[FFmpeg-devel] WIP: Loudness analysis filter with EBU R.128

Clément Bœsch ubitux at gmail.com
Sun Sep 16 22:28:59 CEST 2012

On Sun, Sep 16, 2012 at 09:49:29PM +0200, Marton Balint wrote:
> On Sun, 16 Sep 2012, Clément Bœsch wrote:
> >Hi folks,
> >
> >First, I'm sorry it's again a WIP... I again need some comments to finalize it
> >properly.
> >
> >The main point of this filter is to graph the loudness (related:
> >http://tech.ebu.ch/loudness, https://en.wikipedia.org/wiki/Loudness_war). As a
> >consequence, a video output is available, but is optional: at some point this
> >filter could be used just to inject the loudness metadata in the filtergraph
> >for further processing (like normalization), and thus the video output wouldn't
> >be required. Concerning the audio, it's passed through unchanged to the next
> >filter in both cases (because you likely want to hear what's being graph in
> >real time, and it would be simpler to have a "ebur128,normalize" filtergraph
> >than splitting the audio).
> Great job! I had something similar in mind, but never had the time
> to implement it.

I'm glad you didn't, because it was very fun to do ;)

> >
> >Preview:
> >
> >   ./ffmpeg -nostats -i ~/ebur128/samples/seq-3341-2011-8_seq-3342-6-24bit-v02.wav -filter_complex ebur128=video=1 -y loudness.webm
> >   => http://lucy.pkh.me/loudness.webm
> >
> >There is one main problem I still can't figure out: there are some A/V sync
> >issues with ffplay (but not with ffmpeg as shown in the above loudness.webm
> >output):
> >
> >   ./ffplay -f lavfi -i "amovie=input.mp3,ebur128=video=1 [out0][out1]
> >
> >I'm not sure where the problem is, but since no real-time is possible with the
> >filter at the moment because of this issue.
> I just posted a patch that should fix the ffplay issue.

That's awesome, I confirm it fixed the issue, which simplify things a lot.
I was afraid to be messing within the filter...

Also, it seems your patch fixed a long standing issue I had with ffplay
with my webradio... thanks a lot!


Clément B.
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