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• how to combine several video random any one to create 1 new video ? using ffmpeg ?

  22 décembre 2016, par Sky Moon

  how to combine several video random any one to create 1 new video ?
  for example, I have 10 videos : 01.mp4 ; 02.mp4 ... 10.mp4
  I want to combine random 5 of them to create 1 video
  example :
  (01.mp4+ 03.mp4+ 04.mp4+ 06.mp4 + 08.mp4) = 1 new video

  (02.mp4+ 04.mp4+ 05.mp4+ 06.mp4 + 09.mp4) = 1 new video

  Similar : random combination of 50 videos of 1000 videos to create 1 new video ?

• Ffmpeg video freeze for longer video

  10 mars 2016, par Vishnu

  I have a video of 30 seconds , I am making it 1 hour video using below code

  echo shell_exec('/usr/local/bin/ffmpeg -y -i universal.mp4  -f lavfi -i "color=black:s=1280x720:r=24:d=3600" -filter_complex "[0][1]concat=n=2:v=1:a=0[v]" -map [v] -c:v libx264 -map 0:1 -c:a libfdk_aac -b:a 256k output.mp4  2>&1');

  So The output.mp4 created using above code is 1 hour long and it is getting freezed by vlc ,windows mediaplayer when I seek to certain minutes.But when I set duration d=300 , output video is perfect. Why does long video gets freezed from above output.

• FFMPEG Audio/Video out of sync after transcoding video in segments

  25 mai 2017, par Idan

  My system transcodes videos in a very specific way.

  1. separating the video and the audio
  2. transcoding the audio stream
  3. segmenting the video
  4. transcoding each of the segments of the video
  5. concat all segments back to 1 video
  6. merging the new transcoded video and audio back together

  While at 99% of the times the process works as it should and the result is a valid video+audio file. in 1% of the times, I get the video and audio out of sync.

  When investigated the issue I noticed that the sync issue appears in a specific segment/s. Meaning, if the video was sliced into 100 segments, the sync can be ok for the first 50 segments, then something happens and the audio or video gets an offset and goes out of sync. It can occur in any number of segments in one video.

  I guess it’s something to do with timestamps getting lost in the process and segments changing their length in the process but I have no idea how I can overcome it. Open for suggestions.

  The commands I use for each step (paths were shorten and may not match, not real issue there) :

  Segmenting the video :

  ffmpeg -fflags +genpts -i $INPUT_FILE -c copy -map 0:0 -flags -global_header -segment_time 10 -break_non_keyframes 0 -reset_timestamps 1 -segment_list segments.list -segment_list_type ffconcat -write_empty_segments 0 -segment_format mp4 -f segment seg-%d.mp4

  Transcoding audio :

  ffmpeg -i $INPUT_FILE  -vn -c:a aac -threads 1 -ac 2 -b:a 125588 audio.mp4

  Transcoding each of the segments :

  ffmpeg -y -i $f -an -vcodec libx264 -threads 4 -r 30 -pix_fmt yuv420p -crf 20 -preset:v fast -profile:v main -level:v 4.1 transcoded/$f

  Concat segments :

  ffmpeg -y -f concat -i segments.list  -c copy -movflags +faststart file_video.mp4

  Combine video and audio :

  ffmpeg -y -i file_video.mp4 -i file_audio.mp4 -c copy -shortest file_out.mp4