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• doc : apply various grammar fixes

  10 août 2013, par Bryce W. Harrington

  doc : apply various grammar fixes
  The first sentence of each of the modified man pages are worded a bit
  
  awkwardly. These minor copy-edits should make them clearer.
  Signed-off-by : Bryce Harrington <b.harrington@samsung.com>
  
  Signed-off-by : Stefano Sabatini <stefasab@gmail.com>
  

  • [DH] doc/demuxers.texi
  • [DH] doc/ffmpeg.texi
  • [DH] doc/outdevs.texi
  • [DH] doc/protocols.texi

• how to merge a mp3 file into a mp4 file with low framerate(0.5) using FFmpeg wrapped in javacv

  21 février 2016, par hychanbb

  The video is with no sound only image and frame rate is 0.5, i want to merge a mp3 file into it, but it seem not work at all. Below it the code

              File folder = Environment.getExternalStorageDirectory();
  
              String path = folder.getAbsolutePath() + "/DCIM/Camera";
  
              long millis = System.currentTimeMillis();
  
              videoPath = path + "/" + "test_sham_"+millis+".3gp";
  
              try {
  
  
  
              //audio grabber
  
              FrameGrabber grabber2 = new FFmpegFrameGrabber(folder.getAbsolutePath()+"/Samsung/Music/Over_the_horizon.mp3"); 
  
  
  
              //video grabber
  
              FrameGrabber grabber1 = new FFmpegFrameGrabber(path+"/20140527_133034.jpg"); 
  
                  grabber1.start();
  
                  grabber2.start();
  
                recorder = new FFmpegFrameRecorder(path
  
                        + "/" + "test_sham_"+millis+".3gp",  grabber1.getImageWidth(), grabber1.getImageHeight(),2);
  
                  recorder.setVideoCodec(avcodec.AV_CODEC_ID_MPEG4);
  
                  recorder.setFormat("3gp");
  
                  recorder.setFrameRate(frameRate);
  
                  recorder.setSampleRate(grabber2.getSampleRate());
  
                  recorder.setVideoBitrate(30);
  
                  startTime = System.currentTimeMillis();
  
                  recorder.start();
  
  
  
                  Frame frame1, frame2 = null; 
  
  
  
                  while ((frame1 = grabber1.grabFrame()) != null || 
  
  
  
                        (frame2 = grabber2.grabFrame()) != null) { 
  
  
  
                      recorder.record(frame1); 
  
  
  
                      recorder.record(frame2); 
  
  
  
                  } 
  
                  recorder.stop(); 
  
                  grabber1.stop(); 
  
                  grabber2.stop(); 
  
                  System.out.println("Total Time:- " + recorder.getTimestamp());
  
  
  
              } catch (Exception e) {
  
                  e.printStackTrace();
  
              }

  I do the above and find out that the video contains no sound. Anyone knows how to deal with the framerate problem...

• Fast accurate video trim like Instagram using FFmpeg Android

  11 août 2016, par dan87

  I know it’s been asked before but I couldn’t find a fast and accurate solution yet, I want to trim videos with a maximum lenght of 15 seconds. Here is what I’ve tried so far, I’m working with this video as example :http://www.sample-videos.com/video/mp4/720/big_buck_bunny_720p_30mb.mp4

  The fastest way

  This is by far the fastest way because it doesn’t need to re-encode the video but it’s very innacurate in this video because the key frames are every 5-10 seconds :

  ffmpeg -i SampleVideo_1280x720_30mb.mp4 -ss 30 -to 50 -c copy -y out.mp4

  Here is how I check the key frames in this video :

  ffprobe -select_streams v -show_frames -show_entries frame=pict_type -of csv SampleVideo_1280x720_30mb.mp4 | grep -n I | cut -d ':' -f 1

  With this command I found out that the second key frame it’s in the 211th frame which means 210 frames between the first key frame and the second, knowing that it’s a 25fps video it would be around 8 seconds between the key frames, so any cut between 1-8 seconds would fall in one of this frames which is a huge difference for a 15 seconds video.

  The accurate way

  This way it’s accurate but it requires to re-encode the video :

  ffmpeg -i SampleVideo_1280x720_30mb.mp4 -ss 30 -to 50 -preset ultrafast -y out.mp4

  The problem is this command takes more than 20 seconds to finish using the ultrafast preset, in a samsung galaxy s6 edge plus which probably would be much more in other devices.

  Nevertheless, if I open the SampleVideo_1280x720_30mb.mp4 in Instagram and trim it they get an accurate trim in less than 2 seconds.

  I also tried to force the keyframes every second, but it also requires to re-encode the video and it affects the video quality :

  ffmpeg -i SampleVideo_1280x720_30mb.mp4 -force_key_frames "expr:gte(t,n_forced*1)" out.mp4

  Does anybody know how Instagram trim the videos or a way to get a fast and accurate trim with FFMpeg ?