Bug#969600: Latest ffmpeg lacks amr encoding support

[wiicontroller@gmail.com]

Package:  ffmpeg
Version:  7:4.1.6-1~deb10u1

Previously (7:4.1.4), Debian's ffmpeg package supported AMR output by  
installing libavcodec-extra.  Currently, it does not.  The rules file of  
ffmpeg shows a FLAVORS array that contains an "extra" item that *would*  
support AMR, but "extra" is not applied to the ffmpeg package:

https://tracker.debian.org/media/packages/f/ffmpeg/rules-74.1.6-1deb10u1#20

Here is the ffmpeg command-line error:

> $ ffmpeg -loglevel warning -i test.flac test.amr
> Automatic encoder selection failed for output stream #0:0. Default  
> encoder for format amr (codec amr_nb) is probably disabled. Please  
> choose an encoder manually.
> Error selecting an encoder for stream 0:0

There seems to be no way to write AMR files on an up-to-date Buster system.

Thank you.