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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