OnRenderImage's unscaledDeltaTime usage is inaccurate

[nicekei]

Hi,

first thank you for the nice featured encoder.
I encountered a strange timing problem on Nexus5x/Android O machine.

On it, the frame rate is recorded much faster. I looked into it and found the inaccurate use of unscaledDeltaTime. It was meant to use in Update/FixedUpdate/LateUpdate, not in OnRenderImage. Sometimes it matches roughly the actual time, but sometimes not.

I recorded Time.time and manually calculated the offset. This way, the problem is solved.