Vorbis dev - Jan 2002 - DVD Audio & Vorbis

I recently bought a DVD Audio disc and I searched the web and wasn't
really able to find much about DVD Audio and Linux.  I have a few
questions that I was hoping some people on this list might be able to
answer.

How can I extract the uncompressed DVD Audio (not the DTS Audio portion
of the disc, but the 96khz/24bit/5.1 pcm part)?

On Thu, 10 Jan 2002, Bryan Stillwell wrote:
> Any idea when vorbis will be able to support all 6 channels?
The vorbis format itself supports 6 channels.  The problem is mostly with
tools.  oggenc will accept 6 channel wav files, but ogg123 cannot reliably
playback 6 channel files on all devices (a limitation of libao).  In the next
month, I'll be getting some 6 channel hardware and will be able to test this
more thoroughly.
> If I could get the data off the DVD, what are my best options right now
> if I wanted to use ogg vorbis?  Is there a program which will sample it
> down to 44.1khz/16bit/stereo which I could then encode to ogg vorbis?
SoX is generally good for doing this sort of conversion.  I'm not sure how
good it will be at converting 6 channels to 2, but the downsampling should be
no problem.


---
Stan Seibert

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> How can I extract the uncompressed DVD Audio (not the DTS Audio portion
> of the disc, but the 96khz/24bit/5.1 pcm part)?
>
> From what it sounds like on the list, 96khz isn't supported as a
> sampling size yet, is this also planned for rc4?
I'm afraid I can't answer either of these questions.
> Any idea when vorbis will be able to support all 6 channels?
That depends on your definition of 'support'. Vorbis today encodes and
decodes N channels, where N is anything from 1 to 255. Unfortunately, the
channel coupling isn't yet implemented for values of N other than 2.
(Channel Coupling isn't that big a deal; it just reduces the bitrate at the
same quality). Also unfortunately, there currently is no way to know which
channel is which. So you'd get your 6 channels back, but they might not all
be coming out of the right speakers. :-)

Both of these problems are going to be fixed before 1.0. I don't know which
ones are planned for rc4.
> If I could get the data off the DVD, what are my best options right now
> if I wanted to use ogg vorbis?  Is there a program which will sample it
> down to 44.1khz/16bit/stereo which I could then encode to ogg vorbis?
I'd be inclined to go to 48/24/stereo from a 96/24 source, but maybe
that's
just me. Of course, this depends on your sound card: If it's an SBLive!,
those cards can't do 44.1 anyway, so your oggs might as well be 48kHz. If
you have an older card that does 44.1 only, you might as well have .oggs
that are 44.1. Either way, vorbis works in a floating-point depth, so
there's no point downconverting to 16.

SoX is a great program for bitrate/bitdepth conversions, but my copy of the
docs says it only works on up to 4 channel files. I have no idea what you'd
use for 5.1->ProLogic matrixing.

Peter Harris

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