[vorbis-dev] Comment Tag for Multichannel Streams

[Ingo Ralf Blum]

Hallo,

the specification in vorbis/doc proposes a set of comment tags, but I think
there's one missing for multichannel configurations. There should be a value for
mapping the individual channels to spatial locations. Lets assume a Vorbis
stream contains 4 channels, two front channels and two back channels, then the
corresponding comment value could be

CHANNELS=FRONT_LEFT,FRONT_RIGHT,BACK_LEFT,BACK_RIGHT

where the first value corresponds to channel 0, the second to 1 and so on.

Using the following values for channel mappings would allow a 1:1 translation
with DirectShow:

FRONT_LEFT
FRONT_RIGHT
FRONT_CENTER
LOW_FREQUENCY
BACK_LEFT
BACK_RIGHT
FRONT_LEFT_OF_CENTER
FRONT_RIGHT_OF_CENTER
BACK_CENTER
SIDE_LEFT
SIDE_RIGHT
TOP_CENTER
TOP_FRONT_LEFT
TOP_FRONT_CENTER
TOP_FRONT_RIGHT
TOP_BACK_LEFT
TOP_BACK_CENTER
TOP_BACK_RIGHT

One can define also special values for commomly used combinations, e.g.

STEREO (=FRONT_LEFT,FRONT_RIGHT) or 5POINT1
(=FRONT_LEFT,FRONT_RIGHT,FRONT_CENTER,LOW_FREQUENCY,BACK_LEFT,BACK_RIGHT).

Of course such a tag is only useful, if it is standardized or at least proposed
like the other tags in the docs.

If there is already a mechanism to map the channels to their spatial locations
please point me to the URL.

One additional question: The date tag should contain a date, I suppose. Do
values of this tag have a special format like the ISO date format, which is used
commonly in databases and is easily parsable, or is it just a text field, that
is not meant to be parsed by applications?

Regards Ingo

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