I have a 7 year old Panasonic tv (TX-P42G20E) that I've connected to my amplifier with an optical cable. When I set the SPDIF format to PCM it works well with «normal» TV broadcasts (no external device), but I get no sound from external devices (cable box, Playstation etc.) connected via HDMI. The sound works well on the TV speakers, but no sound from the external speakers. I've noticed that when I change to HDMI input the SPDIF format setting disappears from sound settings. Does this mean it's not possible for the TV to relay sound from external devices to the amp?