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• Shifting audio in MPEG4 content and manipulating atoms

  10 janvier 2018, par LLL

  1. Shift audio

  I use ffmpeg / avconv quite often ... and usually I hate it.
  Those tools do what they are instructed to do about 30% of the time. I could give you countless examples but I don’t want to start flame war, so please help me with my current problem (really easy one).

  I wanted to shift audio (content is standard mp4 file with aac and h264 tracks), so I have found a "highly upvoted" solution :

  https://superuser.com/a/983153/758887

  the only problem with it is that it doesn’t work. I downloaded latest stable ffmpeg (even on windows as in the thread, so it’s version was 3.4.1) and executed command without changing literaly anything :

  ffmpeg.exe -i "movie.mp4" -itsoffset 3.84 -i "movie.mp4" -map 0:v -map 1:a -vcodec copy -acodec copy "movie-audio-delayed.mp4"

  Result was no shift (I expected audio to be 3.84s late).

  2. Remove MPEG4 atoms

  I would be also grateful if you could recommend some tool for removing MPEG4 boxes from content. For examining MPEG4 content I use MP4 Explorer / Codec Visa (limited) on Windows and AtomicParsley on Linux, however they only print atoms and I would like to edit / remove them. For example MP4Box can remove whole moov->track with "-rem" option but what if I would like to remove moov->track->edts only ?

• Strange error [adding watermark to flv video with ffmpeg on linux centos 6]

  20 juillet 2012, par igor

  I have tried to do the job with following code :

  ffmpeg -i /home/igordr/video.flv -vf "movie=/home/igordr/wm.jpg [watermark]; [in][watermark] overlay=main_w/2-overlay_w/2:main_h/2-overlay_h/2 [out]" /home/igordr/outputvideo.flv

  Also tried :

  ffmpeg -i /home/igordr/video.flv -b:a 300k -ar 22050 -t 10 -f flv -s 352x288 -vf "movie = /home/igordr/wm.png [watermark]; [in][watermark] overlay =0:0 [out]" /home/igordr/out.flv

  I get errors :

  Unrecognized option 'vf'
  
  
  
  Unrecognized option 'b:a'

  Also, I am interested, how I can add just one big image, before video starts, without watermark, and does it possible ?

  How can i check ffmpeg version, and install new one if it's old ?

• How can i stop ffmpeg when no new frame come to /dev/video0

  27 septembre 2022, par itirou tarou

  I'm using ffmpeg in my system like this.

  


  camera => (Frame modifier) => /dev/video0 => ffmpeg => (.ts file)


  


  [camera]

  


  

  1. stream 30fps movie

  


  


  [Frame modifier]

  


  

  1. modify movie frame from camera

  


  2. basically it output 30fps movie

  


  3. sometime it can't process 30 frame in a second and output less than 30 frames

  


  


  I want ffmpeg output .ts file like below.

  


  

  1. 5sec per file

  


  2. always 30fps

  


  3. If input is less than 30fps, duplicate frame

  


  4. If no input in /dev/video0 for 1 second, stop ffmpeg or stop ffmpeg output .ts file until input restart

  


  


  Now I'm using ffmpeg option below.

  


  ffmpeg -f v4l2 -i /dev/video0 -g 150 -vf fps=30 -c:v h264_nvenc -hls_time 5 -hls_segment_filename foo_%d.ts foo.m3u8


  


  It works fine in the situation below.

  


  

  1. when new frame come to /dev/video0

     

     1. it output 30 fps .ts file every 5 seconds

     


     


  


  2. when no frame come to /dev/video0 when I start ffmpeg

     

     1. ffmpeg stop immediately

     


     


  


  


  But it doesn't work in the situation below.

  


  

  1. (start ffmpeg) => (stop input frame to /dev/video0) => (restart input frame to /dev/video0)

     

     1. ffmpeg stop output .ts file when stop input frame to /dev/video0

     


     2. when restart input frame to /dev/video0, ffmpeg output many .ts file at once

        

        1. it contains same still image of time just before camera stopped

        


        2. i don't want ffmpeg output this useless .ts file

        


        


     


     


  


  


  How should I modify ffmpeg option.