audiofilter

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audiofilter

jackyr
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


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

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)
   configuration: --enable-gpl --enable-version3 --disable-w32threads
--enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r
--enable-gnutls --enable-libass --enable-libbluray --enable-libcaca
--enable-libfreetype --enable-libgsm --enable-libmp3lame
--enable-libopencore-amrnb --enable-libopencore-amrwb
--enable-libopenjpeg --enable-libopus --enable-librtmp
--enable-libschroedinger --enable-libspeex --enable-libtheora
--enable-libtwolame --enable-libvo-aacenc --enable-libvo-amrwbenc
--enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxavs
--enable-libxvid --enable-zlib --enable-filter=frei0r
   libavutil      52. 13.100 / 52. 13.100
   libavcodec     54. 86.100 / 54. 86.100
   libavformat    54. 59.107 / 54. 59.107
   libavdevice    54.  3.102 / 54.  3.102
   libavfilter     3. 32.100 /  3. 32.100
   libswscale      2.  1.103 /  2.  1.103
   libswresample   0. 17.102 /  0. 17.102
   libpostproc    52.  2.100 / 52.  2.100
Input #0, flv, from 'chandigarh_architecture_qn4_new.flv':
   Metadata:
     major_brand     : qt
     minor_version   : 537199360
     compatible_brands: qt
     encoder         : Lavf54.37.100
   Duration: 01:13:33.68, start: 0.007000, bitrate: 446 kb/s
     Stream #0:0: Video: h264 (Main), yuv420p, 720x576 [SAR 128:117 DAR
160:117], 380 kb/s, 25 tbr, 1k tbn, 50 tbc
     Stream #0:1: Audio: aac, 22050 Hz, mono, fltp, 56 kb/s
Output #0, mp3, to 'toto.mp3':
   Metadata:
     major_brand     : qt
     minor_version   : 537199360
     compatible_brands: qt
     TSSE            : Lavf54.59.107
     Stream #0:0: Audio: mp3, 44100 Hz, mono, fltp, 64 kb/s
Stream mapping:
   Stream #0:1 -> #0:0 (aac -> libmp3lame)

what is wrong
thanks for your help
jacky


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Re: audiofilter

Nicolas George-2
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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