[FFmpeg-devel] [PATCH] libavfilter/af_showvolume: A Simple Audio Filter for Extracting Volume Information

Lars Kiesow lkiesow at uos.de
Fri Dec 26 00:39:51 CET 2014

On Fri, 26 Dec 2014 00:08:39 +0100
Stefano Sabatini <stefasab at gmail.com> wrote:

> On date Wednesday 2014-12-24 00:51:26 +0100, Lars Kiesow encoded:
> > Hi,
> > I had a more detailed look at this and found a way to do exactly
> > that, thanks for the hint.
> > [...]
> > One question left is, if there is any interest in having a script
> > to to the waveform generation in the tools section. Otherwise I
> > would just add my findings to the ffmpeg wiki.
> Sure, having this on the wiki would be nice, also I'm interested at
> looking at the script, please share.

Hi Stefano,
the basic idea is to generate a specific output format that gnuplot
understands and pipe the output into gnuplot:

  ffmpeg -i in.mp3 -ac 1 -c:a pcm_s16le -f data - | gnuplot -p -e \
    "plot '-' binary filetype=bin format='%int16' endian=little
    array=1:0 with lines;"

That's faster and probably more reliable than parsing the output from
the patch I submitted earlier. It's a bit more problematic to plot
multiple audio channels though, as you cannot extract the data from a
single pipe.

I've attached two short scripts to this mail and will add a sections to
the wiki if Cléments patch won't make it in ... I hope it will.

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