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Making QWebEngineView and libmpv work smoothly together.



  • I have a project that uses libmpv with the opengl widget (as per the examples that come with libmpv) along with a QtWebEngine widget that displays information, graphics and animations (a scrolling ticker for example).

    I found that of the video playback options in Qt, mpv was the smoothest and most reliable. It will play back perfectly smoothly any video up to 1080p.

    However while video is playing, any animations in QtWebEngine are unsmooth and jittery. Video is also slightly less smooth when something is moving in the webpage.

    The system I'm testing with is not struggling for resources (cpu use is around 45%). There is also not any video decoding, as it's playing back raw video (but while it plays back encoded video, the effect is the same, regardless if hardware acceleration is enabled or not).

    I figure that the mpv widget is interrupting the MainWindow thread while it processes frames and causing it to freeze every few milliseconds.

    As far as I know there is no way to separate the mpv thread from the MainWindow thread though.

    I don't know if it'll be possible to make mpv and webengine work together smoothly. I feel like there must be some way to run two widgets at once in one window and not have them mess with each other.

    I'm testing with Ubuntu 18.04, QT 5.11 and the latest mpv from git.

    Does anyone have any advice or pointers for what to try first? I realise this is somewhat of a broad question but my knowledge of graphics is limited. If anyone has advice on a conceptual level, I can hopefully investigate myself.

    Thank you.


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