[FFmpeg-user] silenceremove use

To ny tonynederpel at hotmail.com
Wed Feb 19 20:29:39 EET 2020

Thanks again for your reply.

The first command i copied directly from a forum post.
The recording on my phone doesn't have a noise or sound that exceeds
-20dB until 10 minutes 47 seconds.

The output file left by the first command has the first 2,5 seconds
missing and starts directly with a sound. Where in the recording
on my phone that sound starts at 2,5 seconds.

The second command as it seems left an output file that sounds
like it plays at twice the speed. Coincidentally it's about half
the size and duration. But everything seems to be still there
and nothing is removed.

Unfortunately i can't send a more extensive logging because it seems
when -loglevel or -v is used i get no output in console at all.

Van: ffmpeg-user <ffmpeg-user-bounces at ffmpeg.org> namens Ted Park <kumowoon1025 at gmail.com>
Verzonden: woensdag 19 februari 2020 15:54
Aan: FFmpeg user questions <ffmpeg-user at ffmpeg.org>
Onderwerp: Re: [FFmpeg-user] silenceremove use

>> Hey there,
>> As you’ve noticed you pretty much need to know the basic “profile,” I guess,
>> of the silence in your audio for best results. You could use the show volume
>> filter with ffplay,
> If audio was in any way processed prior to silence removal, like in
> this case with gain, you will certainly get poor results.

I’m not sure if you intended to reply to me, but I didn’t mean to suggest doing that if I have.

> How do you figure results are correct?
> ffmpeg -i '/home/tony/test/Recording_53.wav' -af silenceremove=1:0:-20dB recording53_silences_removed.wav
> this one does'nt remove anything.
> ffmpeg -i '/home/tony/test/Recording_53.wav' -af silenceremove=0:0:0:0:0:-1:0:-20dB:0:0:1:0 recording53_silences_removed.wav
> this one leaves silences of more than a minute. Even though the thresholds are set to remove everything below -20dB.
> ffmpeg -i '/home/tony/test/Recording_53.wav' -af silenceremove=start_periods=1:start_duration=0:start_threshold=-20dB:start_silence=3:start_mode=any:stop_periods=2:stop_duration=3:stop_threshold=-20dB:stop_silence=3:stop_mode=any:detection=peak:window=10 recording53_silences_removed.wav
> and this leaves nothing even though there as sounds louder than -20dB.

If you could provide some sample recordings (maybe if the ones you are working with are too sensitive to share, record some samples with the same settings you used with similar noise) it would make it easier to reproduce the results you are getting. I can only guess with just the commands you used and a qualitative description of the results.

>From the first command and result, I think maybe the recording doesn’t have silence at the beginning?

>From the second, since you gave 0 for the start_threshold, that is what will be used when removing silence from the middle sections. It’s not quite sure how anything is being removed at first glance to me, except for at the end. 0 would be used when, for example, you inserted a “silence” gap or region in Audacity or some DAW and you want to remove it.

For the third, I don’t know what is going on, I would have expected at least 6 seconds to be left after filtering.

Some example files and the unabridged console output for your commands would be useful, perhaps after increasing -loglevel .
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