Nicolas Dufresne authored Nov 24, 2017 and Tim-Philipp Müller committed Dec 09, 2017

The client-draw callback is running on the GL Thread, which will
be required to map the buffer. Map early, and pass the mapped
frame instead. On top of that, make sure to signal any pending
draw before trying to push EOS, as some pad locks might be taken.
This is the cost of using the same thread to control GStreamer and
to render GL.