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Highly technical question about ATV HD playback and output

M

MacinJosh

macrumors 6502a
Original poster
Jan 29, 2006
676
55
Finland
Background:

Although I might not be the first to come up with this idea, I have not seen others do it yet. I came up with the idea of doing anamorphic 1080p -> 720p conversions similar to DVDs. Only this time, instead of 16:9 to 4:3, it would be 2.35:1 or 2.4:1 to 16:9.

Example:

Fellowship of the Rings BluRay appears to be in 2.4:1 ratio resulting in a 1920x800 resolution when the black bars are cropped. Instead of doing a straight scale-down to 1280x528, I decided to utilise every pixel the ATV is capable of pushing. I used Handbrake to convert the 1920x800 to 1280x720 anamorphic resulting in 1728x720 displayed pixels instead of 1280x528.

Those of you who understand anamorphic will be fine with getting this. For those who don't, the movie is encoded to 1280x720 resolution, the Apple TV maximum. Since it's in a different aspect ratio than the original, the picture would be squashed. So, like widescreen DVDs, to play it back properly, the system would stretch the image resulting in 1728x720 displayed resolution.

iTunes, Quicktime, iPad, iPhone and Apple TV all understand the anamorphic coding and stretch it out properly and play it back properly. That's not a problem at all.

Question:

My question is: What benefit will I get out of it on an Apple TV? Sure, if I watch it on my FullHD display on my Mac, I get all the pixels to use. But what about the Apple TV? I don't have a FullHD TV to test it out.

I know the Apple TV is limited to playing back 720p files. But I do know that the ATV can output 1080p. Even the 1st gen one. So, how would the movie in the example playback on an Apple TV hooked to a FullHD display with an output of 1080p?

Will it:

a) Stretch it and scale it to 1280x528 and then send it to the TV as such?
b) Send the movie to to the TV as is and the TV then stretch it to get the maximum potential of the file?

I don't even know how the Apple TV operates in 1080p mode. Does it upscale 720p to 1080p? If so, will it:

c) Stretch it and scale it to 1280x528, upscale to 1080p and then send it to the TV?
d) Stretch it to 1728x720, upscale to 1080p and then send it to the TV?

Thanks for any input.
 
Many people have been doing this since the ATV1 so you're in good company. Short answer, yes there's a real increase in vertical resolution if you're using an ATV1 since it outputs to 1080p as you'd expect, no if you're only using an ATV2 since it only outputs to 720p no matter what, hopefully yes on an ATV3 and of course on any computer outputting to a screen bigger than 720p.
 
peterjcat said:
Many people have been doing this since the ATV1 so you're in good company. Short answer, yes there's a real increase in vertical resolution if you're using an ATV1 since it outputs to 1080p as you'd expect, no if you're only using an ATV2 since it only outputs to 720p no matter what, hopefully yes on an ATV3 and of course on any computer outputting to a screen bigger than 720p.
Click to expand...

Wonderful, thanks a bunch for clearing that up! I do have an ATV1 :)
 
peterjcat said:
Short answer, yes there's a real increase in vertical resolution if you're using an ATV1 since it outputs to 1080p as you'd expect, no if you're only using an ATV2 since it only outputs to 720p no matter what,
Click to expand...
Er, neither atv can output 1080p in stock form. Even hacked the atv2 can't (ask xbmc) but the atv 1 *can* render 1080p to the display running linux with a chd chip.

anything over 720p besides mentioned above is an upscale.
 
dynaflash said:
Er, neither atv can output 1080p in stock form. Even hacked the atv2 can't (ask xbmc) but the atv 1 *can* render 1080p to the display running linux with a chd chip.

anything over 720p besides mentioned above is an upscale.
Click to expand...

Um, yes it can. In stock. From Wikipedia:

AppleTV's video output can be set to either 1080i or 1080p; however, this resolution is limited to the user interface and the viewing of photographs - all other content is simply upscaled to those resolutions. Apple TV cannot play 1080i or 1080p video content (e.g., HD camera video).

I think you should read my first post more thoroughly. I'm not talking about playing back movies beyond 720p which it certainly can't in stock form.
 
er, read your own wiki quote: its *upscaling* your custom anamorphic encode. plus I didn't quote you. I was quoting the person that said the appletv can output 1080p. Any anamorphic beyond 720p on a stock atv is really mostly a waste since it cannot render it to display, it upscales it just like it upscales a dvd. Do what you wish but I am just suggesting stretching things greater using custom anamorphic is not likely to really give you any greater visual quality on an atv.
 
dynaflash said:
er, read your own wiki quote: its *upscaling* your custom anamorphic encode. plus I didn't quote you. I was quoting the person that said the appletv can output 1080p. Any anamorphic beyond 720p on a stock atv is really mostly a waste since it cannot render it to display, it upscales it just like it upscales a dvd. Do what you wish but I am just suggesting stretching things greater using custom anamorphic is not likely to really give you any greater visual quality on an atv.
Click to expand...

I understand what upscaling is. That's why I came here to find out what the Apple TV does and listed the the four questions in my original post. So you're saying that the answer is: c) Stretch it and scale it to 1280x528, upscale to 1080p and then send it to the TV?

I know your reputation as a guru in these matters so I know I can take your word for it.
 
I'm sorry if I've misled anyone and I don't have an ATV1 anymore so can't test, but am going on the conventional wisdom that it's (d) and not (c) for the ATV1 (not the ATV2) since the ATV1 can both render a file of 1280 x 720 pixels and output to a screen at 1080p and I'm not sure of the technical reason why, having successfully decoded the anamorphic 1280 x 720 file, it would have to downscale it to 1280 x 544 before upscaling it again. We assumed that the 1280 x 720 would be upscaled directly to 1080p even on anamorphic encodes. I always thought this was a Nightstorm trick, though I could be remembering that wrong and don't want to cause any disharmony among gurus!
 
no worries, I will talk to NightStorm and find out exactly what he is doing. The main point I was making is ... neither atv can render 1080p to a display which is a common misconception when people see the 1080P setting the atv 1 uses when calibrating to your tv. I am not suggesting you have that misconception but I see it all to often and just wanted to make sure anyone reading it didn't fall into that trap.

Now ... you want to stick a chd into an atv 1 and stick linux xbmc on it ... thats an entirely different story .... but I digress ... ;)
 
Just happened to be looking through threads while sitting in my hotel room at Squaw Valley (on vacation) and happened to see my name so I thought I should post something...

I've been using custom anamorphic for my HD-DVD and Bluray encodes for some time now... I believe back to when I had the original AppleTV. At the time, it was believed that using this method would improve visual quality when selecting 1080p from the settings menu. However, as dynaflash already mentioned, the XBMC team determined that this was not the case.

That said, I've continued to utilize this method as it does help when playing a movie on my iMac (admittedly, I only really do this when playing around with encode settings). I also wanted to have some level of "future proofing" as I fully assumed Apple would release an AppleTV capable of outputting a native 1080p signal.

You might wonder why I don't plan on going back to the source and creating a new 1080p encode to take full advantage of the new unit. For me, it really comes down to the number of encodes I'd have to redo, backward compatibility with a previous generation AppleTV (bedroom), and final size of the encodes. While I have 8TB available to my iTunes library, my iOS devices have far less available on a daily basis and I like being able to load a number of movies and TV shows without having to think about removing other content to make room.

OK, with that said I'm going to go back and watch the blizzard unfold out my window... They are calling for about 3-feet of snow over the next 24-36 hours. :D

EDIT: Just noticed that .9.6 was released today... Congrats dynaflash and the rest of the Handbrake team!
 
Last edited:
Nightstorm: right on brother, right on. we were supposed to have a foot tonight but now its warm so its rain and ice. Go figure :( . Enjoy boarding, you should have plenty of fresh tomorrow!
 
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