Up until now, we have not bothered to propagate queue creation flags when
setting up the ffmpeg device context, but with libplacebo setting flags like
VK_DEVICE_QUEUE_CREATE_INTERNALLY_SYNCHRONIZED_BIT_KHR and newer nvidia drivers
actually supporting this feature, I've now managed to run into this. If the
flags aren't put into the context, ffmpeg code can end up calling
vkGetDeviceQueue2 with the wrong flags, and the driver will return a NULL
queue instead.
I suspect we got this far without hitting this because the only filter that
can currently end up calling vkGetDeviceQueue2 is vf_libplacebo and then only
with the new `inherit_device=1` where the device we set up _from_ libplacebo
goes back to libplacebo. The oroborus is complete.
Philip Langdale
390ebe2eac