How to grab video frames in Qt?

c++ image qt4 video-processing opticalflow
Leonardo Lanchas picture Leonardo Lanchas · Jun 12, 2015 · Viewed 8.1k times · Source

I am new to Qt, I only know the basics: create interfaces and connect slots. In a few words, my knowledge is not deep at all.

I need to open a video file and capture all of its frames to get the R, G, B channels and, later on, process optical flow (this is already done) frame to frame to finally represent it on a window.

Is it possible to get the video frames with Qt? I have researched a lot but not found anything conclusive.

Answer

Rudolfs Bundulis picture Rudolfs Bundulis · Jun 16, 2015

You can use QMediaPlayer to achieve this.

  1. Instantiate the QMediaPlayer.
  2. Subclass the QAbstractVideoSurface.
  3. Set your implementation as the output for the media player via QMediaPlayer::setVideoOutput.
  4. Feed the media player the needed file and eventually it will start calling QAbstractVideoSurface::present(const QVideoFrame & frame) on your implementation of QAbstractVideoSurface if the video was loaded successfully. Then you can access the channels and everything from the QVideoFrame and draw the frame on a widget.

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