elements/gstqtvideosink/gstqtvideosinkbase.cpp set buffer format from caps.
elements/gstqtvideosink/gstqtvideosinkbase.cpp set buffer format from caps.

gstreamer will call set_caps to give the sink the current caps,
so we can save the format for the paint function.

iperry/qt-gstreamer,tswindell/qt-gstreamer,iperry/qt-gstreamer,nasserGanjali/QtGStreamer,tswindell/qt-gstreamer,dejunk/gstreamer,dejunk/gstreamer,freedesktop-unofficial-mirror/gstreamer__qt-gstreamer,detrout/qt-gstreamer,freedesktop-unofficial-mirror/gstreamer__qt-gstreamer,knuesel/qt-gstreamer,detrout/qt-gstreamer,tswindell/qt-gstreamer,GStreamer/qt-gstreamer,nasserGanjali/QtGStreamer,freedesktop-unofficial-mirror/gstreamer__qt-gstreamer,detrout/qt-gstreamer,nasserGanjali/QtGStreamer,knuesel/qt-gstreamer,iperry/qt-gstreamer,knuesel/qt-gstreamer,dejunk/gstreamer,GStreamer/qt-gstreamer,GStreamer/qt-gstreamer