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

[Yuntaek Lim]

Hi,

I've created 5.1 channel aac-lc audio from  5.1 channel  ac-3 audio.
However, the sample entry of "mp4a" box show channel_count as "2", not "6".
Howerver, the  MPEG-4 elementary stream descriptor in "esds" box describes
channel count as 6.

Command
ffmpeg -loglevel debug  -i source.mp4 -filter_complex
"channelmap=map=FL-FL|FR-FR|FC-FC|LFE-LFE|SR-BR|SL-BL:channel_layout=5.1"
-c:v copy -c:a libfdk_aac -profile:a aac_he -f mp4 demo.mp4

I've checked the channel_cout using "
http://download.tsi.telecom-paristech.fr/gpac/mp4box.js/filereader.html".
I've checked the value of the "esds" box with shaka packager and ffrpobe.

Can you explain the reason why the values are different, please?

The source file "source.mp4"
https://drive.google.com/open?id=0B2CC25n6pcNwejM1T3ZQb25hOENJS0xBTlhZcU1nZHZBOUM0


The output file "demo.mp4"
https://drive.google.com/open?id=0B2CC25n6pcNwdnJNUmhQZU4wck1YRUhtVnRFekF1S2JnUU9z

Regards,
Yuntaek Lim