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• python 3 using ffmpeg in a subprocess getting stderr decoding error

  4 mai 2024, par jdauthre

  I am running ffmpeg as a subprocess and using the stderr to get various bits of data like the subtitles stream Id's. It works fine for most videos, but one with japanese subtitles results in an error :

  


  'charmap' codec can't decode byte in position xxx : character maps to

  


  Much googling suggests the problem is that the japanese requires unicode, whereas English does not. Solutions offered refer to problems with files, and I cannot find a way of doing the same with the stderr. Relevent Code is below :

  


  command = [ffmpeg,"-y","-i",fileSelected,"-acodec","pcm_s16le",
                  "-vn","-t","3", "-f",            "null","-"]
print(command)   
proc = subprocess.Popen(command,stderr=PIPE,Jstdin=subprocess.PIPE,
                            universal_newlines=True,startupinfo=startupinfo)
  
stream = ""    
for line in proc.stderr:
    try:
        print("line",line)
    except exception as error:
        print("print",error)
        line = line[:-1]
        if "Stream #" in line:
            estream = line.split("#",1)[1]
            estream =estream.split(" (",1)[0]
            print("estream",estream)
            stream = stream + estream +"\n"  #.split("(",1)[0] 
            stream = stream + estream +"\n"


  


• Revision 17501 : only generate a random serial number for one stream, and increment it ...

  10 octobre 2010, par oggk — Log

  only generate a random serial number for one stream, and increment it for
  the subsequent streams, to avoid a possible (though unlikely) collision
  OK’d by j.

• ffmpeg - overlay a video with rounded corners

  4 novembre 2019, par asi

  I am successfully using overlaying a scaled (smaller) video on top of a larger one but am struggling to understand how could I give the small video a rounded corners mask.

  Edit

  thanks to @loogan comment I’ve managed to get a working command that created applies a circular mask :

  ffmpeg 
  
      -i main.mp4 
  
      -i vignette.mp4 
  
      -filter_complex 
  
        [1:v]scale=300:-1[scaled];
  
        [scaled]split [scaled0][scaled11]; 
  
        [scaled0]trim=end_frame=1,geq='st(3,pow(X-(W/2),2)+pow(Y-(H/2),2));if(lte(ld(3),780*780),255,0)':3:3,loop=-1:1,setpts=N/FRAME_RATE/TB[mask];
  
      [scaled1][mask]alphamerge[cutout];
  
      [0][cutout]overlay=x=W-w:y=0[v];
  
      -map [v] 
  
      -map [a]  
  
      output.mp4

  but how to get from a circle to a rounded rect still eludes me. cant quite get what are the params that geq expects and the math to generate them.

  assuming that the video that needs masking is 200 * 300 and the corners should have a 5px radius, is there a geq command that can create this mask ? maybe en ellipse ?

  or maybe a better way would be to use a pre-made png as a mask ?

  any insights welcome