24bit LPCM audio bug?

[rjamorim]

First, I'm sorry if this bug has already been reported/discussed before, but I could find no practical way to search for something about it (24 has a too little lenght to be acepted by the search engine)

I couldn't reach the DVD2SVCD bug tracker either, I reckon it's down.



I own the David Gilmour In Concert DVD, and one of the audio tracks is in 24bit LPCM stereo.

Last night I tried using DVD2SVCD to convert it. I noticed something was wrong when BeSweet started encoding audio for lenghts much bigger than the DVD playing time. I waited for the process to finish and loaded the mp2 file in Winamp and, sure enough, it was pure noise.

I believe DVD2SVCD is just writing a 16bit header in the demuxed WAV file, not checking first for bit depth (if it's even possible to check for it, I don't know)

So, I just wanted to post this bug here to let you guys know about this issue. I'm not demanding a bug fix or anything, I already solved my problem (Used the 5.1 AC3 instead of the LPCM stream). But I guess a bug fix would be welcome anyway.

Thanks for the great app.

Best regards;

Roberto Amorim.

[BGane]

Robert: Since the problem lies in BeSweet, you could also post this note in the "Audio encoding" forum. I'm not sure if DSPGuru is still monitoring that forum or not. There was some discussion about him taking a hiatus. But he is the author of BeSweet.

[rjamorim]

Hello.

After much banging my head against the wall and searching for answers, I finally found out what is the problem.

@BGane: The problem is partially on BeSweet and partially on DVD2SVCD

What I found out, after doing all kinds of tests and asking around, is that a 24bit LPCM stream doesn't use the same byte ordering of a normal 24bit WAV file. Therefore, the demuxing program (in this case, D2S) must correct the ordering before slapping a WAV header to it and feeding it to BeSweet (of course, BeSweet will have to first be fixed in order to support 24bit audio - or does it support already? I couldn't get it to work on my 24bit samples)

Threads dealing with this issue on other forums:
http://www.hydrogenaudio.org/index.php?showtopic=11996
http://www.avsforum.com/avs-vb/showthread.php?threadid=163722

thomaspf created a tool that takes as input a RAW 24bit LPCM audio stream (demuxed from VOB with, E.G, vStrip) and fixes the ordering, later slapping a WAV header to it.

The tool and sources are available at my site (check the sig), "others" section.

Thanks for your attention.

Regards;

Roberto.