Blocking QAbstractVideoSurface



  • Hi everybody!

    Qt contains great capabilities for video playback on android and is much nicer to handle than the Java Android SDK.

    I am trying to play a video using QMediaPlayer and setting the output to a class derived from QAbstractVideoSurface.
    By overriding the "present" method in QAbstractVideoSurface I can retrieve the frames, convert them to RGB and manipulate them as I want.
    Unfortunately, the "present" method seems to be called asynchronously and in a non-blocking way.
    Since my image manipulation routine takes some time, I lose a lot of frames. They simply get skipped. The MediaPlayer plays the video at normal speed and only calls the "present" method whenever the image manipulation routine is not busy.
    I don't need the video to play in real time or be drawn anywhere, I am (ab)using the QMediaPlayer to get to the frames, playing the frames smoothly is not an issue, I just want to have all the frames without missing any.

    Is there a way to make the "present" method blocking? Meaning that the MediaPlayer only plays a new frame if the "present" method has finished processing the previous frame.

    Thank you in advance!

    Best,

    ogh

    PS: Minimal example:

    @
    QMediaPlayer *player = new QMediaPlayer;
    // DrawVideoSurface is derived from QAbstractVideoSurface
    // and overrides the "present" method to perform image manipulation
    DrawVideoSurface *processor = new DrawVideoSurface();
    player->setVideoOutput(processor);
    player->setMedia(QUrl("file:///home/ogh/video.mp4"));
    player->play();
    @


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