I have an Express+. The HDMI port is connected to my projector and the AV port goes to my 15-year-old receiver. I have used this setup without problems until two or three months ago, when the audio quality deteriorated. It now gets randomly louder/softer and muddy/clear. It's really annoying.
I have tested my receiver, replaced my Roku, replaced the AV cables, and adjusted the audio settings in Roku. But the problem persists.
What can I do? I'm guessing that my receiver doesn't support some new digital audio format, but I hate to invest in a new receiver without knowing whether it will support the new format. When I read about all the various versions of Dolby, my head spins.
When you say your AV port goes to your AVR, what do you mean? When I look up the specs for the Express+, it only shows digital audio out via HDMI. Or does your projector have some kind of audio out from what is coming in via the HDMI cable? . Or is it the white and red RCA analog connections? If it's this, these connections don't support anything but two channel stereo. If your Roku settings are on anything other than stereo, that might be messing with the audio signals. Using these connections you don't need to be concerned about the different audio formats, because they all require a digital audio connection, either via optical or HDMI.
Dan Roku Stick (3600), Ultra (4640), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.
This might be the AAC (and also EAC3) 5.1 downsample on-the-fly to 2.0 making your sound flutter. It goes quiet soft one moment, so hard to hear dialog. Then few moments later, loud as bejesus, where is the remote turn this down. At night it gets hard to find a comfortable sound level without always reaching for the remote. This also affects my Roku Ultra #4640 when using AAC. If I instead have my server transcode this to MP3 2.0 the problem immediately goes away. The roku will advertise(feature or bug?) AAC 5.1 support to applications reading the AudioDecodeInfo() from roDeviceInfo. This is what Roku trained us to do as app developers is to believe this information. Now the Roku takes the AAC 5.1 you give it, strips it down to 2.0 on the device, and outputs this to stereo. This used to cost a slight delay in lipsync. Roku got that bug fixed, but now the new bug is the difference in decibel levels when downmuxing the channels. They seem to not be allowing the center dialog channel to remain or are, but it is cross fading against the stereo too and causing decibel loss. I wish Roku would increase the center channel +6DB before they demuxed the channels. This would at least keep the dialog the loudest part of the stereo signal when downmixing.
BTW, OS9 specifically says it has sound normalization. Might it be the addressing of this very annoying thing? maybe... lol