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• How do I compose three overlapping videos w/audio in ffmpeg ?

  10 avril 2021, par Idan Gazit

  I have three videos : let's call them intro, recording and outro. My ultimate goal is to stitch them together like so :

  


  

  


  Both intro and outro have alpha (prores 4444) and a "wipe" to transition, so when overlaying, they must be on top of the recording. The recording is h264, and ultimately I'm encoding out for youtube with these recommended settings.

  


  I've figured out how to make the thing work correctly for intro + recording :

  


  $ ffmpeg \
  -i intro.mov \
  -i recording.mp4 \
  -filter_complex \
  "[1:v]tpad=start_duration=10:start_mode=add:color=black[rv]; \
   [1:a]adelay=delays=10s:all=1[ra]; \
   [rv][0:v]overlay[v];[0:a][ra]amix[a]" \
  -map "[a]" -map "[v]" \
  -movflags faststart -c:v libx264 -profile:v high -bf 2 -g 30 -crf 18 -pix_fmt yuv420p \
  out.mp4 -y


  


  However I can't use the tpad trick for the outro because it would render black frames over everything.

  


  I've tried various iterations with setpts/asetpts as well as passing -itsoffset for the input, but haven't come up with a solution that works correctly for both video and audio. This tries to start the outro at 16 seconds into the recording (10s start + 16s of recording is how I got to setpts=PTS+26/TB). del, but doesn't work correctly, I get both intro and outro audio from the first frame, and the recording audio cuts out when the outro overlay begins :

  


  $ ffmpeg \
  -i intro.mov \
  -i recording.mp4 \
  -i outro.mov \
  -filter_complex \
  "[1:v]tpad=start_duration=10:start_mode=add:color=black[rv]; \
   [1:a]adelay=delays=10s:all=1[ra]; \
   [2:v]setpts=PTS+26/TB[outv]; \
   [2:a]asetpts=PTS+26/TB[outa]; \
   [rv][0:v]overlay[v4]; \
   [0:a][ra]amix[a4]; \
   [v4][outv]overlay[v]; \
   [a4][outa]amix[a]" \
  -map "[a]" -map "[v]" \
  -movflags faststart -c:v libx264 -profile:v high -bf 2 -g 30 -crf 18 -pix_fmt yuv420p \
  out.mp4 -y


  


  I think the right solution lies in the direction of using setpts correctly but I haven't been able to wrap my brain fully around it. Or, maybe I'm making life complicated and there's an easier approach ?

  


  In the nice-to-have realm, I'd love to be able to specify the start of the outro relative to the end of the recording. I will be doing this to a bunch of recordings of varying lengths. It would be nice to have one command to invoke on everything rather than figuring out a specific timestamp for each one.

  


  Thank you !

  


• Replace frames in an AVI with Java

  12 juillet 2018, par webuster

  I’m recording some screencasts and my crap recorder (Camtasia) recorded 2000 videos with a brief black flash (2-3 frames) at, or near the beginning of each.

  I’m looking for a way to automate the replacement of the black frames inside each video with FFmpeg, and I can currently detect which frames are black.

  The problem I have is now : How can I replace frame number X with the content of frame number X-1 in an AVI video ? Not looking to shorten the video, but just to replace a frame in-place.

  Here’s what I have so far :

  FFmpegFrameGrabber g = new FFmpegFrameGrabber("res/video.avi");
  
  g.start();
  
  
  
  FFmpegFrameRecorder recorder = new FFmpegFrameRecorder(new FileOutputStream(new File("res/video_out.avi")), g.getImageWidth(), g.getImageHeight(), 2);
  
  
  
  recorder.setFormat("avi");
  
  recorder.setPixelFormat(AV_PIX_FMT_YUV420P);
  
  recorder.setFrameRate(30);
  
  recorder.setVideoCodec(AV_CODEC_ID_H264);
  
  recorder.setVideoQuality(10);
  
  recorder.setSampleFormat(AV_SAMPLE_FMT_FLTP);
  
  recorder.setSampleRate(48000);
  
  recorder.setAudioCodec(AV_CODEC_ID_AAC);
  
  recorder.setAudioQuality(10);
  
  
  
  g.setFrameNumber(1);
  
  recorder.setFrameNumber(2);
  
  recorder.record(g.grab());
  
  
  
  g.close();
  
  recorder.close();
  
  recorder.release();

  And I’m getting a video back with empty frames (not even black), so I might be messing something here.

  Anyone with experience with FFmpeg ?

• Is there a way to convert a VP9 webm video into CIELAB colourspace in FFMPEG to improve alpha compositing

  18 août 2022, par OneWorld

  I was wondering if there is an option / command to convert a webm VP9 video into CIELAB colour space in FFMPEG ?

  


  I did a search for CIELAB colour space in FFMPEG and couldn't find anything.

  


  I want to reduce the appearance of black edges by pushing into CIELAB space before doing the overlay / alpha compositing. See this post here :-

  


  moviepy black border around png when compositing into an MP4

  


  How can I do that in FFMPEG ?

  


  Any help would be much appreciated.

  


  Kind regards