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• avcodec/ffv1enc : replace the remaining log2() by magic

  30 mars, par Michael Niedermayer

  avcodec/ffv1enc : replace the remaining log2() by magic
  big secret, reading a float as the corresponding integer is a good
  
  approximation of log2() for numbers not too close to 1.0. At the same
  
  time it maintains strict monotonicity
  this reduces run time from 19sec to 17sec for the slowest of my testcases
  
  (with default remap_optimizer 3)
  Compression is about the same :
   rw-r----- 1 michael michael  497603370 Mar 30 15:23 float-303503-fixed-40-optim-3-1log2F.nut
  
   rw-r----- 1 michael michael  497603374 Mar 28 11:27 float-303503-fixed-40-optim-3b.nut
  
   rw-r----- 1 michael michael  549938852 Mar 28 11:27 float-303503-float16-40-optim-3b.nut
  
   rw-r----- 1 michael michael  549938857 Mar 30 15:23 float-303503-float16-40-optim-3-1log2F.nut
  
   rw-r----- 1 michael michael 1150827841 Mar 28 11:28 float-303503-float-40-optim-3b.nut
  
   rw-r----- 1 michael michael 1150832913 Mar 30 15:22 float-303503-float-40-optim-3ref-log2F2.nut
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/ffv1enc.c

• FFmpeg command to loop an audio starting from a sample twice and add a fade out

  27 juin 2022, par Victor Lopes

  I have some audio files and I want to use FFmpeg to loop them twice, but starting from a given sample (I have the sample numbers), and add a 5 seconds fade-out at the end. The output has to be a video : a static .png on the same folder with the audio playing on top of it (copying the same audio codec to preserve the quality).

  


  For example, for this input audio I am supposed to get this output video. Here I used Audacity to loop and fade the audio starting from the sample 43190, and the following FFmpeg command to add the image to it :

  


  ffmpeg -r 1 -loop 1 -i "Sonic 3 Tile.png" -i "Angel Island Zone Act 1 - LOOP.ogg" -acodec copy -r 1 -shortest -vf scale=1280:1280 "Angel Island Zone Act 1.mkv"


  


  The thing is, I want to be able to do it all at once, using FFmpeg to loop and fade instead of Audacity. Is it possible ? If so, what command should I use ? Just a reminder, the audio has to be looped twice.

  


• h264_mp4toannexb : Don't forget numOfPictureParameterSets

  14 décembre 2019, par Andreas Rheinhardt

  h264_mp4toannexb : Don't forget numOfPictureParameterSets
  The format of an AVCDecoderConfigurationRecord, the out-of-band
  
  extradata of H.264 in mp4, is as follows : First four bytes containing
  
  version, profile and level, one byte for the length size and one byte
  
  each for the number of SPS, followed by the SPS (each with its own size
  
  field), followed by a byte containing the number of PPS followed by the
  
  PPS with their size fields. While the number of SPS/PPS may be zero, the
  
  bytes containing these numbers are mandatory. Yet the byte containing
  
  the number of PPS has been ignored in two places :
  
  1. In the initial check for whether the extradata can contain an
  
  AVCDecoderConfigurationRecord. The minimum size is 7, not 6.
  
  2. No check is made for whether the extradata ended right after the last
  
  byte of the last SPS of the SPS array. Instead the first byte of the
  
  padding is read as if it were part of the extradata and contained the
  
  number of PPS (namely zero, given that the padding is zeroed). No error
  
  or warning was ever raised.
  
  This has been changed. Such truncated extradata is now considered
  
  invalid ; the check for 2. has been incorporated into the general size
  
  check.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/h264_mp4toannexb_bsf.c