[FFmpeg-user] audiofilter

[Nicolas George]

Le duodi 2 floréal, an CCXXI, jacky a écrit :
> Hi
> I have some trouble undestanding volumedetect  audiofilter
> depending on mp3 or aac files
> I do not get the same values (including n_samples)
> I have a flv file AVC/AAC if I run
> ffmpeg -f lavfi -i amovie=toto.flv,volumedetect -f null -  2> toto.txt
> I am getting

You forgot to paste the output.

> if I demux the audio
> ffmpeg -i %f_in%  -vn   -acodec libmp3lame -ar 44100 -ab 64k  -y toto.mp3

You are not just demuxing, you are transcoding.

> and run again volumedetect
> 
> ffmpeg -f lavfi -i amovie=toto.mp3,volumedetect -f null -  2> toto.txt
> 
>    n_samples: 194644271
>    mean_volume: -27.2 dB
>    max_volume: 0.0 dB
>    histogram_0db: 67
>    histogram_1db: 857
>    histogram_2db: 967
>    histogram_3db: 1669
>    histogram_4db: 9089
>    histogram_5db: 7714
> 
> the aac is 22050hz and 56k are these values responsable for these changes ?

I can not answer that, not being able to know how large are the changes.

> details from ffmpeg console input
> ffmpeg version N-48731-g7e5c5fa Copyright (c) 2000-2013 the FFmpeg
> developers
>   built on Jan 10 2013 19:47:49 with gcc 4.7.2 (GCC)

This is a bit old, there was a lot of changes in filters since then.

Regards,

-- 
  Nicolas George
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