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• lavu/riscv : CPU flag for the Zbb extension

  2 octobre 2022, par Rémi Denis-Courmont

  lavu/riscv : CPU flag for the Zbb extension
  Unfortunately, it is common, and will remain so, that the Bit
  
  manipulations are not enabled at compilation time. This is an official
  
  policy for Debian ports in general (though they do not support RISC-V
  
  officially as of yet) to stick to the minimal target baseline, which
  
  does not include the B extension or even its Zbb subset.
  For inline helpers (CPOP, REV8), compiler builtins (CTZ, CLZ) or
  
  even plain C code (MIN, MAX, MINU, MAXU), run-time detection seems
  
  impractical. But at least it can work for the byte-swap DSP functions.
  

  • [DH] libavutil/cpu.c
  • [DH] libavutil/cpu.h
  • [DH] libavutil/riscv/cpu.c
  • [DH] tests/checkasm/checkasm.c

• Creating periodic offsets with ffmpeg segment muxer for seamless ffmpeg-concat transitions

  30 janvier 2021, par Soren Wray

  Suppose I begin with a 1 minute video with a framerate output of 24 frames/second and then use ffmpeg's segment muxer to split it into 60 equal parts of 1 second each with the timesptamps reset :

  


  ffmpeg -i input.mp4 -map 0 -f segment -segment_time 1 -reset_timestamps 1 -g 24 output_%03d.mp4

  


  I then use ffmpeg-concat to string output_000.mp4-output_059.mp4 together into a single video with a periodic 0.5 second dreamy transition effect between each segment : ffmpeg-concat -t dreamy -d 500 -o dreamy.mp4 output_*.mp4

  


  Unfortunately, the transition effects introduce a negative 0.5 second offset between the segments, resulting in a video that is 32 seconds in duration. I don't want to deform the audio and video in this manner. I want to use transition effects without changing the duration or creating any other syncing issues. How to best achieve these seamless transitions is the question.

  


  One potential solution would be to add an offset to the segments, e.g. 0.25 seconds at the beginning and end of every segment, such that the segment muxer produces 60 segments of 1.5 second duration from a 1 minute video. In this manner, the 0.5 second transition effects should blend seamlessly into the offsets.

  


  I don't know where to begin to achieve this potential solution. I've read the official guide, but I can't decipher the relevant filter options for this particular use case. ffmpeg-concat doesn't seem to provide any native options around this problem either.

  


• utvideoenc : Enable support for multiple slices and use them

  14 février 2014, par Jan Ekström

  utvideoenc : Enable support for multiple slices and use them
  The official Ut Video decoder only threads with slices, thus until
  
  now any files encoded by the libavcodec encoder have only been
  
  decodable with a single thread. The default slice count is now
  
  set to subsampled_height / 120.
  Also sets slices to 1 for the Ut Video encoder tests to keep them
  
  green.
  Signed-off-by : Derek Buitenhuis <derek.buitenhuis@gmail.com>
  

  • [DBH] libavcodec/utvideoenc.c
  • [DBH] tests/fate/utvideo.mak