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• 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.

  


• FFMPEG Conact Demuxer Re-Encoding When Trying to Merge MP4s

  6 avril 2022, par Kyle Sinko

  I am trying to merge MP4 recordings straight out of OBS together into one MP4. From what I understand, I am using the concat demuxer to achieve this as it merges the files "extremely quickly" without re-encoding.

  


  I am using the command

  


  ffmpeg.exe -f concat -safe 0 -i "mylist.txt" -c copy video.mp4


  


  as explained in this post

  


  


  

  2. concat demuxer Use this method when you want to avoid a re-encode and your format does not support file-level concatenation (most files
used by general users do not support file-level concatenation).

  


  


  


  The command runs successfully, but the process takes a very long time. I assume the videos are being re-encoded as this is what shows :

  


  


  Output #0, mp4, to 'video.mp4' : Metadata :
encoder : Lavf58.51.100
Stream #0:0(und) : Video : h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x2160 [SAR 1:1 DAR 8:9], q=2-31, 1

  


  


  I'm unsure as to why the process is taking so long and want to know how I can merge the MP4 files into a single MP4 output file almost instantly.

  


• fftools/ffplay : do not write out of rdft visualization texture

  3 mars 2021, par Marton Balint

  fftools/ffplay : do not write out of rdft visualization texture
  If the window is resized it was possible that xpos pointed outside the
  
  visualization texture. By rearranging the overflow check we make sure this (and
  
  a crash) does not happen.
  We also don't have to use xleft for start position, as that is 0 anyways, and
  
  if we ever want to take into account xleft then the texture should be
  
  positioned accordingly when rendering.
  Signed-off-by : Marton Balint <cus@passwd.hu>
  

  • [DH] fftools/ffplay.c