After an hour of searching, I anyway finally found the right option to disable the output of Dolby Sony (optical output, set to "non-compliant devices"). Since everything is OK. The sound is very good it is to blu-ray origin, Freebox or TNT.
A competitor appliance (CYP) not much more expensive support Dolby said: I would have taken had I understood the technical data (but the descriptive products on Amazon are difficult to spot, they should be more separated from business ties and other sections).
