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• 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.

  


• ffmpeg overlay time offset

  24 juillet 2012, par Produitbrut

  I'm trying to add overlays to an input video with ffmpeg that appear after a time period after the video starts.

  The basic way to add an overlay is :

  ffmpeg -i myvideo.avi -vf "movie=my_overlay.avi [ovl]; [in][ovl] overlay=0:0 [out]" output.avi

  But this simply adds the overlay video (or image) from the start of the input video until the input video ends or the overlay video ends.

  I know how to offset the overlay video using movie=my_overlay.avi:seek_point=1.4, but what about an offset on the input video ?

  I could always clip the video to the desired point, add overlay on the second clip, then stitch the two but that's not very efficient.

• Double subtitles when hardcoding from .mkv container

  4 novembre 2022, par Goran Hinic

  I'm trying to hardcode subtitles into a file that's in .mkv container, using one of the subtitle strams from the container. I want subtitles to have a black background on them. I'm also trying to keep 10bit encoding and preserve high quiality. Result is ok, except that all subtitles are doubled. So there is a layer of good subtitles in white on black background, and also, half of the font size down, same subtitles in black. Can someone point out the issue with my command ?
Thank you.

  


  Ran this command :

  


  


  ffmpeg -i movie.mkv -vf "subtitles=movie.mkv:si=0:force_style='OutlineColour=&000000000,BorderStyle=3,Outline=3,Shadow=0,MarginV=20'" -c:v libx265 -crf 23 -preset slow -x265-params profile=main10 -c:a copy movie_subs.mkv

  


  


  Expected : White subtitles on black background
Actual : White subtitles on black background with black subtitles half font size down