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• avcodec/msrledec : implement vertical offset in 4-bit RLE

  29 novembre 2016, par Daniel Verkamp

  avcodec/msrledec : implement vertical offset in 4-bit RLE
  The delta escape (2) is supposed to work the same in 4-bit RLE as in
  
  8-bit RLE.  This is documented in the MSDN Bitmap Compression page :
  
  https://msdn.microsoft.com/en-us/library/windows/desktop/dd183383(v=vs.85).aspx
  The unchecked modification of line is safe, since the loop condition
  
  (line >= 0) will check it before any pixel data is written.
  Fixes ticket #5153 (output now matches ImageMagick for the provided sample).
  Signed-off-by : Daniel Verkamp <daniel@drv.nu>
  

  • [DH] libavcodec/msrledec.c

• avcodec/mpeg4videodec : Fix runtime error : signed integer overflow : 134527392 * 16...

  3 mars 2017, par Michael Niedermayer

  avcodec/mpeg4videodec : Fix runtime error : signed integer overflow : 134527392 * 16 cannot be represented in type ’int’
  This checks the sprite delta intermediates for overflow
  
  Fixes : 716/clusterfuzz-testcase-4890287480504320
  Found-by : continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/targets/ffmpeg
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/mpeg4videodec.c

• How to detect two identical audio/video files with different volume level ?

  3 juillet 2017, par Marina Rappoport

  I’m working on program that could compare 2 video files and show difference.
  I compare audio track of files using SOX and FFMPEG :

  1. invert one of the files (sox)
  2. merge other file and invert version of first (sox)
  3. detect silence (ffmpeg)

  But if two file differs only by volume level - all audio track will be detected as non-silent ranges.

  How to understand that 2 files have the same audio track, but with different volume level ?

  I tried to change sound level via sox : sox -v 1.1 input.wav output.wav
  And then compare statistical information (-n stat).
  It works fine. Result of division parameters audio2/audio1 :

      Samples read 1.00;
  
      Length (seconds) 1.00;
  
      Scaled by 1.00;
  
      Maximum amplitude 1.10;
  
      Minimum amplitude 1.10;
  
      Midline amplitude 1.10;
  
      Mean norm 1.10;
  
      Mean amplitude 1.00;
  
      RMS amplitude 1.10;
  
      Maximum delta 1.10;
  
      Mean delta 1.10;
  
      RMS delta 1.10;
  
      Rough frequency 1.00;
  
      Volume adjustment 1/1.10;

  BUT ! When I tried ffmpeg to change volume of video : ffmpeg -i input.mp4 -vcodec copy -af "volume=10dB" output.mp4 (or volume=volume=0.5) and than compared sox audio statistic : I can’t find any patterns...

  Samples read    1.00
  
  Length (seconds)    1.00
  
  Scaled by   1.00
  
  Maximum amplitude   0.71
  
  Minimum amplitude   0.64
  
  Midline amplitude   -2401.73
  
  Mean    norm    0.34
  
  Mean    amplitude   0.50
  
  RMS     amplitude   0.36
  
  Maximum delta   0.37
  
  Mean    delta   0.34
  
  RMS     delta   0.36
  
  Rough   frequency   0.99
  
  Volume adjustment   0.71

  I will be grateful for any ideas and help.