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• Make segments of equivalent duration

  27 octobre 2014, par Code_Ed_Student

  According to ffmpeg I can slpit a video file using -f segment option. I followed the documentation I found HERE. The only problem is that it segments the video but not in equivalent duration for each segments. It seems that it segments at the nearest0i-frame. I was able to get it to work but I had to re encode the video. Therefore making the process very slow. Is there a better way to segment a video in segments of equivalent duration ?

  Normal segmenting

  ffmpeg -i input.mp4 -c copy -map 0 -segment_time 9 -f segment output%03d.mp4

  Rencoding and segmenting

  ffmpeg -i input.mp4 -codec:v libx264 -crf 23 -preset medium -map 0 -segment_time 9 -g 225 -r 25  -sc_threshold 0 -force_key_frames expr:gte(t,n_forced*9) -f segment -codec:a copy -movflags faststart -vf scale=-1:720,format=yuv420p output -%03d.mp4

• ffmpeg - creating segments of equivalent duration

  13 octobre 2014, par Code_Ed_Student

  I am testing out segment to split a video into segments of 10 seconds each, but I’m noticing some unusual results. In particular, some of the segments generated have varying lengths from 5 seconds to 11 seconds. I’ve tried playing around with segment_time_delta and force_key_frames to make the segments as close to 10 seconds as possible, but it doesn’t seem to be working out so well. How could I make all segments the same duration ?

  ffmpeg -i input.mp4 -force_key_frames 10,20,30,40,50,60,70,80,90,100,110,120 -c copy -map 0 -segment_time 10 -f segment output%01d.mp4

  Results :

  My_vid.mp4 – total duration - 00:02:08
  
  Output1.mp4 00:00:07
  
  Output2.mp4 00:00:07
  
  Output3.mp4 00:00:08
  
  Output4.mp4 00:00:08
  
  Output5.mp4 00:00:09
  
  Output6.mp4 00:00:09
  
  Output7.mp4 00:00:10
  
  Output8.mp4 00:00:10
  
  Output9.mp4 00:00:10
  
  Output10.mp4 00:00:11
  
  Output11.mp4  00:00:11
  
  Output12.mp4 00:00:11
  
  Output12.mp4 00:00:13

• Script - split video file in equivalent segments

  4 octobre 2014, par Code_Ed_Student

  I am currently using ffmpeg to slice video files. I automated the process through a script called ffmpeg_split.sh. To view the full script click HERE.
  When I ran this script on a few .mp4 files I had, it would return nothing :

  __DURATION_HMS=$(ffmpeg -i "$__FILE" 2>&1 | grep Duration | \
   grep '\d\d:\d\d:\d\d.\d\d' -o)

  NOTE : This is line #54.

  So without this value, the calls that come after it to the function parse_duration_info() are returning the error message.

  According to the comments in the original script, there should be 2 arguments to parse_duration_info().

  # arg1: duration in format 01:23:45.67
  
  # arg2: offset for group 1 gives hours, 2 gives minutes, 
  
  #       3 gives seconds, 4 gives milliseconds

  Here is the syntax to slice a video with script : ffmpeg_split.sh -s test_vid.mp4 -o video-part%03d.mp4 -c 00:00:08

  Belowe is where I parse the duration :

  function parse_duration_info() {
  
      if [[ $1 ]] && [[ $2 -gt 0 ]] && [[ $2 -lt 5 ]] ; then
  
          __OFFSET=$2
  
          __DURATION_PATTERN='\([0-9][0-9]\):\([0-9][0-9]\):\([0-9][0-9]\)\.\([0-9][0-9]\)'
  
          echo "$1" | sed "s/$__DURATION_PATTERN/\\$__OFFSET/"
  
      else
  
          echo "Bad input to parse_duration_info()"
  
          echo "Givven duration $1"
  
          echo "Givven offset $2"
  
          echo "Exiting..."
  
          exit 1
  
      fi
  
  }