AppleTV 4K Source Behind-the-Scenes Format (HDR/Dolby Vision) & Refresh Rate Questions

guptasa1

macrumors newbie
Original poster
Oct 19, 2017
14
3
Hi all,

I apologize for the technical nature of this thread, but I've been trying to figure this out for two days, and I still can't find a 100% answer despite some excellent threads I've read, some of which seem to contradict.

A little background on my setup, but hopefully others will find this discussion useful. I'm running a LG 65E6P with a Marantz SR7011 receiver. Originally I had the AppleTV going through the receiver, but due to a problem with Dolby Vision at 24Hz and poor audio sync, I have the AppleTV connected directly to the TV and am using ARC (which seems like it's working properly).

I'm aware that it's always best to output the source as something that goes evenly into the TV's refresh rate. Ie, for a Blu-Ray player that outputs 24fps, a 24Hz refresh is perfect. But I'm not sure it's that simple with a streaming box like AppleTV 4K, because there's no way to tell exactly what the source format is, as far as I can tell anyway. I am aware you have to manually set the output if you want to change refresh and between HDR and Dolby Vision. What I don't know is if, when I set the refresh rate to 24Hz, if it's trying to play a 24fps source "natively", or if it's taking a source that should be at 24, upconverting it the preferred Apple format of 60, then downconverting it AGAIN back to 24, which would seem weird, but I could see it possible since Apple seems to really want 60Hz as its ideal setting... If the latter was true, it would mean refresh rate wouldn't matter much and the fastest available should always be used.

Some specific examples to illustrate what I'm trying to determine:

1.) I play a movie I rented or bought on iTunes in 4K w/ Dolby Vision. My choices for Hz are 30, 25, and 24. Now, I know a Blu-Ray would be at 24Hz. So setting it to 24 should result in the least judder. BUT, I can't find confirmation of what the video SOURCE file is. I've seen some things that made me think that everything iTunes sends is at 60 and the AppleTV does the down-conversion, in which case, would setting it to 24 even help in any way? Or am I actually getting a 24fps signal that works with the 24Hz refresh rate optimally?

2.) The same question, but with Netflix. I found a neat trick on the computer to see frames sent if I watch Netflix in a browser. (Try CTRL-ALT-SHIFT-D while watching something.) That seems to indicate ~24fps for the content I tried. Does this equate to the AppleTV app? If so, it would again mean 24Hz is the best setting, but again, I don't know if somehow behind the scenes the AppleTV receives all sources in 60 or converts to that before outputting at whatever refresh rate is chose (I wouldn't think so tho'.).

3.) Basically the same as the other two, but for HDR where 60Hz is available. I know some TV's double the 60 to 120 so 24 can fit in evenly, but does it still make sense to watch at 24 where available, or again, is moot because of what the AppleTV is doing behind the scenes with the source?

4.) For SDR, since the choices are only 50 or 60Hz, is it best to just stick to the 60? Any benefit going for 50 on 24Hz sources like movies, since it's closer to 48?

Thanks for anyone who can shed any light on this! It's driving me nuts!
 
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BODYBUILDERPAUL

macrumors 68000
Feb 9, 2009
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Barcelona
Fascinating and exactly what i was wondering Guptasa1. How does it look to your eyes during the playback of iTunes movies and Netflix? Do you notice any of that horrible judder during panning?

I saw the new film 'The Last Face' rented from iTunes last night on a ATV4 and there was a lot of panning throughout the whole film and the judder was really really really horrible! It was everywhere. Charlize Theron was absolutely stunning in it and the photography with natural light was breathtaking. A very dark but beautiful film based on a true story. A great film for testing frame rates!!!

I'm getting a ATV 4K but definitely waiting for things like this to get sorted if they ever do.
 

guptasa1

macrumors newbie
Original poster
Oct 19, 2017
14
3
Hey Paul!

I have noticed some judder while panning (I keep all artificial Motion Smoothing off), but I haven't played with it enough to say anything 100%. I do think 4K Dolby Vision at 24Hz seems smoother than 30Hz (the movie I was testing with was Pacific Rim, and that movie has a lot of shaky cam, etc. - it sounds like "The Last Face" makes for a really interesting showcase as well). I had an AppleTV 4 previous to that, and as I recall it was mainly locked at either 50 or 60Hz, so there was never a perfect option, even if it did output 24fps.

I just wish someone knew what in fact it *is* putting out, as I have yet to see that verified!

The 4K is definitely a good box, and I think once I get it set up and have things figured out as far as what all I'm doing for all types of content (as manual switching between SDR, HDR, and Dolby Vision is a must for me), I'll really enjoy it...but these limitations and the fact that it's so hard to determine what's actually being output is frustrating.
 

archer75

macrumors 68030
Jan 26, 2005
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Oregon
I have a LG B6 and I do leave the motion option on but custom. It has de-judder and de-blur. One I set at 9 and one I set at 2. I'm at work so I can't tell you which is which but to my eyes it takes away all judder without causing the soap opera effect.

As far as the rest goes, I don't sweat it. I set it to whatever looks fine. Since I don't see judder I tend to leave it at 60hz or 30hz as 24hz makes the gui slow.
 

guptasa1

macrumors newbie
Original poster
Oct 19, 2017
14
3
Yeah, I'm beginning to think just sticking with 60 for everything but Vision and 30 for that is probably the simplest solution. 24 might be a bit smoother to my eyes, but it causes audio issues for me. I might have to play around with True Motion - we'll see.

Still would love to know what's actually being output, tho'!
 

BODYBUILDERPAUL

macrumors 68000
Feb 9, 2009
1,533
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Barcelona
Yeah, I'm beginning to think just sticking with 60 for everything but Vision and 30 for that is probably the simplest solution. 24 might be a bit smoother to my eyes, but it causes audio issues for me. I might have to play around with True Motion - we'll see.

Still would love to know what's actually being output, tho'!
Hi Guptasa1!
When I move over to the ATV 4K i'm beginning to think that again, i'll leave it on 60fps setting. But i'll try all of the other settings. Apple are usually so thorough with their R&D that they must have a true reason for leaving it on the 60fps.
I was kind of hoping big time, that they would have decided some Apple technology equivalent to the ProMotion on the iPad Pro and the NEXT iPhone X S model in a years time ;) where by, it adjusted perfectly from 24fps to 60 (or in the iPad Pro's case, 24 to 120). Now that would of been amazing.
As a poster wrote a few weeks ago, we'll have to see what HDMI 2.1 (or is it 2.2?) brings but then, that'll be for the ATV 6 maybe :)
[doublepost=1508589328][/doublepost]
Yeah, I'm beginning to think just sticking with 60 for everything but Vision and 30 for that is probably the simplest solution. 24 might be a bit smoother to my eyes, but it causes audio issues for me. I might have to play around with True Motion - we'll see.

Still would love to know what's actually being output, tho'!

Also the FIRST in-depth review comparing 4K UHD BluRay from the Opposite 203 with 4K iTunes!!!
 

guptasa1

macrumors newbie
Original poster
Oct 19, 2017
14
3
Thanks for the very interesting posts.

Yeah, I've decided I'll probably go with:
- SDR at 60Hz
- HDR at 60Hz
- Dolby Vision at 30Hz (maximum my TV will allow).

It could be argued Vision would be less juddery at 24Hz, but that introduces audio sync problems for me not present at 30Hz, so I'd have to try to figure out the proper offset for my receiver and reset it every time I want to watch Dolby Vision content. I thought about doing this, but the reality is, 3:2 pulldown can be adjusted to, and I really don't think I'll have an issue with it, especially if I get used to it. (Those of you with 2017 models instead can do the 60Hz for everything.)
 

cynics

macrumors G4
Jan 8, 2012
11,313
1,696
Thanks for the very interesting posts.

Yeah, I've decided I'll probably go with:
- SDR at 60Hz
- HDR at 60Hz
- Dolby Vision at 30Hz (maximum my TV will allow).

It could be argued Vision would be less juddery at 24Hz, but that introduces audio sync problems for me not present at 30Hz, so I'd have to try to figure out the proper offset for my receiver and reset it every time I want to watch Dolby Vision content. I thought about doing this, but the reality is, 3:2 pulldown can be adjusted to, and I really don't think I'll have an issue with it, especially if I get used to it. (Those of you with 2017 models instead can do the 60Hz for everything.)
With both your TV and receiver you (depending on your setup, ie receiver to tv, or tv to receiver via ARC/Toslink) can manually adjust audio sync.

I believe LG calls the setting AV Sync Adjust and Marantz calls it Audio Delay.
 

guptasa1

macrumors newbie
Original poster
Oct 19, 2017
14
3
With both your TV and receiver you (depending on your setup, ie receiver to tv, or tv to receiver via ARC/Toslink) can manually adjust audio sync.

I believe LG calls the setting AV Sync Adjust and Marantz calls it Audio Delay.
Thanks for the input! Yes, I did figure out how to do this on the Marantz (the LG can only do it if going through the TV first) and a ballpark offset for it that works. The issue is, it would need to be changed back and forth every time I switch refresh rates or sources, and with the way the menu system works, that takes a bit of time sadly. So it's not my preferred solution, but it is one if there's no other way.