Normally, it will try first to do hw accel path, and fallback to software if it fails
If the failure happens later, you might need to disable it manually (and restart avidemux)
The build in progress is mostly ok, except :
* refresh is not working correctly. if you get a black frame, go left/right to force a new display
* The bridge is not working, there is an extra copy
Meanwhile, i've spotted that the audio part is consuming a lot of CPU on windows
i.e.
playing a 720p h264 video with all DXVA/DXVA, no sound => 4% cpu
playing a 720p h264 video with all DXVA/DXVA, with sound => 30% cpu =>

?