Re: normalize audio in mp4s

[Reco <recoverym4n@enotuniq.net>]

	Hi.

On Wed, Mar 11, 2020 at 05:00:21PM +0100, Emanuel Berg wrote:
> Reco wrote:
> 
> > Can you provide an output of (you may need to install ffmpeg
> > package):
> >
> > ffprobe -hide_banner <mkv here>

Perfect, thanks. This:

>     Stream #0:1(por): Audio: ac3, 48000 Hz, 5.1(side), fltp, 448 kb/s (default)

Or this, dependent on your preferred language

>     Stream #0:2(eng): Audio: ac3, 48000 Hz, 5.1(side), fltp, 448 kb/s

Is the likely source of your problem.

This particular video has 5.1 audio, and you most probably have only two
audio channels to play it.

If you're using mpv, you can try adding --audio-channels=stereo, but
(YMMV of course) I find its downmix lacking.

Personally I just reencode audio in such cases.
For instance (0:1 is the first audio track, use 0:2 for english):

ffmpeg -i ford-v-ferrari-2019.mkv -map 0:0 -map 0:1 \
	-c:v copy \
	-c:a libopus -b:a 128k -ac 2 -clev 1.414 -slev .5 \
	ford-v-ferrari-2019.good_audio.mkv

Reco