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• imagemagick -auto-level in ffmpeg

  29 août 2024, par Sagi Mann

  I've been looking for a solution to perform the equivalent of magick -auto-level in ffmpeg but am unable to find anything. There are some references stating I should first manually discover the levels using other software like GIMP, however, I'm looking for an automated and simpler solution. Any ideas how to address this ?

  


  I've tried the following - the first enhanced the image which was initially prettry dark, but the second over-exposed it, causing it to become mostly white :

  


  convert img.jpg -auto-level img2.jpg
ffmpeg -i img.jpg -vf "normalize" -y img2.jpg


  


  Note : I apologize I cannot share the image as it is restricted by privacy policy

  


• input seek in ffmpeg-python

  14 octobre 2022, par Mauro Gentile

  ffmpeg -ss 00:05:20 -i input.mp4 -t 00:10:00 -c:v copy -c:a copy output3.mp4
extracts the video segment quickly because of the input seek -ss being placed before -i.

  


  Which is the equivalent expression in ffmpeg-python ?

  


• aarch64 : vp9 : Implement NEON loop filters

  13 novembre 2016, par Martin Storsjö

  aarch64 : vp9 : Implement NEON loop filters
  This work is sponsored by, and copyright, Google.
  These are ported from the ARM version ; thanks to the larger
  
  amount of registers available, we can do the loop filters with
  
  16 pixels at a time. The implementation is fully templated, with
  
  a single macro which can generate versions for both 8 and
  
  16 pixels wide, for both 4, 8 and 16 pixels loop filters
  
  (and the 4/8 mixed versions as well).
  For the 8 pixel wide versions, it is pretty close in speed (the
  
  v_4_8 and v_8_8 filters are the best examples of this ; the h_4_8
  
  and h_8_8 filters seem to get some gain in the load/transpose/store
  
  part). For the 16 pixels wide ones, we get a speedup of around
  
  1.2-1.4x compared to the 32 bit version.
  Examples of runtimes vs the 32 bit version, on a Cortex A53 :
  
                                         ARM AArch64
  
  vp9_loop_filter_h_4_8_neon :          144.0   127.2
  
  vp9_loop_filter_h_8_8_neon :          207.0   182.5
  
  vp9_loop_filter_h_16_8_neon :         415.0   328.7
  
  vp9_loop_filter_h_16_16_neon :        672.0   558.6
  
  vp9_loop_filter_mix2_h_44_16_neon :   302.0   203.5
  
  vp9_loop_filter_mix2_h_48_16_neon :   365.0   305.2
  
  vp9_loop_filter_mix2_h_84_16_neon :   365.0   305.2
  
  vp9_loop_filter_mix2_h_88_16_neon :   376.0   305.2
  
  vp9_loop_filter_mix2_v_44_16_neon :   193.2   128.2
  
  vp9_loop_filter_mix2_v_48_16_neon :   246.7   218.4
  
  vp9_loop_filter_mix2_v_84_16_neon :   248.0   218.5
  
  vp9_loop_filter_mix2_v_88_16_neon :   302.0   218.2
  
  vp9_loop_filter_v_4_8_neon :           89.0    88.7
  
  vp9_loop_filter_v_8_8_neon :          141.0   137.7
  
  vp9_loop_filter_v_16_8_neon :         295.0   272.7
  
  vp9_loop_filter_v_16_16_neon :        546.0   453.7
  The speedup vs C code in checkasm tests is around 2-7x, which is
  
  pretty much the same as for the 32 bit version. Even if these functions
  
  are faster than their 32 bit equivalent, the C version that we compare
  
  to also became around 1.3-1.7x faster than the C version in 32 bit.
  Based on START_TIMER/STOP_TIMER wrapping around a few individual
  
  functions, the speedup vs C code is around 4-5x.
  Examples of runtimes vs C on a Cortex A57 (for a slightly older version
  
  of the patch) :
  
                           A57 gcc-5.3  neon
  
  loop_filter_h_4_8_neon :        256.6  93.4
  
  loop_filter_h_8_8_neon :        307.3 139.1
  
  loop_filter_h_16_8_neon :       340.1 254.1
  
  loop_filter_h_16_16_neon :      827.0 407.9
  
  loop_filter_mix2_h_44_16_neon : 524.5 155.4
  
  loop_filter_mix2_h_48_16_neon : 644.5 173.3
  
  loop_filter_mix2_h_84_16_neon : 630.5 222.0
  
  loop_filter_mix2_h_88_16_neon : 697.3 222.0
  
  loop_filter_mix2_v_44_16_neon : 598.5 100.6
  
  loop_filter_mix2_v_48_16_neon : 651.5 127.0
  
  loop_filter_mix2_v_84_16_neon : 591.5 167.1
  
  loop_filter_mix2_v_88_16_neon : 855.1 166.7
  
  loop_filter_v_4_8_neon :        271.7  65.3
  
  loop_filter_v_8_8_neon :        312.5 106.9
  
  loop_filter_v_16_8_neon :       473.3 206.5
  
  loop_filter_v_16_16_neon :      976.1 327.8
  The speed-up compared to the C functions is 2.5 to 6 and the cortex-a57
  
  is again 30-50% faster than the cortex-a53.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavcodec/aarch64/Makefile
  • [DBH] libavcodec/aarch64/vp9dsp_init_aarch64.c
  • [DBH] libavcodec/aarch64/vp9lpf_neon.S