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

[Yuntaek Lim]

Thanks Gyan.

2019년 2월 14일 (목) 오후 3:45에 Gyan <ffmpeg at gyani.pro>님이 작성:

>
>
> 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
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