[opus] [Patch] Non-diegetic support for channel mapping 254

[Drew Allen]

Hey Jean-Marc,

sorry about that... extra lines... was it whitespace? If so, sorry about
that.

Thanks!

Cheers,
Drew

Cheers,
Drew

On Fri, Apr 28, 2017 at 2:43 PM, Jean-Marc Valin <jmvalin at jmvalin.ca> wrote:

> Oops, looks like we both should have been more careful. The patch had
> some extra lines that shouldn't have been there.
>
>         Jean-Marc
>
> On 28/04/17 12:59 PM, Drew Allen wrote:
> > My apologies for the confusion, I think I have the mapping layout
> > correct in this patch.
> >
> > Cheers!
> >
> >
> >
> > On Tue, Apr 25, 2017 at 10:07 AM Jean-Marc Valin <jmvalin at jmvalin.ca
> > <mailto:jmvalin at jmvalin.ca>> wrote:
> >
> >     On 25/04/17 10:12 AM, Drew Allen wrote:
> >     > We assume that the input file is ordered first by ACN ambisonic
> >     channels
> >     > followed by a (possible) stereo track, and we want to swap the
> >     order for
> >     > the API in order to couple the stereo for coding.
> >
> >     Well, if you look at section 5.1.1 of RFC7845:
> >
> >            The 'coupled stream
> >            count' field indicates that the decoders for the first M Opus
> >            streams are to be initialized for stereo (two-channel) output,
> >            and the remaining (N - M) decoders are to be initialized for
> mono
> >            (a single channel) only.
> >
> >     In other words, it says that in the file itself (regardless of what
> you
> >     do in the API), you need to have the stereo channels first, followed
> by
> >     the mono channels. Where the channels go in the API itself is another
> >     question and you're free to put the non-diegetic stereo at the end
> >     for that.
> >
> >     > The mapping code
> >     > appears to be working on files I've tested it on so far.
> >
> >     Well, even if you get the mapping wrong, it's still going to work.
> It's
> >     just that your non-diegetic stream will be made from two mono streams
> >     and two of your directional channels will be coupled. That's one of
> the
> >     limitations of simple testing, since it's not going to catch these
> kinds
> >     of errors.
> >
> >             Jean-Marc
> >
>
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