[FFmpeg-devel] [PATCH] decklink: support all valid numbers of audio channels

[Matthias Hunstock]

Am 20.12.2015 um 13:16 schrieb Carl Eugen Hoyos:
> Matthias Hunstock <atze <at> fem.tu-ilmenau.de> writes:
> 
>> +    /* Check audio channel option for valid values: 2, 8 or 16 */
>> +    switch (cctx->audio_channels) {
>> +        case 2:
>> +        case 8:
> 
> If decklink provides 8 channels, are they supposed 
> to be in a specific layout or could they implement 
> any layout?
> Since some time, FFmpeg unfortunately acts very 
> unreasonable if no layout is set;-(

SDI just transports 16 mono channels of audio, without any implied
semantic of what is in there. So the closest matching layouts are 2.0,
8.0 and 16.0, if they existed.

Using FFmpeg to capture these leads to "using channel layout 7.1" oder
"guessing hexadeco..something" being printed out, but it actually works
fine.

Someone using this will very probably be using a channel mapping anyway.
My use case for example is having live translation in a different
language on some of the channels. This is mapped to multiple 2ch audio
tracks in the output.

Regards