youtube-dl should display ffmpeg errors

[illumilore]

Whenever ffmpeg gives out errors, youtube-dl should give that feedback to the user. As it is now, it only gives the last line:[ffmpeg] Correcting container in "A.m4a"
ERROR: file:A.temp.m4a: Invalid argument

But it would be better if it gave the whole error so that I would know that the error has to do with mp4 codec: Requested output format 'mp4' is not a suitable output format
file:A.temp.m4a: Invalid argument

[fstirlitz]

-hide_banner -loglevel warning (or -loglevel error) can be passed to ffmpeg instead of silencing it completely, unless --verbose was given to youtube-dl. This way you'll get less verbose messages that can be even forwarded to the terminal directly.