[Vorbis-dev] Multi-channel labels in Vorbis comments

[Daniel James]

Hi devs :-)

At the Mozilla Festival in London recently, I took part in a Hack the DJ
workshop, looking at ways to take digital DJ'ing to the next level:
http://www.bbc.co.uk/blogs/researchanddevelopment/2011/11/setting-a-dj-challenge-at-the.shtml

One of the ideas proposed was stem mixing, using multichannel files in
DJ applications. A proprietary implementation of this idea is Fireplayer
(http://itunes.apple.com/gb/app/fireplayer-remixer/id367791455?mt=8) but
this app is built with the intention that users will buy remixable
versions of (a very limited number of) well-known songs from an in-app
store.

We would like to work towards a new open standard for stem mixing,
something that is compatible with sharing our mixes on the open web -
legally, of course - but could also be used by record labels that sell
tracks to DJs.

For example, eight channel Ogg Vorbis files where the first two tracks
are a stereo mix of the drums, third and fourth stereo bass, fifth and
sixth stereo vocals, and seventh and eighth tracks everything else. This
means that you can mute or solo individual stems in the mix, giving you
the versatility of four-deck or eight-deck mixing but without the
problems of keeping many decks in sync.

It seems that Ogg Vorbis already has all the features we need in a stem
format for DJs, but there's the question of how we identify individual
channels within the file. There are conventions for 5.1 and 7.1 surround
mixes, of course, but we're not aware of any published convention for
stems. So it would be useful to have a text label for each channel saved
in a UTF-8 Vorbis comment which could be displayed in applications. I
was thinking of something like:

CHANNEL1=Drums L
CHANNEL2=Drums R
CHANNEL3=Bass L
CHANNEL4=Bass R
CHANNEL5=Vocals L
CHANNEL6=Vocals R
CHANNEL7=Synth L
CHANNEL8=Synth R

The labels could be edited for different languages, while preserving the
audio content - for example if you had a Soundcloud-type site for DJs in
Russia, you might would want to label the channels in Russian.

Is there any chance that a standard for labelling channels might make it
into the official Vorbis comment spec? Or would it be rejected as
'structured data'?

Cheers!

Daniel