Just wanted to add my voice here - I also am having this issue with my 2019 Q70R 75 inch tv. I've done a TON of troubleshooting, and can confirm that the delay happens with any external source that is attempting to play Dolby Digital content (tested 5.1 and Atmos). I tested this with a Samsung 4k disc player, xbox one x, and chromecast ultra. I can recreate this with sonos playbar via optical, sonos arc via HDMI, and onkyo receiver via optical. I am convinced the issue happens regardless of the external speakers that are being used. I had a tech come out after opening a ticket, they confirmed it did not appear to be a hardware issue but that it is likely something to do with the software. I also went ahead and made an (unlisted) youtube video to show the delay (not sure if we are allowed to put links here, so if somebody wants to see it I guess just message me), which I measured to be approximately 300ms. FWIW I work in the telephony industry and 200ms is the top end of what we would consider "acceptable" before you start running into crosstalk and other similar issues, so 300ms is very much noticable, and for me, I can't even watch a movie with this delay it's so distracting. The ticket it still open, but I don't feel great about it. Otherwise I love this tv. PCM is *not* a good solution, although it removes the delay, it is a *stereo* track, as in, 2 channels. Dolby uses either 5.1 or 7.1 for a completely different and significantly enhanced experience. I'll try to update this post with whatever samsung responds with.
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