This allows user to specify values and not rely on libplacebo's estimations.
In practice this fixes issues when stale estimate inside libplacebo is producing bogus frame mix. For example after changing refresh rate significantly.
Also users might have better idea what is going on and what those values should be so unconditional estimate even if provided by user is not that great.
VPS and FPS are still estimated regardless if used, so that when the no_estimate is changed during runtime we have already estimate ready.
VideoLAN code repository instance