> Even so, that would still be lossy. > There is no way to go from analog to digital without quantisation loss. > LaserDisc is analog. AVI (or whatever) is digital.
While technically correct, that's not really a useful thing to say. Any analog signal will have some level of noise. Beyond a certain point, increasing bit depth just captures the noise in more detail - it doesn't capture any more information from the signal. Similarly, if a signal is band-limited you gain no information by increasing the sampling frequency once it's past twice the highest-frequency component of the source material.
In a LaserDisc, there are only two levels (pit/land). The noise comes in from manufacturing tolerances that cause the lengths of the pits to vary, and ageing effects on the discs as they distort from temperature changes. You only need 1-bit samples of a sufficiently high frequency that the period between samples is smaller than the manufacturing tolerances of the pressing process to get an effectively lossless capture. Increasing the sample rate would capture noise in more detail.
Separating the carriers and demodulating the audio and video is inherently lossy. Any conversion to an A/V container format, even using lossless codecs, is going to be lossy as it requires carrier separation and demodulation. The archival dumps will not be in an A/V container format.
I don't know what the exact figures you need to get an effectively lossless capture of a LaserDisc, but I trust that the guys working to archive the Domesday Project material know what they're doing.