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• ffmpeg - How to auto crop Harry Potter moving newspaper style video ?

  18 mai 2019, par hahahhhhhha

  The Harry Potter moving newspaper is like a video overlay on a static background. Here is an example youtube video :
  https://youtu.be/qQUUNmd3aco?t=1m17s the video starting from 1min, 17sec.

  HOWTO crop only the video part ? I have an image to show what i mean by the moving newspaper and what area does the video locate and what is the static background part. Please refer to the image. The area I draw by pink is where i mean by real video and any area except the video, is the static part.

  here is an illustration image :
  https://imgur.com/s6vRqek

  I understand if the frame size of the video does not change, I can specify the w, h, x, y to crop. But what if the frame size changes ? ie. w, h, x, y changes.(w, h : width, height of the video. x, y： Coordinate system starting point ) Is there a way to autodetect the static part and only crop the real video part ? like ffmpeg cropdetect for letterboxing. I tried cropdetect but failed. Any suggestion is welcome and I prefer using ffmpeg but any other softwares are welcome !

• Why does ffmpeg return a different framecount than ffprobe for the same file ?

  5 mars 2018, par Greg

  I’m trying to count the number of frames in a video but ffmpeg and ffprobe are giving me two different answers.

  $ time ffprobe -v error -count_frames -select_streams v:0 -show_entries stream=nb_read_frames -of default=nokey=1:noprint_wrappers=1 myvideo.mp4
  
  2858
  
  
  
  real    0m2.987s
  
  user    0m2.740s
  
  sys     0m0.172s

  When I check the same file with ffmpeg I get 2 more frames...

  $ time ffmpeg -y -i myvideo.mp4 -vcodec copy -acodec copy -f null /dev/null 2>&1 | grep 'frame=' | awk '{print $2}'
  
  2860
  
  
  
  real    0m0.127s
  
  user    0m0.080s
  
  sys     0m0.032s

  I used ffprobe to output all of the frames and count the number of "[FRAME]"s in the resultant output...

  ffprobe -i myvideo.mp4 -show_frames -v error | grep -o '\[FRAME\]' | wc -l
  
  2858

  Which as you can see shows the number ffprobe thought there were.

  Obviously I would prefer to use ffmpeg here because it is significantly faster than ffprobe and I am dealing with thousands of videos that need parsing and indexing. However the failure isn’t consistent across multiple videos ; sometimes it’s 1 out, other times it’s 2 or more...

  Unfortunately, I have been counting frames for the past two years using the ffmpeg method, so I have a significant library of videos to reprocess now ... he gulps... I guess its a good way to verify the readability of the files on the cluster... even so, its going to take probably a few weeks to recalculate all of the existing video frame sizes.

• How to play every audio frame using python-ffpmeg ?

  15 octobre 2019, par Gflunky

  I have audio frames (numpy.ndarray) and i want to play them in real time using ffmpeg. How can i do that ?