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• FFMPEG extract frame-accurate video fragments with minimal transcoding

  9 mars 2018, par Leeroy

  How can I extract frame-accurate video or audio fragments using FFMPEG without transcoding the full portion ?

  ffmpeg -i input.mp4 -ss 00:00:01.234 -to 00:00:05.678 output.mp4 works because it re-encodes... If I use -codec: copy then it disregards the precision of my start and end time arguments and instead uses the closest keyframe (I understand).

  Is there a command or combination of commands to instruct FFMPEG to transcode only what’s needed, the bits near the start/end markers, up to keyframes ?

  EDIT : A bit of context... I’m trying to write this function to process video piped from youtube-dl, perhaps even as a service. So it matters that I minimize bandwidth (downloading to timestamp and discarding after) and CPU utilization (re-encoding all of the fragment).

• Why frameGrabber.start() Not Grabbing the Frames From Video File

  17 mars 2017, par Danish Sharma

  Here the Below code in JAVA

  public class Read

  public static void main(String []args) throws IOException, Exception, InterruptedException, ExecutionException
  
  {

  // Runtime.getRuntime().exec("ffmpeg -r 1 -i sample%d.png -s 320x240 -aspect 4:3 CHANDIGARH.mp4") ;
  FFmpegFrameGrabber frameGrabber = new FFmpegFrameGrabber("C :/Users/Danish/Music/CHANDIGARH.mp4") ;
  frameGrabber.setFrameNumber(0) ;
  frameGrabber.start() ;

      IplImage i;
  
  
  
  
  
  
  
      try {
  
          for(int ii=0;ii<=frameGrabber.getLengthInFrames();ii++){
  
  
  
              OpenCVFrameConverter.ToIplImage converter = new OpenCVFrameConverter.ToIplImage();      
  
  
  
                Java2DFrameConverter paintConverter = new Java2DFrameConverter();
  
               i = converter.convert(frameGrabber.grab());
  
  
  
  
  
              Frame frame = converter.convert(i);
  
              BufferedImage img=paintConverter.getBufferedImage(frame,1);
  
              IplImage iplImage = converter.convert(paintConverter.convert(img));
  
  
  
          String path = "F:\\"+ii+".png";
  
          ImageIO.write(img,"png", new File(path));
  
  
  
          }
  
          frameGrabber.stop();
  
      } catch (Exception e) {
  
          // TODO Auto-generated catch block
  
          e.printStackTrace();
  
      }
  
  
  
  
  
  }

• VLC cant read some audiotracks created by ffmpeg

  18 juin 2021, par skanarr

  I have two different .mkv files of the same movie. One contains the English, German, Italian, Spanish and French audio and subtitle tracks, the other contains Japanese Audio and Subtitle tracks. Since I want to have all tracks in one file I tried to 'merge' them using ffmpeg.

  


  $ ffmpeg -i Movie.mkv -i Movie_jp.mkv -map 0:v -map 0:a -map 1:a:2 -map 0:s map 1:s:1 -map 1:s:2 -map 1:s:3 -c:v copy -c:a copy -c:s copy tmp.mkv


  


  Full Command Output from ffmpeg
That is the command I used and even though it took a while, I got my tmp.mkv.
However Playing it in VLC none of the Tracks from Movie_jp.mkv are working properly.
There are short periods where there is audio and then it is gone again for some minutes.
Also tmp.mkv freezes at 4:44 and freezes VLC for some time, before only audio continues top play.
Looking under Messages this is what I got

  


  main error: module not functional
main error: failed to create audio output


  


  Then a bunch of warnings
and a ****load of

  


  main error: Timestamp conversion failed (delay 1000000, buffering 100000, bound 9000000)
main error: Could not convert timestamp XY for FFmpeg
main warning: early picture skipped


  


  And finally

  


  main error: buffer deadlock prevented


  


  (All Message from VLC )
I don't know what I did wrong. The Japanese tracks are working in Movie_jp.mkv.
The all non-japanese Tracks are still working in tmp.mkv.
Also there are working Tracks with the same codecs on tmp.mkv (dts) as well as subtitles (pgs).