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• Faster way to split up video and remerge clips using FFMPEG

  7 mai 2021, par Joemgu

  I'm trying to take a video file (mp4, mkv), split it up into frame-accurate smaller clips and re-merge those clips together into a single video without losing much quality and keeping a similar filesize and all that as fast as possible.

  


  The clips can get very short (less than a second) and I need them to be frame-accurate. Therefore it seems that using -c copy as encoder isn't an option, as cutting by keyframe isn't accurate enough in this case. (Tried it out, doesn't work, input/output seeking didn't make a big difference)

  


  Right now I am re-encoding them when splitting the video up with -c:v libx264 -preset ultrafast, and on merge I then use -c copy, which takes a lot of time but I wonder if there is a faster way to do the same thing. I tried using the concat-demuxer or directly reencoding from the original video using a file with the original videoname and timestamps but no luck.

  


  

  1. Is there a way to make this two step process faster (cutting -> merging) ?

  


  2. Is there a way to directly merge sections of the original video together without need of intermediate clips, possibly making the process faster ?

  


  


  (I looked out for other tools than ffmpeg, but it seems like there isn't anything out that can do any better)

  


• How to create video and audio files for the Media Source Extension API ?

  5 décembre 2018, par Aman

  I have created a video player from the Media Source Extension API. I have split the video and audio from the original.mp4 (1 minute duration). I have split the video and audio into small 5 second files (12 files in total). I’m getting each one of them and playing them together. But the video stops playing at around 45-47 seconds. I cannot understand to why the video is stopping/buffering. I cannot understand whether the problem is in the javascript code or the video files ?

  I have uploaded all the resources here (https://drive.google.com/file/d/1NHc_yNRU0tvaU18aohLy74Js3y7UHD4N/view?usp=sharing). And written the commands I used to construct my video and audio files below. I have also noticed that this problem only occurs with Google Chrome and works perfectly and smoothly on Microsoft Edge. Thanks

  Making the Media files:

  Extracting video from original.mp4: MP4Box -single 1 original.mp4

  Extracting audio from original.mp4: MP4Box -single 2 original.mp4

  Splitting the video and audio into 5 second parts: ffmpeg -ss starting-time -to end-time -i (video.mp4 OR audio.mp4) (video_part.mp4 OR audio_part.mp4)

  Fragmenting all the video and audio parts: MP4Box -dash 1000 -rap -frag-rap(video_part.mp4 OR audio_part.mp4)

  Then using the fragmented video and audio files to be played via the Media Source Extension API video player. e.g. (video_part_dashinit.mp4 OR audio_part_dashinit.mp4)

• Is there a way to extract a video frame, encode a sentence behind it, put it back, and then decode it ?

  29 juillet 2021, par Jesse Hix

  I am trying to do stenography on an MP4 video where I am pulling a frame out at a certain time, 5.52 sec, saving that frame as a jpg or jpeg using any image stenography tool, in this case stegosuite, to encode a sentence behind the image and then reinsert that image back into the video at the same time and then extract it again with the same command and using the same steno tool read the message.

  


  Up until decoding the message everything runs without issue.
I know that it is not working because the videos are not the same in size meaning that the frankenstein video is not the same as the original and thus messing up the frame extraction.

  


  Question :
  Is there a way to extract a frame encode a sentence behind it put it back and then decode it ?

  


  What I tried :
  
Used to extract the frame both times :

  


  ffmpeg -ss 5.52 -i original.mp4 -vframes 1 frames_%d.jpg


  


  Used to combine the image back into the video :

  


  ffmpeg -i original.mp4 -i frames_1_embed.jpg -filter_complex "[1]setpts=5.52/TB[im];[0][im]overlay=eof_action=pass" -c:a copy out_1.mp4