A brand new Vizio P55-F1 television
A Roku Ultra connected via HDMI
A Sonos Playbar+surrounds+sub connected to the Vizio by optical cable
On my previous TV - a Vizio E420i - I set the Roku into forced Dolby D+ mode, and the TV transcoded it down to Dolby Digital. I got proper surround sound out of all Roku apps - Plex, Netflix and Prime Video.
Here is the issue I am seeing with my new Vizio. The Roku can be set to Auto or Dolby D+ and I will get these same results. If I start playing a video in Plex with an AC3 5.1 track, it plays fine all the time. But if I play a video in Plex with a TrueHD or DTS track, I get no audio between the Roku and the Vizio. If I then open the Vizio settings and change the audio away from Bitstream (ie: to PCM or Dolby D), audio will start playing. I can then change it BACK to Bitstream and the audio will work properly. At that point I can verify that the TV is transcoding the incoming audio to DD, and that I’m getting proper 5.1 sound out of the Sonos setup (both in the Sonos app and with my ears).
So this is definitely *not* a format transcoding issue. It seems like it’s some sort of handshake issue… the Roku isn’t communicating to the Vizio that the audio format has changed, but switching the Vizio’s audio setting renegotiates the audio settings and everything comes back to life.
One other question: Is “Dolby D” on the Vizio audio settings to *allow passing* of Dolby D audio? Or is it to *force* a transcode to Dolby D audio? The manual says that you must use Bitstream to pass >2 channels, but any mode other than “PCM” seems to allow that.