QT5, video playback over Wayland questions.

James Hughes James.Hughes at dspg.com
Wed Oct 28 10:01:45 PDT 2015

Hello all,

I have some questions about running QT5.5 over Wayland, and playing back video using a gstreamer pipeline, on an embedded system. We have a QT application and performance is much slower than when using gstreamer gst-launch1.0 directly. We have determined that the cause of this is that the video pipeline ends up using a QGstreamerVideoRenderer rather than something based wayland sink. This means, we suspect, an extra copy of the video data, meaning we don't the the same performance.

Looking at the code in qgstreamerplayerservice.cpp, we have

#if defined(Q_WS_MAEMO_6) && defined(__arm__)
    m_videoRenderer = new QGstreamerGLTextureRenderer(this);
#elif defined(HAVE_MIR) && defined (__arm__)
    m_videoRenderer = new QGstreamerMirTextureRenderer(this, m_session);
    m_videoRenderer = new QGstreamerVideoRenderer(this);

So there are a couple of implmentations of video surface renderers for specific backends, in this case gl and mir.

My thoughts are that I need to add a new class, something like QGstreamerWaylandRenderer that I can insert at this point to provide a wayland backend for the video player.

Does this seem like the correct approach? I've been trundling through the code (and Google) and am making very slow progress , but if there is anyone out there who can point me in the right direction for documentation or any sort of architectural information on how all this bolts together, it would definitely make my life easier!

I do find it a bit odd that there isn't already something in place for this. There is a QTWayland backend for general GUI stuff, but this gstreamer video stuff doesn't seem to have the right backend in place to take advantage of the acceleration of Wayland that we have on the platform.


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James Hughes
Senior Software Engineer
Phone: +44 (0)1223772209

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