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• How to specify an offset and a seek position for a video stream of a mp4 container ?

  29 mai 2019, par maximedupre

  It seems like I can have one or the other (-ss or -itsoffset), but never both at the same time, or they kind of cancel each other.

  I create output.mp4 with this command :

  ffmpeg -i input.mp3 -itsoffset 4 -t 4 -ss 3 -i input.mp4 -c:v copy output.mp4

  With this command, I expect the audio to start playing right away, and the video to start playing 4 seconds later, seeked at 3 seconds into the video.

  However, when I play input.mp4, the video starts only one second later than the audio (as opposed to 4 seconds). I suppose it does a "offset - seek = 1" type of thing.

  How can I prevent the seeking from affecting the offset ?

  Cheers !

• avformat/mux : Call check_packet() more directly

  16 mai 2020, par Andreas Rheinhardt

  avformat/mux : Call check_packet() more directly
  Call it directly from write_packets_common() instead of indirectly
  
  through prepare_input_packet().
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/mux.c

• ffmpeg output images filename with time position

  6 novembre 2020, par AoEmaster

  I am using ffmpeg to get some jpg from my video at a specific rate (one screenshot every 5 seconds) with this command :

  



  ffmpeg -i source -f image2 -r 1/5 %d.jpg


  



  This works and give me sequential filenames :

  



  1.jpg
2.jpg
3.jpg
4.jpg


  



  What if I need to know at which time those screenshots have been taken ? Something like a timestamp :

  



  00:00:00.0000.jpg
00:00:05.0000.jpg
00:00:10.0000.jpg
00:00:15.0000.jpg


  



  or the number of seconds :

  



  0.jpg
5.jpg
10.jpg
15.jpg


  



  I tried again with the new -frame_pts option :

  



  ffmpeg -i source -f image2 -r 1/5 -frame_pts 1 %d.jpg


  



  I got similar sequential filenames, but now they are starting from zero :

  



  0.jpg
1.jpg
2.jpg
3.jpg