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

[Conrad Parker]

On 17 November 2011 07:39, Conrad Parker <conrad at metadecks.org> wrote:
> On 16 November 2011 18:54, Daniel James <daniel at 64studio.com> wrote:
>> 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'?
>
> Hi Daniel,
>
> Sounds like a fun application :)
>
> Rather than a single multi-channel Vorbis file, you could also use a
> file with multiple Ogg tracks, each containing a stereo Vorbis stream.
> Then you would only need to label each stream once without numbering
> or re-assigning stereo channels:
>
> PART="Bass"
> PART_RU="бас"
>
> and existing panning, stereo compression etc. would continue to work
> for each stream (or indeed, each stream could be surround if that's
> your thing). Also it'd be straightforward to losslessly rip out any of
> these streams into an independent file, and to merge streams without
> re-encoding.

PART is probably the wrong word here, it is already suggested for
labelling temporal parts (movements in a symphony etc.) in:
http://age.hobba.nl/audio/mirroredpages/-tagging.html
http://reallylongword.org/vorbiscomment/

Conrad.