For dolby digital to work you have to have the optical or coax cable hooked up to the reciever ,The HDMI cable is for digital video and audio output but does not support dolby digital out the cable into your reciever , so just turn off the dolby digital on your reciever and you should hear the sound.
here is more info
is an advanced lossless
multi-channel audio codec developed by Dolby Laboratories
which is intended primarily for high-definition home-entertainment equipment such as Blu-ray Disc
. It is the successor to the AC-3 Dolby Digital
surround sound codec which was used as the audio standard for DVD discs. In this application, Dolby TrueHD competes with DTS-HD Master Audio
, another lossless codec from Digital Theater System
Dolby TrueHD uses Meridian Lossless Packing
(MLP) as its mathematical basis for compressing audio samples. MLP was used on the earlier DVD-Audio
format, but details of TrueHD and DVD-Audio differ substantially. A Dolby TrueHD bitstream can carry up to 14 discrete sound channels. Sample depths up to 24 bits/sample and audio sample rates up to 192 kHz
are supported. Like the more common legacy codec Dolby Digital, TrueHD bitstreams
carry program metadata. Metadata
is separate from the coding format and compressed audio samples, but stores relevant information about the audio waveform. For example, dialog normalization
and Dynamic range compression
are controlled by metadata embedded in the TrueHD bitstream.