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• avisynth : adapt 239d02eff3ffe9f7d40caa21dde50fb4a0e94c24 to dlsym

  30 mars 2019, par Stephen Hutchinson

  avisynth : adapt 239d02eff3ffe9f7d40caa21dde50fb4a0e94c24 to dlsym
  This commit was merged in a couple years ago as a no-op because we
  
  had already switched from GetProcAddress to dlsym some time before
  
  that.  However, not applying the actual cast causes warnings about
  
  FARPROC and when attempting to build FFmpeg in MSVC with AviSynth-GCC
  
  32-bit compatibility, those FARPROC warnings turn into FARPROC errors.
  

  • [DH] libavformat/avisynth.c

• Getting motion vector side data from ffmpeg from the compressed domain (without performing full decode)

  4 mai 2019, par John Allard

  The ffmepg source code comes with a file extract_mvs.c which is quite helpful in showing how to extract the motion vectors from an h264-encoded video file. Unfortunately, it performs a full decode before getting the motion vectors from the side data of the stream.

  One should be technically able to (as was confirmed by FFMPEG developer Carl Eugen in this thread https://ffmpeg.org/pipermail/libav-user/2016-December/009913.html) get the motion vectors from the compressed domain before performing a full decode step. This would obviously be less computationally intensive as one wouldn’t have to perform a full decode.

  Is it possible to do this with ffmpeg/libavcodec as is ? I know Carl said that it wasn’t possible but that was 3 years ago. If it is not currently possible, does anyone have any hints on how one would go about modifying the ffmpeg source code to do this ?

  Thanks

• I am trying to use the IMA audio encoder and all I get is silence (warning:noob !)

  9 avril 2019, par TerryYim

  o internet !

  As the tree said to the lumberjack, I’m stumped. I downloaded ffmpeg for the first time today and have had quite a lot of fun experimenting with it. So far, I’ve managed to get videos encoded and playing on my Mac OS 9 installation (in Quicktime) using the ’svq1’ video encoder and 16 bit pcm audio. I use this command :

  .\ffmpeg.exe -i .\cat.mp4 -vcodec svq1 -acodec pcm_s16le -ar 44.1k -ac 2 cat_cmon.mov

  However, when I try to switch the audio to adpcm_ima_qt (which I believe is what I should be using for Quicktime 4 - bear in mind that this software is 20 years old) all I get is silence. However, I’m getting silence when I try to play them in Windows too, so I know it’s not the Mac that’s at fault. Here’s what I’m trying to use :

  .\ffmpeg.exe -i .\rivalries.mp4 -vcodec svq1 -acodec adpcm_ima_qt -ar 44.1k -ac 2 rival.mov

  So I’m totally stumped. Am I doing something wrong ? If I am, it’s not something I can see myself. Would anyone be able to lend some wisdom as to how to get the IMA-encoded audio working ?

  Thank y’all !

  ADI.

  Edit : And, just to explain, the reason I want to use adpcm_ima_qt is because PCM is laggy and results in larger file sizes.