Apple TV 4K


Sorry I don’t buy that argument about the A8 in the ATV4. As others have pointed out the chip (or rather the PowerVR GX6450 GPU) must decode 24P video because that is what Apple streams to it for movies. If the HDMI circuitry can’t output 24P then that’s a different matter but the ATV4 is HDMI 1.4 compliant so should have no issue with this. I have no reason to believe Apple couldn’t enable 24P on the ATV4 from a technical point of view.

The other arguments about HDR processing and power use seem perfectly valid.


Just got the Apple TV 4K after using the 4th generation with Channels. On the LG OLED65B7A, Channels guide and video have the washed out look of the rest of the user interface when set to 4K HDR mode on the Apple TV. Switching to 4K SDR improves everything.

My TV settings are fine (used rtings as guide) since a sample 4K HDR clip from the YouTube app looks amazing.

Plex is also very washed out with 4K HDR enabled.

I understand iOS 11.2 is supposed to fix switching but wonder if the devs can do this on the app level for Channels. It’ll be a LONG time before we have HDR let alone 4K to watch via cable TV. No reason not to default to SDR and 4K or 1080p if iOS allows you to change on an app level.


Yes it looks like tvOS 11.2 allows us to force SDR mode for our entire app.

So far there’s no public API available to let us force 50hz mode for DVB users. Hopefully some public methods will be added to AVDisplayCriteria in future betas.

We haven’t been able to try anything out yet, because the 11.2 beta broke network based XCode deployments, and the new ATV4K doesn’t have a USB-C port. But by the time 11.2 comes out, we will be fully integrated with any new available APIs.


So in the interim on ATV 4K (Manual Settings) playing to an LG Oled E6:

Channels - Set at 4K SDR
ITunes Movies (4K DV movies) - Set at 4K Dolby Vision 24Hz

Is this correct?


This is just what happens when watching non HDR content in an HDR mode. This is expected. That’s why everyone went bananas when the 4K shipped with it always on. It most defiantly should be operated in SDR mode and switched to HDR mode for the times you watch HDR content.

Thanks god for tvOS 11.2

tvOS 11.2 is what introduces the ability to let us switch at the app level. We won’t have the ability to do it until then. Hopefully it all comes soon!


yep, @DebbieFL!


Don’t Apple recommend not doing at the App level but for individual video assets?

I’ve just got home and installed 11.2 and have to say Apple have done a very good job with this if the App uses the native video player. Because HDR sources have to be identified as such in a video manifest then the ATV switches to HDR automatically with the Movies App and even Netflix HDR content such as Star Trek Discovery. Anything without an HDR entry in the manifest is assumed SDR and it switches to SDR. The App UIs don’t trigger a change in colour depth. Also 11.2 seems a lot better in HDR mode than 11.0 and 11.1 were but still get some dimming with SDR content. The dashboard/launcher whatever it’s called seems a LOT better. Although very interestingly the aerial screen saver does not trigger a change to HDR (in Preview at least, I haven’t paused long enough for it to trigger automatically yet).

Channels behaves as expected - the UI and video remain in whatever the chosen system default is because of your use of a custom player. There is still the overlay dimming/undimming issue as expected.

I’m keeping my aTV in 4K SDR with dynamic switching turned on. My TV (Samsung series 6) blanks for about 0.5 seconds but nothing unpleasant - no flashes or popups saying mode change has happened.

Overall I’m very happy with 11.2 now.


Sounds like they did a great job, awesome.

Don’t Apple recommend not doing at the App level but for individual video assets?

We plan to do this because it guarantees less switching. What Apple suggests is for devs to strategize mode switches so that they happen the least amount possible. People tend to change channels a lot while watching TV vs putting on a 2 hour movie. If we only switched when video played, it would be a lot of toggling for Channels users. Since we 100% know for sure that none of our video is HDR, we’ll switch when the app starts, so that there’s only a single switching moment.

And again, we suggest that you live in SDR mode by default, like you said you planned on doing. If that’s the case, there will be no switching at all.


Also using 11.2. It is fantastic. The HDR / frame rate switches very quickly. I don’t even notice it. Can verify with the ‘info’ button on the TV remote that frame rate has changed to 24fps for movies and HDR is turned on. Everything looks great now!


@shepherdr your bandwidth theory is debunked. Apple allows framerate switching on the ATV4K to match source content, regardless of HDR. Automatic HDR switching is a separate option.


I agree with @maddox – force Channels to 50Hz SDR for DVB countries and 60Hz SDR for US/Canada when the app opens. I’m on 11.2 beta and have set my default as 4K 50Hz SDR, and on other apps its switching the correct format most of the time.


@djcastaldo I think I said as much myself about the bandwidth theory - I was spitballing trying to work out Apple’s motives. I still maintain this is not some A/V buff benevolence from Apple though. They said themselves that framerate switching and colour depth switching was inelegant when they launched the 4K. They have done a U-turn on this. I do not think they would have done so if SDR looked good on HDR screens in HDR mode and people weren’t going “bananas” as @maddox phrased it. I also think they would not have allowed framerate switching if they had chosen HDR10 rather than DV. They have to enable framerate switching (down to 24P) to facilitate HDR switching for DV on screens that can’t do DV above 30Hz. Yes you can turn on framerate switching without depth switching but I don’t think that implies Apple would have offered it without the hoo-ha about HDR. Anyway this is a Channels forum not Arstechnica so perhaps we should call this X-files debate to a halt.

@stoli412 I think @tmm1 said that as yet there are no APIs that force 50Hz. When you set the aTV to 50Hz so there is no stutter on Channels DVB content does Netflix/TV etc change it to 60Hz for their content?

Now I can get the kids off watching their movie I’ve had a play myself- yes Netflix does alter 50Hz to 60Hz. But the results are very interesting about what formats Netflix stream things in (basically the original framerate) - Movies are as expected 24P. Older US TV shows are 60fps. Modern US TV shows (like Star Trek Discovery and Big Bang Theory) are also streamed in 24P. UK shows (Doctor Who for example) are actually in 50fps. So there is quite a bit of resolution switching even within an app like Netflix.

When Channels gets updated to use this capability could we have betas with both switching the App entirely and per video or a setting to choose?


Okay my holiday is over so I promise to stop posting!! One last thought though.

I had no idea most of the primetime US TV shows my family watch are all filmed on digital film cameras at 24fps and that UK content was streamed at 50fps even on iTunes or Netflix (I assumed big providers like Apple and Netflix telecine them to 60fps to benefit the much larger US/Canada market). So there really was never a big reason to have set my aTV at 60Hz which I have done for years. For shows that are 60fps with tvOS11.2 the device will switch anyway now. Therefore I’m just going to set my UI to 50Hz and so Channels won’t need a framerate lock after all.

However as a purist I would like Channels, if possible, to detect what the framerate is and switch automatically. You never know someone somewhere might have an ATSC and DVB HDHR attached or move an aTV/DVR combo between countries and therefore have mixed framerate recordings.

Channels 3.1.4 on tvOS 11.2 public beta - UK

I think Apple did it because it is a better way to do it and allows for smoother, higher-quality video. And because many many users had asked for it. Why did apple include 4k? Or HDR? They will always try to move hardware and software in a direction of progress.


Loaded 11.2 Beta today and set Match Content…Range and Frame Rate

For now:

Set ATV 4K at: 4K SDR (for watching Channels recordings)
When I play an iTunes (4K DV) Movie, it now automatically changes to Dolby Vision 24Hz
Automatically changes back to 4K SDR when playing Channels recordings


Will be totally awesome when Channels employs the API to change to 4K SDR, then I can set the ATV 4K to 4K HDR (and can view the screensavers in the best quality) and the ATV will change to 4K SDR for Channels Recordings & HD iTunes movies or will change to Dolby Vision for the 4K DV movies.


almost. The whole ATV UI, iTunes movie menus, Netflix interface, youTube UI, etc, looks awesome in 4k SDR. The only time you want DV(HDR) is when HDR content is being displayed, in which case the ATV4K now switches automatically and displays the correct color / frame rate for the source content.


If the ATV 4K is set to 4K SDR, the screensaver doesn’t auto switch to 4K HDR.

So if I’m only using ATV for Channels playback and iTunes Movies why wouldn’t I want to set base to 4K HDR (once Channels adds API switch).


OK, I think I understand now.

If ATV 4K is set to 4K HDR, iTunes HD will not auto switch to SDR, it will stay on HDR.

Too bad for screensavers.


No, if you have it set to 4K HDR, iTunes HD will auto switch to SDR, then switch back to HDR when you’re done playing.


Aaacckk! :thinking: :scream: