Moth3r said:
Very interesting.
Ripping AC3 or DTS off Laserdisc is something I've always wanted to try but never got around to attempting. From what I've heard, the problems stem from the tendency of some sound cards to resample the SPDIF input while recording, which of course destroys any encoded data.
However, some members (e.g. Karyudo, Darth Editous and Adywan) have successfully accomplished this.
Please keep us updated with your progress, it will be a useful for others who want to attempt this in the future.
PCM Stereo recorded out of the box, but I'm sure you're correct in that the sound card resamples the SPDIF input. Dolby Digital might be easier to capture since it is more widely used than DTS and programmers tend to know and support it [better]. I did not try capturing an AC3 stream, but others claim that it isn't affected by resampling. Here's a post from techarena.in, which shows it as being just a little bit of work.
10-03-2009
RoninBlade
Re: Need to decode AC3/DTS using Xonar?
You can try this:
>>>If the AC3 source is from something with an RF AC3 output (like a LaserDisc player), you will need an RF demodulator to convert the RF-modulated AC3 to SPDIF coax or optical (TosLink).
The least expensive one available is the Yamaha APD-1
>>>Now, you need to capture the SPDIF stream into the computer.
There are a few relatively inexpensive sound cards that can do this.
After you install one of the soundcards, you will run a professional sound editor (CoolEdit Pro or Sound Forge) and set the input the the SPDIF connector on the sound card, and begin recording.
However, the sound editor application knows NOTHING about IEC61937 non-PCM datastreams, and will think that what you've captured is PCM audio. When you play it back, it will sound like white noise.
>>>Save that white noise as a .wav file, and run BeSplit on it with a type of ddwav. BeSplit will un-encapsulate the SPDIF framing from the file and will leave you with an .ac3 file.
That will get your AC3 audio captured digitally into the computer.
I do have quite a few Dolby Digital LaserDiscs and a Lexicon RF Demodulator, but output is coaxial and I'd need to route it through my video processor to convert the signal to optical, since I don't have a coaxial input on my recording device.
Seeking out a capable sound card is proving to be harder than expected. Sound card manufacturers are under pressure from the recording industry to exclude on-board Dolby/DTS decoding, so not many cards were capable to begin with and acquiring one of the capable cards means shelling out more money than I can afford to spend :( Really wish the JP Blu-ray came out earlier, as I had a motherboard with onboard audio that supported Dolby and DTS inputs, but it died over the summer after 6 years of service.
My weekend comes in the middle of the week, so I'll be able to search for the old, possibly capable sound card that I had and run a few tests with it soon.
It's my understanding that the LaserDisc DTS tracks were direct duplicates of the mixes used in theaters. I've never done an A/B comparison between the Jurassic Park DTS LaserDisc and the (fixed) DTS DVD, but I wonder if they are the same mix. If they are, then that makes my work for this project irrelevant as the only DTS LD titles I have are the original Jurassic Park and Scream 2 (and Fluke, but that doesn't count, since it's DTS Stereo and the only reason I picked it up was because it was $1 and had a DTS logo on it). I do not recall being disappointed with the DTS DVD version of Jurassic Park, but I'm confident that the LaserDisc mix is the theatrical mix.
...'til next time...