Roku won't work with my older AVR but Apple TV does?
I have an old Onkyo AVR that will decode DD and DTS. I've connected the optical out of my Vizio TV to my AVR (my AVR doesn't have HDMI inputs). If I watch, say, Frozen II on the Amazon app built into my Vizio TV then my AVR sees DD. If I watch the same thing with the Amazon app on Apple TV 4k my AVR also sees DD. If I watch Frozen II with the Amazon app on my Roku Ultra my AVR does not see DD and does stereo. I've tried all the audio settings to no avail.
Have I missed something? I realize I could purchase a new AVR. But if I want to keep it will I have to return the Ultra and get Apple TV?