[ogg-dev] oggfile, skeleton and vorbis tools

illiminable ogg at illiminable.com
Thu Mar 9 16:56:20 PST 2006

----- Original Message ----- 
From: "Ian Malone" <ibmalone at gmail.com>
To: <ogg-dev at xiph.org>
Sent: Friday, March 10, 2006 8:42 AM
Subject: Re: [ogg-dev] oggfile, skeleton and vorbis tools

> Re-reading Monty's email: when you talk about vorbis-only vorbisfile and
> the concurrent vorbis stream case do you mean vorbisfile will need to be
> able to choose?  I'd been thinking (as above) about cases where there is
> a Vorbis stream in with other stuff, the first two examples are
> realities.  The obvious applications for multiple concurrent Vorbis
> streams are the same as for DVD: multiple languages, commentaries,
> scores (possibly needing mixing).  Deciding what to play needs
> application involvement; how much should vorbisfile be able to do, and
> how much should wait until oggfile (and how much should be left to media
> players that understand all the complexities involved)?

Re: multiple audio tracks, there are quite a few ogm files out there with 
multiple vorbis streams, typically the default language is first. So if you 
made vorbisfile drop unknown streams, these are potential files people might 
try to play with it.

The other case, i have a few such files for testing, is two audio streams 
designed to play concurrently. For example a dj type scenario... 
intentionally playing two files over the top of each other. An even more 
useful case is for example an online stream, where the music is in one 
stream, and the dj/announcer can voiceover in the other stream... i've got a 
few test files like this also. Vorbis+Vorbis and Speex+Vorbis examples. I 
think somewhere i've got a file that plays four songs simultaneously, even 
though this file is not particularly useful, it was just a good test to see 
how my directshow filters would handle it. Another scenario where this would 
be useful might be having different instruments in each track.

Obviously neither vorbis file nor a player can tell whether the file author 
intended for the streams to play at the same time or be alternates... or 
even more complicated would be groups that are alternates, ie either play 
these two together, other wise play these two together... or always play 
this one with the music, and choose one from voiceover streams to play 
concurrently with the music.

VLC for example will let you choose an audio stream, however there is no 
option for playing them at the same time.

This is something we might want to extend skeleton to support, i know we've 
talked about this kind of thing before. So that skeleton can provide some 
kind of mapping as to how the various streams relate to each other.



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