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• avcodec/ffv1 : flip half of float16 and Compactify floats

  18 janvier, par Michael Niedermayer

  avcodec/ffv1 : flip half of float16 and Compactify floats
  float16 (and more so float32) have many odd values
  
  half the values are negative, many are larger than "1.0"
  
  and many values are very close to 0.
  Storing the 16bits as is, looses compression because of the mixture
  
  of dense and sparse regions and also many completely unused ones.
  This simply remaps the 65536 values so no unused values remain
  
  This improves compression by about 1.5% for the ACES_OT_VWG_SampleFrames testset
  
  (this testset contains all kind of funny values including many images
  
   with negative rgb values)
  The space needed for the map is insignificant compared to the
  
  compression gained
  This patch also flips half the float range as it can be done
  
  using the same table.
  Sponsored-by : Sovereign Tech Fund
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/ffv1.h
  • [DH] libavcodec/ffv1dec_template.c
  • [DH] libavcodec/ffv1enc_template.c

• ffmpeg problem video duration of an hour and a half

  14 mai 2024, par Bruno Munné

  When start record i call an api /start-record which does :

  


  const ffmpeg = spawn("ffmpeg", [
        "-i",
        rtsp,
        "-c:v",
        "copy",
        "-an",
        "-f",
        "flv",
        `${filename}.flv`,
      ]);
ffmpegProcesses[rtsp] = {
        process: ffmpeg,
        filename,
      };


  


  When stop the record i call an api /stop-record which does :

  


  ffmpegProcesses[rtsp].process.kill("SIGKILL");
ffmpegProcesses[rtsp].process.on("exit", async () => {
   const ffmpeg = spawn("ffmpeg", [
          "-i",
          `${filename}.flv`,
          "-c:v",
          "libx264",
          "-preset",
          "fast",
          "-crf",
          "30",
          "-an",
          `${filename}.mp4`,
        ]);

    ffmpeg.on("exit", async () => {
        uploadToS3()
    })

})


  


  If the recording is less than or equal to approximately 1 hour it works perfectly, but if the recording is 1 and a half hours it already breaks and it does not correctly generate the files, nor the flv nor the conversion to mp4

  


  I hope my program works the same way it does for 1 hour recordings

  


• riscv : set fast half-precision conversion

  16 novembre 2023, par Rémi Denis-Courmont

  riscv : set fast half-precision conversion
  This is only supported at compilation time. If Zfhmin is supported, then
  
  conversions are fast, which is what the flag is used for. At this time,
  
  run-tiem detection is not possible, as in not supported by Linux. But even
  
  if it were, the current FFmpeg approach seems unable to deal with it (same
  
  problem as on x86, really).
  

  • [DH] configure