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• avformat/utils : Move the reference to the packet list

  20 septembre 2019, par Andreas Rheinhardt

  avformat/utils : Move the reference to the packet list
  Up until now, ff_packet_list_put had a flaw : When it moved a packet to
  
  the list (meaning, when it ought to move the reference to the packet
  
  list instead of creating a new one via av_packet_ref), it did not reset
  
  the original packet, confusing the ownership of the data in the packet.
  
  This has been done because some callers of this function were not
  
  compatible with resetting the packet.
  This commit changes these callers and fixes this flaw. In order to
  
  indicate that the ownership of the packet has moved to the packet list,
  
  pointers to constant AVPackets are used whenever the target of the
  
  pointer might already be owned by the packet list.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  
  Signed-off-by : James Almer <jamrial@gmail.com>
  

  • [DH] libavformat/utils.c

• Looping 2 videos simultaneously until audio file ends in FFMPEG

  20 septembre 2022, par Fin Cottle

  I'm very new to ffmpeg, learning quickly but struggling to find a solution to the following.

  


  I would like to be able to loop 2 videos until the end of an extra audio file.
One of the videos will be a base & the other will be an overlay of 50% opacity on top of the base.

  


  I've got the gist of how to execute these within other operations (e.g. the 50% opacity, or the looping of a single video until the end of an audio file, these don't need to be answered here), but the looping of both videos until the end of the separate audio is proving challenging.

  


  Here's where I've got so far :

  


  ffmpeg -stream_loop -1 -i base.mp4 -i overlay.mp4 -i audio.mp3 -filter_complex "[0:v]setpts=PTS-STARTPTS[top]; [1:v]setpts=PTS-STARTPTS, format=yuva420p,colorchannelmixer=aa=0.5[bottom]; [top][bottom]overlay=shortest=1[v1]" -map "[v1]" -map 2:a -vcodec libx264 -y out.mp4


  


  This loops the base until the end of the overlay, but then freezes the base & overlay until the end of the audio (as the audio is longer).

  


  One solution may be to loop v1 until the end of the audio ? How would I go about this ?

  


  Either way, no matter the length of either video, the final output should be the length of the audio.

  


  My implementation could be pretty messy as my attempts are all amalgamations of internet answers & research without knowing the full meaning of each param, so please let me know if anything is wrong.

  


  Thanks in advance.

  


• Piping input AND output of ffmpeg in python

  5 mars 2019, par bluesummers

  I’m using ffmpeg to create a video, from a list of base64 encoded images that I pipe into ffmpeg.

  Outputting to a file (using the attached code below) works perfectly, but what I would like to achieve is to get the output to a Python variable instead - meaning piping input and piping output but I can’t seem to get it to work

  My current code :

  output = os.path.join(screenshots_dir, 'video1.mp4')
  
  
  
  cmd_out = ['ffmpeg',
  
             '-y',  # (optional) overwrite output file if it exists
  
             '-f', 'image2pipe',
  
             '-vcodec', 'png',
  
             '-r', str(fps),  # frames per second
  
             '-i', '-',  # The input comes from a pipe
  
             '-vcodec', 'png',
  
             '-qscale', '0',
  
             output]
  
  
  
  pipe = sp.Popen(cmd_out, stdin=sp.PIPE)
  
  
  
  for screenshot in screenshot_list:
  
      im = Image.open(BytesIO(base64.b64decode(screenshot)))
  
      im.save(pipe.stdin, 'PNG')
  
  
  
  pipe.stdin.close()
  
  pipe.wait()

  This results in a working mp4, but I would like to avoid saving to local.

  Running the same code with changing output to '-' or 'pipe:1' and adding stdout=sp.PIPE results in an error

  [NULL @ 0x2236000] Unable to find a suitable output format for ’pipe :’