Linux video playback is using the opengl driver by default.
Should be using the VDPAU driver for best performance .
Current Radeon VDPAU for PowerPC seems to be broken or not enabled in most distributions .

Caseycullen has compiled a version of Mesa and appears to have the Radeon VDPAU driver working.
So we can probably ask him about VDPAU video playback .
Link

[ Edited by Spectre660 19.06.2018 - 22:12 ]