chrisgeary Wrote: > could you confirm whether the spdifconvert utility will correctly handle > 24bit DTS? I've tried ripping the Monster soundtrack by BT and some of > the channel levels sound out to me. Also, the first track had a bit of, > what I can only describe as, jitter noise. > > I ended up with 16 bit 48khz wav files - and whilst I can't find > anything on google to help me decipher whether they should be 16bit or > 24bit, I had a feeling that it was 24 bit.Interesting question. My main > answer: I don't know for sure.
I've just been looking through some of the notes I made when writing the utility, and I see that I read and interpreted the bits at the head of a DTS frame when testing (from "test.dts" unfortunately, so I don't know what the source of the file was; I assume it was one of the 5.1 music tracks I've successfully played through the SB2, but that's not certain). That file was 24-bit 48kHz, so assuming I played it back successfully post-conversion, the utility supports those files. (Supports them intrinsically, that is, without any special handling.) Here's what I _think_: the fact that the WAV files are 16-bit 48kHz should not be an issue. When converted to WAV, it's one format supported by the SB2/3, so it's a handy way for us to package things. (Different sample sizes and rates for FLAC might be supported though, so if it turns out to be useful, we can consider encoding to a different WAV format.) The S/PDIF-ready DTS stream packed inside the WAV is not itself necessarily stored in 24-bit quantities: DTS is lossily compressed, so 24-bit samples for 6 channels sampled at 48kHz would give us a bitrate of about 6.75 mbit/s (16-bit 48kHz stereo WAV ~= 1.5mbit/s; multiply by three for the extra channels and add half for the increased sample size). Rather, I think that the DTS data is stored in a special format which doesn't rely on being transmitted in discrete 16-bit chunks. It's a bitstream rather than a sequence of 16-bit quantities. That bitstream may not be 24-bit, but will be decoded to 6 channels of 24-bit data by the receiver. I could be wrong, of course; as I've said before, I'm no expert in surround-sound encoding or the transmission thereof. Having said that, I'd be surprised if the channel levels sounding odd could be explained by the 16- versus 24-bit situation here. My experience with DTS files has been that if something's wrong, you hear nothing sensible; there don't seem to be half-measures whereby some parts would sound okay and some wouldn't. Everything has to be perfect for the receiver to be able to spot a DTS stream and begin to decode it, as far as I know. Jitter noise: I gather that for standard stereo PCM this is an effect caused by the timing of the transmitted bytes not being perfectly regular. Is that right? So some samples would be received (and played) fractionally earlier or later than others. I don't know how that sounds; I don't think my ears would be able to detect it. I don't know if DTS data suffers from jitter problems; I'd always thought that the bitstream would need to be slightly buffered anyway, and that the receiver would decode and play back based on its own clock. (But again, I'm not an expert -- my q6 Oggs sound indistinguishable from WAVs to me, and the imperfections detectable to some people are, fortunately, inaudible to my ears.) Perhaps you could try something: queue up the first track on your SqueezeBox, and queue up the DVD also. Try switching between the two (blindfolded, with somebody else doing the switching, if possible) to see if the incorrect sound levels are as mastered, or uniquely a problem with the converted track. If there's definitely a difference, reply back to this thread and we'll see what else we can think of. -- smst ------------------------------------------------------------------------ smst's Profile: http://forums.slimdevices.com/member.php?userid=752 View this thread: http://forums.slimdevices.com/showthread.php?t=19260 _______________________________________________ ripping mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/ripping
