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• Why the output of the ffmpeg-python doesn't match the image shape ?

  9 novembre 2019, par Swi Jason

  I used the ffmpeg-python module to convert video to images. Specifically, I used the code provided by the official git repo of ffmpeg-python, as below

  out, _ = (
  
      ffmpeg
  
      .input(in_filename)
  
      .filter('select', 'gte(n,{})'.format(frame_num))
  
      .output('pipe:', vframes=1, format='image2', vcodec='mjpeg')
  
      .run(capture_stdout=True)
  
  )
  
  im = np.frombuffer(out, 'uint8')
  
  print(im.shape[0]/3/1080)
  
  # 924.907098765432

  The original video is of size (1920, 1080) and pix_fmt ’yuv420p’, but the outputs of the above code is not 1920.

  I have figured out by myself that the output of ffmpeg.run() is not a decoded image array, but a byte string encoded by JPEG format. To restore the image into a numpy array, simply use the cv2.imdecode() function. For example,

  im = cv2.imdecode(im, cv2.IMREAD_COLOR)

  However, I can’t use opencv on my embeded Linux system. So my question now is that, can I get numpy output from ffmpeg-python directly, without the need of converting it by opencv ?

• ffmpeg - seamless crossfade loop for the part of video

  14 janvier 2021, par Flamin GO

  I need to apply crossfade to the last X frames of a video with the first X frames in order to obtain a seamless loop, but making this for the necessary part of video.

  


  Here's the answer for looping the entire video.

  


  Currently what I have :
(Whole video duration = 25. Cutted (result) part = 15 sec (from 5 to 20 sec pos). Transition = 1 sec.)

  


  ffmpeg -i input.mp4 -ss 5 -to 20 -filter_complex
    "[0]split[body][pre];
     [pre]trim=duration=1,format=yuva420p,fade=d=1:alpha=1,setpts=PTS+( (15+(5-1)) /TB)[jt];
     [body]trim=1,setpts=PTS-STARTPTS[main];
     [main][jt]overlay"  -c:v libx264 -preset veryslow -b:v 2500K output.mp4
 


  


  In this case, everything works, but at the end of the resulting video, a piece from the original video is superimposed, which starts from 0 to 1 second, and not from 4 to 5 seconds of the original video, as it should be.

  


  I read the official ffmpeg documentation, tried some actions on "start/end" parameters for "trim/fade" with changing of "setpts", but I always got just another batch of bugs.

  


• Need available FFMPEG transition effect commands for single video file in android ?

  16 juillet 2019, par Gopinathan B

  I am able to produce Fade In & Fade Out transition effect for single video file. I am fail to get other transition effects for single video. Some of the transition commands are not correct. There is no official documentation to do.

  This will fade in video for 5 sec in start.

  "-y", "-i", masterVideoFile!!.absolutePath, "-acodec", "copy", "-vf", "fade=t=in:st=0:d=5", outputFile.absolutePath

  This will fade out video for 5 sec in end.

  "-y", "-i", masterVideoFile!!.absolutePath, "-acodec", "copy", "-vf", "fade=t=out:st=$finalTime:d=5", outputFile.absolutePath

  I need video to transition from Right to Left, Left to Right, Top to Bottom & Bottom to Top and start playing video afterwards.