I have a Roku Ultra #4800R and cannot get Dolby digital output from it.
I am using a HDMI cable to connect it to my Panasonic TC-P60ST50 TV. The TV is connected to my home theater amp with a digital optical cable. In the audio setup for the ROKU I have tried the auto detect, auto pass through and Dolby digital settings. When selecting the auto detect and pass through settings the ROKU tells me it is detecting stereo and I am only receiving stereo/pro logic at the amp. In any of the Dolby digital modes selected on the ROKU I get no sound to the amp. The TV has Netflix and other apps loaded on it and I get Dolby digital from the apps that offer it, as well as the other components connected to the TV, all running through the digital optical cable to my amp. I have checked the HDMI settings for audio on the TV and it is set to digital like the rest of the HDMI inputs on the TV. I have updated the ROKU as well.
By default, optical digital output is PCM/stereo which is why you're not getting surround. Once you find out which HDMI ports on both the TV and AVR support ARC (Audio Return Channel), us an HDMI cable to connect them. Make sure the TV audio output is set to HDMI/ARC rather than optical PCM. Then when selecting these HDMI ports on both, you should get DD surround.
Power User (film maker) Mill Valley, CA
Jonathan Roku Ultra 4800R; LG OLED55B7A, Marantz SR-6005, Panasonic Blu Ray, Definitive Studio Monitor 450 (L/R), Definitive LCR 2000 (center), Definitive 10" sub-woofer, Definitive surrounds.