[FFmpeg-trac] #4376(avfilter:closed): FFmpeg amerge multi input create an output with a lower volume
FFmpeg
trac at avcodec.org
Thu Mar 19 19:55:24 CET 2015
#4376: FFmpeg amerge multi input create an output with a lower volume
-------------------------------------+-------------------------------------
Reporter: wouha | Owner:
Type: defect | Status: closed
Priority: normal | Component: avfilter
Version: git-master | Resolution: invalid
Keywords: | Blocked By: low
filter_complex amerge volume | volume
Blocking: | Reproduced by developer: 1
Analyzed by developer: 1 |
-------------------------------------+-------------------------------------
Changes (by Cigaes):
* priority: important => normal
* resolution: => invalid
* status: new => closed
* component: ffmpeg => avfilter
* version: 2.6 => git-master
Comment:
More precisely, it is exactly six times lower in terms of linear
intensity. This is the expected behaviour. A lot of PCM hardware and
software code samples in a bounded interval, usually equivalent to the
[-1,1] interval after normalization. The problem is that 0.9+0.9=1.8 does
not fit to the interval; you have to do an average, not a sum:
(0.9+0.9)/2.
That is exactly what "FL<..." does: it is equivalent to "FL=(...)/N",
where N is the number of channels you added. You are perfectly free to
write "FL=c0+c2+..." instead of "FL<...". You will get normal volume but
possibly clipping.
I do not remember if FFmpeg has soft-clipping filters.
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Ticket URL: <https://trac.ffmpeg.org/ticket/4376#comment:1>
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