I can't say for sure when the behavior changed, but as of this morning at least three channels (Netflix, Amazon, HBO GO) produce no sound when playing content which has an AC3 5.1 audio track. Another channel (Plex) works just fine. In all three cases my Yamaha soundbar shows that it is receiving a digital surround track (it only has a single light for this purpose, so I can't tell what it thinks it is seeing), but for two of them there is no sound at all.
I'm using a Roku Ultra, model 4460X, serial number YJ00GK857796. Software version is 8.0.1 build 4047-46, and I just checked for updates and restarted the unit. It's using a wired Ethernet connection so there is no concern about signal strength. The HDMI output of the Ultra is fed into an HDMI-over-IP network and then to a Yamaha soundbar (and then into an LG TV), but since the behavior varies by channel it's hard to imagine how the HDMI connection could be at fault. Audio mode is set to "Auto (Dolby D+, DTS)" and HDMI is set to "Dolby D+, DTS".
Thanks for any guidance you can provide, this is really odd behavior.
Hey all. It's looking like this may be related to a the 8.0.1 build 4047-46 firmware update. We are unable to replicate this on 8.0.1 4042-29. There are reports of this affecting more channel than just Plex. We will work with Roku to try and isolate the issue and update this thread when we have more info.[/size][/color]
@trekkeriii, the soundbar is a Yamaha YAS-207BL. The owner's manual doesn't list the specific Dolby and DTS formats that are supported, but from what I've read Dolby Digital Plus is compatible with any Dolby Digital decoder.
So it appears that Plex put a workaround into their channel, which of course no effect on any other Roku channels.
Is there any way to get the Roku (Ultra, in my case) to display the details of the HDMI stream it is sending out? I'd like to be able to confirm that audio format being sent to my system so that I can troubleshoot this further.
Just closing this out: this was indeed a soundbar issue. My soundbar did not support Dolby Digital Plus, and the Roku channels I listed above all use it for 5.1 surround. After switching to a DD+-supporting soundbar, the channels are working as they should.