I notice, that Windows (10, 1909) task manager show Video Encoder utilization when youtube video is playing in MS Edge instead of decode. See attached screenshot, please. Observed with with driver 20.4.2 on RX5700.
Driver 20.5.1 has same behaviour.
AMD should have known this but why not fixed it, its problem since early Radeon Software 2020 in December 2019.
My Vega 11, Vega 3 not having this with Radeon Software 19.11.3 installed.
there's already an answer, https://community.amd.com/message/2972396 , we just have to wait