The following is a summary of forum comments about the UHD65 HDR banding issues and suggested cures plus my own observations.
Definition of issue:
Occasionally the UHD65 is interpreting an 8bit color source video as HDR (BT.2020 10/12 bit) content resulting in an image which shows a posterization or banding effect especially noticeable in outdoor sky scenes. This undesirable image corruption is most distracting and greatly impacts the value of HDR sources on the UHD65.
My own finding indicated that the projector does not use any sophisticated graphics processing to fill (dither) in the missing color data. The results are patches of identical colors especially noticeable in sky to horizon scenes.
- Have your source device configured to either 4:2:2 or 4:4:4 when sending HDR content
- Have your source device do better dithering of 8 bit color (a device capability dependent comment)
- Force a non-HDR signal from your source device (e.g. BT.709 8bit) so the UHD65 will not try to display a HDR 10bit color space
Forum posts that describe methods to resolve the HDR banding issue (YMMV):
My own experience with HDR banding and my eventual resolution:
My only sources of HDR content is Netflix, Amazon Instant video and YouTube, all from a Roku Ultra. Before I had my UHD65, I'd read a forum post that the a Roku's "Settings->System->Advanced System Settings->HDR subsampling" should be set to 4:2:0 particularly for [email protected]
sources. Well using that setting was a big mistake, on my part, as I did not realize that stripping the 10bit color data down to 8bit caused the projector's image to band.
Once I changed the Roku Ultra settings "Settings->System->Advanced System Settings->HDR subsampling->4:2:2" and of course "Settings->Display Type->4K HDR 60Hz TV" banding was all but eliminated. Additional UHD65 HDR image profile modifications resolved the slight banding that remained due to color saturation issues which are present in the default HDR settings.
Test video's that were used to both demonstrate banding and to test modifications during resolution analysis.
- Real 4K HDR: Cannon Beach Oregon HDR UHD (Chromecast Ultra) This is an all sky/sunset video, if you do not see banding in this one you've likely resolved the issue
- Real 4K HDR: TCL Four Basic Colors in HDR This one is excellent for not only revealing banding but also the colors settings in your UHD65's HDR image settings. Look out for saturation issues especially in the red dominate beginning of the video. Starting at 01:01 mm:ss check if you can see feather details on the parrot's throat while hanging upside down from a branch. The throat feathers are not distinct when red is saturated.
Marco Polo Season 1 Episode 7, starting at 21:40 mm:ss. Watch the brief wrestling scene for sky color banding. Right after that scene are wonderful examples of the richness of HDR10 colors seen in the blues and golds of the actor's costumes.
Problems still to be resolved:
Although my HDR banding has been eradicated, even in blacked out viewing conditions, the image is simply too dark. Unfortunately my current temporary solution, specific to Netflix, is to set the Roku Ultra "Settings->Display Type->4K 60Hz TV", this tricks the Netflix app into streaming it's HDR content as "Ultra HD 4K" (BT 709 8it). Effectively Netflix streams 4K video with properly dithered 8 bit color avoiding banding. You get a great bright 4K image but lose the richness of HDR color. So I'm still looking for image settings that can result in a brighter HDR image. Make sure Netflix is identifying the video as "Ultra HD 4K" as I once saw the change in Roku settings ignored by the Roku Netflix app which still identified the video as "HDR".
I'd love to hear from anyone with a Roku Ultra that achieved an acceptably bright HDR image and no banding on their UHD65.
Edit: The Netflix from Roku Ultra solution described above was also tested and confirmed as working with Amazon Prime HDR videos (e.g. Bosh).
Edit: After some research on "HDR images being too dark", it appears that culprits range from the streaming device used (e.g. Roku Ultra HDR too dark
) to the quality of the HDR compression by the streaming vendor to inherent limits of HDR10 to compensate versus Dolby Vision. Surprisingly multiple people chose to configure the source stream so that the original HDR source was effectively downgraded to a SDR BT.709 8bit stream. Sad but I guess that is currently a bleeding edge reality with HDR. At least this is not a specific UHD65 issue which oddly makes me feel better, just not fully satisfied.