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• Skipping silent parts of video with ffplay

  3 février 2021, par handy

  so I saw that I can cut the silent parts of an audio file. Is it possible to play a video file with ffplay and make it auto skip the silent parts using those audio filters ?

  


  Like using e.g. https://ffmpeg.org/ffmpeg-filters.html#silenceremove on the audio stream and then tell ffplay "skip the video where the silenceremove filter detects silence".

  


  I know that there are cases where the video might change in silence. That does not matter in my case. I know that https://github.com/WyattBlue/auto-editor could help me in any such edge case since it implements motion detection but I want to skip the generation of a new video file since it just takes too much ressources.

  


• How can I programmatically write and read random video watermarks ?

  13 novembre 2017, par GreenTriangle

  I spent a few minutes trying to think of a clearer way to word my title, but I couldn’t manage it, sorry.

  I want to essentially canary trap video files : I am (hypothetically, this is not real but a personal exercise) offering them up to 5,000 different people, and if one gets leaked, I want to know who leaked it. Metadata is too easily emoved, so what I’d like to do is add a random and subtle watermark to each file, and store information about that in a database.

  For example : on Joe Smith’s copy, a 10x10 pixel 80% transparent red square in the upper left corner for 5 frames. On Diane Brown’s copy, a full-width 5-pixel 90% transparent black bar on the bottom edge for 15 frames. Then, if I find a leaked copy, I could check it against the database.

  I know this still isn’t foolproof : cropping would break co-ordinates, hue/brightness transforms would break colour reading, cutting time would break timestamps. But if I did want to do this anyway, what would be a good strategy for it ?

  My idea was to generate PNG overlays randomly, split the video into parts with mkvtoolnix/ffmpeg, re-encode the middle part with ffmpeg + overlay filter, and then rejoin them. But is this silly when there’s a "proper" way to do it ? And what would I be doing to read the watermarks, which I can’t even really conceive of ?

• x86 : videodsp : Properly mark sse2 instructions in emulated_edge_mc as such.

  24 octobre 2013, par Ronald S. Bultje

  x86 : videodsp : Properly mark sse2 instructions in emulated_edge_mc as such.
  Should fix crashes or corrupt output on pre-SSE2 CPUs when they were
  
  using SSE2-code (e.g. AMD Athlon XP 2400+ or Intel Pentium III) in
  
  hfix or hvar single-edge (left/right) extension functions.
  Signed-off-by : Janne Grunau <janne-libav@jannau.net>
  

  • [DH] libavcodec/x86/videodsp.asm
  • [DH] libavcodec/x86/videodsp_init.c