Dolby Digital Not Working

I currently have my DTV receiver hooked up to my TV (Samsung LN52B750) thru HDMI input, and have my TV hooked up to my AVR thru digital optical. And the Dolby Digital will not work unless I have the digital optical connected directly to the AVR from the DTV receiver. I have a Panasonic SC-PT770 that does not have any HDMI inputs and one digital optical input, so I have to hook it up this way. I know TVs usually don't transfer Dolby, but I have my PS3 and Xbox 360 setup for Dolby Digital, and they are hooked up in the same way. Does anyone know of anyway getting Dolby to work by having it setup this way? Any help would be appreciated, thanks.