Update - After a very long day, turns out that opencv lib was linked to gstreamer0.10, qt to 1.0. This did not work well obviously.
When compiling opencv with linking to gstreamer1.0, works ok.
You can subclass QQuickItem to create a custom item that you can then use in a Qt Quick scene. In this subclass you can use gstreamer to render a video. So, yes, you can use QQuickItem here. Simply speaking, this is what the Qt Quick Video Item does, too. But please don't ask me how to use gstreamer directly because I have no idea :-)
@LuJoRi hello!
I'm very sorry for the so late reply, but I just had some urgent problems, and I had to leave this forum and work with another things.
I see that you shared your advice and sample for this issue as you promised.
So I want to thank you for this!
Unfortunately, I had to do other things, but I think that you helped other users (including chaudhry) to solve this not simple task! :)
Sorry and thank you one more time!