[FFmpeg-user] Wrong Channel count value on mp4a sample entry

[Gyan]

On 14-02-2019 06:39 AM, Yuntaek Lim wrote:
>
> I could not find any constraints about channel count, cannot describe greater
> than 2, for audioSampleEntry from iso 14496-12:2015.
> However, I've found "When values greater than 2 are used, the codec
> configuration should identify the channel assignment."

The standard then goes on to say,

     "The audio output format (samplerate, samplesize and channelcount 
fields) in the sample entry should be considered definitive only for 
codecs that do not record their own output configuration. If the audio 
codec has definitive information about the output format, it shall be 
taken as definitive; in this case the samplerate, samplesize and 
channelcount fields in the sample entry may be ignored, though sensible 
values should be chosen (for example, the highest possible sampling rate)"

For AAC, ASC is added from codec extradata, and provides the definitive 
info.

It may still be helpful to accurately record channel count for AAC, but 
it's not required.

Gyan