[FFmpeg-user] r128 usage?

[Clément Bœsch]

On Tue, Oct 02, 2012 at 01:50:06AM -0400, David Rice wrote:
> 
> On Oct 2, 2012, at 12:22 AM, Roger Pack wrote:
> 
> >> a. From what i understand the r128 filter was implemented?
> >> b. What would be the usage (cli example) for correcting entire clip
> >> volume? (so called "integrated" norm)
> > 
> > Your goal is to normalize?
> > A list of filters is here:
> > http://ffmpeg.org/ffmpeg.html#Audio-Filters
> 
> I'm also trying to normalize based off information gained from the ebur128 filter. The information from the ebur128 filter is returned in loudness units. The two ffmpeg audio filters that I can find that can normalize are 'pan' (through the gain setting) and 'volume'. Both pan and volume filters take a multiplier to adjust the input audio and the volume filter also accepts an adjustment in dB. But I'm uncertain how to utilize information from ebur128 to determine either a multiplier or dB level is make a volume adjustment. What is the usage to use ebur128 data in order to normalize?

Hey guys :)

The online documentation is not re-generated yet, but you can
read/generate it from the source¹ (the filter was committed a few hours
ago).

This filter only gives you the loudness information (see the examples for
usage), under 'I'. If you want to normalize, you can use the volume filter.

Example: assuming you have I = -12 LUFS, and you want I = -23 LUFS (what
you are likely aiming for), -23 - (-12) = -11 LU. So basically, just use
-af volume=-11dB and here you go. If you re-run an ebur128 analysis after
this operation, you should get I = -23 LUFS.

Any feedback on this new filter is very welcome!

[1]: look for "ebur128" on
http://git.videolan.org/?p=ffmpeg.git;a=blob;f=doc/filters.texi;hb=HEAD

-- 
Clément B.
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