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• FFMPEG - C# - Audio and Video out of sync on certain videos after concatenation

  10 décembre 2016, par iamanoob

  Hey guys I’ve been trying to make this work for a while now and I can’t seem to find how to make the audio/video synced after the concatenation, I’ve searched and tested some solutions but couldn’t get it working.

  Here is what I do right now, Everything is working but I must be doing something wrong.

  So First, I split the videos into the video that I want

  System.Diagnostics.Process.Start(ffmpegPath, "-i " + 
  
  video.Path + " -ss " + StartTime + " -t " + Duration + " " + video.Output);

  After "cutting/splitting" the videos that I want like I want, I tried concatenating the videos together ( using -safe 0 to use the absolute path, else it wasn’t working ) :

  System.Diagnostics.Process.Start(ffmpegPath, 
  
  "-f concat -safe 0 -i " + txtFile + " C:\\Downloads\\Build\\" + rdn.Next(0,1000) + ".mp4");

  After that , I’ve noticed the audio/video was sometime out of sync so I searched and found this

  so I decided to Pad all the videos after splitting them :

  System.Diagnostics.Process.Start(ffmpegPath, 
  
  "-i " + video.Output + " -af apad -c:v libx264 -shortest -avoid_negative_ts make_zero -fflags +genpts -report " + padding);

  and then building it again, but it ended up having the same audio desync.

  It’s my first time working with mp4s and with FFMPEG and I’m sure I’m missing something.

• Find Percentage of differences between two Videos Using FFMPEG

  5 novembre 2015, par Jai

  I am working with Video comparison using ffmpeg on java. I would like to know there is any option available for Find the Percentage of differences between two Videos Using ffmpeg.

• Concatenating chunks of videos with different formats using FFmpeg

  11 avril 2014, par SCC

  I was exploring the functionalities of FFmpeg recently. I have two different videos with different formats (e.g. mov and mp4). I will first split these videos up into smaller chunks, and concatenate them back with a mix of chunks from these two videos. However the concatenated video wasn't able to show properly. I did some research and found that mp4 cannot be concatenated using the normal concatenation method since it contains extra headers and information. Therefore I first converted all the videos into mpg, split them up, concatenate an convert back to mp4. However, still no luck on that.

  Below are the commands I used :

  // convert input (1st video) to mpg
  
  ffmpeg -i input.mp4 input.mpg
  
  
  
  // convert to keyframe video
  
  ffmpeg -i input.mpg -strict -2 -g 20 keyframe_input.mpg
  
  
  
  // split keyframe_input into smaller chunks
  
  ffmpeg -i keyframe_input.mpg -acodec copy -f segment -segment_time 0.3 -segment_list  s.m3u8 -vcodec copy -reset_timestamps 1 -map 0 split_input-%d.mpg
  
  
  
  // convert input2 (2nd video) to mpg
  
  ffmpeg -i input2.mov input2.mpg
  
  
  
  // convert to keyframe video
  
  ffmpeg -i input2.mpg -strict -2 -g 20 keyframe_input2.mpg
  
  
  
  // split keyframe_input2 into smaller chunks
  
  ffmpeg -i keyframe_input2.mpg -acodec copy -f segment -segment_time 0.3 -segment_list  s.m3u8 -vcodec copy -reset_timestamps 1 -map 0 split_input2-%d.mpg
  
  
  
  // concatenate video according to the video files written in mylist.txt
  
  ffmpeg -f concat -i mylist.txt -c copy output.mpg

  When I tried to concatenate these chunks of videos, errors were thrown out saying buffer underflow, packet size too large.

  Any FFmpeg experts out there to give some advices ?