[FFmpeg-trac] #6071(ffmpeg:new): loudnorm filter always returns LRA of 0.0 LU with short files (less than ~3 seconds)

[FFmpeg]

#6071: loudnorm filter always returns LRA of 0.0 LU with short files (less than ~3
seconds)
----------------------------------+--------------------------------------
             Reporter:  p49k26x5  |                     Type:  defect
               Status:  new       |                 Priority:  normal
            Component:  ffmpeg    |                  Version:  git-master
             Keywords:  loudnorm  |               Blocked By:
             Blocking:            |  Reproduced by developer:  0
Analyzed by developer:  0         |
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 I was trying to execute a 2 pass loudnorm filter on a file less than 1
 second and it wouldn't work properly - the output of the second pass was
 not changed by much and the target output values were missed by a long
 way.
 On the first pass, the measured input_lra value was always 0.0 which seems
 wrong  and the output_i is nowhere near the target.

 I verified my build was working ok by running a test on the
 loudnorm_before.mp3 found at http://k.ylo.ph/2016/04/04/loudnorm.html

 ffmpeg version N-83034-gf48b6b8 Copyright (c) 2000-2017 the FFmpeg
 developers
   built with gcc 4.8.3 (GCC) 20140911 (Red Hat 4.8.3-9)
   configuration: --prefix=/root/ffmpeg_build --extra-
 cflags=-I/root/ffmpeg_build/include --extra-
 ldflags='-L/root/ffmpeg_build/lib -ldl' --bindir=/root/bin --pkg-config-
 flags=--static --enable-gpl --enable-nonfree --enable-libfdk_aac
   libavutil      55. 43.100 / 55. 43.100
   libavcodec     57. 71.100 / 57. 71.100
   libavformat    57. 62.100 / 57. 62.100
   libavdevice    57.  2.100 / 57.  2.100
   libavfilter     6. 68.100 /  6. 68.100
   libswscale      4.  3.101 /  4.  3.101
   libswresample   2.  4.100 /  2.  4.100
   libpostproc    54.  2.100 / 54.  2.100



 I setup a new test file and concatenated it together several times.  The
 file bonjour.wav is 1.17 seconds long and the LRA could not be measured.
 The file bonjour_twice.wav is 2.33 seconds and the LRA could not be
 measured.
 The file bonjour_three.wav is 3.49 seconds and the LRA CAN be measured.

 I have successfully used those measurements to properly normalise all 3
 input files.  ie. the normalisation pass works properly on small files.


 ffmpeg -i bonjour_twice.wav -af
 loudnorm=I=-16:tp=-1.5:LRA=11:print_format=json -f null -

 size=N/A time=00:00:02.33 bitrate=N/A speed=74.1x

 {
         "input_i" : "-22.85",
         "input_tp" : "-10.19",
         "input_lra" : "0.00",
         "input_thresh" : "-32.85",
         "output_i" : "-22.33",
         "output_tp" : "-9.66",
         "output_lra" : "0.00",
         "output_thresh" : "-32.33",
         "normalization_type" : "linear",
         "target_offset" : "6.33"
 }




 ffmpeg -i bonjour_three.wav -af
 loudnorm=I=-16:tp=-1.5:LRA=11:print_format=json -f null -

 size=N/A time=00:00:03.49 bitrate=N/A speed=46.2x

 {
         "input_i" : "-22.84",
         "input_tp" : "-10.19",
         "input_lra" : "0.30",
         "input_thresh" : "-32.84",
         "output_i" : "-15.94",
         "output_tp" : "-3.29",
         "output_lra" : "0.00",
         "output_thresh" : "-25.94",
         "normalization_type" : "dynamic",
         "target_offset" : "-0.06"
 }

--
Ticket URL: <https://trac.ffmpeg.org/ticket/6071>
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