Poor HDR 10+ streaming on on Vizio M658-G1
My Vizio M658-G1 streams 4k HDR on you tube fine. I have Comcast with a 4k box and 25mbs internet speed. When I stream Prime Video 4k HDR10+ picture is poor whether I use the cable box app or the app built in to the TV. TV is updated and shows HDR10+ when I press the info button. Can't figure out what is wrong. Is it possible Prime Video will only stream properly on a 4k fire TV device. I don't have netflix for comparison.
Any advice is appreciated.