[FFmpeg-devel] [PATCH 3/7] swresample/rematrix: treat 22.2 as 5.1 (back) when mixing

[Jan Ekström]

On Sat, Aug 1, 2020 at 9:52 PM Michael Niedermayer
<michael at niedermayer.cc> wrote:
>
> On Sat, Aug 01, 2020 at 02:07:26PM +0300, Jan Ekström wrote:
> > Only this sub-set of channels actually follows the bit mask order
> > in the official 22.2 channel mapping. Additionally, the 5.1 channels
> > are there for backwards compatibility with the previous system.
> >
> > This enables the utilization of 22.2 content until a proper down/up
> > matrix is added into swresample.
> > ---
> >  libswresample/rematrix.c | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
>
> assuming this is true and theres no issue with order
> it should be ok
>

Thanks for taking a look.

Yes, the first 6 channels in 22.2 are mapped the same as 5.1 (back),
and the AAC decoder code reorders the coding units accordingly to
match specification. This change was then verified using
`-channel_layout "5.1"` with ffmpeg.c to just take the first six
channels.

Jan