I have an Apple TV running through a Pioneer Elite SC-LX801 to a Samsung UN49KS8000 Quantum Dot LED UHD TV. The image quality of the Channels app is very poor, with extreme posterization in dark parts of the video. I tried using the HD Homerun app on an Xbox One X, and the video is way better (looks the way you'd expect). Anyone else run into this and have any suggestions on what I can do to fix this?
What hdhomerun model and channels?
How does it look on the ATV using the InstaTV or VLC apps?
Another thing to check is whether the ATV4K is set to SDR mode or HDR mode.
HD Homerun model is HDHR3-CC (HD Homerun Prime 6 unit with a cable card). Firmware is up-to-date.
Channels app is latest.
I actually hadn't known about those other apps' compatibility w/HDHR. I just tried them both, and found the same poor video quality.
I had it set in HDR mode. I also have AppleTV set to match frame rate and range. However, if I set AppleTV to SDR mode, then the video looks fine. Is this a known bug in AppleTV--obviously, the cable HD channels aren't in HDR, so why is it trying to display them in HDR?
There is a setting in the Channels app that will force the app to switch your TV to SDR mode. You can tell it when you want to do it, since it can take a few seconds and will black out the screen (either do it when the app launches, or every time you play video only).
You’ll get the best results out of your Apple TV by keeping it in 4k SDR mode as the default, and letting Match Content do it’s job when you play videos.
We were watching the Oscars live last night and the picture quality was the worst I've ever seen on the Channels app. Even people who know nothing about picture quality were asking what the problem was. Any dark shadows showed massive pixilation.
TV is set to SDR mode. Tuner is new HDHomeRun Quatro
Basically same issue here. The picture is generally not very clear and at times is pixelated. I’ve messed with the picture settings over and over which helped a little. However when compared to other apps the clarity isn’t even close. I’m wondering if it’s associated with poor deinterlacing?
I’ve been having similar issues, mostly in the dark areas of the screen. AppleTV 4K was set to HDR (not aure when) so I changed it to SDR and we’ll see what happens. For the Channels App, is there a setting for Match Content? I see the SDR switching setting, which is set to Off right now.
For the Channels App, is there a setting for Match Content? I see the SDR switching setting, which is set to Off right now.
It's a tvOS system-level setting. You can find it in the Settings app. More information here: https://support.apple.com/en-us/HT208288
Got it! I was assuming it was a Channels App setting and not finding it 
I tried updating those settings as well with no change. The issue doesn't seem to be there live, but only with the DVR recordings.
I’ve tried the recommendations on this thread, but so far nothing has helped. The picture quality is way better using the HD Homerun app on I my Xbox One X. I like the Channels app interface better (plus prefer the quicker startup of using Apple TV vs Xbox), but the quality is so inferior I’m continually thinking of switching. Anyone solved this problem???
I wonder what app you are using? The one from the app store or beta?
I've recently downloaded the beta version and I found HD channels to be a lot more sharper (a lot more!)
I'm using the released version on the Apple TV app store.
I have more information that may shed some light on this problem.
When I was playing around with this previously, I’d set my AppleTV to SDR, and when I didn’t observe the posterization I set it back to HDR (in an attempt to confirm the difference), but didn’t see it then either. Thinking maybe this was fixed, I left it at HDR, but days later once again observed the really bad posterization.
I just performed a new experience that demonstrates what happened. I used the DVR to record a commercial that exhibits the posterization (AppleTV set to HDR mode):
I then set the AppleTV to SDR mode and the posterization went away:
Next, I put the AppleTV back into HDR mode, and the posterization was still gone. However, then I rebooted AppleTV, and the posterization was back again.
So I believe this proves that it is possible for the Channels app to correctly display content in SDR, irrespective of whether AppleTV is set to HDR or SDR mode. (BTW, I have AppleTV set to “match frame rate and dynamic range”.)
I too am having this issue. What I find interesting is the other streaming apps I use like Netflix, Prime Video and Sling don't have this problem. Therefore, I have to believe it is an issue with the Channel DVR app.
I did some more investigation, and submitted logs for successful and failing scenarios. I’ve confirmed that this is reproducible, so Channels app developers should be able to reproduce/fix this...
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After restarting Apple TV (set to HDR 4:2:2 mode), I played a DVR’ed segment that demonstrates the problem (source of the screen grabs I previously submitted). I confirmed the posterization was visible.
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I submitted logs
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I changed the Apple TV to SDR mode
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I re-played the DVR’ed segment, and confirmed that the posterization no longer occurred.
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I submitted logs again
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I changed the Apple TV back to HDR 4:2:2 mode
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To confirm the Apple TV was actually back in HDR 4:2:2 mode, I ran the HDR connection check. It came back reporting everything was OK.
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I re-played the DVR’ed segment, and confirmed that the posterization was still not occurring.
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I submitted the logs again
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As a final confirmation, I restarted the Apple TV again (without changing any settings—Apple TV still in HDR mode), and replayed the DVR’ed segment again. I confirmed that the posterization once again was visible.
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I submitted the logs one final time.
What was the "SDR Mode Switching" setting in the Channels app set to during this test?