech papers that confuse
> the hell out of me.

Which leads us to question :
What "digitally remastered" actually means ?



casm
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Re: Question about ALG driver status new [Re: R. Belmont]
#367218 - 06/25/17 05:25 PM


> Arcade laserdiscs are analog video in NTSC format. That means that 480I (640x480
> interlaced) is the limit of the detail you can get out of it, and in practice it was
> probably a bit lower.

Not to mention that there's info in the VBI that also needs to be encoded, saved, and decoded at playback time.

Aaron himself wrote about this nearly a decade ago, and while it's entirely possible that things have changed in that time, I believe that the basic issue still remains:

http://aarongiles.com/?p=234

He did come up with a suite of tools to help with capturing the VBI data:

https://github.com/aaronsgiles/VBIUtils

But I have no idea how things progressed past that point; other than some minor side interest in DEXTER, I haven't really been keeping up with the technical side of what's happening with it for the past few years. It's a format that's beyond dead, unfortunately, and disc rot is making 'ideal' preservation efforts increasingly-impossible as time drags on.

For the original poster: take a look at Aaron's 'About Laserdiscs' series. There's some good info in there not only about how the format works, but also regarding the challenges faced when attempting to preserve the data that it holds.

http://aarongiles.com/?p=236
http://aarongiles.com/?p=237
http://aarongiles.com/?p=238
http://aarongiles.com/?p=239



anikom15
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Re: Finding real technical information of LaserDisc is hard work. new [Re: Olivier Galibert]
#367220 - 06/25/17 06:19 PM


At least twice the highest detectable frequency of the signal is exactly what you need to sample at, after anti-aliasing filtering.

Generally we would much rather demodulate all the signals first and then digitize them, since they would all be in baseband and thus require the least amount of space for a particular stream. Alternatively we would digitize the composite signal. While demodulation adds noise, it's generally assumed the noise is insignificant compared to other sources.



anikom15
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Re: Finding real technical information of LaserDisc is hard work. new [Re: CTOJAH]
#367221 - 06/25/17 06:40 PM


Digitally remastered simply means mastering a digital source, like a DVD, from original analog sources, usually assumed to be film stock or tapes, rather than a transfer from a previous digital form.



anikom15
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Re: Question about ALG driver status new [Re: casm]
#367222 - 06/25/17 06:48 PM


A LaserDisc player-emulator could extract the VBI from a composite video signal in real-time. It would not be difficult, but it would require that the LaserDisc media be preserved as a composite video signal.

The possibility for information to be stored in the VBI in any analog video media is a good argument for working with video signals directly, in my opinion.



uman
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Re: Question about ALG driver status new [Re: casm]
#367225 - 06/25/17 10:07 PM


@casm: many thanks for the links, that was very helpful.

I still have some questions regarding the VBI data. I am not a expert, but i assume it is something like the copyprotection from a VHS, just complete different data and no copyprotection. I dont know, but wouldnt it be enough, to capture the stuff with underscan enabled from a broadcast monitor, so that you have the "whole" frame? Capturing with a good card like a Blackmagic in lossless format?



Olivier Galibert
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Re: Finding real technical information of LaserDisc is hard work. new [Re: anikom15]
#367228 - 06/25/17 11:15 PM


> At least twice the highest detectable frequency of the signal is exactly what you
> need to sample at, after anti-aliasing filtering.

I notice an interesting lack of information about some practical matters such as "what should be the frequency cutoff of the filtering?".

http://www.laserdiscarchive.co.uk/laserdisc_archive/how_laserdiscs_are_produced.htm

OG.



anikom15
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Re: Finding real technical information of LaserDisc is hard work. new [Re: Olivier Galibert]
#367231 - 06/26/17 12:44 AM


There likely is no defined standard. Broadcast video signals have a minimum attenuation of -30 dB at the stopbands. But that's AM. Laserdisc is FM, so things are a bit different. The frequency deviation is not going to be any greater than 7.1 MHz. Broadcast video is limited to 4.2 MHz, with audio, 6 MHz. The carrier is quite low-frequency compared to the message signal. The transmission is also very low-noise. For this reason I suspect there is no hard band-limiting applied, and rather things are just left to their natural devices. This page seems to support this:
http://machineryequipmentonline.com/vide...nal-processing/

The PWM is actually just a clipped sine and adds harmonics. These are so high-frequency compared to the carrier that they can be filtered out and do not interfere with the message at all. This is the reason FM is popular for music. The transmitted signal can be clipped with no loss of information, unlike AM. This is perfect for a disc format due to jitter between the laser head and the platter.

I think it should be sufficient to use a brickwall lowpass filter at 14.2 MHz, sample at least 28.4 MHz. There will likely be nothing but junk at the high frequencies, but it shouldn't be very noisy anyway.

From there you can either demodulate it into a standard NTSC or PAL composite video signal (or a video format) and store it, or store it as is.



Vas Crabb
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Re: Finding real technical information of LaserDisc is hard work. new [Re: anikom15]
#367232 - 06/26/17 01:41 AM


A brick wall filter is a hypothetical concept that can't be practically implemented. Also, attempting to approximate a brick wall filter often ends up giving you significant phase distortion and ringing, which would have a very detrimental effect on recovering the FM signal. The dominant harmonic introduced by clipping is 3rd harmonic, so the frequency of harmonics definitely isn't too high to cause trouble. You need to find a trade-off between how close you can filter to the maximum signal frequency vs sample bit depth. I don't know what the "right" numbers are, but it's definitely not a simple problem.



casm
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Re: Question about ALG driver status new [Re: uman]
#367234 - 06/26/17 02:12 AM


> @casm: many thanks for the links, that was very helpful.
>
> I still have some questions regarding the VBI data. I am not a expert, but i assume
> it is something like the copyprotection from a VHS, just complete different data and
> no copyprotection.

To be perfectly honest, I don't know enough about how Macrovision and other related VHS copy protection schemes work in order to be able to draw a comparison, and really don't want to give you an answer based on a quick skim of a couple of articles. The same applies to any similar schemes used for laserdiscs.

As relates to the VBI on laserdiscs, however: the VBI data needs to be preserved for a number of reasons, but one of the main ones relates to how laserdiscs store and access data. More on that below:

> I dont know, but wouldnt it be enough, to capture the stuff with
> underscan enabled from a broadcast monitor, so that you have the "whole" frame?
> Capturing with a good card like a Blackmagic in lossless format?

OK... Think about how a laserdisc stores video for a moment. Each frame is stored individually, like on film - which is totally unlike how, say, VHS stores its video, which is essentially a stream.

So, going back to what Aaron said here for a moment (and I realise you may already understand this, but I'm going to work through it for the benefit of anyone reading this post):

"At first, the VBI part of the scan just contained a couple of special signals for synchronization, but over time, people started adding data to them."

We now know that there's more than just basic start & end of frame info in there. Combining that with this statement a bit further down the page:

"The thing I discovered about laserdiscs, though, is that they encoded several very important bits of metadata on some of the VBI lines. Specifically, line 12 has what is known as a "white flag", line 16 contains some control bits, and lines 17-18 contain information about the current frame number and chapter. Even more importantly, all of this metadata is crucial to the way laserdiscs are controlled and operated in video games."

Putting it all together: the VBI contains, in essence, data attached to each individual frame used for control and playback of the frame in question. The original players referenced this data in order to be able to do things like skip to or pause on a specific frame.

Now, coming back to your question re: capturing the VBI data using something like a Black Magic card: sure, it's possible. But the issue then becomes what to do with the data stored in the VBI when the LD frames are converted to a digitally-stored streaming file. You also need to be able to play back those video files without the VBI data visible, which brings its own set of headaches.

DAPHNE worked around this issue through its use of framefiles, and possibly the best overview of how those work is here. However, framefiles allow DAPHNE to ignore VBI data altogether (see Matt Ownby's posts in this thread for more info on that). This is fine for playing the games, but from the standpoint of historical preservation it's less than desirable.

(Side note for anyone who has read this far: in one of the posts in the above-referenced thread, Matt Ownby said the following: "Daphne is focused on PRESENTATION. MAME is focused on DOCUMENTATION. Both are worthy goals, so let's not get into a war about which one is better." I happen to agree with him on both counts, and would prefer if that didn't happen here.)

This leaves us with other options to consider that might satisfy the requirements of storing the video digitally from both a presentation and preservation standpoint.

A format such as Motion JPEG may be an option, since it does store frames individually and plays them back one after the other rather than as a stream of data. VBI data could be preserved as part of each frame, and, potentially, referenced by an emulated (or simulated) laserdisc player.

For streaming formats, it may also be possible to read two video streams in sync: one containing the VBI data, and one containing the video. Again, the emulated or simulated player could use the VBI data as a marker by which it would access video in the streaming format - but that would come back to the issues of not being able to land on an exact frame division within the stream, and not storing the data in a format as close to original as possible.

All of the above gets trickier when you get into emulation of corner cases such as Williams' Star Rider - the VBI was used extensively in that game for in-game data (look here for example video from Matt Ownby that shows this), and it also had hardware that did panning of the video frame as it was displayed. But things like that are the exception rather than the rule.

Personally, I feel that the best approach is a Motion JPEG or similar codec capable of storing the entire video frame with VBI, followed by playback through an emulated or simulated LD player. But I'm a preservationist at heart, and can see where other considerations may not make that a universal fix.

In any case, we need to be preserving these discs at the highest possible quality, now, and while we still can. I do realise that efforts in this direction have not been lacking, but if we are going to settle on a 'universal' method of doing this now would really be the time since a lot of re-ripping will likely be involved and the time to be able to do that successfully is only decreasing.



casm
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Re: Question about ALG driver status new [Re: anikom15]
#367235 - 06/26/17 02:16 AM


> A LaserDisc player-emulator could extract the VBI from a composite video signal in
> real-time. It would not be difficult, but it would require that the LaserDisc media
> be preserved as a composite video signal.
>
> The possibility for information to be stored in the VBI in any analog video media is
> a good argument for working with video signals directly, in my opinion.

I do agree with you on both points, and had I seen your reply before I made this post may have replied slightly differently. If you have time, take a look at that one and let me know your thoughts - I'm mainly interested in how it may be possible to store a composite video frame in a digital format such that the individual composite elements could be broken back out again.



anikom15
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Re: Finding real technical information of LaserDisc is hard work. new [Re: Vas Crabb]
#367240 - 06/26/17 03:26 AM


Let me be clear, I'm assuming the anti-aliasing filters are sufficient to get a good digital signal conversion, and that the filter is used before resampling down to 28.4 MHz for storage.

The harmonics don't contain information and thus we only need to sample at the highest frequency deviation for the FM signal. A good ADC will reduce aliasing from the harmonics. Clipping is a normal stage in FM systems. In this case it's just done at the transmitter stage instead of at the receiver.

If we want to preserve the disc signal itself (i.e. the pulses), and not just the composite signal, we'd want to sample at at least twice the bandwidth of the optical detector.

I've heard that the SNR is around 50 dB for video and 110 dB for audio. This is regarding the demodulated signals however. For FM, we will only need 1 bit per signals. The dynamic range is only dependent on the frequency deviation.

With all this said we have some choices:

1) Store the PWM signal
This is the most similar to how the disc is stored. It requires a lot of bandwidth, and the emulator has to demodulate everything.

2) Store the FM signal
This is essentially the same as above but I don't think it can easily recreate the original medium. It requires less bandwidth though.

3) Store the streams
This demodulates the audio and video but doesn't process the video signal. The emulator has to do it.

4) Capture the video
This demodulates everything and also converts the video to some lossless format. You also have to define a format for v-blank data.



anikom15
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Re: Question about ALG driver status new [Re: casm]
#367241 - 06/26/17 03:41 AM


Theoretically you should be able to read the VBI data directly from the MJPEG frame. This would be problematic with MPEG however. I would recommend capturing at least 1440 px per scanline. The vertical doesn't matter as long as you are getting all 525 lines (526 stored lines since one line is displayed as two half-lines)

We'd probably want a lossless frame compression too. MJPEG wasn't designed for the discontinuities found in the VBI. In other circumstances I actually wouldn't mind for lossy for video.



Vas Crabb
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Re: Finding real technical information of LaserDisc is hard work. new [Re: anikom15]
#367245 - 06/26/17 07:52 AM


A good ADC won't do anything about aliasing. You'll get some aliasing any time you have any input frequency components at or above the Nyquist frequency. You can't completely eliminate higher frequencies with a practical filer, because realistically it's going to have some kind of roll-off curve. If you want to preserve just the pulses, you need to sample with 1-bit resolution at a substantially higher rate than twice the bandwidth of the FM detector's front-end. It's not as straightforward to do this in the real world as you seem to be implying.



TrevEB
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Re: Question about ALG driver status new [Re: DarkMoe]
#367247 - 06/26/17 08:20 AM


Many years back I spoke with Aaron about any need for LD titles as my friend has all of the laserdisc titles in the warehouse. Aaron assured me that all titles had been dumped.

As far as I know, all laserdiscs games have been aquired and dumped at least to the same standard as cliff hanger, cube quest, and the other few titles in Mame. There had been a plan to perhaps do it all again in a using a better method, but I don't think that happened. Sadly for reasons unknown to me, the other titles remain unreleased.

DL and SA wont be in Mame and thats fine. We have plenty of alternative ways to get our DL fix. The blu-ray and ipad versions are fantastic.

As for all the other titles, they sure would be a welcome addition.



MooglyGuy
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So are you volunteering to do the hardware side of things? new [Re: anikom15]
#367249 - 06/26/17 11:40 AM


Unless you're willing to look into getting a logic analyzer and finding a good model of LD player that lets you easily tap the relevant signals, this is more or less just mental masturbation.

That's not to say it isn't good to figure out these issues beforehand, but you're basically arguing what kind of radio you want in a car that hasn't even been built yet.



anikom15
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Re: Finding real technical information of LaserDisc is hard work. new [Re: Vas Crabb]
#367250 - 06/26/17 11:47 AM


Admittedly I'm not a filter expert and my poor vocabulary undoubtedly gave the wrong impression that this was a 'straightforward' problem. It's not, but I'm trying to offer my understanding to try to shed some light on the situation and eliminate some of the fear of analog technology. I believe this is a problem that can be solved with some compromise.

A 'good' ADC has an anti-aliasing filter that will do the job. If it doesn't have one built-in then you add one to make it a 'good' ADC. The anti-aliasing filter needs to attenuate unwanted frequencies such that when those frequencies are aliased by the ADC they do not significantly alter the signal.

The design of these filters is out of my scope, but generally we care about the cutoff frequency, stopband frequency, and stopband attenuation. The amount of attenuation and the stopband frequency determine the required rolloff characteristic of the filter. We design for this depending on the information we are digitizing, the tolerance of the signal to distortion and how that distortion affects the perception by us.

At this point we go to the digital domain. We will likely need to resample the data to the Nyquist frequency for the purposes of space saving. For this we usually use a brickwall filter. I've always used 'brickwall' to refer to FIR approximations of the unrealizeable sinc filter. If I was suggesting an impossible filter I would've stated 'sinc'. That said, there are applications where Gaussian and other filters should be used instead.

Perhaps you are misconstruing my lingo as exact in place of good enough. If good enough is not good enough, and you want an absolute perfect preservation of an analog medium, then of course there is no practical way of digitizing the signal. At that point the problem will be unsolvable.

It's best to clarify what we want to preserve by specifying which of those four numbers I outlined would be best desirable (or something else I didn't consider). They go in order from most difficult to simplest, where 1 is the most difficult.

We can also look at these by dissecting a LaserDisc player:

1 leaves only the platter and laser reader mechanism. We store that 'laser data'

2 adds part of the demodulation circuitry, but everything is still one signal.

3 adds the filters to separate the video from the audio and also demodulates them.

4 is essentially reading the composite output and applying rec. 601 on it, with the addition of saving that VBI data.

The only reason I can think of for doing 1 is if we wanted to start adding LaserDisc players to MAME (or do we have some already?) Otherwise my vote is for 3. Capture the outputs from a good LaserDisc player. It's a solved problem and we can read the VBI data in real-time like the original hardware, unless I'm misunderstanding something.



anikom15
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Re: So are you volunteering to do the hardware side of things? new [Re: MooglyGuy]
#367251 - 06/26/17 11:50 AM


Well yeah pretty much.

Someone said something about using a blu-ray optical detector to do it. I have no idea how possible that actually is but I have a feeling it's not easy at all.



uman
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Re: Question about ALG driver status new [Re: casm]
#367254 - 06/26/17 12:43 PM


> > A LaserDisc player-emulator could extract the VBI from a composite video signal in
> > real-time. It would not be difficult, but it would require that the LaserDisc media
> > be preserved as a composite video signal.
> >
> > The possibility for information to be stored in the VBI in any analog video media
> is
> > a good argument for working with video signals directly, in my opinion.
>
> I do agree with you on both points, and had I seen your reply before I made this post
> may have replied slightly differently. If you have time, take a look at that one and
> let me know your thoughts - I'm mainly interested in how it may be possible to store
> a composite video frame in a digital format such that the individual composite
> elements could be broken back out again.

Again big thanks, casm. I hope i can read everything in the evening after job-time. I agree with anikom15, MJPEG is not good enough, as it is not a lossless codec. We used MJPEG only for creating proxies that are smaller in size and better to work with. Nearly every lossless codec has each frame saved individually but without compression/degrade.

After reading your first post, i also understand now, that it would be silly to convert the games to codecs that would generate smaller sizes, as they cant be accurate enough, to jump to exact frame numbers, but this shouldnt be a problem nowadays with a average PC setup and a big enough HD.

Back to anikom15 suggestions, i maybe can help with point 4, which sounds the easiest to do. Ok, it may be not the "best and most accurate" method, but the result would be the same IMHO and only different seen by someone who goes into very technical details (sorry if i am totally wrong with that). MAME already has some compromise for systems like atari2600 i.e., why not for laserdiscs? Can only repeat anikom15 here:

"If good enough is not good enough, and you want an absolute perfect preservation of an analog medium, then of course there is no practical way of digitizing the signal. At that point the problem will be unsolvable."


From what i try to understand, the laserdisc-players seems to be the main problem, so i need to ask, what kind of laserdisc-player is needed for those games? i assume that a consumer model (those that played just movies at that time) will not work. what kind of models would work? some exact model-numbers would help me.

Edited by uman (06/26/17 12:45 PM)



taz-nz
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Re: Finding real technical information of LaserDisc is hard work. new [Re: anikom15]
#367255 - 06/26/17 12:48 PM


> With all this said we have some choices:
>
> 1) Store the PWM signal
> This is the most similar to how the disc is stored. It requires a lot of bandwidth,
> and the emulator has to demodulate everything.
>
> 2) Store the FM signal
> This is essentially the same as above but I don't think it can easily recreate the
> original medium. It requires less bandwidth though.
>
> 3) Store the streams
> This demodulates the audio and video but doesn't process the video signal. The
> emulator has to do it.
>
> 4) Capture the video
> This demodulates everything and also converts the video to some lossless format. You
> also have to define a format for v-blank data.

Option 1 still seems like the logical choice, it's the closest we can get to a digital source, and offer the least amount of noise or distortion, disk space is cheap, it really doesn't matter if the disc image is the size of Blu-Ray rip, it's doesn't have to be the final format used by the emulator. We aren't trying to emulate the laserdisc player, just it's output (or at least at this point)

My thought is, that if we have as close to raw source copy as possible, all the demodulation and post processing can be done digitally, everything is a calculation and 100% repeatable. We can produce a near lossless and consistent image of disc contents that is also practical to use in MAME.

The other option, introduce more and more analogue noise, and by the time you get to option 4 you would be lucky if one frame matched out of a thousand captures of the same disc, every capture would different from the last, so you always missing something.

A raw option 1 rip is impractical as the final format, but offers the most control over the quality. It also makes capture to capture comparisons more practical, if your trying to eliminate variances, or to build a composite disc image from more than one copy of the same game, like if your dealing with bit rot.

I can see how the demodulated option are attractive, but they seem to come with a lot of compromises.

Again I'm no electrical engineer, this is just what I think would give the best results.



If all else fails, Burn the manual.



uman
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Re: Finding real technical information of LaserDisc is hard work. new [Re: taz-nz]
#367256 - 06/26/17 01:11 PM


> The other option, introduce more and more analogue noise, and by the time you get to option 4 you would be lucky if one frame matched out of a thousand captures of the same disc, every capture would different from the last, so you always missing something.

This is something i dont understand. I assume that the VBI data is the most important that we need to have. If good broadcast equipment is used, i cant believe that there is so much "noise" introduced to the signal, that you dont have accurate VBI data. I am in no way a expert here, but this sounds very unbelievable to me. For the picture quality itself, it would be true, that every capture would look different, but not to a degree, that you would see that with just your eyes. As long as the VBI data is intact and there is for sure a tolerance to noise, it should be fine.



taz-nz
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Re: So are you volunteering to do the hardware side of things? new [Re: anikom15]
#367257 - 06/26/17 01:15 PM


> Well yeah pretty much.
>
> Someone said something about using a blu-ray optical detector to do it. I have no
> idea how possible that actually is but I have a feeling it's not easy at all.

I made the comment about using a Blu-ray pickup, for a couple of reasons, the last laserdisc player was designed in 1999, and technology has improved a bit since then, by necessity a Blu-ray pickup requires better auto focus, but also includes the 780nm laser diode used for CD (which I believe is common to laserdisc), Blu-ray pickups like the Toshiba PHR-803T found in the xbox 360 are cheap common and have at least been partly reverse engineered and documented, and it likely there are others that are well documented and suitable to the task.

Finding data on the optical pickups in laserdisc player is likely a lot harder, and they are likely dependant on more supporting electronics.



If all else fails, Burn the manual.



casm
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Re: Question about ALG driver status new [Re: uman]
#367273 - 06/27/17 12:40 AM


> Again big thanks, casm.

No worries; just glad it's useful. And part of the reason for doing this is so that I have a reference as well - it's been a decade since I had to deal with a lot of this, so it's helping me to bolster my memory.

> I hope i can read everything in the evening after job-time. I
> agree with anikom15, MJPEG is not good enough, as it is not a lossless codec.

True, and I do agree on that point (which is why I mentioned using MJPEG or similar). To my mind, the basic idea behind MJPEG is essentially what we're looking for - each individual frame stored as a frame, not a stream. What I'm not sure of is if there's a lossless equivalent that can store the data in the same basic way.

Per-frame compression may be acceptable depending on how much of a performance hit that would cause in playback (and I admit that that might be unrealistic in a gaming environment), but lossless codecs are the key. See also:

> After reading your first post, i also understand now, that it would be silly to
> convert the games to codecs that would generate smaller sizes, as they cant be
> accurate enough, to jump to exact frame numbers, but this shouldnt be a problem
> nowadays with a average PC setup and a big enough HD.

I understand where you're going with this. My gut feeling is that whatever format is used should be capable of randomly (and directly) accessing frames, the same as an LD player would have, without landing on a frame transition. In theory, this should never happen in a properly-designed codec since one frame doesn't necessarily stream into another, interlacing possibilities aside.

However, the more I think about it, the more I think that what I'm describing is a codec specifically tailored to playback of media sourced from laserdiscs. It might also be able to be used for teleciné-style film transfers, but to the best of my knowledge nothing like this currently exists in the format being described.

> Back to anikom15 suggestions, i maybe can help with point 4, which sounds the easiest
> to do. Ok, it may be not the "best and most accurate" method, but the result would be
> the same IMHO and only different seen by someone who goes into very technical details
> (sorry if i am totally wrong with that). MAME already has some compromise for systems
> like atari2600 i.e., why not for laserdiscs? Can only repeat anikom15 here:
>
> "If good enough is not good enough, and you want an absolute perfect preservation of
> an analog medium, then of course there is no practical way of digitizing the signal.
> At that point the problem will be unsolvable."

True, but that can be said of any analogue to digital conversion. There is no good way in a digital domain to store the infinite possibilities within a finite analogue range. About the best you can do is decide on what constitutes acceptable loss and move on.

> From what i try to understand, the laserdisc-players seems to be the main problem,

Not really. We know how they work, and there's not very much stopping them from being emulated (other than someone having the motivation to do so). The thing is, though, because we understand how the video is stored and structured on the discs we can pretty much bypass the players altogether for digital playback. This is a good thing, because given how laserdisc players are dying off and there are very, very few people able to repair them, we will hit a point fairly soon where there just aren't any useful ones left.

> so i need to ask, what kind of laserdisc-player is needed for those games?

It depends on the game. Many, many models were used, and it's largely game-dependent. See http://www.d-l-p.com/games/ for examples; you'll need to pull up each individual game and check its Tech Center entry for the info.

> i assume that
> a consumer model (those that played just movies at that time) will not work. what
> kind of models would work? some exact model-numbers would help me.

Some consumer models *may* work. In general, though, industrial players are preferred as they generally had better playback, output, and build quality.



Haze
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Re: Question about ALG driver status new [Re: TrevEB]
#367319 - 06/28/17 02:13 PM


> Many years back I spoke with Aaron about any need for LD titles as my friend has all
> of the laserdisc titles in the warehouse. Aaron assured me that all titles had been
> dumped.
>
> As far as I know, all laserdiscs games have been aquired and dumped at least to the
> same standard as cliff hanger, cube quest, and the other few titles in Mam
e. There
> had been a plan to perhaps do it all again in a using a better method, but I don't
> think that happened. Sadly for reasons unknown to me, the other titles remain
> unreleased.
>

badly then.... some of the stuff in MAME even gives 'disc error' messages because the data isn't good enough.



uman
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Re: Question about ALG driver status new [Re: Haze]
#367326 - 06/28/17 04:52 PM


So i assume, it wasnt captured good enough. Is that VBI data so sensible?



uman
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Re: Question about ALG driver status new [Re: Haze]
#367883 - 07/15/17 08:39 PM


Ok, my problem is that i need to know a LD player model, that can play NTSC and PAL and has a RS 232 connection. Before i spend a few hundred euros for a working hardware setup and asking a lot of people for help, i need to know some stuff. i have read a lot of articles now, but i still got questions.

Copyright/License problems: i talked with SailorSat who has 4 working games captured, but it came out, that there are still copyright problems (WTF!) with some games.

Capturing problems: i didnt found any decent/good card, that could capture the whole 525 lines of a frame. At least not without hacking drivers. However with a Blackmagic card, i could capture 3 VBI lines of my choice (i.e. line 11, 16 and 17 etc.), which would be enough according to Aarons article here:

http://aarongiles.com/?p=238
and here:
http://aarongiles.com/?p=234

But i bet, that the LD tool from MAME would expect something different (i.e. whole frame with 525 lines) and the whole thing wouldnt work again.
So if i understand it correctly, we would need a rewritten tool that only expect those three (ok there are four, but one is just a copy) VBI lines and not the whole frame. Would that be possible?

I hope you can answer some or all of these questions. So that SailorSat and me could create some setup, that would work.



anikom15
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Re: Question about ALG driver status new [Re: uman]
#367884 - 07/15/17 08:56 PM


Our best bet is to use a DAQ, oscope, or similar general purpose device. We don't know what's going on in a blackbox composite-to-X device or a capture card. We can't trust the results from those things. You are free to capture these for educational and development purposes but I'm going to assert that captures should not be considered a good dump.



uman
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Re: Question about ALG driver status new [Re: anikom15]
#367886 - 07/15/17 09:34 PM


That didnt help much, but ok. If you really need DAQ, Logic Analyzers and such, to make some rocket science of LD games (and most of them are in a quality range more worse than a very bad VHS copy), then its that. I wish you all good luck with your goal (and i truly mean it).

Well if you cant trust a Blackmagic Decklink card, while it is a de facto standard in every good post production house for capturing stuff, i still have hope that your approach with DAQs, Analyzers and what not, will create much better results.



casm
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Re: Question about ALG driver status new [Re: uman]
#367892 - 07/16/17 01:21 AM


> Ok, my problem is that i need to know a LD player model, that can play NTSC and PAL
> and has a RS 232 connection.

I'm not aware of one that meets all of those requirements. However, you may be able to feed an NTSC LD player out to a video recorder capable of NTSC playback on PAL via S-Video, then capture the PAL output. It doesn't matter if the video recorder can play tapes or not as long as the S-Video input works and it can output to SCART or similar for capture.

The thing with this is that you're going to end up with a capture that is not the same as the original source. I don't remember all of the ins and outs of doing this as I haven't had to in nearly 20 years, but one of my recollections is that NTSC source material is typically recorded for a 60Hz sync, whereas PAL is usually (Brazil aside) recorded for 50Hz sync. You'll get NTSC to play back on PAL using this method, but there are issues with syncing video frames correctly in this scenario.

Just find a video capture card that can handle NTSC directly and connect your source straight to it. It'll simplify things greatly.

> I hope you can answer some or all of these questions. So that SailorSat and me could
> create some setup, that would work.

From what I recall, virtually every laserdisc game ever released used NTSC as its on-disc video format. There may be exceptions to this (the Web Picmatic games such as Zorton Brothers *may* be an exception, though I don't believe so), but I'm not aware of any.

Assuming that the above is correct, just do straight NTSC capture. There is no advantage to converting the video to PAL - unless you're converting to the 60Hz PAL-M format used in Brazil, there are going to be sync issues with frame (and therefore VBI) timing. Even then you're going to be changing the video from the format it was originally stored in as (IIRC) PAL was 625 lines total.



uman
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Re: Question about ALG driver status new [Re: casm]
#367916 - 07/16/17 09:09 PM


I wanted such a LDP model, just for being more flexible while capturing. I would rather buy 2 LDP models, then going your adviced route. Going such a long signal route, would degrade the material for sure. There are PAL LD-games outthere, at least SailorSat´s Dragons Lair is in PAL, for example.

Anyway, there is no interest in captured dumps, so this discussion is pointless.



John Doe
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Re: Question about ALG driver status new [Re: uman]
#367927 - 07/17/17 08:30 AM


> Well if you cant trust a Blackmagic Decklink card, while it is a de facto standard in
> every good post production house for capturing stuff,

It's not just the capture card, you can't trust the laser disc player output.

Someone needs to duplicate this setup.

http://www.jammaplus.co.uk/forum/forum_p...rdisc-emulation

I don't know if there are people already working towards it.

Edited by John Doe (07/17/17 08:34 AM)



uman
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Re: Question about ALG driver status new [Re: John Doe]
#367934 - 07/17/17 01:46 PM


> It's not just the capture card, you can't trust the laser disc player output.

As long as the LDP has a RS 232 connection, we are able to capture each frame, can seek and jump to each frame and start with frame 0 or 1, which is crucial. Using one of the last produced LDPs, would assure better quality output, than a model from the eighties. So i can trust the LDP output and there is absolutely no reason why i should not (especially for some last generation LDP models), but the MAME devs cannot it seems. Your linked thread also does not prove your POV at all. Nowhere in the thread, talk someone about LDPs that are untrustable, only about the quality you can get out of them, which is a logical thing, considering a lifetime production span for nearly 2 decades. It is out of question, that a latest model, will output more decent quality, but the medium that is played is 90% junk in terms of quality. It is not a premium LD from Star Wars New Hope.

I quote some of the important stuff of this long 14pages thread from your link:


Quote:


The circuitry in the LDV8000 introduces a moderate amount of noise, but given the **** quality of the FF disc, where multiple generation edits have been done with some seriously noisy gear, it doesn't really matter that much.




And Firefox, is one of the best looking games here. 90% of the LD games will look way more ugly. They where produced very fast and very cheap with the lowest eighties technology.


Quote:


For playback on a PC, you'd most likely get better results by just using a capture card as it will have a TBC, 3d (hopefully) comb filter, etc. As I was ultimately going to play out composite, going through that process and then back to composite again would degrade the picture.

The Mame image, for instance, looks fine on a PC, but nasty when remodulated. The explosions, in particular, are covered in artefacts where the comb filter hasn't managed to get rid of the crosstalk between luma and chroma.




At the end of the day, thats what will be happening for LD games anyway. They will be played on a PC. Even if we want to be able, that the games can be "remodulated", we would need to keep the interlace/fields and would need realtime deinterlace shaders, so that it doesnt look ugly on a PC. There are systems already in MAME that sacrificed exactly these things. Why the devs cannot do the same here, i dont know. Losing the fields is a degrade process in itself and only CRTs are capable of displaying it properly.


Quote:


Going the route of not designing any new hardware, using a digital i/o card would be doable, it's just a lot of cash to spend to then find yourself limited by the 8-bit ADC in the LDV8000. Better results could be had by using an A->D card and capturing the composite out from a player with an analogue-only path from disc to composite port. I looked into this when I started, but I couldn't find a cheap card which retained the composite signal without processing it.



Dave talked about cheap cards in a 4 years old thread. A Blackmagic is not even cheap today, but a lot more than 2010. More important, it doesnt process the composite signal, what comes in, comes out with interlace/fields or without (depending on input) and with VBI data.


Quote:


Adding your own hardware increases the choices a bit. If I were planning to do lots more of these, I'd design an A->D board which could hook in as early in the signal path as possible and grab video + audio before they've been split. I'd have a digital signal coming out the back to be captured by any means necessary... FPGA dev board, my LD emulator PCB or one of Colin's I/O cards. Net result would be the same as hacking wires into the LDV8000, only with more bits coming out. The risk is that the additional circuitry introduces so much noise that the results aren't as good as a straightforward capture from the composite out.




Again, like Dave, annikom and me already said, the result is questionable, in terms of "will it be a better capture" or better "If good enough is not good enough, and you want an absolute perfect preservation of an analog medium, then of course there is no practical way of digitizing the signal. At that point the problem will be unsolvable.". Even with the intended rocket science setup, the result can differ from one laser to another laser, cables used etc.

Example: Its like listening to a classic concert, a record of it, will never be the same, like the real life experience. The difference here is, that the audio you listening to, is a cheap box radio mono tune, compared to the classic concert and you are trying to capture that with equipment and science that belongs more to the classic concert.

I doubt that anyone will see a difference in a capture done like you intend and a "normal" capture with good equipment coming from the last years of analog production lifetime. There will be no better equipment (for capturing) in the future, as this technology was buried in the past.

All i know is, that time for the LD medium is running out, day by day.


Quote:


Grabbing a combined a/v signal seems like a good idea in theory, but isn't really necessary in practice. I sampled the Firefox audio twice, once with one channel hooked up to the composite out. Vertical sync falls within the audio band (composite is designed this way to allow sync separation with really noddy electronics) and can easily be seen on the captured waveform or detected by a bit of software.

Cutting the audio 'perfectly' doesn't give ideal results because there appears to be quite a bit of a/v sync variation in the master. You'll also never have a perfect cut because the audio is bandwidth-limited and can't instantaneously switch from one level to another. The original player would have lost the audio for approx 2 ms or so when doing fast seeks and I suspect the disc was mastered with the audio slipped back a fraction to move the transitions into the time period where the output would be muted. 2 ms is a guestimate based on Atari blanking 32 lines in each field to hide video disruption.





Quote:


How to tell if an LD player has an analogue output path: an analogue player cannot freeze frame a CLV disc. Get a copy of the service manual for a candidate to be absolutely sure as there may be some players with no frame buffer, but a small digital path for noise processing and TBC. Don't know of any fitting into the latter category, just speculating.

Bits for sampling: I would use 10 or more, although that's just a rough estimate based on thinking the 8-bits in the LDV8000 is right on the edge of not being enough. Doesn't matter about overkill mind you because you can always use more and throw away what you don't use.

There are loads of players with digital frame stores. The Pioneer CLD-D925, for example, has an 8-bit digital signal path, just like the LDV8000.




The last Blackmagic card, that has composite input and does 525i and 525p with VBI capturing, samples with 10bit 4:2:2 which is more than enough for SD material. Also the Pioneer CLD-D925 (1996) has a way more decent signal path, judging by all reviews i have read about this model (it even has PAL/NTSC), it sadly has no RS 232 connection and so it falls out for my choice of capturing.



casm
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Re: Question about ALG driver status new [Re: uman]
#367936 - 07/17/17 03:20 PM


> I wanted such a LDP model, just for being more flexible while capturing. I would
> rather buy 2 LDP models, then going your adviced route. Going such a long signal
> route, would degrade the material for sure.

Agreed. That suggestion, BTW, was based in part on a misunderstanding on my behalf; more on that below:

> There are PAL LD-games outthere, at least
> SailorSat´s Dragons Lair is in PAL, for example.

OK, that clears things up a bit. I'm aware of the existence of the Dragon's Lair and DL2 Euro hardware, but didn't know that the discs (and, presumably, players) used in those games were PAL. This makes sense, since Atari and Sidam had manufacturing rights in Europe for those games - but IIRC, Firefox was also released in Europe (in *very* small numbers) in US-manufactured cabinets with NTSC players. Ditto other games originating in the US or Japan.

Either way, that brings up some interesting points: firstly, that there would need to be captures done of both PAL and NTSC media from native players (i.e., no conversion of source formats); secondly, whether or not the DL and DL2 PAL discs were full PAL remasters from the source films or if they were NTSC to PAL conversions from master tapes.

I don't know enough about the potential differences between an NTSC and PAL DL disc to say if the following is feasible or not, but if the content is the same between both then doing an NTSC to PAL conversion and capture from an NTSC disc would produce a functionally-similar end result. Not exactly the same and ultimately pointless because PAL discs exist, but it may be an option.

> Anyway, there is no interest in captured dumps, so this discussion is pointless.

My feeling is that it's not so much a case of there being no interest in captured dumps as much as it is that there's no-one currently working on the issue and no agreed-upon format for storing the video in a way that suits preservation goals. That person will need access to discs, players, and capture hardware, as well as video codecs capable of preserving the video output in a way that can be read, manipulated, and displayed true to the original hardware. Even if a person who can meet those criteria is found, they still need to have the time and motivation to take this project on as a volunteer. That's a tall order.



casm
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Re: Question about ALG driver status new [Re: uman]
#367938 - 07/17/17 04:16 PM


> Using one of the last produced LDPs, would assure better quality output, than a model from the
> eighties.

Maybe.

Particularly towards the end of Laserdisc's life, there were a number of cost-reduced players released. While I don't recall specifics, many of them had inferior output to models that were over a decade old at that point. I understand your point that later models *should* be better, but that wasn't always the case. Hell, even in the '80s there were noticeable variances in playback quality and features between machines - which is one reason why industrial players were generally preferred over consumer-grade models.

> It is out of question, that a latest model, will output more decent
> quality, but the medium that is played is 90% junk in terms of quality. It is not a
> premium LD from Star Wars New Hope.

Even some of those Star Wars: A New Hope discs are suffering from laser rot. On a long enough timeline, all of them will. It's just that the laserdisc games have had longer to get to that point and so have statistically-greater instances of degradation.

> And Firefox, is one of the best looking games here. 90% of the LD games will look way
> more ugly. They where produced very fast and very cheap with the lowest eighties
> technology.

I disagree with that statement to a certain point. Remember that LD technology was not cheap at the time or over its lifetime, and that many games used multiple revisions of or completely different players during their production runs as reliability issues (which were usually, but not always, mechanical) surfaced. The players could only be bought in from the manufacturers at specific price points, and pressing LDs may have actually been *more* expensive for games than retail titles due to the relatively low numbers of discs produced.

As for the PCBs, wiring, controls, cabinets, and all other components that would be common to any arcade game... Sure, those would have been cost-reduced by the accountants as much as possible prior to production. But the LD hardware itself was going to account for a significant chunk of the overall manufacturing costs of each machine, and that was a cost largely controlled by the supplier of that hardware.

Now, one thing that we don't control (or really have good insight into) is the quality of mastering and/or pressing that may have taken place during disc production. It is possible that certain games may have used lower-quality processes in this regard as a way to reduce unit cost; this almost certainly will have an effect on both disc longevity and playback quality outside of the capabilities of the players themselves.

However, this is an unsolvable problem as we're working solely with the media that was generated under those circumstances, and even the greatest LD player ever made can't make a disc pressed from crappy source material look better than the material on the disc itself. If we had access to pressing masters things might be better to a certain point, but I'm willing to bet that by now all of those are long since discarded and/or destroyed.

> Going the route of not designing any new hardware, using a digital i/o card would be
> doable, it's just a lot of cash to spend to then find yourself limited by the 8-bit
> ADC in the LDV8000. Better results could be had by using an A->D card and capturing
> the composite out from a player with an analogue-only path from disc to composite
> port. I looked into this when I started, but I couldn't find a cheap card which
> retained the composite signal without processing it.
> Dave talked about cheap cards in a 4 years old thread. A Blackmagic is not even cheap
> today, but a lot more than 2010. More important, it doesnt process the composite
> signal, what comes in, comes out with interlace/fields or without (depending on
> input) and with VBI data.

OK, so here's a question from my somewhat limited understanding of how NTSC video actually works: what options exist other than a Blackmagic card? Basically, I'm wondering if this is something that couldn't be accomplished with the use of studio equipment in a pre-processing phase ahead of digital capture on some other equipment, or possibly even the same as proposed.

My thinking is that if the specific fields required can be broken out to a separate digital stream (or frame), the codec that captures and plays back the digital file can take care of the combinatory problem at playback.

This won't capture an 'original' frame, but then again trying to completely reproduce an analogue signal in a digital medium is a path to madness. You made that point very well here:

> "If good enough is not good enough, and
> you want an absolute perfect preservation of an analog medium, then of course there
> is no practical way of digitizing the signal. At that point the problem will be
> unsolvable.". Even with the intended rocket science setup, the result can differ from
> one laser to another laser, cables used etc.

Which brings us back to the point earlier in the thread that what constitutes acceptable losses need to be determined in advance and worked with to preserve as much of the original *as possible*. We know that we can't move everything on the disc from the analogue to digital domain in a perfect reproduction, so rather than getting bogged-down in worrying about that specific problem we should seek to find a workable solution to it.

> The last Blackmagic card, that has composite input and does 525i and 525p with VBI
> capturing, samples with 10bit 42 which is more than enough for SD material. Also the
> Pioneer CLD-D925 (1996) has a way more decent signal path, judging by all reviews i
> have read about this model (it even has PAL/NTSC), it sadly has no RS 232 connection
> and so it falls out for my choice of capturing.

There are likely several ways in which this issue could be worked around, but one that springs to mind is the following:

Homebrew an interface allowing a PC to directly piggyback onto the IR port for the remote control and frame-step from the PC as needed by faking IR frame seek commands; if the IR port can accept direct input of specific frame numbers, bonus.

Whether or not this will allow access to frame zero is another question, however: that capability may be reserved for the player internally and may not be user-accessible from the remote. In that case, start tapping the busses that govern this behaviour and see what sort of command injections might be possible.

Here's a thought: what did Digital Leisure do to accomplish their transfers? What was their source media, and how did they digitise it? They likely didn't care about things like VBI info since they were transferring to DVD, but it may make for an interesting comparison against methods commonly at one's disposal. It may also be completely pointless as this is an area of research that could easily lead to 'they crammed it into an MPEG at source', but could generate some useful info.



uman
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Re: Question about ALG driver status new [Re: casm]
#367941 - 07/17/17 06:11 PM



Quote:


> > Using one of the last produced LDPs, would assure better quality output, than a model from the eighties.>

> Maybe.

> Particularly towards the end of Laserdisc's life, there were a number of cost-reduced players released. While I don't recall specifics, many of them had inferior output to models that were over a decade old at that point. I understand your point that later models *should* be better, but that wasn't always the case. Hell, even in the '80s there were noticeable variances in playback quality and features between machines - which is one reason why industrial players were generally preferred over consumer-grade models.>




Thats not exactly what i meant with my explanation. Of course, industrial players where more durable, had better components and what not, but what i wrote would still apply to those "industrial" players too. I am not a expert for LDP models and thats why i asked for some model-nr., so that i can continue with my search.


Quote:


> Even some of those Star Wars: A New Hope discs are suffering from laser rot. On a long enough timeline, all of them will. It's just that the laserdisc games have had longer to get to that point and so have statistically-greater instances of degradation.>

> > And Firefox, is one of the best looking games here. 90% of the LD games will look way more ugly. They where produced very fast and very cheap with the lowest eighties technology.>

> I disagree with that statement to a certain point. Remember that LD technology was not cheap at the time or over its lifetime, and that many games used multiple revisions of or completely different players during their production runs as reliability issues (which were usually, but not always, mechanical) surfaced. The players could only be bought in from the manufacturers at specific price points, and pressing LDs may have actually been *more* expensive for games than retail titles due to the relatively low numbers of discs produced.>




I am sorry, but you got me completely wrong here and i should explain that more clearly. Its not the LD medium itself (this in fact, was awesome at that time). I meant more the "content" of it, the what you called "master". This content was produced fast, very cheap and with low-quality standards and is that, what was mentioned by Dave about Firefox for example and Firefox is one of the better "masters". I have seen four captures from SailorSat and three of them, are just "quick and dirty" work. Only Mad Dog looked "acceptable", but still far from a good "master".

Which brings us to the next point you wrote:


Quote:


> However, this is an unsolvable problem as we're working solely with the media that was generated under those circumstances, and even the greatest LD player ever made can't make a disc pressed from crappy source material look better than the material on the disc itself. If we had access to pressing masters things might be better to a certain point, but I'm willing to bet that by now all of those are long since discarded and/or destroyed.>




With this, you answered your own questions regarding Digital Leisure and DL, Space Ace and so on. They had Don Bluth and they had the original masters. As this is basically a animation movie, it was quite easy to recapture stuff and even create a HD release of it. Stuff that you simply cannot do with Mad Dog and all the other games, with real actors. Those games where not recorded on film (nearly resolution independent, huge colorspace), but rather on video (fixed small resolution, small colorspace). So even if you have the masters, you will not come far with it.


Quote:


OK, so here's a question from my somewhat limited understanding of how NTSC video actually works: what options exist other than a Blackmagic card? Basically, I'm wondering if this is something that couldn't be accomplished with the use of studio equipment in a pre-processing phase ahead of digital capture on some other equipment, or possibly even the same as proposed.




Of course there is other studio equipment like a Betacam SP, but you would still be in the analog world and we need to go digital in some form, to make it accessible for normal people. There is no workaround for this.


Quote:


> My thinking is that if the specific fields required can be broken out to a separate digital stream (or frame), the codec that captures and plays back the digital file can take care of the combinatory problem at playback.>




I dont know, what you exactly want here. If you mean interlacing/fields, i am not aware of any codec on this planet, that can do this. If you mean the VBI data, this can be done and is written in Aarons arcticles you linked previously.

IMHO here lies a problem. Nearly all capture cards, where not designed to capture the "whole" frame. Even in the Firefox thread, you will not see such a capture (starting with page 1). Professional equipment will capture VBI data, but not the whole frame. You may achieve this with hacked videodrivers, but this is not recommended and a ideal solution at all. I consider it very hard to do it the right way, especially if you want to keep the interlace/fields intact, which would be crucial for further processing. To be honest, i could be wrong here as i never seen the original captures, but i think the captures from Aaron have errors regarding this topic. We only need to know, which lines of the VBI data are needed, but we dont need the whole frame, this will cause only trouble. This is the reason why i asked if the software for proving captures, could be rewritten. Professional equipment doesnt work that way (cheap stuff neither), like it is expected in the article of Aaron. So the approach of the LD tool in MAME is wrong, regarding the VBI data, as it is expecting the "whole" frame (525lines).

Which brings me to the last point. Yeah, you can hack all kind of stuff, like the IR remote for exact frame jumping and what not, capturing straight from the laser lens to your eye. I think we should avoid as much as possible of this hacks. The interlace/fields, analog sources/noise, VBI data etc. all of this, is very delicate and very picky and with a single shifted scanline, you will break all your capturing effort into useless shit. Keep it simple, treat the source right, capture it uncompressed/lossless and thats it.



Rygar9
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Re: Question about ALG driver status new [Re: uman]
#367954 - 07/18/17 01:57 AM


> IMHO here lies a problem. Nearly all capture cards, where not designed to capture the
> "whole" frame. Even in the Firefox thread, you will not see such a capture (starting
> with page 1). Professional equipment will capture VBI data, but not the whole frame.
> You may achieve this with hacked videodrivers, but this is not recommended and a
> ideal solution at all. I consider it very hard to do it the right way, especially if
> you want to keep the interlace/fields intact, which would be crucial for further
> processing. To be honest, i could be wrong here as i never seen the original
> captures, but i think the captures from Aaron have errors regarding this topic. We
> only need to know, which lines of the VBI data are needed, but we dont need the whole
> frame, this will cause only trouble. This is the reason why i asked if the software
> for proving captures, could be rewritten. Professional equipment doesnt work that way
> (cheap stuff neither), like it is expected in the article of Aaron. So the approach
> of the LD tool in MAME is wrong, regarding the VBI data, as it is expecting the
> "whole" frame (525lines).
>
> Which brings me to the last point. Yeah, you can hack all kind of stuff, like the IR
> remote for exact frame jumping and what not, capturing straight from the laser lens
> to your eye. I think we should avoid as much as possible of this hacks. The
> interlace/fields, analog sources/noise, VBI data etc. all of this, is very delicate
> and very picky and with a single shifted scanline, you will break all your capturing
> effort into useless shit. Keep it simple, treat the source right, capture it
> uncompressed/lossless and thats it.

Could you expand on this please? As I understand it, part of the issue with laser disc support is the ongoing discussion of accuracy.

Disclaimer: I'm not presuming to question MAME design decisions, I'm just wondering about a different path.

What caught my attention is this: What you're proposing sounds to me like you're discussing the capture of the parts of the "frame" that are relevant to the game and disregarding the parts of the "frame" that are present only because of the requirements of the co-opted technology (Laserdisc).

I'm wondering if that is an interesting discussion point as MAME doesn't attempt to emulate all of the intricacies of the underlying technology (Not counting discrete circuits). MAME isn't attempting to emulate any frequencies outside of the human range of hearing for example, so I'm wondering if not grabbing unused frame information might be similar?



anikom15
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Re: Question about ALG driver status new [Re: uman]
#367959 - 07/18/17 07:41 AM


> That didnt help much, but ok. If you really need DAQ, Logic Analyzers and such, to
> make some rocket science of LD games (and most of them are in a quality range more
> worse than a very bad VHS copy), then its that. I wish you all good luck with your
> goal (and i truly mean it).
>
> Well if you cant trust a Blackmagic Decklink card, while it is a de facto standard in
> every good post production house for capturing stuff, i still have hope that your
> approach with DAQs, Analyzers and what not, will create much better results.

Congratulations. You have just proven to me that you really have absolutely no understanding of data preservation or scientific measurement. You also seemed to ignore the fact that I stated that using captures should be TOTALLY ADEQUATE for developing and testing emulators in MAME. We do that with systems that have crappy or missing dumps already.

But yes please continue to defend black boxes as de facto standards for data acquisition when there are actual de jure standards for measuring analog data.



anikom15
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Re: Question about ALG driver status new [Re: Rygar9]
#367960 - 07/18/17 08:03 AM


> > IMHO here lies a problem. Nearly all capture cards, where not designed to capture
> the
> > "whole" frame. Even in the Firefox thread, you will not see such a capture
> (starting
> > with page 1). Professional equipment will capture VBI data, but not the whole
> frame.
> > You may achieve this with hacked videodrivers, but this is not recommended and a
> > ideal solution at all. I consider it very hard to do it the right way, especially
> if
> > you want to keep the interlace/fields intact, which would be crucial for further
> > processing. To be honest, i could be wrong here as i never seen the original
> > captures, but i think the captures from Aaron have errors regarding this topic. We
> > only need to know, which lines of the VBI data are needed, but we dont need the
> whole
> > frame, this will cause only trouble. This is the reason why i asked if the software
> > for proving captures, could be rewritten. Professional equipment doesnt work that
> way
> > (cheap stuff neither), like it is expected in the article of Aaron. So the approach
> > of the LD tool in MAME is wrong, regarding the VBI data, as it is expecting the
> > "whole" frame (525lines).
> >
> > Which brings me to the last point. Yeah, you can hack all kind of stuff, like the
> IR
> > remote for exact frame jumping and what not, capturing straight from the laser lens
> > to your eye. I think we should avoid as much as possible of this hacks. The
> > interlace/fields, analog sources/noise, VBI data etc. all of this, is very delicate
> > and very picky and with a single shifted scanline, you will break all your
> capturing
> > effort into useless shit. Keep it simple, treat the source right, capture it
> > uncompressed/lossless and thats it.
>
> Could you expand on this please? As I understand it, part of the issue with laser
> disc support is the ongoing discussion of accuracy.
>
> Disclaimer: I'm not presuming to question MAME design decisions, I'm just wondering
> about a different path.
>
> What caught my attention is this: What you're proposing sounds to me like you're
> discussing the capture of the parts of the "frame" that are relevant to the game and
> disregarding the parts of the "frame" that are present only because of the
> requirements of the co-opted technology (Laserdisc).
>
> I'm wondering if that is an interesting discussion point as MAME doesn't attempt to
> emulate all of the intricacies of the underlying technology (Not counting discrete
> circuits). MAME isn't attempting to emulate any frequencies outside of the human
> range of hearing for example, so I'm wondering if not grabbing unused frame
> information might be similar?

There are actually two things that need to be accomplished here, which is a source of confusion.

1) MAME's primary goal is emulating the system. For this we can ignore information that has no effect on emulation requirements. In this sense all we theoretically need for debugging is VBI data and 'images' where images are parts of the video data consumers actually care about. AFAIK it doesn't even matter what the images are because the emulated system didn't actually depend on the content of these images.

2) MAME's secondary goal is having some method of verifying 'software' which is really just 'data' which is either digital or analog. Digital is very easy to preserve compared to analog. In order to properly preserve analog data we need to use a transparent process that has a guarantee in processing. That is, if I were to use a capture card, I would have to be able to determine what it is doing to the signal, stochastically speaking. Capture cards demodulate the signal which is problematic for a number of reasons. Therefore there is no capture card that can adequately represent the data as it was represented from the LD player.*

IMO 1 is much easier than 2 and so we should be putting our efforts into that, but we must also not conflate 1 and 2. 2 is something that should at least be recognized as needing to be accomplished.

*Even if we do preserve the video signal, we need to note the model of the LD player. That is, the output video signal is dependent on the LD player. I still consider this an adequate preservation because (a) a reasonably limited number of models were used for these games and (b) these are devices that were coupled with the media during their time.



Vas Crabb
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Re: Question about ALG driver status new [Re: anikom15]
#367961 - 07/18/17 08:24 AM


> 1) MAME's primary goal is emulating the system. For this we can ignore information
> that has no effect on emulation requirements. In this sense all we theoretically need
> for debugging is VBI data and 'images' where images are parts of the video data
> consumers actually care about. AFAIK it doesn't even matter what the images are
> because the emulated system didn't actually depend on the content of these images.

And here, yet again, you show your fundamental misunderstanding. MAME's primary goal is to document the hardware and preserve and document the software. Usable emulation is a nice side-effect, but it is very much not the primary goal.

Emulators like Daphne have playable emulation as their primary goal. That's why Daphne takes the easy route with conventional video files and auxiliary "frame files" containing additional data, including information the players/games get from the vertical blanking period.

If that was MAME's goal, we would have already gone down that path. We probably would have used pre-decrypted NeoGeo graphics ROMs, and kept the CPS2 XOR files. We also likely would've faded into irrelevance just like NeoRageX.



uman
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Re: Question about ALG driver status new [Re: Rygar9]
#367967 - 07/18/17 12:23 PM Attachment: 20136348_10209925983488974_2020747436_n.png 644 KB (0 downloads)


> Could you expand on this please? As I understand it, part of the issue with laser
> disc support is the ongoing discussion of accuracy.
>
> Disclaimer: I'm not presuming to question MAME design decisions, I'm just wondering
> about a different path.
>
> What caught my attention is this: What you're proposing sounds to me like you're
> discussing the capture of the parts of the "frame" that are relevant to the game and
> disregarding the parts of the "frame" that are present only because of the
> requirements of the co-opted technology (Laserdisc).
>
> I'm wondering if that is an interesting discussion point as MAME doesn't attempt to
> emulate all of the intricacies of the underlying technology (Not counting discrete
> circuits). MAME isn't attempting to emulate any frequencies outside of the human
> range of hearing for example, so I'm wondering if not grabbing unused frame
> information might be similar?

I also dont want to question MAME design decisions, but in this case i would just like to know more about, how and why the tools for LD games work that way.

With my bad english, i will still try to describe my concerns with the current approach of MAME (and the LDverify tool in general), of capturing the whole frame (525 lines).

I attached screenshots from (LDverify tool approved) capturings that SailorSat did on some games. If you take a close look at the first 20 or so lines, you will see a lot color noise and distortion, but normally the VBI range has no color subcarrier, this only happened because the capture card was forced to grab the whole frame. In practice this is not how professional equipment is working. In practice the card would capture seperately the relevant VBI data and put that on top of the capture, resulting in a clean (from distortion and color) frame, at least for the VBI data.

So the downsides of the LDverify tool are:

- forcing/hacking a capture card to capture the whole frame.
- by this method also driving a cheap card to the absolute limits, resulting in more poor capturing.
- predetermined errors while in verify-process, because of distortion and colornoise and you will often need to capture a source like 3-4 times and make a single working capture of it, that is finally approved by LDverify tool.
- capturing the whole frame, introduce a high risk that you destroy/break the fields. Remember that just one shifted scanline can make the capture useless.

I dont write this to bitch on the MAMEdevs or the tools, i just want to show why the approach is not the best. VBI data was initially introduced for subtitles in broadcast stations, however LD games abused this technique for their own purpose. Only three lines are relevant to get this working (the 4th line is just a copy for safety). A good card just needs to know, which lines needs to be captured. Different manufacturers, used different techniques, that resulted in different lines that are needed.

So the initial approach of the LDverify tool is perfect, if you have no clue, which lines are important, to make the game work properly.

[ATTACHED IMAGE]

Attachment



SmitdoggAdministrator
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Re: Question about ALG driver status new [Re: uman]
#367973 - 07/18/17 07:36 PM


Keep in mind using a cheap card or cheap equipment doesn't need to be part of the equation. It doesn't need to be a solution for the common man because there are so few laser disc games, even 1 person could realistically do them all himself.



John Doe
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Re: Question about ALG driver status new [Re: casm]
#367977 - 07/18/17 08:58 PM


> as well as video
> codecs capable of preserving the video output in a way that can be read, manipulated,
> and displayed true to the original hardware.

As soon as you start talking about capturing video then you've failed. The video output of a laser disc player is generated by the player, using sub standard circuits which haven't gotten better with age. It may not affect arcade games, but it's possible for discs to have audio stored in multiple formats and capturing all of them when thinking about video capture is not going to be easy.

Capturing the signal from the disc, before it's been degraded by the laser disc player is the therefore the only practical solution. It's been proven to be possible, it is just going to take a while for the gears to get in motion.



John Doe
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Re: Question about ALG driver status new [Re: uman]
#367980 - 07/18/17 10:48 PM


> There are loads of players with digital frame stores. The Pioneer CLD-D925, for
> example, has an 8-bit digital signal path, just like the LDV8000.

How is capturing the output of a frame store getting you all of the data on the disc?

You can attach close to the laser pick up and get a perfect dump of the laser disc, it's been proven. We just need to either get the guys co-operation or duplicate the work.

Anything else is a waste of time.



uman
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Re: Question about ALG driver status new [Re: Smitdogg]
#367982 - 07/18/17 11:08 PM



Quote:


Keep in mind using a cheap card or cheap equipment doesn't need to be part of the equation. It doesn't need to be a solution for the common man because there are so few laser disc games, even 1 person could realistically do them all himself.




Sorry, but i dont really understand what you mean by this.

I am fine, as long as we can hold a discussion like grown-ups. Of course even 1 person could capture all LD games, but he still would need at least two weeks, maybe more. He still would need to know, what he is doing to meet the requirements. I am not going through this hassle of work just for educational and development purposes and that those captures afterwards would not be considered a good dump and nobody (the public) will ever use it for gaming.

Yes its true, i have no clue about DAQs, Logic Analyzers and such, but to be honest for this purpose, i am maybe to dumb to see the relevance for such a setup. It doesnt make much sense at all for me, because the benefit is minimal to none. This is a conclusion which even Dave from the Firefox thread has come, a man that build a hardware emulation of a LDP. If the MAME devs think, all of this is needed, i sadly think that some of those games will be gone forever.

On the other hand, i have a clue, how to do a proper capturing from a composite output. I worked long enough in a tv station and in different post production houses, that i know how to do it. How to treat interlaced material and so on. I explained my concerns in the previous posts and why i think the approach in the past is not ideal. I am open and interested to hear from you, why i am maybe wrong with my conclusion.

Most of the source material (content/master) is so bad, that the wanted scientific setup will not make it better, rather and possibly more worse (why? it is explained in the firefox thread). The gain (if there is any) is not worth such a effort, it would also differ from LDP model to LDP model, there is no 100% accurate and there are possibly even things that you will need to sacrifice (like the interlaced content). So you need to ask yourself, what you want and what will you do afterwards.
Its a dying medium and we can be happy if people have a working game. Dont get me wrong, i understand the preserving factor and i am interested in keeping it, as far and good as possible with my knowledge and equipment, what i would use for that task.


Quote:


"Capture cards demodulate the signal which is problematic for a number of reasons. Therefore there is no capture card that can adequately represent the data as it was represented from the LD player."




Again, i dont understand this as a whole. My capture would be a single stream, with clean VBI data. Reading Aarons articles, the VBI data of course, would be different for some games, just like it is on the original LD medium. Interpreting the differencies in VBI data, is the task of the emulation. It needs to work like the Dexter hardware, that needs to be set properly prior starting any LD game (i.e. choosing the right LDP model). But the 525 lines expecting approach is wrong, for the reasons i previously wrote. VBI data should not be treated (by the capture card) like picture content, like it was done and expected in the past.

If you are willing to discuss the topic, i am gladly in. If you think i am just typing here for fun and only a stupid troll, i at least would know its pointless for me to go further.



SmitdoggAdministrator
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Re: Question about ALG driver status new [Re: uman]
#367983 - 07/18/17 11:17 PM


I guess I should have quoted, I was just referring to when you mentioned a cheap card and the drawbacks. It made me think you were looking for a wide many person solution because why else would a cheap card be used.



uman
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Re: Question about ALG driver status new [Re: Smitdogg]
#367986 - 07/19/17 12:29 AM


Again my bad... cheap is not the right term... better said a only SD capable card. I guess Aaron did use such a card (because HD was not common at that time and/or really expensive) and i guess the capturings have broken fields. I think that because, in Dave´s Firefox thread, he is talking about the MAME version capture of Firefox using with the original hardware and that some things are not looking good as the original (in his example the explosions). I watched HD Firefox Youtube videos and i saw broken fields with artefacts, this could be due to Youtube or by the capturing, hard to say. You can live with artefacts, but if you break the fields, motion might appear jaggy/jittering. If you capture interlaced content in progressive mode, this is something that could easily happen.



SmitdoggAdministrator
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Re: Question about ALG driver status new [Re: uman]
#367987 - 07/19/17 12:38 AM


The current issue there from what I've been told is the video is encoded keeping the interlacing but mame's playback doesn't support a deinterlacing option, so on modern monitors it lines out on areas of movement.



uman
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Re: Question about ALG driver status new [Re: Smitdogg]
#367988 - 07/19/17 01:45 AM


Yeah ok, but Dave is playing back the MAME version on a CRT. I know what you mean with your description, but this is "normal" and thats how interlace look on modern monitors. Like i said, it could also be just Youtube compression. I need to catch some of the MAME LD stuff, to see it for myself.

The posts where they talk about it


Quote:


Dave: It would be better to build a little board capable of capturing the signal before the audio was split off, that way you'd get as close to a perfect capture as possible. The circuitry in the LDV8000 introduces a moderate amount of noise, but given the **** quality of the FF disc, where multiple generation edits have been done with some seriously noisy gear, it doesn't really matter that much.

For playback on a PC, you'd most likely get better results by just using a capture card as it will have a TBC, 3d (hopefully) comb filter, etc. As I was ultimately going to play out composite, going through that process and then back to composite again would degrade the picture. The Mame image, for instance, looks fine on a PC, but nasty when remodulated. The explosions, in particular, are covered in artefacts where the comb filter hasn't managed to get rid of the crosstalk between luma and chroma.

Matt Ownby wrote:
How do you know this wasn't caused by your NTSC encoder hardware?

Dave´s answer:
Because the artefacts are clearly visible when playing Firefox in Mame. Tongue Mind you, it's arguable that the effects of composite to RGB and back again would be dwarfed by the poor results produced by Firefox's demod board.






anikom15
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Re: Question about ALG driver status new [Re: Vas Crabb]
#367994 - 07/19/17 04:27 AM


> > 1) MAME's primary goal is emulating the system. For this we can ignore information
> > that has no effect on emulation requirements. In this sense all we theoretically
> need
> > for debugging is VBI data and 'images' where images are parts of the video data
> > consumers actually care about. AFAIK it doesn't even matter what the images are
> > because the emulated system didn't actually depend on the content of these images.
>
> And here, yet again, you show your fundamental misunderstanding. MAME's primary goal
> is to document the hardware and preserve and document the software. Usable emulation
> is a nice side-effect, but it is very much not the primary goal.
>
> Emulators like Daphne have playable emulation as their primary goal. That's why
> Daphne takes the easy route with conventional video files and auxiliary "frame files"
> containing additional data, including information the players/games get from the
> vertical blanking period.
>
> If that was MAME's goal, we would have already gone down that path. We probably would
> have used pre-decrypted NeoGeo graphics ROMs, and kept the CPS2 XOR files. We also
> likely would've faded into irrelevance just like NeoRageX.

No I totally agree with you. I think I just have a strict definition of 'emulation'. I never considered HLE techniques to be full emulation. What I meant to say was that documenting the hardware and preserving the software are two separate, although almost always coupled, goals.

I am no way advocating that we do things like Daphne.



anikom15
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Re: Question about ALG driver status new [Re: John Doe]
#367995 - 07/19/17 04:31 AM


Do you have anything concrete, block diagrams, circuits, specific hardware that someone needs to do this straight from the LaserDisc itself?

Someone then needs to make the demodulator in software.



anikom15
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Re: Question about ALG driver status new [Re: uman]
#367996 - 07/19/17 05:09 AM


> Yes its true, i have no clue about DAQs, Logic Analyzers and such, but to be honest
> for this purpose, i am maybe to dumb to see the relevance for such a setup. It doesnt
> make much sense at all for me, because the benefit is minimal to none. This is a
> conclusion which even Dave from the Firefox thread has come, a man that build a
> hardware emulation of a LDP. If the MAME devs think, all of this is needed, i sadly
> think that some of those games will be gone forever.
>
> On the other hand, i have a clue, how to do a proper capturing from a composite
> output. I worked long enough in a tv station and in different post production houses,
> that i know how to do it. How to treat interlaced material and so on. I explained my
> concerns in the previous posts and why i think the approach in the past is not ideal.
> I am open and interested to hear from you, why i am maybe wrong with my conclusion.

Doing a video capture is not a dump. That's the point. A dump of analog data should be representative of the original analog medium, which in this case is an electrical video signal. A Rec. 601 translation is not a dump of the data. It is a conversion to a modern format, and it is not reversible. Rec. 601 filters and samples the signal, which is exactly what we will have to do, but it also demodulates the signal and applies a comb filter, which, primarily for flexibility, is something we should do digitally with shaders.

It's similar to why I don't consider samples to be adequate in place of discrete audio. We need to get as 'close to the source' as practical. Sampling the video signal is certainly practical (admittedly expensive, though only one person needs to do it). If the direct laser thing turns out to be practical (and reliable) we should do that instead.



casm
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Re: Question about ALG driver status new [Re: John Doe]
#368004 - 07/19/17 03:31 PM


> > as well as video
> > codecs capable of preserving the video output in a way that can be read,
> manipulated,
> > and displayed true to the original hardware.
>
> As soon as you start talking about capturing video then you've failed. The video
> output of a laser disc player is generated by the player, using sub standard circuits
> which haven't gotten better with age.

You're essentially talking about the difference between frames read directly from the disc and the picture output by the player. Yes, it's understood that those are two different things.

However, given that the end goal is to transfer the analogue frames on the disc to a usable digital medium, there will always be some form of alteration of the original out of necessity as well as as part of the analogue-to-digital conversion process.

Additionally, no digital format that I'm aware of has a concept of picture fields in the same way as NTSC (or PAL, or SECAM) does, so even taking a direct read of a frame from a disc without further analogue processing would still require combining those fields into a single frame for digital capture.

Again, my understanding of how NTSC (and other TV standards) work at a low level is somewhat limited. But unless I'm misunderstanding something in your reply, there's no way to do this without having to process the video between reading it from the disc and storing it digitally using {insert codec here}.

> It may not affect arcade games, but it's
> possible for discs to have audio stored in multiple formats and capturing all of them
> when thinking about video capture is not going to be easy.

Also understood. But arcade games are the focus here, not retail discs - and nothing is currently in place (that I'm aware of) to back up either type of disc except for player output. Now, if something is developed to back up arcade game discs that can later be extended out to the more unusual retail titles, great, but retail titles aren't MAME's focus.

> Capturing the signal from the disc, before it's been degraded by the laser disc
> player is the therefore the only practical solution. It's been proven to be possible,
> it is just going to take a while for the gears to get in motion.

Sure, it's possible; nobody's suggesting otherwise. But if we want to get really nitpicky about it, we should be reading the video from each disc using only the players originally used by each game.

The thing is that while we're both in agreement that post-read processing (passive or otherwise) doesn't create an ideal output signal, we don't have "a while" to wait for the ideal solution. This is one of the reasons why I'm advocating that we need to figure out what constitutes acceptable losses and back up to the best of our present ability.



casm
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Re: Question about ALG driver status new [Re: uman]
#368006 - 07/19/17 04:08 PM


> > > And Firefox, is one of the best looking games here. 90% of the LD games will look
> way more ugly. They where produced very fast and very cheap with the lowest eighties
> technology.>

Agreed on that point. But we can't do anything about source material that was poorly-produced from the start. We're just stuck with the final results in the form of the discs that we have to work with. More:

> I am sorry, but you got me completely wrong here and i should explain that more
> clearly. Its not the LD medium itself (this in fact, was awesome at that time). I
> meant more the "content" of it, the what you called "master". This content was
> produced fast, very cheap and with low-quality standards and is that, what was
> mentioned by Dave about Firefox for example and Firefox is one of the better
> "masters". I have seen four captures from SailorSat and three of them, are just
> "quick and dirty" work. Only Mad Dog looked "acceptable", but still far from a good
> "master".

I think I might see where some confusion of terminology has crept in, and I should have been clearer in my use of the term 'master'.

When referring to a 'master', I'm speaking solely about the disc used to press all of the discs that would have originally shipped with the games. These pressing masters would have determined what we are working with today as source material; we don't (as far as I am aware) have access to any media that's further upstream from pressed copies and which would have been used to create the pressing masters. Because of this, pressed copies as our source material are as good as it gets.

> With this, you answered your own questions regarding Digital Leisure and DL, Space
> Ace and so on. They had Don Bluth and they had the original masters.

Maybe. It's possible that they did transfers from Beta or other sources used in the creation of pressing masters; it's possible that they just read them from existing pressed discs. We just don't know, short of a Digital Leisure employee chiming in and saying, "yep, here's how we did it."

One thing we can probably safely assume, though, is that Digital Leisure wasn't concerned with preservation in the sense that we are as they were creating a commercial product. Ignoring the VBI would have been beneficial to them from the standpoint of (at the very least) saving space on the DVDs. Given that they were transferring to a format that didn't need that data for gameplay or video playback, its loss was likely a non-issue for them.

Again, though, this is speculation on my behalf, but it seems reasonable to my mind. Unfortunately, I don't have my Space Ace or Dragon's Lair DVDs close by so can't check on this.

> As this is
> basically a animation movie, it was quite easy to recapture stuff and even create a
> HD release of it. Stuff that you simply cannot do with Mad Dog and all the other
> games, with real actors. Those games where not recorded on film (nearly resolution
> independent, huge colorspace), but rather on video (fixed small resolution, small
> colorspace). So even if you have the masters, you will not come far with it.

I take your points regarding the differences between film and video, but the frames stored on the discs were either PAL- or NTSC-formatted. Ultimately, that creates a fixed resolution of either 625 or 525 lines, respectively, with a colourspace determined by clock frequency and available picture bandwidth (if I'm understanding the broadcast format workings correctly).

What this means is that we are working with a fixed amount of output per frame from the player - each frame should be the same size, determined by the broadcast standard the disc is pressed for and that the player outputs (which should be the same).

In this case, the source material used to create the pressing masters isn't relevant: it may have been created in higher quality than either PAL or NTSC are capable of reproducing, but since we're working with source material in those two formats a digital capture solution should be tailored to those standards.

Realistically, though, I'm low on ideas at this point. And while there have been a lot of really good ideas kicked around, until both a capture method and format are settled on this is all very much academic. Good to discuss, to be certain, but not really moving anything forward.



casm
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Re: Question about ALG driver status new [Re: anikom15]
#368007 - 07/19/17 04:22 PM


> Doing a video capture is not a dump. That's the point. A dump of analog data should
> be representative of the original analog medium, which in this case is an electrical
> video signal. A Rec. 601 translation is not a dump of the data. It is a conversion to
> a modern format, and it is not reversible. Rec. 601 filters and samples the signal,
> which is exactly what we will have to do, but it also demodulates the signal and
> applies a comb filter, which, primarily for flexibility, is something we should do
> digitally with shaders.
>
> It's similar to why I don't consider samples to be adequate in place of discrete
> audio. We need to get as 'close to the source' as practical. Sampling the video
> signal is certainly practical (admittedly expensive, though only one person needs to
> do it). If the direct laser thing turns out to be practical (and reliable) we should
> do that instead.

OK, let me pose this question in relation to the above: does this mean that MAME should also emulate the laserdisc players in their entirety for the games that used them? Digitised disc data could be fed to a virtual laser pickup, the VBI decoded within the LD player virtual machine, and the appropriate frame data fed from the virtual player's video output to MAME's framebuffer for display.

Granted, I am being slightly silly in asking that question, but not entirely. Given that we're talking about reproduction of an analogue medium in a digital format, we're always going to be stuck with the 'how far do we go' and 'where do we stop' questions.

I do actually agree with your points re: a dump vs. conversion and getting as close to the source as possible, but it is possible to agree on the storage method first, then worry about the finer points of reproduction later. The use of samples are a good example of this: it allowed placeholders (samples) to show what should happen until it was possible to make it happen more accurately.



Vas Crabb
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Re: Question about ALG driver status new [Re: casm]
#368009 - 07/19/17 04:33 PM


> OK, let me pose this question in relation to the above: does this mean that MAME
> should also emulate the laserdisc players in their entirety for the games that used
> them? Digitised disc data could be fed to a virtual laser pickup, the VBI decoded
> within the LD player virtual machine, and the appropriate frame data fed from the
> virtual player's video output to MAME's framebuffer for display.

Yes it should. And it should output the composite video so we can decode it in a programmable shader and provide a set of dynamic picture controls like you'd get with a real system.

> Granted, I am being slightly silly in asking that question, but not entirely. Given
> that we're talking about reproduction of an analogue medium in a digital format,
> we're always going to be stuck with the 'how far do we go' and 'where do we stop'
> questions.

And people said storing home computer tape software as WAV files and emulating the front-end was silly (rather than just storing bytes), or emulating keyboard MCUs and interface chips was silly (rather than just faking it at protocol level), and emulating CPS2 encryption was silly (rather than just using XOR files), or requiring encrypted NeoGeo GFX ROM images was silly (rather than using pre-decrypted GFX like NeoRageX), yet here we are.



casm
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Re: Question about ALG driver status new [Re: uman]
#368010 - 07/19/17 04:36 PM


> Again my bad... cheap is not the right term... better said a only SD capable card. I
> guess Aaron did use such a card (because HD was not common at that time and/or really
> expensive) and i guess the capturings have broken fields.

Question (and this is for anyone who may be able to provide some insight, not specifically directed at uman):

What would be the advantage of a high-definition capture of laserdisc frames over capturing it at the standard definition it was originally stored at on the disc?

Here's my thinking behind this: if the goal is preservation, then we presumably want to capture in an as-close-to-original-as-possible format. In this case, that would mean at standard definition as determined by the broadcast standard the disc was manufactured for, so either 525 lines for NTSC or 625 lines for PAL and in a 4:3 aspect ratio.

I understand that advances in display technology mean that display standards will only continue to move to higher resolutions over time (note that it took less than a decade to go from 1080p to 4K, and 16:10 aspect ratio displays aren't uncommon) so having captures at a resolution capable of anticipating those improvements makes sense. But doing so moves away from using as-close-to-source-as-possible material.

This is something I'm genuinely curious about as I don't have any good answers to the question and can see advantages and disadvantages both ways.



casm
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Re: Question about ALG driver status new [Re: Vas Crabb]
#368011 - 07/19/17 04:44 PM


> And people said storing home computer tape software as WAV files and emulating the
> front-end was silly (rather than just storing bytes)

Funnily enough, that was actually the example I had in mind when posing the virtual LD player question. One extension of that idea that I've always wanted to see has been emulated modems - it would make running a dialup BBS on BITD software without having to worry about the failure of nearly 40-year-old hardware a possibility.

If this is something that's already implemented, please pardon my ignorance. The reality is that I just don't do a lot of home computer-related emulation these days so am not totally up to speed on the state of things in that regard.



StilettoAdministrator
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Re: Question about ALG driver status new [Re: Vas Crabb]
#368012 - 07/19/17 05:53 PM


> > OK, let me pose this question in relation to the above: does this mean that MAME
> > should also emulate the laserdisc players in their entirety for the games that used
> > them? Digitised disc data could be fed to a virtual laser pickup, the VBI decoded
> > within the LD player virtual machine, and the appropriate frame data fed from the
> > virtual player's video output to MAME's framebuffer for display.
>
> Yes it should. And it should output the composite video so we can decode it in a
> programmable shader and provide a set of dynamic picture controls like you'd get with
> a real system.

In my mind, the final "laserdisc dump" format should contain enough information that if someone had the ability to master a new laserdisc, that it would contain all the information required to do just that and result in a reasonable duplicate without significant data loss, understanding that with the number of analog-digital and digital-analog transitions we've been discussing here, wouldn't be exactly the same.

Also, because we also have console systems to worry about, that whatever format we develop would also work fine for all the various usages of laserdisc in console videogame and computer systems, both in entertainment, edutainment and productivity.

And eventually have enough bells and whistles that if, say, someone from various laserdisc movie collecting societies wanted to use our format and the dumping hardware and software solution created to preserve their rare discs, that it could do that.

It may take us several iterations to get there, but it's pointless to limit it to just what arcade needs simply because that's what concerns us right now.

And yes, virtual laserdisc players - in all their various models - is generally the end goal. We already load several player ROMs in MAME, eventually we'll model their video and audio processing as well.

- Stiletto



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Re: Question about ALG driver status new [Re: casm]
#368013 - 07/19/17 06:07 PM


> Also understood. But arcade games are the focus here, not retail discs - and nothing
> is currently in place (that I'm aware of) to back up either type of disc except for
> player output. Now, if something is developed to back up arcade game discs that can
> later be extended out to the more unusual retail titles, great, but retail titles
> aren't MAME's focus.

Well, console laserdisc systems like the LaserActive are also MAME's focus. But I don't think they'll offer more laserdisc features than the arcade systems. See my other post in this thread for more.

- Stiletto



Vas Crabb
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Re: Question about ALG driver status new [Re: Stiletto]
#368014 - 07/19/17 06:10 PM


> Well, console laserdisc systems like the LaserActive are also MAME's focus. But I
> don't think they'll offer more laserdisc features than the arcade systems. See my
> other post in this thread for more.

Pioneer PX-7 (MSX) Laserdisc games load program data from one of the audio tracks, and control the players with Pioneer SystemRemote protocol. That will be plenty of fun to emulate if we ever get dumps.



StilettoAdministrator
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Re: Question about ALG driver status new [Re: Vas Crabb]
#368016 - 07/19/17 06:36 PM


> > Well, console laserdisc systems like the LaserActive are also MAME's focus. But I
> > don't think they'll offer more laserdisc features than the arcade systems. See my
> > other post in this thread for more.
>
> Pioneer PX-7 (MSX) Laserdisc games load program data from one of the audio tracks,
> and control the players with Pioneer SystemRemote protocol. That will be plenty of
> fun to emulate if we ever get dumps.

alright then.

- Stiletto



Pernod
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Re: Question about ALG driver status new [Re: Vas Crabb]
#368018 - 07/19/17 07:15 PM


> Pioneer PX-7 (MSX) Laserdisc games load program data from one of the audio tracks,
> and control the players with Pioneer SystemRemote protocol. That will be plenty of
> fun to emulate if we ever get dumps.

I believe the Domesday laserdiscs do too, for use with the BBC Master AIV. There's details on how they're currently being dumped at http://stardot.org.uk/forums/viewtopic.php?f=3&t=12381.



uman
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Re: Question about ALG driver status new [Re: Stiletto]
#368020 - 07/19/17 07:30 PM


> > Yes it should. And it should output the composite video so we can decode it in a programmable shader and provide a set of dynamic picture controls like you'd get with a real system.>

If that is to be true, will you also bring back interlaced content for systems, where it is already throw out? I remember discussions, where the conclusion was, "no one use a CRT anymore and it is to hard to maintain", but in this case here you will do it???

> In my mind, the final "laserdisc dump" format should contain enough information that if someone had the ability to master a new laserdisc, that it would contain all the
information required to do just that and result in a reasonable duplicate without significant data loss, understanding that with the number of analog-digital and
digital-analog transitions we've been discussing here, wouldn't be exactly the same.>

No one will ever be able again to do that, except he owns the industrial park that you would need for that task.
"significant data loss" is exactly what? the capturings? The loss is so small, that you wouldnt see it with your eyes, if its done properly. Also a capturing that has the VBI data intact wouldnt be a 100% clone, but a very close and good functional copy and not something with "significant data loss".

> And eventually have enough bells and whistles that if, say, someone from various laserdisc movie collecting societies wanted to use our format and the dumping hardware and software solution created to preserve their rare discs, that it could do that.>

The theory sounds nice, but the practice (currently and how you wish to setup the hardware) is to open already rare and hard to replace hardware, probably with soldering included, just to get a doubtful result (that also needs to be proved, if it is really better) with a potential risk, to render the hardware out of commission. It is not something, where you can easily connect your setup and its done. Therefore i dont think you will find those people, who will gladly agree to this and have the knowledge to operate such a setup.

As we are at audio examples: It is like capturing a WAV from a lousy 128kb mp3 file with decent audio equipment and 192khz AD converters and expect a better result vs. just do a 320kb mp3 of it again. Both could be transfered back again to a CD/DVD.

If artefacts are such a concern, write a video-capturing app than can capture frame by frame (LDPs with RS 232 are there, you can jump from frame to frame). It will take a while to finish a capture as it is not in realtime, but i am very sure that visible/blocky artefacts will be gone. Since most of you are more into software writing, it could be done. You would have a setup, that would work non-destructive to any LDP hardware. All you need is a capture card, that you support with your written software.



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Re: Question about ALG driver status new [Re: Pernod]
#368022 - 07/19/17 07:50 PM


> > Pioneer PX-7 (MSX) Laserdisc games load program data from one of the audio tracks,
> > and control the players with Pioneer SystemRemote protocol. That will be plenty of
> > fun to emulate if we ever get dumps.
>
> I believe the Domesday laserdiscs do too, for use with the BBC Master AIV. There's
> details on how they're currently being dumped at
> http://stardot.org.uk/forums/viewtopic.php?f=3&t=12381.

Specifically: http://stardot.org.uk/forums/viewtopic.php?p=175440#p175440
Good lord, that's perfect timing. Maybe we can all support each other...

Anyone know what hardware that LaserActive preservation project is using, or the MegaLD project?
https://laseractive.wordpress.com/
http://gendev.spritesmind.net/forum/viewtopic.php?f=17&t=1647

- Stiletto



casm
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Re: Question about ALG driver status new [Re: Stiletto]
#368023 - 07/19/17 08:05 PM


> > Pioneer PX-7 (MSX) Laserdisc games load program data from one of the audio tracks,
> > and control the players with Pioneer SystemRemote protocol. That will be plenty of
> > fun to emulate if we ever get dumps.
>
> alright then.

M.A.C.H. 3 and Us. Vs. Them also do this, although in their cases it's for in-game target data and not executable code (IIRC).



casm
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Re: Question about ALG driver status new [Re: Stiletto]
#368024 - 07/19/17 08:12 PM


> In my mind, the final "laserdisc dump" format should contain enough information that
> if someone had the ability to master a new laserdisc, that it would contain all the
> information required to do just that and result in a reasonable duplicate without
> significant data loss, understanding that with the number of analog-digital and
> digital-analog transitions we've been discussing here, wouldn't be exactly the same.

Agreed. And reconverting the digital conversion to analogue, sending it straight into the laser pickup of a player, and having the player both act on the VBI data and display the image it was sent would be an excellent demonstration of the success of the process without needing to build a disc-pressing plant

> Also, because we also have console systems to worry about, that whatever format we
> develop would also work fine for all the various usages of laserdisc in console
> videogame and computer systems, both in entertainment, edutainment and productivity.
>
> And eventually have enough bells and whistles that if, say, someone from various
> laserdisc movie collecting societies wanted to use our format and the dumping
> hardware and software solution created to preserve their rare discs, that it could do
> that.

This was actually something I was hoping would come out of MAME's laserdisc preservation efforts. More:

> It may take us several iterations to get there, but it's pointless to limit it to
> just what arcade needs simply because that's what concerns us right now.

Also agreed. My thinking was that by focussing on arcade games at the start the basics could be established then built on from there. Most arcade laserdiscs were not overly-complex by laserdisc standards (video plus two analogue audio tracks, for the most part), which is common to the fundamental retail laserdisc.

> And yes, virtual laserdisc players - in all their various models - is generally the
> end goal. We already load several player ROMs in MAME, eventually we'll model their
> video and audio processing as well.

Understood - that was partly a rhetorical question on my behalf, but it should definitely be the end goal.



anikom15
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Posts: 209
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Re: Question about ALG driver status new [Re: uman]
#368025 - 07/19/17 08:24 PM


> If that is to be true, will you also bring back interlaced content for systems, where
> it is already throw out? I remember discussions, where the conclusion was, "no one
> use a CRT anymore and it is to hard to maintain", but in this case here you will do
> it???

Yes. I was not a part of that discussion mind you.


> As we are at audio examples: It is like capturing a WAV from a lousy 128kb mp3 file
> with decent audio equipment and 192khz AD converters and expect a better result vs.
> just do a 320kb mp3 of it again. Both could be transfered back again to a CD/DVD.

Um no it is not like that at all actually. I don't think you have any idea what you are talking about.



casm
Cinematronics > *
Reged: 08/27/07
Posts: 646
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Re: Question about ALG driver status [Re: Stiletto]
#368027 - 07/19/17 08:45 PM


> > I believe the Domesday laserdiscs do too, for use with the BBC Master AIV. There's
> > details on how they're currently being dumped at
> > http://stardot.org.uk/forums/viewtopic.php?f=3&t=12381.
>
> Specifically: http://stardot.org.uk/forums/viewtopic.php?p=175440#p175440
> Good lord, that's perfect timing. Maybe we can all support each other...

Wow. I'm nowhere near all the way through that thread (and I'm going to have to go through the whole thing in order to understand what's going on better), but getting in touch with them sounds like it would be an excellent idea.

> Anyone know what hardware that LaserActive preservation project is using, or the
> MegaLD project?
> https://laseractive.wordpress.com/
> http://gendev.spritesmind.net/forum/viewtopic.php?f=17&t=1647

Need more time to go through it all, but one thing stands out in that second link:

"This dumping process uses a custom program loaded through the PAC-S1/S10 module to read the disk contents and stream them over the controller port to a computer."

I'd like to know what it is that he's sending out over the controller port. Trying to send video out that way just seems painful if not impossible, but I can't understand why executable code or data stored on the disc would be moved over that path if it could just be read from the disk.

Again, quick skim, may be missing out on something, but am curious about that statement.



BIOS-D
MAME Fan
Reged: 08/07/06
Posts: 1547
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Re: Question about ALG driver status [Re: casm]
#368028 - 07/19/17 08:53 PM


> M.A.C.H. 3 and Us. Vs. Them also do this, although in their cases it's for in-game
> target data and not executable code (IIRC).

Correct me if I'm wrong but wasn't M.A.C.H. 3 practically the reason MAME realized capturing output frames from a Laserdisc player and then store them lossless into a CHD was not an optimal idea to keep preserving data this way?



Pernod
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Reged: 01/12/04
Posts: 54
Loc: UK
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Re: Question about ALG driver status [Re: Stiletto]
#368029 - 07/19/17 09:11 PM


> > I believe the Domesday laserdiscs do too, for use with the BBC Master AIV. There's
> > details on how they're currently being dumped at
> > http://stardot.org.uk/forums/viewtopic.php?f=3&t=12381.
>
> Specifically: http://stardot.org.uk/forums/viewtopic.php?p=175440#p175440
> Good lord, that's perfect timing. Maybe we can all support each other...
>
> - Stiletto

If anyone wants to reach out to them with constructive collaboration suggestions then their website would be the place to contact them http://www.domesday86.com/



casm
Cinematronics > *
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Posts: 646
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Re: Question about ALG driver status [Re: BIOS-D]
#368030 - 07/19/17 09:27 PM


> > M.A.C.H. 3 and Us. Vs. Them also do this, although in their cases it's for in-game
> > target data and not executable code (IIRC).
>
> Correct me if I'm wrong but wasn't M.A.C.H. 3 practically the reason MAME realized
> capturing output frames from a Laserdisc player and then store them lossless into a
> CHD was not an optimal idea to keep preserving data this way?

I really don't know anything about that decision; someone else would have to answer the question.

That said, from having read through the MAMEtesters bug that you linked to, I'm not sure what that would have to do with lossless storage in a CHD. The bug makes it sound as though the real issue was that the video and audio were captured from a damaged disc, and that damage would render the game unplayable past a certain point.



uman
MAME Fan
Reged: 04/15/12
Posts: 351
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Re: Question about ALG driver status [Re: anikom15]
#368031 - 07/19/17 10:05 PM


> > If that is to be true, will you also bring back interlaced content for systems,
> where
> > it is already throw out? I remember discussions, where the conclusion was, "no one
> > use a CRT anymore and it is to hard to maintain", but in this case here you will do
> > it???
>
> Yes. I was not a part of that discussion mind you.
>
>
> > As we are at audio examples: It is like capturing a WAV from a lousy 128kb mp3 file
> > with decent audio equipment and 192khz AD converters and expect a better result vs.
> > just do a 320kb mp3 of it again. Both could be transfered back again to a CD/DVD.
>
> Um no it is not like that at all actually. I don't think you have any idea what you
> are talking about.

you are right, i am wrong.
i am dumb, you are not.
all is fine, solution is around the corner. i trust you guys, you will somehow do it. like always.

Edited by uman (07/19/17 10:09 PM)



Rygar9
MAME Fan
Reged: 12/08/08
Posts: 43
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Re: Question about ALG driver status [Re: Vas Crabb]
#368032 - 07/20/17 12:21 AM


> > OK, let me pose this question in relation to the above: does this mean that MAME
> > should also emulate the laserdisc players in their entirety for the games that used
> > them? Digitised disc data could be fed to a virtual laser pickup, the VBI decoded
> > within the LD player virtual machine, and the appropriate frame data fed from the
> > virtual player's video output to MAME's framebuffer for display.
>
> Yes it should. And it should output the composite video so we can decode it in a
> programmable shader and provide a set of dynamic picture controls like you'd get with
> a real system.
>
> > Granted, I am being slightly silly in asking that question, but not entirely. Given
> > that we're talking about reproduction of an analogue medium in a digital format,
> > we're always going to be stuck with the 'how far do we go' and 'where do we stop'
> > questions.
>
> And people said storing home computer tape software as WAV files and emulating the
> front-end was silly (rather than just storing bytes), or emulating keyboard MCUs and
> interface chips was silly (rather than just faking it at protocol level), and
> emulating CPS2 encryption was silly (rather than just using XOR files), or requiring
> encrypted NeoGeo GFX ROM images was silly (rather than using pre-decrypted GFX like
> NeoRageX), yet here we are.

Permit me another question?

This seems to me to be crossing from emulation to simulation?

The laserdisc is an analogue to a hard drive, so it feels to me like extending this means that MAME should simulate the cylinders and head(s) of a hard drive, the IRQ's generated, the ISA/PCI bus, memory controller, etc. The laserdisc player isn't really that different from the hard drive as it is just the medium that reads out the bytes stored on a "Storage platter".

I feel like laserdiscs are being held to a higher standard than hard drives with respect to being supported in MAME. Shouldn't the support requirements be the same for both mediums?

I completely get why we want to have the laserdisc itself converted into a series of bits to represent the physical layout of data on the disc, I'm just wondering why the laserdisc player itself isn't emulated?

That requirement for the laserdisc player to be simulated seems to me to be the thing preventing laserdisc inclusion in MAME as it seems to me to be setting an impossibly high requirement. Though of course, since I've never been involved in MAMEDev discussions I could be unaware of other requirements preventing it.



redk9258Moderator
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Reged: 09/21/03
Posts: 3954
Loc: Troy, Illinois USA
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Re: Question about ALG driver status [Re: Rygar9]
#368034 - 07/20/17 01:12 AM


LaserDisc does not store data like a HDD or CD / DVD. It is an analog signal, not digital.


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