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• Clip long video segment quickly

  30 janvier 2020, par PRMan

  Let’s say I have a video called Concert.mp4. I want to extract a performance from it quickly with minimal reencoding. I want to do the equivalent of this, but faster :

  ffmpeg -i "Concert.mp4" -ss 00:11:45 -to 00:18:15  -preset veryfast -y artist.mp4

  This takes 17 seconds, which is way too long for our needs.

  Now, it turns out that 11:45 and 18:15 don’t fall on iframes, so if you try this you will get a 3 second delay at the beginning before the video shows :

  ffmpeg -i "Concert.mp4" -ss 00:11:45 -to 00:18:15 -c copy -y artist.mp4

  Running this command, we can see where we need to cut :

  ffprobe -read_intervals "11:00%19:00" -v error -skip_frame nokey -show_entries frame=pkt_pts_time -select_streams v -of csv=p=0 "Concert.mp4" > frames.txt

  So what we need to do is encode the first 3.708 seconds, copy the middle, and then encode the last 5.912 seconds.

  I can get the 3 segments to all look perfect (by themselves) like this :

  ffmpeg -ss 698.698 -i "Concert.mp4" -ss 6.302 -t 3.708 -c:v libx264 -c:a copy -c:s copy -y clipbegin.mp4
  
  
  
  ffmpeg -ss 708.708 -to 1089.088 -i "Concert.mp4" -c copy -y clipmiddle.mp4
  
  
  
  ffmpeg -ss 1089.088 -i "Concert.mp4" -t 5.912 -c:v libx264 -c:a copy -c:s copy -y clipend.mp4
  
  
  
  ffmpeg -f concat -i segments.txt -c copy -y artist.mp4

  segments.txt of course contains the following :

  file 'clipbegin.mkv'
  
  file 'clipmiddle.mkv'
  
  file 'clipend.mkv'

  I saw this solution presented here, but no amount of tweaking gets it to work for me :

  https://superuser.com/a/1039134/73272

  As far as I can tell, this method doesn’t work at all. It crashes VLC pretty hard no matter what I try.

  The combined video keeps glitching after the 3 seconds, probably because the PTS times are different or something (using some options, I have seen warning messages to this effect). Is there anything I can add to the commands above to get this to work ? The only requirement is that the middle command must not re-encode the video, but must do a fast copy.

  Thanks in advance.

• aac : Fix TNS decoding for the 512 sample window family.

  24 décembre 2013, par Alex Converse

  aac : Fix TNS decoding for the 512 sample window family.
  

  • [DH] libavcodec/aacdec.c
  • [DH] libavcodec/aactab.c
  • [DH] libavcodec/aactab.h

• Gstreamer : Invalid address family

  3 mars 2023, par Goonturr

  May I ask how do you make sense of this error from gstreamer ?

  


  

  


  I am trying to stream a rtsp server which ffmpeg and vlc are able to but gstreamer is giving me the above error.