[opus] Proposal - Extended Channel Layouts in Opus

[Rodger Combs]

> On Oct 25, 2018, at 23:19, Martin Leese <martin.leese at stanfordalumni.org> wrote:
> 
> On 10/25/18, Rodger Combs wrote:
>> 
>>> On Oct 25, 2018, at 12:47, Martin Leese <martin.leese at stanfordalumni.org>
>>> wrote:
> ...
>>> An alternative approach is to only define
>>> popular layouts.  For more obscure layouts,
>>> such as 2.1 and Mid/Side, assume that the
>>> person doing the encoding knew what they
>>> put in, and so knows what will come out.
>> 
>> I'm not sure what you mean here. There are a few ways to push some encoder
>> API work onto the user (or API consumer), but there has to be some way to
>> communicate the layout in-stream to the decoder, or else (as is currently
>> the case) we'd be forcing anyone encoding less-than-universal layouts to
>> pass that information out-of-band to anyone wanting to decode the stream.
> 
> Yes, passing the details of obscure layouts
> out-of-band is exactly what I meant,
> particularly as the person decoding the file is
> probably also the person who encoded it.  As
> you will have seen in the OggPCM spec, there
> are an awful lot of possible layouts.  2.1 is not
> a *consumer* format, so the need to create a
> standard for it is not great.
> 

I've seen 2.1 in PCM on commercial BDs. It's also not unheard of to see 7.0 there, and in addition to stereo+SL+SR, it also supports 3.0+back center.
None of these are common formats, but they do exist in consumer media.

> Regards,
> Martin
> -- 
> Martin J Leese
> E-mail: martin.leese  stanfordalumni.org <http://stanfordalumni.org/>
> Web: http://members.tripod.com/martin_leese/ <http://members.tripod.com/martin_leese/>
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