@zdanek Do you have the ability to test under Windows?

Yes I do.

Thank so much for looking at this.

[!] at D:\a\qgroundcontrol\qgroundcontrol\src\VideoReceiver\GstVideoReceiver.cc:1370 - "GStreamer error: Could not initialize window system"

log.txt

I vaguely seem to remember fixes in the qmlsink thingy for Windows. Maybe we lost those somewhere along the way?

I obtained some important information through https://www.qt.io/blog/graphics-in-qt-6.0-qrhi-qt-quick-qt-quick-3d. Qt Quick aims to accelerate rendering using hardware. By default, it will be built on the low-level graphical API that is most suitable for the target platform. For example, on Windows, it will default to Direct3D, while on macOS, it will default to Metal.

So here, this line of code cannot run properly.
https://github.com/mavlink/gst-plugins-good/blob/5ff0a6af0e1fd29bafc9f6644e728d24349d0ce7/ext/qt6/qt6glitem.cc#L527

In this way, we can simply bypass it by adding QQuickWindow:: setGraphicsApi (QSGRenderInterface:: GraphicsApi:: OpenGL); to the main function. I successfully verified it on my MacBook m2. I think Windows can do the same. On Windows, it may also be possible to implement it through QCoreApplication: setAttribute (Qt:: AA_UseOpenGLES); or QCoreApplication: setAttribute (Qt:: AA_UseSoftwareOpenGL);.

However, I am not sure if doing so is correct. Does it have an impact on performance?

@NiiAAip great finding! Thank you.
I will check it with Windows. I don't have an access to Mac. Can you create a PR with a fix?

I switched Mac builds to OpenGL. I also tested and it works there at least.

+1 for this. I have the same issue: video still doesn't work as of a commit d785993 (master).

At the same time, builds of Stable branches have video working ok (at least UDP RTP h264/h265, RSTP; MPEG-TS video isn't shown, but can be recorded with button).

To make video work in master build I've tried changing decoder from decodebin3 to decodebin in GstVideoReceiver.cc and QQuickWindow::setGraphicsApi(QSGRendererInterface::OpenGL); in main.cc.
Still no luck :'(

Windows 11 23H2, Qt 6.6.1/5.15.2 MSVC2019 64bit