[FFmpeg-user] amr_nb in mp4 container?

[Ferdi Scholten]

The AMR audio format is not specified as a valid audio format for the 
mp4 container (see *ISO 
<https://en.wikipedia.org/wiki/International_Organization_for_Standardization>/IEC 
<https://en.wikipedia.org/wiki/International_Electrotechnical_Commission> 
14496-14:2003)*. So managing to get it in does not mean it can be played 
or transcoded by other software that conforms to the mp4 specifications.

Should you want it to be registered as such, you can do that here: 
https://mp4ra.org/request
You can find all officially supported codecs and other streams on that 
site as well.