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• Cannot open ".mp4" video files using OpenCV 2.4.3, Python 2.7 in Windows 7 machine

  28 December 2015, by tjmonsi

  I am currently working on a project that involves reading mp4 video files.
  The problem I encountered is that it using Python 2.7 (32 bit), OpenCV 2.4.3 (cv2.pyd) in a Windows 7 machine.

  The code snippet is as follows:

  try:
  
          video = cv2.VideoCapture("video.mp4")
  
  except:
  
          print "Could not open video file"
  
          raise
  
  print video.grab()

  "video.grab()" always returns false: meaning it doesn’t read the file "video.mp4"
  But when we try this:

  try:
  
          video = cv2.VideoCapture("video.avi")
  
  except:
  
          print "Could not open video file"
  
          raise
  
  print video.grab()

  "video.grab()" returns true: meaning it is able to read ".avi" files.

  Another is we have tried this same snippet on Linux and Mac and it seems to work fine, meaning it is able to read both mp4 files and avi files.

  This problem is similar to this problem and this problem. Both still don’t have a clear and workable answer.

  I would appreciate any help or workaround aside from just using Linux or Mac for programming this as I need this to work on all three systems.

• Displaying Bitmaps sequentially, "like a video"

  15 July 2015, by Wamasa

  I’m trying to reproduce a video that is not android supported (like a .wmv video) in my app, and actually I’m able to grab every frame and create a Bitmap of it.

  So, now, I’m trying to show those bitmaps in a VideoView (or any other view), sequencially, something like a video.

  Some code:

  while (true) {
  
                  frame = frameGrabber.grab();
  
                  if (frame == null)
  
                      break;
  
                  frame2 =
  
                          IplImage.create(frame.width(), frame.height(),
  
                                  opencv_core.IPL_DEPTH_8U, 4);
  
                  opencv_imgproc.cvCvtColor(frame, frame2,
  
                          opencv_imgproc.CV_BGR2RGBA);
  
  
  
                  bm =
  
                          Bitmap.createBitmap(frame2.width(),
  
                                  frame2.height(), Bitmap.Config.ARGB_8888);
  
                  bm.copyPixelsFromBuffer(frame2.getByteBuffer());
  
                  canvas = new Canvas(bm);
  
                  mVideoView.draw(canvas);
  
                  canvas.save();

  It looks like I can grab every frame of the video (using ffmpeg), but I just don’t know how to display them.

  By the way, I’ve already tried encoding this video to a .mp4 file and playing it on the VideoView, but it takes much time to process the whole video (1 hour), so, now, I’m trying to display it right away, without encoding it do .mp4 (or any other android supported video)

  Any advices?

• VLC libx264 build error - "undefined reference to 'x264_encoder_open_128'"

  17 January 2013, by Tyler Scott

  Primary issue

  Steps to attempt to repeat this error.

  • Download latest git (git://git.videolan.org/x264.git).
  • Run ./configure - You can use any options, the error is present with all.
  • Run sudo make - It will compile all of the code but when it comes time to link the code it runs into the error

    /usr/local/lib/libavcodec.a(libx264.o): In function 'X264_init':
    /.../libx264.c:418: undefined reference to 'x264_encoder_open_128'

  This will then fall out and exit make. I have removed all apt packages relating to x264. I have searched my computer for any possible libraries that might be related and removed them. This problem persists. Can someone explain what is going wrong and the simplest way to solve this?

  Additional info

  This error also shows up when building avconv. It also fails at linking time with the same error. So I can assume it is nothing wrong with that directory or source.