[FFmpeg-user] Audio filter: removesilence doesn't appear to do anything

Paul B Mahol onemda at gmail.com
Mon Sep 25 12:57:01 EEST 2017

On 9/25/17, Quinn Wood <mtcjayne at gmail.com> wrote:
> I have removed the video and am getting the same results.
> silenceremove is not removing silence.
>   ffmpeg -i ../2017-09-24T123913.mp4.done -vn -af
> silenceremove=0:0:0:-1:0.5:-20dB:1 output.m4a
> https://pastebin.com/raw/xcGQFs30

Are you sure? Output file duration is smaller than input one.

>   ffprobe -i output.m4a
> https://pastebin.com/raw/183KLwZY
>   ffmpeg -i output.m4a -af silencedetect=n=-20dB:d=0.5 -f null -
> https://pastebin.com/raw/4304SzMh
> Using peak detection makes no difference:
> https://pastebin.com/raw/KwqXudSw https://pastebin.com/raw/462yRwQ7
> https://pastebin.com/raw/s362n0wd
> On Mon, Sep 25, 2017 at 1:45 AM, Quinn Wood <mtcjayne at gmail.com> wrote:
>> I thought I'd extracted the video by simply using the m4a extension-
>> that's not the way that works and I should have noticed that. I bet
>> the audio has been truncated but the video remains the full length.
>> Let me strip out the video and try it.
>> On Mon, Sep 25, 2017 at 12:59 AM, Quinn Wood <mtcjayne at gmail.com> wrote:
>>> I have used the following command
>>>     ffmpeg -i input.m4a -af silenceremove=0:0:0:-1:0.5:-20dB output.m4a
>>> on a file. When I use another tool (Audacity) to truncate periods over
>>> 0.5 seconds of under -20dB volume it removes upwards of an hour from
>>> the input file. When I run this command ffmpeg doesn't remove a single
>>> second. I have tried numerous variations of the command and numerous
>>> input files, and am simply unable to replicate the effect Audacity is
>>> producing.
>>> The input files have a period of silence at the beginning that is
>>> predictable, intermittent periods of silence throughout the file of
>>> unknown quantity and length, and a period of silence at the end that
>>> is predictable.
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