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• fftools/ffmpeg_demux : Don't use fake object with av_opt_eval

  6 octobre 2023, par Andreas Rheinhardt

  fftools/ffmpeg_demux : Don't use fake object with av_opt_eval
  The av_opt_eval family of functions emits errors messages on error
  
  and can therefore not be used with fake objects when the AVClass
  
  has a custom item_name callback. The AVClass for AVCodecContext
  
  has such a custom callback (it searches whether an AVCodec is set
  
  to use its name). In practice it means that whatever is directly
  
  after the "cc" pointer to the AVClass for AVCodec in the stack frame
  
  of ist_add() will be treated as a pointer to an AVCodec with
  
  unpredictable consequences.
  Fix this by using an actual AVCodecContext instead of a fake object.
  Reviewed-by : Anton Khirnov <anton@khirnov.net>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] fftools/ffmpeg_demux.c

• Glitchy mp4 File saved with Matplotlib Animation via ffmpeg

  9 janvier 2024, par Jacob Ivanov

  I am attempting to save an .mp4 file using matplotlib.animation to output some simulation results. The relevent section is as follows :

  


  ANI = FuncAnimation(fig, update, init_func = lambda : None, frames = range(0, 21300, 50))
ANI.save("[removed]/anim/v6 256 unforced 0.02.mp4", dpi = 600, fps = 30, writer = 'ffmpeg')


  


  However, it appears that there is some issue in the produced .mp4 file, as when I use macOS Quicktime to view the file, it pauses on certain frames, and restarts later on. It appears to consistently pause on the same frame a few seconds in. In order to check if Quicktime was the problem, I opened some random .mp4 files I found in a family group chat, and did not have this issue.

  


  I also tried viewing this .mp4 file with VLC, which had no issue, and played without any glitches. The Slack media viewer built into the app pauses similar to Quicktime.

  


  The following are all relevant versions :

  


  

  • macOS : 14.2.1 (23C71)

  


  • Python : 3.10.9 via Homebrew

  


  • Matplotlib : 3.6.2

  


  • ffmpeg : 6.1.1

  


  


  If it would help, I can also provide the .mp4 file itself, but I'm not quite sure how to upload it. I will be happy to provide any additional information as well.

  


  Unfortunately, I'm not very familiar with video rendering, but I would appreciate any help anyone could provide. Thank you in advance !

  


• lavu/random_seed : use arc4random() when available

  7 décembre 2015, par Ganesh Ajjanagadde

  lavu/random_seed : use arc4random() when available
  arc4random() was designed as a superior interface for system random
  
  number generation, designed for OpenBSD and subsequently incorporated by
  
  other BSD’s, Mac OS X, and some non-standard libc’s. It is thus an improvement to
  
  use it whenever available.
  As a side note, this may or may not get included in glibc, and there is
  
  a proposal to create a posix_random family based on these ideas :
  
  http://austingroupbugs.net/view.php?id=859.
  Tested on Mac OS X.
  Signed-off-by : Ganesh Ajjanagadde <gajjanagadde@gmail.com>
  

  • [DH] configure
  • [DH] libavutil/random_seed.c