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• given a list of mp4, generate fmp4 and concatenate

  6 août 2021, par onion

  my input is a list of mp4 (for example each one is 10s), each mp4 will have correct timestamp, for example the second mp4 represents from 10s - 20s data.

  


  To simulate my input, I generate a list of mp4 this way

  


  ffmpeg -i ../origin-long-video.mp4 -map 0 -c copy -f segment -segment_time 10 -force_key_frames "expr:gte(t,n_forced*2)" -reset_timestamps 0 videos/output_%03d.mp4


  


  Note I use reset_timestamps 0 so that the timestamp is preserved.

  


  Then I convert each mp4 to fragment mp4 by using

  


  ffmpeg -y   -i videos/output_001.mp4   -force_key_frames "expr:gte(t,n_forced*2)"   -sc_threshold 0   -s 1280x720   -c:v libx264 -b:v 1500k   -c:a copy   -hls_time 100   -hls_playlist_type vod   -hls_segment_type fmp4   -hls_segment_filename "hls1/file%d.m4s"  -copyts hls1/index.m3u8


  


  The above cmd is for the first mp4 file, i did same operation for other mp4 in the list.
Note I used a large hls_time so that each mp4 will result in one fmp4, and also I use copyts to preserve the timestamp.

  


  Then I want to concatenate for example the 2nd and the 3rd fmp4 to generate one mp4, I used

  


  cat init.mp4 > rs.mp4
cat 2nd fmp4 >> rs.mp4
cat 3rd fmp4 >> rs.mp4


  


  However when trying to play the generated rs.mp4, it is 20s black screen then 10s video (corresponding to the 3rd mp4).

  


  I tried another approach which just generated a list of fmp4 directly like this :

  


  ffmpeg -y   -i ../origin-long-video.mp4   -force_key_frames "expr:gte(t,n_forced*2)"   -sc_threshold 0   -s 1280x720   -c:v libx264 -b:v 1500k   -c:a copy   -hls_time 10   -hls_playlist_type vod   -hls_segment_type fmp4   -hls_segment_filename "videos/file%d.m4s"   videos/index.m3u8


  


  And then if I concatenate the 2nd and 3rd generated fmp4 use the same way above, the result mp4 plays well.

  


  I wonder what is the difference between the generated fragment mp4 of the two approach so that they leads to different behavior when concatenation. Thank you !

  


• ffmpeg : Convert gif to video

  7 décembre 2016, par Aminesrine

  I want to convert a gif file to a video with ffmpeg.
  I’m using :

  ffmpeg -y -i /gif/583fd7661b46d.gif -strict -2 -an -b:v 32M /gif/mp4/583fd7661b46d.avi

  The duration of my gif in photoshop is 27 seconds, but the duration of the video "583fd7661b46d.avi" generated is 15 seconds.
  How can I get the same duration of my gif in the video generated ?

  I execute this :

  ffplay file.gif

  It steel read without stoping and the "M-V" is incremented
  

• FFmpeg : high quality animated GIF ?

  19 février, par David Hope

  I'm generating animated a GIF from a video on my server.

  



  The generated GIF is not really high quality and it looks like the pixels are huge.

  



  Example :

  



  

  



  This is how I generate the GIF :

  



  shell_exec("/usr/bin/ffmpeg -i video.mkv -vf scale=500:-1 -t 10 -r 10 image.gif");


  



  I did a search on Google and came across this :

  



  shell_exec("/usr/bin/ffmpeg -i video.mkv -r 20 -f image2pipe -vcodec ppm - | convert -delay 5 - output.gif");


  



  But the command above doesn't do anything and no output.gif is being generated at all.

  



  There are some tutorials that I came across but none of them worked for me and some of them involve using ImageMagick which I dont have access to.

  



  Could someone please let me know if there is a clear way to generate a high-quality GIF using FFmpeg ?