seanadams Wrote: > In theory ANY bitstream, PCM or not, that can be sent over s/pdif at > standard sample rates should be pass-throughable by SB2. The only > challenge is the ripping. I'm looking for ideas about sending DTS (from a DVD) in this way. I'll explain what files I've got, and what I've tried, first. After that I'll be asking for advice/suggestions on sending digital data over the SB2 without a WAV wrapper.
I've ripped a DTS file from a DVD (an audio DVD (but DVD-Video!) with a DTS stream), by using standard DVD ripping software to grab the VOB and VOBrator to pull the DTS file out. That gives me a file with extension .DTS, which has the correct sync word (0x7ffe8001) at the start and plays in VideoLAN (downmixed to stereo -- I've just used VLC to determine whether the file is parseable). I've then converted the DTS file to a DTSWAV file, by converting each successive 14-bit value to a big-endian 16-bit value (with sign bit extended into the top two bits), and wrapping the whole thing in a WAV file with appropriate headers. (Aside: if I cheat a bit and tell the WAV file that its rate is 44100 instead of 48000, then burn it to CD, I can get my amp to recognise the DTS stream. But it sounds like, as somebody else said on these forums, a horse galloping round the room.) But the file doesn't play through the SB2, nor does it play through VLC. I can successfully play other DTSWAV samples through the SB2 (such as those from Kelly Industries), and I believe my file conversion was successful. (Aside: I originally did the conversion with a third-party utility, but when the file didn't play I did it myself with a quick Python script. The resultant file does contain the expected sync values at regular intervals, so it looks proper to me.) I think the sticking point is the bitrate: the DTS specs mention three bitrates. 768 kbits/s and 1536 kbits/s (my DVD uses the latter) are used for DVD-Video, but seem to be forbidden for a DTS CD; it's a DTS CD which uses the WAV wrapper I constructed above, so my guess is that any decoder which receives a DTS signal in that format will refuse to decode it (and may not even be capable of handling the bitrate). (Aside: I may try transforming a sample DTSWAV the other way, to DTS, to see if VLC will play that... I think the DTS CD bitrate is forbidden in DTS-Video, so that probably wouldn't work either.) To summarise, I've tried wrapping a raw DTS file sourced from DVD-Video in a WAV file, the goal being to use the WAV file as a simple already-understood transport mechanism so that the underlying DTS data can be passed through the SB2 to the DTS-aware receiver. It doesn't work for my DTS file, so I'm wondering how I could apss the original bitstream straight through to the receiver. I don't know how to do this, and I have a number of questions related to it (some of which may be invalid to start with... I have an insufficient understanding of all this!): How do I configure SlimServer to pass a DTS file straight through (no conversion)? Is that enough to get the bitstream out of the SB2's S/PDIF? Or does the firmware need to be able to grok the stream's contents somewhat? Does it perhaps just need to know that there's another format, even more "raw" than WAV (and not to expect WAV-related transport data)? I have too little technical knowledge here! If it's helpful, I could provide the DTS file I've ripped (and my converted DTSWAV file, if somebody thinks I've missed something in that area -- I'd be happy with it if it could be made to work as it's not hard to do the conversion). The DTS file is about 50MB, and doesn't lose much when zipped. BTW, IMO re-encoding is not an option. For one thing it would require a non-free (beer and speech) utility to do so; for another, it's a lossy encoding applied over an existing lossy encoding, so the quality is going to suffer. And it's not so elegant. :) Thanks in advance for any suggestions! Cheers, Steve -- smst _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
