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• avformat/avformat.h : Correct some comments

  9 août 2019, par Andreas Rheinhardt

  avformat/avformat.h : Correct some comments
  1. When set_parameters was removed from AVOutputFormat in 2fb75019, it
  
  was forgotten to remove the comment pertaining to it. Said comment now
  
  appeared to apply to interleave_packet() ; it is of course nonsense and
  
  has been replaced by an accurate description.
  
  2. The description of av_write_uncoded_frame() suggested
  
  av_interleaved_write_frame() as a replacement if the input is not
  
  already correctly interleaved ; it also referred to said function for
  
  details. Given that said function can't write AVFrames and that the
  
  specifics of writing uncoded frames are explained in the description
  
  of av_interleaved_write_uncoded_frame(), both references have been fixed.
  
  3. Removed an outdated comment about avformat_seek_file().
  Reviewed-by : Marton Balint <cus@passwd.hu>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/avformat.h

• 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 ?

• How to specify how lossy/lossless a .webm conversion will be (in ffmpeg) ?

  16 février 2021, par DistantDigit

  I can't seem to understand how to make the conversion lossless (or at least visually lossless) ? The outputs have some fast moving parts at times, and the output would become blocky ; I would like to keep it as lossless as possible, while still maintaining some compression. What would I have to tweak at the command line ? Thanks you 

  


  ffmpeg -c:v libvpx-vp9 -i in.webm -c:v libvpx -vf scale=400:416,hue=h=45:s=1 -auto-alt-ref 0 out.webm