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• avformat/avisynth : remove atexit() handler

  7 juillet 2024, par Stephen Hutchinson

  avformat/avisynth : remove atexit() handler
  The atexit() handler in the avisynth demuxer was added because
  
  there was a conflict in AvxSynth that arose due to their use
  
  of C++ global objects, particularly in relation to having
  
  added a logging function relying on log4cpp.
  This conflict was responsible for causing a segfault on exit.
  
  It did not affect Windows with the (at the time) upstream
  
  AviSynth 2.5 and 2.6, nor does it affect AviSynth+.
  Unfortunately, none of this was actually shielded by ifdefs
  
  indicating the fact it was only needed for AvxSynth, so four
  
  years ago when AviSynth+ replaced AvxSynth as the handler
  
  for AviSynth scripts on Unix-like OSes, the fact that the
  
  atexit handler was no longer necessary was overlooked.
  Signed-off-by : Stephen Hutchinson <qyot27@gmail.com>
  

  • [DH] libavformat/avisynth.c

• lavu/riscv : grok B as an extension

  22 juillet 2024, par Rémi Denis-Courmont

  lavu/riscv : grok B as an extension
  The RISC-V B bit manipulation extension was ratified only two months ago.
  
  But it is strictly equivalent to the union of the zba, zbb and zbs
  
  extensions which were defined almost 3 years earlier. Rather than require
  
  new assembler, we can just match the extension name manually and translate
  
  it into its constituent parts.
  

  • [DH] libavutil/riscv/asm.S

• Construct fictitious P-frames from just I-frames [closed]

  25 juillet 2024, par nilgirian

  Some context.. I saw this video recently https://youtu.be/zXTpASSd9xE?si=5alGvZ_e13w0Ahmb it's a continuous zoom into a fractal.

  


  I've been thinking a whole lot of how did they created this video 9 years ago ? The problem is that these frames are mathematically intensive to calculate back then and today still fairly really hard now.

  


  He states in the video it took him 33 hours to generate 1 keyframe.

  


  I was wondering how I would replicate that work. I know by brute force I can generate several images files (essentially each image would be an I-frame) and then ask ffmpeg to compress it into mp4 (where it will convert most of those images into P-frames). I know that. But if I did it that way I calculated it'd take me 6.5 years to render that 9min video (at 30fps, 9 years ago).

  


  So I imagine he only generated I-frames to cut down on time. And then this person somehow created fictitious P-frames in-between. Given that frame-to-frame are similar this seems like it should be doable since you're just zooming in. If he only generated just the I-frames at every 1 second (at 30fps) that work could be cut down to just 82 days.

  


  So if I only want to generate the images that will be used as I-frames could ffmpeg or some other program just automatically make a best guess to generate fictitious P-frames for me ?