[vorbis-dev] Multi-stream vorbis...

[illiminable]

----- Original Message ----- 
From: "Arc Riley" <arc at xiph.org>
To: <vorbis-dev at xiph.org>
Sent: Sunday, May 30, 2004 6:16 PM
Subject: Re: [vorbis-dev] Multi-stream vorbis...

<p>> On Sun, May 30, 2004 at 03:04:47PM +0800, illiminable wrote:
> > I've been testing my multi-stream mux directshow filter. And have
created
> > some files with 2 tracks of vorbis... varying from 2 mp3s transcoding to
> > vorbis interleaved to one mp3 transcode to vorbis in one stream, and
live
> > muxed spoken audio encoded to vorbis in the other. Simliarly some with
> > vorbis in one stram and speex encoded voice-overs in the other.
>
> Note that according to spec "Ogg Vorbis" files are not muxed.  One
> vorbis stream, possibly chained at the end to another vorbis stream,
> nothing muxed (concurrent).
>

Ok... i understand it's not a valid Ogg Vorbis file, but it is (assuming my
muxer works properly) a valid ogg file.

Is there some reason why players can't/don't simultaneously play multiple
streams of audio ? Surely if they can demux the stream they can see there
are two streams and play both of them ?

Is there a reason for that limitation on Ogg Vorbis files is what i'm
getting at ?

And obviously a mixed speex and vorbis file is not going to be a valid ogg
vorbis file because it isn't just vorbis.

Which kind of gets back to my previous question a few weeks back, with the
single .ogg extension. Without a partial demux, how can a player tell if it
is an ogg vorbis file or just a generic ogg file which may contain anything.
I assume there is a similar restriction to theora ? Which would prevent a
video being encoded with multiple audio tracks in different langauges for
example. And how can a player (which may only play audio, or only ogg
vorbis) know determine if it should let a user load a file. How can it sort
audio only .ogg files from A/V .ogg file from some other kindo f .ogg files.

It was mainly just a test of the muxer, before i write the theora encoder,
to see whether my muxer can properly interleave stuff, it was just a side
effect of the way directshows graph architecture works that it doesn't realy
matter to it how many or what sort of streams are contained... if it knows
the stream, it will play it.

> So you're breaking new ground here, and as such, you won't find much
> support from current players.
>

Hmmm... ok, i guess that means i'll need to write the theora encoder to have
any other point of comparison for the operation of the muxing process.

Thanks,

Zen.
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