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• Using ffmpegFrameRecorder the merged video is short ?

  10 février 2014, par stack5

  I am using ffmpegFrameRecorder from JavaCV Api to merge several mp4 videos to one . Here is my code :

  FrameGrabber grabberlist[] = new FFmpegFrameGrabber[filenamelist
  
                      .size()];
  
  
  
  for (int i = 0; i < grabberlist.length; i++) {
  
  
  
                  System.out.println("FILES" + filenamelist.get(i));
  
                  grabberlist[i] = new FFmpegFrameGrabber(filenamelist.get(i));
  
                  grabberlist[i].start();
  
  
  
              }
  
  
  
              FrameRecorder recorder = new FFmpegFrameRecorder(
  
                      Environment.getExternalStorageDirectory()
  
                              + "/Apptavia/output.mp4",
  
                      grabberlist[0].getImageWidth(),
  
                      grabberlist[0].getImageHeight(), 1);
  
  
  
              recorder.start();
  
  
  
              for (int i = 0; i < grabberlist.length; i++) {
  
  
  
                  Frame frame;
  
                  while ((frame = grabberlist[i].grabFrame()) != null) {
  
  
  
                      recorder.record(frame);
  
  
  
                  }
  
              }
  
  
  
              for (int i = 0; i < audioList.size(); i++) {
  
  
  
                  recorder.record(audioList.get(i));
  
              }
  
  
  
              recorder.stop();
  
  
  
              for (int i = 0; i < grabberlist.length; i++) {
  
  
  
                  grabberlist[i].stop();
  
              }
  
          }

  The output video is created but the video length is less . I have debugged the number of frames from .grab() method is less than the total frames. What could be the solution for this . Please help.

• avcodec/h264 : reduce noisiness of "mmco : unref short failure"

  25 octobre 2013, par Michael Niedermayer

  avcodec/h264 : reduce noisiness of "mmco : unref short failure"
  Do not consider it an error if we have no frames and should discard one.
  
  This condition can easily happen when decoding is started from an I frame
  Fixes Ticket2811
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavcodec/h264_refs.c

• How to convert VP8 track with different frame resolution to h264

  13 septembre 2016, par Nikita

  I have a .webm file with VP8 track, recorded from WebRTC stream by external service (TokBox Archiving). The stream is adaptive, so each frame in track could have different resolution. Most players (in webkit browsers) use video resolution from track description (which is always 640x480) and scale frames to this resolution. Firefox and VLC player uses real frame resolution, changing video resolution respectively.

  I want to achieve 2 goals :

  1. play this video in Internet Explorer 9+ without additional plugin installation.
  2. change frames resolution to one fixed resolution, so the video will look identically in different browsers.

  So, my plan is :

  • extract frames from source webm file to images with real frame resolution (e.g. PNG or BMP) (how could I do that ?)
  • find max width and max height of images
  • add black padding to images, so smaller frames will be in the center of a new frame (of size MAX_WIDHTxMAX_HEIGHT)
  • combine images to h264 track using ffmpeg

  Is all correct ? How can I achieve this ? Can this algorithm be optimized some way ?

  I tried ffmpeg to extract images, but it does not parse real frame resolution, using resolution from track header.
  I think some libwebm functions can help me (to parse frame headers and extract images). Maybe someone has some code snippets to do this ?

  Example .webm (download source, do not play google-converted version) : https://drive.google.com/file/d/0BwFZRvYNn9CKcndhMzlVa0psX00/view?usp=sharing

  Official description of adaptive stream from TokBox support : https://support.tokbox.com/hc/en-us/community/posts/206241666-Archived-video-resolution-is-supposed-to-be-720x1280-but-reports-as-640x480