Apple TV 4K: Flickering near-blacks in 1080p SDR content

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Apple TV 4K: Flickering near-blacks in 1080p SDR content

I recently got a new ATV4K and love it. I set default output to 4K SDR, so that anything below 4K was getting upscaled to 4K by the ATV4K. I had frame rate matching and dynamic range matching both turned on, to allow for content natively available in Dolby Vision or HDR10 to be presented in that format, while all SDR content stayed in that format.

The problem I started noticing is that, when watching 1080p SDR content output in 4K SDR, near-black parts of darker scenes would flicker rapidly. At first I thought maybe the flickering was actually part of the original video but it isn't. I can pause the video and still see various groups of pixels around the screen flicker. It doesn't happen with every dimly lit scene but I've still noticed it quite a bit. I saw it throughout The Hateful Eight on Netflix. However, when I went to the exact same scene in The Hateful Eight in the Showtime Anytime app on the ATV4K, I didn't see it. And when I went to the exact same scene in the same movie in the Netflix app built into my LG B6 OLED, I didn't see any flickering. But then I saw the same issue at various spots in an episode of The Chi in Showtime Anytime on the ATV4K. It's not restricted to a particular app but it does appear to be restricted to SDR HD content that's being upscaled to 4K. I haven't seen it at all with content natively available in 4K and/or HDR/Dolby Vision. If I set output of the ATV4K to 1080p SDR (and let the TV do the upscaling to 4K), it reduces flickering, although it doesn't seem to completely get rid of it. If I set output to 4K HDR and turn off dynamic range matching, it gets rid of the problem but then that forces SDR content to be falsely presented as HDR, which is not ideal, IMO.

I thought the problem might be with my HDMI cable, so I purchased a new "Premium Certified HDMI" cable that's been tested and is guaranteed to support 18 Mbps throughput, including support for HDR. Unfortunately, the new cable made no difference. And keep in mind that I see no problems at all with content natively available in 4K. Changing various picture settings on my TV didn't solve the issue either. The problem seems to lie in the way that ATV4K upscales HD content to 4K while still keeping it in its original SDR dynamic range.

Unfortunately, this issue affects the vast majority of content available from streaming sources. Think about it: most of what's out there is in HD (1080p) SDR.

Apple TV 4K, iOS 11.2.2

Posted on Jan 23, 2018 9:47 AM

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Answer 1

Feb 13, 2018 1:37 AM in response to Teemster

Hello,

Recently, I discovered the same problem. I have Apple TV 4k, and I use everyday 1080p format as primary to watching movies. I have no 4k TV so I didn't test this mode.

In my setup 1080p 24 fps flickering occurs wiht some dark scenes. Even when I pause the movies some area flickers. Indeed playing the same movie on other player didn't give such bad phenomena.

So, I would like to pay attention, the problem is common with 1080p mode also, not only 4k. Always with 24 fps. With 60 fps the situation is much better.

There is one more problem. When I tested flickering phenomena I used test patterns with many bars near black level and below black level. I was very surprised, Apple TV 4k, does clip everything below 17 black level and everything above 234 white level. Why? I tested 4 different sources: bluray player, philips media player, LG built-on TV player, TS sat decoder player and all of them palayed this area of black and white correctly. Why Apple TV 4k don't do it also? Wihtout this black and white bars there is very difficult to set brighntess and contrast of TV to match picture to Apple TV.

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