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• Is there a way to extract a video frame, encode a sentence behind it, put it back, and then decode it ?

  29 juillet 2021, par Jesse Hix

  I am trying to do stenography on an MP4 video where I am pulling a frame out at a certain time, 5.52 sec, saving that frame as a jpg or jpeg using any image stenography tool, in this case stegosuite, to encode a sentence behind the image and then reinsert that image back into the video at the same time and then extract it again with the same command and using the same steno tool read the message.

  


  Up until decoding the message everything runs without issue.
I know that it is not working because the videos are not the same in size meaning that the frankenstein video is not the same as the original and thus messing up the frame extraction.

  


  Question :
  Is there a way to extract a frame encode a sentence behind it put it back and then decode it ?

  


  What I tried :
  
Used to extract the frame both times :

  


  ffmpeg -ss 5.52 -i original.mp4 -vframes 1 frames_%d.jpg


  


  Used to combine the image back into the video :

  


  ffmpeg -i original.mp4 -i frames_1_embed.jpg -filter_complex "[1]setpts=5.52/TB[im];[0][im]overlay=eof_action=pass" -c:a copy out_1.mp4


  


• Revision 6253cc9279 : Speed setting review. Substantial reworking of the speed vs quality trade offs

  1er octobre 2013, par Paul Wilkins

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

  
   Modify /vp9/encoder/vp9_onyx_if.c

  
   Modify /vp9/encoder/vp9_onyx_int.h

  
   Modify /vp9/encoder/vp9_rdopt.c

  
  
  Speed setting review.

  Substantial reworking of the speed vs quality trade offs for
  speed 1 and 2.

  In this patch I am attempting to freeze the "quality" meaning of
  speeds 1 and 2 relative to speed 0 so that in future we can
  better evaluate progress.

  I am targeting :
  Speed 1 quality -5% vs speed 0.
  Speed 2 quality -10% vs speed 0

  It is inevitable that quality will still fluctuate a little as we adjust
  settings and add new features, but we will attempt to keep as
  close as possible to these values. Above speed 2 things will remain
  a bit more fluid for now.

  In this patch speed 1 is approximately 4-5x as fast as speed 0. This
  is similar to before but the quality hit is a lot less. Likewise speed 2
  is approximately 2x as fast as speed 1 but is similar in quality to the
  previous speed 1 configuration.

  Also slight change to behavior of FLAG_EARLY_TERMINATE to insure
  all reference frames get at least one rd test. Important for very low
  variance regions.

  WIP :- Added a new speed level with old speed 4 becoming speed 5.
  Speed 3 and 4 tradeoffs still WIP

  Change-Id : Ic7a38dd7b5b63ab1501f9352411972f480ac6264

• doc/ffmpeg : improve -disposition, -stats, and -progress documentation

  17 octobre 2024, par Soma Lucz

  doc/ffmpeg : improve -disposition, -stats, and -progress documentation
   disposition :
  
  Clarify the meaning of the default value, and how the '+' and '-'
  
  prefixes work. Add more examples.
   stats :
  
  Clarify that it appears as an "info"-level log.
   progress :
  
  Add info about the "progress" key's value being "continue" or "end".
  
  Add an example of logging to stdout.
  Signed-off-by : Soma Lucz <luczsoma@gmail.com>
  
  Signed-off-by : Anton Khirnov <anton@khirnov.net>
  

  • [DH] doc/ffmpeg.texi