Opencv VideoCapture set CV_CAP_PROP_POS_FRAMES not working

Question

I am using opencv to read frames from a video output from a Vivotek Camera using the mpeg compression. I am trying to use the function to start the video from a particular

Answer 1

A bit too late but searching on same topic (not specific to Vivotek Camera but more on mpeg problem with openCV) :

• Video is encoded
• OpenCV uses FFMPEG
• Encoding use key frames
• When skipping some frames encoding can't give you the exact frame you want

see similar question :

• Getting individual frames using CV_CAP_PROP_POS_FRAMES in cvSetCaptureProperty

• How can I get one single frame from a video file?

• Problem with CV_CAP_PROP_POS_FRAMES setting next frame number

  desired position        key frame (this is where the cursor will stop)
   |   |                       |                    |
   |   >                       |                    |
   |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
  

  Sample code using openCV 2.4.8 / VS2013 with trackbar :

• tested with AVI format [MPEG4 Video (H264)] : setting frame position works fine

• tested with MPG format [MPEG1/MPEG2] : setting frame position works fine

  double currentPos = capture.get(CV_CAP_PROP_POS_FRAMES);
  std::cout << "CV_CAP_PROP_POS_FRAMES = " << currentPos << std::endl;
  
  // position_slider 0 - 100
  double noFrame = position_slider*nbFrames / 100;
  
  // solution 1
  bool success = capture.set(CV_CAP_PROP_POS_FRAMES, noFrame);
  // solution 2
  double frameRate = capture.get(CV_CAP_PROP_FPS);
  double frameTime = 1000.0 * noFrame / frameRate;
  bool success = capture.set(CV_CAP_PROP_POS_MSEC, frameTime);
  
  if (!success) {
      std::cout << "Cannot set frame position from video file at " << noFrame << std::endl;       
      return;
  }
  
  currentPos = capture.get(CV_CAP_PROP_POS_FRAMES);
  if (currentPos != noFrame) {
      std::cout << "Requesting frame " << noFrame << " but current position == " << currentPos << std::endl;
  }
  
  success = capture.read(frame_aux);
  if (!success) {
      std::cout << "Cannot get frame from video file " << std::endl;
      return;
  }
  imshow("test", frame_aux);