I just created an account to suggest something (sorry for the bad english):

There is a very easy (and dirt cheap) way to playback and record BITPERFECT via digital inputs with the cheapest soundcard imaginable. You just have to finde a card with a cmedia chip use the (freeware) c-media drivers:

Read further:

http://code.google.com/p/cmediadrivers/wiki/Bitperfect

I think they already did, what we want (that is: to capture the unaltered PCM signal with no alteration at all [it appears to be random noise, but is - in fact - the DTS Bitstream] ). Click the link below, to see what they did to test if a card is bitperfect:

http://www.zen98696.zen.co.uk/Projects/CIM8738_Mods.html

They used this method: A simple test to confirm that a file is not being altered/resampled is to feed a DTS-encoded file such as this Swedish Radio DTS test file from the PC into a DTS-capable AV receiver. Even small changes to the file will result in failure, with just noise being output.

To my understanding the DTS Output of the LD Player (Optical-Toslink or Coaxial, the AC-3 rf is another thing) would be exaclty like the "Swedish Radio DTS Test" file (PCM based).

You just would have to capture what comes out of the LD player and would have got the bitperfect stream form the LD!! In the graphic above, PC1 would be the LD Player, PC2 would be the capturing pc.

I would try it myself, I even own a bitperfect soundcard with optical i/o (the DTS test works) and an LD Player (Pioneer CLD 515)... but the LD Player has no digital optical out and therefor i never got any DTS laserdisc...

I think this is very promising, or am i totally wrong? I hope it works!