- ac3pid has to be set to -1 for some German channels, because otherwise these channels stay black
- this is the case, if the channels claim to transmit ac3 streams (Sat.1-ProSieben group), although only some of them use it and only for some movies at all

-> workaround: set ac3pid for such channels to -1
-> drawback: even if ac3 exists for movies then, the mpeg stream is being used, because of ac3pid manually set to -1
-> possible solution for 0.1.4.0: trying to auto-detect the absence of an ac3 stream