I feel quite the dilettante trying to educate someone on this when I've learnt this stuff so recently myself, but...
Most (all?) laserdiscs have analogue audio (hopefully with CX encoding) - you just use the L/R phono out to capture this.
More recent discs (mid 80s onwards) have digital PCM as well (aka digital SOUND) - with support for up to 2 channels - which you can capture via the optical output with a suitable soundcard. This is my typical method, Star Trek II no exception.
Top-notch discs include a modulated AC-3 stream (which can accommodate, and may always consist of, 5.1 channels). You need an RF decoder just to hear this. I do not own one.
DTS I know less about, though I believe it comes in a packaged bitstream which you can decode direct from the optical (as you would with a DVD).
I'm sure someone far more knowledgeable will correct me on part (or all) of this - it's been a steep learning curve since I've ignored laserdiscs entirely until the last two months. The lure of all these original soundmixes proved impossible to resist...