GStreamer video display into a Qt6 QWidget

[Terry Barnaby]

Hi,

Does anyone have any pointers on how I can display a gstreamer video 
pipelines output into a Qt6 QWidget these days ?

We are programming a system on a NXP iMX8mp Yocto embedded platform. 
This has Wayland/Weston with Qt6 and uses low level iMX8mp 2D/3D 
hardware engines.

In the past we were using Qt5 and managed to use waylandsink setting the 
surface to draw into from a QWidget's native Wayland surface and 
resizing the waylandsink overlay to match the QWidget size. Basically 
use was made of gst_video_overlay_set_window_handle() and 
gst_video_overlay_set_render_rectangle() and used the Qt5 
QPlatformNativeInterface API to get the QWidget's Wayland surface. This 
worked reasonably well (a bit dodgy with Qt5 Wayland support, 
Weston/Wayland issues, and IMO messy) but it worked and was efficient.

However with the latest NXP Yocto including Qt6 this does not work 
correctly. Although the code (and a simple test case) runs and the video 
appears on the screen, it is not actually within the QWidget. If I build 
the same test example on Fedora, the application jut fails with lots of 
waylandsink errors printed.

Is there a better and simple way of getting a gstreamer pipe line to 
display video in a QWidget these days ? I have seen there is the Qt QML 
based QMultimedia system, but that adds all of the complexity of QML and 
I have heard is quite inefficient and no longer supports a manual 
program controlled gstreamer pipeline that we need for our application.

Terry