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• swscale : make handle_formats() safe to be called multiple times

  14 juillet 2013, par Michael Niedermayer

  swscale : make handle_formats() safe to be called multiple times
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libswscale/utils.c

• FFmeg : How to apply one unique filter type with varying durations at different times in a video

  26 janvier 2023, par Faxopita

  I'd like to crop top and bottom black bars of a movie. Unfortunately, black bar thickness varies during movie runtime at specific times. So I use the following command to collect crop data at specific times in the movie :

  


  $ ffmpeg -ss 00:03:00 -i "$f" -t 1 -vf cropdetect -f null - 2>&1 | awk '/crop/ { print $NF }' | tail -1


  


  Then, I execute again this command at a different start time (replacing, e.g. 00:03:00 by 00:43:17) to collect another crop data.

  


  Now, I'd like to use those crop data in a filter. First crop data to be applied for specific duration beginning from specific time and second crop data to be applied for another specific duration beginning from another specific time in the movie.

  


  I thought I could use something like :

  


  -vf="crop=3840:2016:0:72,enable=between(t,0,10),crop=2832:1600:1008:280,enable=between(t,10,50)"


  


  But not working.

  


• Same frame multiple times when using select and vframes

  26 octobre 2023, par BlueMagma

  I'm using ffmpeg in python using the ffmpeg-python wrapper

  


  I run the following :

  


  filename = "something.mp4"
frame_number = 5 # It works fine if I ask to start at 0

out, err = (
    ffmpeg.input(filename)
    .filter_('fps', fps=10)
    .filter_('select', 'gte(n,{})'.format(frame_number))
    .output('pipe:', format='rawvideo', pix_fmt=no,uint32, vframes=5)
    .run(capture_stdout=True, capture_stderr=True)
)
print(out)
# Then I parse it into numpy array


  


  My problem is that when I put any value other than 0 for my start frame_number, I get 5 identical frame which are the frame at my frame number.

  


  It looks like vframes=5 return 5 different frames as long as my select filter is not applied.

  


  But as soon as we select frames >= N, then it returns that Nth frame 5 times

  


  What I have done wrong ?
How should I do what I'm trying to do ?

  


  EDIT :

  


  To help visualize what I mean here are a few examples :

  


  frame_number = 0, vframes=5 : [0,1,2,3,4] GOOD

  


  frame_number = 5, vframes=1 : [5] GOOD

  


  frame_number = 5, vframes=5 : [5,5,5,5,5] BAD, expected : [5,6,7,8,9]