Apple TV 4K


#61

The new ATV has a 24hz output option, I would guess its there because so many people who watch movies requested it. 120hz would be the best compromise to watch both frame rates without switching the output setting, but I don’t know if the ATV4k does this. I know my TV won’t do 4k at 120hz.
Manually switching is not a huge deal for me though, I don’t watch movies often enough for it to bother me. But having the output frame rate automatically switch to the frame rate of the source content would be a cool feature, even if it takes a second to switch.


#62

Yup me too. I’m exhausted complaining about it at his point. At least we finally have a 24hz option. And I’m in the same boat about movies, I don’t warch enough for it to be a pain to switch so I’m just happy I can at all, heh.


#63

Personally I set mine to 4K SDR. With a 1080p UI or video source the TV or the ATV will just pixel double anyway and I can’t tell the difference whichever does it. With 4K sources then I don’t have to switch. The only time I would have to switch is with a HDR source but my TV is worse in HDR than in SDR so I don’t bother (Samsung 60” Series 6 LCD).


#64

From the tvOS 11.2 beta notes (below). Could this finally be the answer to our requests?! @tmm1 @maddox

Mode Switching

Notes

AVKit uses automatic frame rate and dynamic range switching for fullscreen video playback on Apple TV 4K under most circumstances. tvOS 11.2 adds APIs for these features for apps that don’t use AVKit for video playback. For information, see https:// developer.apple.com/fall17/503.


#65

Still waiting on the documentation for AVDisplayCriteria to be published, but it sounds like this would let us force 50hz in the Channels video player (although perhaps only on the new 4K model).


#66

This was the first thing I thought of when I read this on macrumors. Lol. Here’s hoping! Good excuse to upgrade my Apple TV to 4K… then I guess a new 4K TV as well?? :thinking:


#67

4k tvs are cheap. And 4k streaming is really awesome to look at. Everyone who watches movies should get one. If all you use is Channels, it works the same. It would be nice if there were 4k OTA broadcasts already, but I think they will come in 2019. But I’ve currently settled on the ATV 4k SDR 60hz setting for everything, which looks great in the USA. My wife is not going to bother manually switching resolutions. I would welcome the auto-switching to match native movie frame rates though.


#68

Thank goodness Apple have come around to frame rate and range switching. 24Hz for movies and I can keep the SDR setting and only switch to HDR with HDR content.

Glad they have also done APIs for apps like Channels that use its own player rather than AVKit. On the subject of which - does Channels use AVKit for h264 and h265 and only use mplayer for mpeg2 or does it use mplayer for everything??

Any news of bitstream sound output in 11.2 to support Atmos? Also we all want the Dolby/DTS lights on our receivers to light up too rather than use PCM even though the quality is identicle!!


#69

We use VideoToolbox to decode h264/hevc but playback is still via the custom player.

Unlikely to happen, since the ATV needs to decode the audio to add in any system sounds before outputting to the speakers. Bitstream pass-through would not allow for navigation and other system sounds effects.


#70

Yes that was the reason for only outputting PCM with the XBO as well. However MS eventually had to add bitstream to support Atmos/DTS:X. It is a selectable option in the BluRay disc settings - streamed video isn’t supported.

I suspect Apple will too even though you will lose navigation sounds in fullscreen video. How many of us are going to miss a little beep when we press play/pause?? Games and the ATV UI can still output PCM so no issue there. PIP would be an issue but as this isn’t implemented on the ATV it isn’t.


#71

Yes of course. Forgot you have to deinterlace it as well.

So will Channels be able to use the new APIs to set frame rate to 50Hz or 60Hz to match the broadcast frame rate?. I don’t know of any broadcasters that change frame rates to 24Hz for movies or whether this is even possible with ATSC or DVB. If it is perhaps (I hope) it’s only a matter of time before broadcasters just broadcast in the original framerate and let the TV adapt to it. How many fixed frequency TVs are there out there that are digital compatible anyway if such a thing ever existed.


#73

Just watched the Apple developer video. It recommends leaving the app UI in the system default (which is more than likely going to be 60Hz) and only switching framerate when playing full screen video. This is so the app UI remains “fluid”.

For the Channels app this makes little sense as the choice is only going to be between 50 and 60Hz both of which are fluid. The UI animations only suffer at 24Hz and Channels won’t be using this framerate. If Channels does follow the Apple guidelines in the countries with 50Hz TV it will mode switch back and forth with each play/stop with annoying TV flickers/blanks if you are a channel hopper. However if you are an app hopper then that could be annoying too if the Channels UI was in 50Hz.

The video is also specific about only the 4K ATV supporting the the new feature. I guess that makes sense for depth switching if the driver for this is that Apple is fed up getting complaints about how crap SDR content looks in HDR mode on many common TVs. Not Apple’s fault but they get the fallout.

Don’t know why they offered framerate switching though. Are there TVs that don’t offer HDR 60Hz? Or are the current Movies streamed at 60Hz and they want to save bandwidth by being able to stream at native 24Hz???


#74

Frame rate switching has nothing to do with bandwidth, but it has everything to do with removing judder and 3:2 pulldown. Its currently working in Netflix, Hulu, and iTunes Movies that I’ve tested and it’s working amazing.


#75

Right, the movies are filmed at 24fps, and the stream is 24fps. Whatever hz your TV is set to, it compensates by adding/dropping frames. This produces a slight judder at certain intervals and is mostly evident in scenes where there is panning or scrolling. 24hz allows for one screen refresh for exactly every single movie frame. You are viewing the source content as it was intended to be viewed.


#76

That’s not what I was referring to. I think we are all aware of tellecine judder.

What I was asking was why offer this option only on the 4K model? Apple’s video implied that the ATV4 would not get the option at all. What has caused Apple to offer it if they have gotten along without it for so long? Other streamers also get along quite profitably without dynamic framerate switching. The only devices I know that output at 24fps are disc players that have 24fps sources.

So were Apple’s sources for the ATV4 (and lower models) 24fps for movies or were they higher framerates to avoid judder (ie optimally telecined at source rather than on device). I never noticed any judder with movies with the ATV set to 60fps but did on 50fps. I should notice it on both if the source was 24fps shouldn’t I?

I was just guessing that maybe 30fps video source vs 24fps for HD movies isn’t worth worrying about bandwidth but for 4K it is.

I’ll have a play tomorrow when I get home from holiday and load up the 11.2 public beta now it is available on my ATV4K.

Has anyone put 11.2 on an ATV4? Is framerate switching available on it?


#77

Okay just answered my own question through a simple search (doh). Framerate matching has been implemented on the 4K only so that Movies with Dolby Vision will switch to 24fps HDR rather than stay at 60Hz HDR because some TVs only support DV at 30Hz or lower and HDR10 above this.

I’ve always found that whenever Apple changes a decision it previously made it is because of a new unanticipated hassle for them to support. I’m sure the only reason they have done this after 10 years of ATV having a fixed resolution is because people are complaining that their very expensive 4K TVs look worse in HDR mode with SDR content (like I did) and DV isn’t working with the device set to 60Hz.

However back to Channels! Are there plans to offer framerate matching for Channels?


#78

Apple doesn’t re-encode the movies on iTunes to insert extra frames. They are the same framerate as would be on a DVD, Blu-Ray, or on the original film as filmed by movie cameras. A movie filmed at 24fps will be encoded at 24fps, because the movie contains that many frames to encode per second. It will be like this from Netflix, Amazon, iTunes, etc. Some devices are better at the 3:2 pulldown, but it is still there.


#79

Yes thanks. I was desperately trying to find a reason why Apple would make the change. The simple answer of matching output to source to eliminate telecine judder is attractive but as Apple hasn’t done this in the 10 year history of the ATV when they could have made me sceptical that was the reason. I have been racking my brains why they would therefore have reason to do it otherwise and initially played with ideas like bandwidth saving etc. However I feel that the reason I mention above is what drove the decision. I think the “smoking gun” evidence for this is that framerate switching is not implemented on the ATV4.


#80

Interestingly, and more pertinent to Channels, movies broadcast OTA will be adjusted to 50 or 60fps interlaced. Also I have noticed when Netflix/iTunes etc stream UK content that was shot in PAL 50Hz they have converted it to 60Hz to match the much larger US content. And it’s for that reason I won’t be just switching my ATV to 50 Hz mode even though I can now watch movies at 24fps automatically. Channels would look better for UK OTA content but streaming apps would suffer for TV shows. However I don’t know if other video apps will switch to 60Hz from 50Hz if I did. This could turn into a bit of a lottery with regards to which apps choose to adjust and which do not.


#81

The issue with the Apple TV 4 is that the CPU was never made to support 24Hz, only 60Hz and 50Hz. The CPU in the Apple TV 4K was made to actually support up to 120Hz and spin down to 24Hz with the new iPads and the “ProMotion” display.

The other issues with running the ATV4K in HDR all the time was that the conversion processes actually adds artifacts to the video (I personally tested this) which would degrade the video. Running the TV in HDR constantly also causes a huge increase in power usage on the TV itself, unless you have an OLED (I have an OLED and a LED). Those two aren’t real issues when just running it at 60Hz so Apple never really needed to address it since judder wasn’t much of an issue on the Apple TV.