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• Using FFMPEG and Open CV and encoding webcam stream to h264 in VC 2010

  22 novembre 2013, par Osaid

  I am trying to capture video stream and at the same time willing to encode it to h264 and save it to a file. I am using OpenCV to capture stream but am having problem converting them to h264 via FFMPEG. OS is WINDOWS XP and VC 2010 is the environment.

  I referred the encoding_decoding (refer video encoding section) provided by the FFMPEG. FFMPEG uses AVFrame i.e.

  AVFrame *frame;

  structure in which there is image data at frame->data but in OpenCV I am capturing frames in

  Mat WebCamFrame;
  
  cap >> WebCamFrame;   //Captures frame from webcam and puts it to WebCamFrame

  For encoding I have to get this captured WebCamFrame to frame->data then encode it using the

  avcodec_encode_video2(c, &pkt, frame, &got_output);

  in the encoding_decoding example a dummy image is created as

  /* prepare a dummy image */
  
  /* Y */
  
  for(y=0;yheight;y++) 
  
  {
  
      for(x=0;xwidth;x++)
  
      {
  
          frame->data[0][y * frame->linesize[0] + x] = x + y + i * 3;
  
      }
  
  }
  
  
  
  /* Cb and Cr */
  
  for(y=0;yheight/2;y++)
  
  {
  
      for(x=0;xwidth/2;x++) 
  
      {
  
          frame->data[1][y * frame->linesize[1] + x] = 128 + y + i * 2;
  
          frame->data[2][y * frame->linesize[2] + x] = 64 + x + i * 5;
  
      }
  
  }

  I do not want to use this dummy image rather the frame captured from webcam to encode it to h264. One more thing, the data type of WebCamFrame is MAT and that of frame is AVFrame. I would really appreciate a hint to proceed further. In a nutshell I want to process Mat frames (webCam video Stream) of OpenCV in FFMPEG avcodec_encode_video2() and write the video to a file.

• With ffmpeg's image to movie feature, is it possible to pass in frames over a period of time versus all at once ?

  2 novembre 2013, par Zack Yoshyaro

  For the purpose of making a time lapse recording of desktop activity, it is possible so "stream" the frame list to ffmpeg over time, rather than all at once in the beginning.

  Currently, it is a two step process.

  1. save individual snapshots to disc

     im = ImageGrab.grab()
     im.save("frame_%s.jpg" % count, 'jpg')

  2. compile those snapshots with ffmpeg via

     ffmpeg -r 1 -pattern_type glob -i '*.jpg' -c:v libx264 out.mp4

  It would be nice if there were a way to merge the two steps so that I'm not flooding my hard drive with thousands of individual snapshots. Is it possible to do this ?

• How to append 2 seconds of silence to an existing movie MP4 with ffmpeg ?

  27 février 2020, par Marie

  I would like to append 2 seconds of silence to an existing video using ffmpeg.
  I would like to keep the last frame displayed while the 2 seconds of video playsback not a black screen.

  Thank you.