(I posted this in the Roku Player forum too, not sure which is proper)
First, my set up:
New 2020 TCL Roku 6 series (R35).
Older Onkyo TX-NR414 AV Receiver, connected via HDMI out to the eARC in on the TCL
Apple TV 4k connected to HDMI 3 on the TCL (connecting it to the TV because the Onkyo doesn't support 4k)
Here's the issue:
If I choose, under audio settings, "Auto Passthrough" for the s/pdif and eArc setting, I lose Dolby sound if I rewind or fast-forward a movie scene from any app on the TCL itself. For example, watching Inception (to test my surround sound) from Amazon Prime on the TCL.....I start the movie, my receiver shows the Dolby codec. If I rewind a scene, the receiver loses the codec and the surround is gone. I tested this with other native apps (Netflix, Disney+...same thing). So, to get it back I'd have to exit the movie and re-start it.
Now, if I watch the same movie from the same app (Inception, from Amazon Prime) but this time from the Apple TV.....I do NOT lose Dolby when fast forwarding or rewinding.
So, that's issue #1, why am I losing Dolby if I rewind or fast-forward a movie or show from the TCL source.
Now, issue #2 is this: If I change the s/pdif and eArc setting to Auto Detect....my receiver shows the Dolby Digital Plus codec.....NO MATTER what the source.......for example, Casablanca is not DD+. The codec does NOT disappear when I rewind or fast forward, but it doesn't appear to be accurate. For example, using the same movie, Inception, it shows DD+ but it's really just DD.
I cannot for the life of me figure out what's going on here. (On an unrelated, or possibly related note, depending on which s/pdif setting and depending on if I'm using TCL or Apple, the lip sync in Amazon Prime video only can be quite off or dead on, and this seems to be only in Prime)
Just to eliminate the possibility, I did put new HDMI cables on all the connections.