Two changes, compounded into one since they affect the same logic:
1. Never use linearization for HDR downscaling
2. Always use linearization for interpolation
Instead of fixing p->use_linear at the beginning of pass_render_frame,
we flip it on "dynamically" as needed. I plan on killing this
p->use_linear frame (along with other per-pass metadata) and moving them
into their own struct for tracking the "current" state of the video, but
that's a separate/upcoming refactor.
As a small bonus, reduce some code duplication in the interpolation
logic.
Fixes#4631
Niklas Haas
241d5ebc46