QoS issues with live preview pipeline

[philn]

With this pipeline the sink starts quite early on to drop buffers

gst-launch-1.0 rpicamsrc preview=0 fullscreen=0 ! h264parse ! queue ! omxh264dec ! queue ! glimagesink

Setting sync=0 on the sink works around the problem but ideally I think we'd prefer it to stay synchronized on the clock.

[philn]

One part of the problem is that the rpicamsrc element doesn't handle latency queries I think. I tried to add that but the issue still remains :(

[philn]

Pushed my wip branch there: https://github.com/philn/gst-rpicamsrc/tree/wip-latency
Clearly needs some more work :)