[FFmpeg-devel] [RFC] Audio normalization

Michael Niedermayer michaelni at gmx.at
Fri Feb 22 20:39:30 CET 2013

On Fri, Feb 22, 2013 at 12:22:38AM +0100, Clément Bœsch wrote:
> Hi,
> So here is a first attempt to add automatic audio normalization on the fly with
> FFmpeg. The basic idea is to make EBU R.128 filter inject metadata about the
> loudness analysis every audio frame of 100ms (BTW, a big thanks to Nicolas
> George for the {min,max}_samples features in lavfi), and then make volume do
> the normalization according to these data.
> How to test it:

>     ./ffplay -f lavfi -i 'amovie=in.mp3,ebur128=video=1:metadata=1[r128-before][a]; [a]volume=metadata=lavfi.r128.I,ebur128=video=1[r128-after][out1]; [r128-before] pad=iw*2 [padded]; [padded][r128-after] overlay=w'

some newlines and indention would help the readability of this example
and lavfi examples in general
what iam thinking of is something like:

                     amovie=    in.mp3,
                     ebur128=   video=1:metadata=1  [r128-before][a];

                 [a] volume=    metadata=lavfi.r128.I,
                     ebur128=   video=1             [r128-after][out1];

       [r128-before] pad=       iw*2                [padded];

[padded][r128-after] overlay=   w

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Into a blind darkness they enter who follow after the Ignorance,
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to the Knowledge alone. -- Isha Upanishad
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