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• Revision f5209d7e01 : Remove rate component adjustment for AQ1 In AQ1 a rate adjustment was applied f

  21 novembre 2014, par Paul Wilkins

  Changed Paths :
   Modify /vp9/encoder/vp9_encodeframe.c

  
  
  Remove rate component adjustment for AQ1

  In AQ1 a rate adjustment was applied for blocks coded with a
  deltaq. This tends to skew the partition selection and cause
  rate overshoot.

  For example, consider a 64x64 super block where some but not all
  sub blocks are in a low q segment and some are in a high q segment.
  The choice of Q when considering large partition and transform sizes
  is defined by the lowest sub block segment id (currently this implies the
  lowest Q). If some parts of the larger partition are very hard this will
  cause a high rate component.

  The correct behavior here is for the rd code to discard the large partition
  choice and break down to sub blocks where some have low and some
  have high Q. However the rate correction factor above mask the high
  cost of coding at a larger partition size.

  Change-Id : Ie077edd0b1b43c094898f481df772ea280b35960

• ffmpeg -ss and -to (no re-encoding) doesn't cut at keyframes [closed]

  8 septembre 2023, par ZYinMD

  From a video, I want to clip out a part I like. It's roughly from 12:34 to 43:21, so I do :

  


  ffmpeg -i "input.mp4" -ss 12:34 -to 43:21 -c copy "output.mp4"


  


  The result is cut exactly at those timestamps, not at keyframes, so I get a few seconds of audio with frozen image at both ends. I believe this is due to negative start time.

  


  How do I tell ffmpeg to cut at closest keyframes ?

  


  I've tried -noaccurate_seek -i "input.mp4" -ss 12:34 but it has no effect.

  


  I've tried putting -ss in front, like -ss 12:34 -i "input.mp4", this does start the clip at a keyframe, but it makes 12:34 the new 00:00, so my -to won't work the same. Now I need to manually calculate the duration of my clip and put the duration after -to, but the calculation is too hard to be the best solution.

  


  I also tried adding -copyts suggested by this article, it sort of works, but it messes up the timeline, and the progress bar in the player shows a wrong total video length.

  


  (In case it matters, I'm using ffmpeg v6.0, input v=AVC and a=AAC)

  


• How to close a stream opened by FFmpeg ?

  31 mars 2016, par Daneo

  I’m currently playing around with FFmpeg, and based myself on this github project.

  I’d like the ability to close the stream when I want it to close.

  How could I achieve this ?
  If I just extract the part in the dealloc method and call that when needed it crashes.

  I’ve read about an interrupt callback that needs to be called, but I have no idea how to do so. (C-code isn’t in my current skillset, so understanding it is a bit hard).

  Callback I referred to, but have no idea how to use :

  pFormatCtx->interrupt_callback.opaque;
  
  pFormatCtx->interrupt_callback.callback;

  Is there a certain order I need to respect, things I need to do upfront or in the other methods ?

  Thanks !

  Current :

  -(void) stopCapturing {
  
      if (pFrame) av_free(&pFrame);
  
      if (pCodecCtx) avcodec_close(pCodecCtx);
  
  
  
      if (img_convert_ctx) sws_freeContext(img_convert_ctx);
  
      avpicture_free(&picture);
  
      if (pFormatCtx) avformat_close_input(&pFormatCtx);
  
  }