[FFmpeg-user] HOW TO APPLY LOUDNESS R128 PROFILE

[Paul B Mahol]

On Wed, Sep 23, 2020 at 03:30:25PM +0200, Marco Mircoli wrote:
> Thanks Motitz,
>    this is a one pass norm.
> Is there a way to implement 2 pass?

Yes there is a way, you can search google among other things.

First run loudnorm to get report of loudness values, after that
use that reported values in new, 2nd pass.

> Thanks.
> S.
> 
> 
> Il giorno mer 23 set 2020 alle ore 14:42 Moritz Barsnick <barsnick at gmx.net>
> ha scritto:
> 
> > On Wed, Sep 23, 2020 at 14:16:31 +0200, Marco Mircoli wrote:
> > > Just bought a php script that use ffmpeg.
> >
> > I hope it's worth it. ;)
> >
> > > this is the line
> > > $shell     = shell_exec("$ffmpeg_b -i $audio_file_full_path -map 0:a:0
> > -b:a
> > > 96k $audio_output_mp3 2>&1");
> > >
> > > I'm wondering if it is possible to include in the conversion the audio
> > > level normalization to R128 loudness profile.
> > > I think it is possible, but I don't know how to do it :-(
> >
> > Sure. You just need to insert a filter to the command line. The R128
> > filter is even described here:
> >
> > https://trac.ffmpeg.org/wiki/AudioVolume#LoudnessNormalization
> >
> > > $shell     = shell_exec("$ffmpeg_b -i $audio_file_full_path -map 0:a:0
> > -b:a 96k $audio_output_mp3 2>&1");
> >
> > Just add the loudnorm filter:
> >
> > $shell     = shell_exec("$ffmpeg_b -i $audio_file_full_path -map 0:a:0 -af
> > loudnorm -b:a 96k $audio_output_mp3 2>&1");
> >
> > To fine tune the filter's behavior, check ffmpeg's filters
> > documentation, or
> >
> > $ ffmpeg -h filter=loudnorm
> >
> > Good luck,
> > Moritz
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