vaapidecode doesn't create enough surfaces for glimagesink
Submitted by Víctor Manuel Jáquez Leal
glimagesink stores internally more buffers than vaapidecode creates, leading to a deadlock.
The workaround is to add a vaapipostproc in the middle, something that vaapidecodebin normally does.
A real solution is to increase the number that vaapidecode creates, and verify that the gl buffer pool requires the exact minimum number of buffers.