[FFmpeg-devel] [PATCH] avfilter/f_ebur128: add dualmono measurement option

Clément Bœsch u at pkh.me
Wed Sep 30 14:21:56 CEST 2015

On Mon, Sep 28, 2015 at 10:32:28AM -0500, Kyle Swanson wrote:
> > questions:
> >
> > - what happens if you resample the input (by prefixing ebur128 with
> >   aformat=channel_layout=stereo)?
> > - if I'm reading the blog correctly ("Note that In my discussions with
> >   leading experts in the space, it has come to my attention that this
> >   approach may not be sustainable. Many pros feel it is the responsibility
> >   of the playback device and/or delivery system to apply the necessary
> >   compensation.") this is not a standard behaviour at all. Do you confirm
> >   this?
> ffmpeg -nostats -i mono.wav -filter_complex
> "aformat=channel_layouts=stereo,ebur128" -f null -
> does not give the appropriate output. It looks like
> `channel_layouts=stereo` is intelligent enough to
> apply pan law gain to each channel before remapping, but this results
> in the same inaccurate loudness
> measurement.  A `dualmono=true` flag is convenient way to use the same
> ffmpeg call to measure
> loudness for all files, including multichannel files beyond stereo.
> See also: a similar option is enabled by default in R128GAIN -
> http://r128gain.sourceforge.net/

OK. I will test & apply this week-end unless you're in a hurry. In the
meantime, maybe just drop the V flag in the options (these options are
related to the audio only).

Thanks, and sorry of the delay

Clément B.
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