dxva: fix c/p error after b92d51f9fc3ad40da13aa0c153a13e278937ecee
dxva: temp fix for borked video surface handling
pvr: avoid closing stream players on channel switch
fix unregiser of observer/observable
Merge pull request #5347 from FernetMenta/observer

fix unregiser of observer/observable
Merge pull request #5342 from FernetMenta/switch

pvr: avoid closing stream players on channel switch
Merge pull request #5346 from FernetMenta/dxva

DXVA: fixes related to ffmpeg 2nd.
dxva: fix RelBuffer, use correct CDecoder object