I’ve discovered a solution (better a workaround)!
To my surprise there is no offset between sound and video when I DEACTIVATE HW acceleration. Then all videos are played fine (but the processor is more busy). But I seem to be limited to 720p - that’s not an isue in Germany since all our HD channels are 720p.
These are my settings:
System>Player>Videos>adjust display refresh rate> set to on start/stop
System>Player>Videos>use DRM PRIME decoder> set to no
Addons>User Addons>Video player InputStream Addons>InputStream Adaptive>max. resolution> set both to 720p
Addons>ARDundZDF>Allgemein>Sofortstart> set to on
Addons>ARDundZDF>Modul-Einstellungen>Videoformat> set to HLS(adaptive)
Addons>ARDundZDF>Modul-Einstellungen>Videoqualität> set to 1280x720
I guess that the settings within ARDundZDF are overrruled by the settings for InputStream adaptive.
Thanks to darwindesign for bringing InputStream Adaptive into my mind.
Regards, Michael