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• Improve ffmpeg scene detection in particular scenario

  17 septembre 2021, par Nobody-Knows-I-am-a-Dog

  I have 50 hours of video where a speaker is in the lower right corner of the video and the by far larger part of the video consists of slides in the center. The speaker moves a bit, the slides transition into the video. I need to detect the time codes of the slide transitions. +- 1 second precision is fine. I am playing around with select filters in ffmpeg such as ffmpeg -i lecture.mp4  -filter:v "select='gt(scene,0.1)',showinfo"   -f null - but I have remaining problems where some help or hint would be highly appreciated.

  


  Problem 1 : Speaker movement occasionally triggers false positives. If there is some possibility to restrict frame comparison to a certain (spatial, cropped) area of the scene then I could focus on the slide area and this would greatly help.

  


  Problem 2 : Speed of slide transition is slow so I occasionally miss a transition since the change from frame(n) to frame(n+1) is too small. It would be great if I could compare, for example, frame(n) to frame(n+10) for threshold detection. ffmpeg scene detection : check only every nth frame ? does not help here, because it only checks every n-th frame but still compares a frame with its immediate neighbor.

  


  Of course, both problems can be solved by producing a cropped version with reduced framerate. However, I am looking for a solution where I can do this in a single pass with some complex filter expression ... and this is exactly the place where my own experience with ffmpeg fails me and where I would appreciate some help.

  


  Problem 3 : Occasionally a single slide transition triggers several times in a row throughout the transition. I have no idea how to solve this in ffmpeg.

  


• Combining audio and multiple videos with FFMPEG [closed]

  6 novembre 2023, par Lee P

  I am working on a ffmpeg script to combine two videos with one audio file. The first video file should start after about 6 seconds and the second after about 40 seconds, and there should be a padding with a black screen between the two videos.
However, it only seems to add the first video clones the final frame as the padding.

  


  Here is my current script :

  


  ffmpeg -i video_0.mp4 -i video_1.mp4 -i audio.mp4 -filter_complex "[0:v] tpad=start_duration=5927ms:start_mode=add:color=black:stop_mode=add:color=black; [1:v] tpad=start_duration=44901ms:start_mode=add:color=black:stop_mode=add:color=blackconcat=n=2" -map 2:a -f mp4 -movflags +faststart composite_recording.mp4


  


  The final video timing should be :

  


  00:00-00:06 — black screen
  
00:06-00:24 — first video
  
00:24-00:40 — black screen
  
00:40-00:48 — second video

  


  I tried setting different values for the tpad start_duration for the second video and expected it to start the second video at around 40 seconds into the audio, however it didn't change anything.

  


• Anomalie #2745 : Icone des Itruc

  18 décembre 2013, par b b

  Pour info, la règle à ajouter au htaccess :

  RewriteRule ^apple-touch-icon(-(\d+x\d+)) ?(-precomposed) ?[.]png$ spip.php ?page=apple-touch-icon.png&size=$2 [QSA,L]