How does UHD BD compare to the files used by proper digital movie theaters?

[bhampton]

Does anyone know by the numbers how UHD BD compares with the files used in movie theaters?

I have heard many theaters get encrypted hard drives containing movie releases.

I have also heard (but I do not know for sure) that digital movie theater projectors are 4K.

UHD BD claims theater quality sound and video at home and seems to deliver. I wonder if actual theaters still have higher bit rates. I know some theaters have higher frame rates.

-Brian

[koberulz]

It's completely different in every way.

[benricci]

It's a mixture of 2K and 4K screens (we'll leave IMAX out of it for now), with a lot of theaters actually using 2K setups, not 4K (keep in mind, this is still high enough quality for a super-huge theatre screen).

Digital Cinemas, as opposed to home video formats, get files up to 250 Mb/s (many films reaching up to 150GB in file size, if I remember correctly) which is a higher bitrate than home formats like UHD and normal blu-ray. So there's going to be less compression employed at the cinema than at home, though your ability to actually perceive those differences depends on a lot of factors.

I'm sure there are those with more expert knowledge than me, but that's the general gist of it. They're not just popping in a UHD disc and pressing play, if that's what you were wondering. it's an entirely different setup.

You can go down the rabbit hole and get lost in lots of tech specs here: https://en.wikipedia.org/wiki/Digital_Cinema_Package

[Geoff D]

Basically, it's all so different that it's not worth trying to compare them on file sizes alone.

[silentbob]

I haven’t worked at a greater in 7 years. Basically lost my job because we went all digital. Still, yeah they came on HDD but more were heading forward with Digital Downloads. When we had 2-4 Theaters each print had to loaded onto each theatre HDD and build the print in a drag and drop sort of way. Input your 4 ques for the theatre lighting and you have yourself a print. We were all 2k projectors but 2-4 of them were capable of being upgraded to show 4K (if I remember correctly) Good chunk of your Theaters are more then likely just 2K projectors. The gentleman who trained me installed a few and said he really didn’t notice much if any difference. He also help setup the first IMAX theatre in Toronto at Ontario Place all them years ago. We’re buying glass tube audio components from local HiFi stores he said before normal audio setups happened. My theatre used Christie Projectors (2040 and 3020 I believe were the model numbers) Like you mention as well, yes they are encrypted. Depending on the studio the digital key to unlock your print were usually good 2-3 weeks before needing another digital key after that to continue playing the film. I think Sony was the only distributor we had that allowed their prints to stay unlock for 3-4months. They ranged in film size from 74GB to well over 100GB for the 3D Avatar like films.

[meremortal]

Originally Posted by benricci

It's a mixture of 2K and 4K screens (we'll leave IMAX out of it for now), with a lot of theaters actually using 2K setups, not 4K (keep in mind, this is still high enough quality for a super-huge theatre screen).

Digital Cinemas, as opposed to home video formats, get files up to 250 Mb/s (many films reaching up to 150GB in file size, if I remember correctly) which is a higher bitrate than home formats like UHD and normal blu-ray. So there's going to be less compression employed at the cinema than at home, though your ability to actually perceive those differences depends on a lot of factors.

I'm sure there are those with more expert knowledge than me, but that's the general gist of it. They're not just popping in a UHD disc and pressing play, if that's what you were wondering. it's an entirely different setup.

You can go down the rabbit hole and get lost in lots of tech specs here: https://en.wikipedia.org/wiki/Digital_Cinema_Package

Bolded part certainly is worth noting. I've seen movies at arthouse theaters where they just used the blu ray as the source from what looked like a computer or htpc kind of setup since I've seen a media player and scrolling mouse projected onto the screen at times. And they looked pretty good to me even on a huge cinema screen in 1080p. I've sat close to the front rows, towards the middle, or in the back rows and pretty much anywhere has looked pretty nice on a theater screen. If blu ray can look great in a cinema, then I'd like to see some uhds in that setting for comparison.

[avs commenter]

It’s only convenient to compare bitrate and file size when comparing HT digital vs physical

[Geoff D]

Originally Posted by avs commenter

It’s only convenient to compare bitrate and file size when comparing HT digital vs physical

...because they use the same masters, chroma subsampling, compression schemes etc. It's more or less 'like for like' when it comes to the underlying standards, unlike digital cinema vs home cinema

[avs commenter]

Originally Posted by Geoff D

...because they use the same masters, chroma subsampling, compression schemes etc. It's more or less 'like for like' when it comes to the underlying standards, unlike digital cinema vs home cinema

So we’re done with bitrate? These will be the new buzzwords?

[Phil92]

Originally Posted by bhampton

UHD BD claims theater quality sound and video at home and seems to deliver. I wonder if actual theaters still have higher bit rates. I know some theaters have higher frame rates.

-Brian

DVDs and Blu-rays said the same thing once upon a time.

In short, it’s not comparable at all.

[brian9229]

Some theaters download the files from satellites, through whatever studio.

[s_har]

Originally Posted by avs commenter

It’s only convenient to compare bitrate and file size when comparing HT digital vs physical

Comparing bitrate when it comes to streaming VS physical is a comparison that makes more sense though.
They are both HEVC encodes (theaters use a different file format entirely so a direct comparison in bitrate doesn’t make sense).
On top of that streaming and physical are both watched under the exact same circumstances in our homes using the same displays, viewing distance etc so those are basically an apples to apples comparison, which theatrical is not, imo.

[Fjodor2000]

Originally Posted by benricci

Digital Cinemas, as opposed to home video formats, get files up to 250 Mb/s (many films reaching up to 150GB in file size, if I remember correctly) which is a higher bitrate than home formats like UHD and normal blu-ray. So there's going to be less compression employed at the cinema than at home

DCP is just a series of JPEG 2000 images, and simply speaking the encoder looks for similarities within a single frame when compressing. H.264/265 as is used on BD/UHD on the other hand look for similarities in a number of subsequent frames, and can use that to compress more efficiently. If there is not much differences between subsequent frames (i.e. typically little movement & low noise), this will result in much better compression. DCP vs H264/265 are completely different encoders, and this was just one example where they differ.

So it's apples vs oranges as others also has mentioned. You cannot look only at the bitrate when comparing.

[ditcin]

All I know when I went to see Fathom's release of CLOSE ENCOUNTERS it was horrible. Blurry, and bad color. It was nothing like any of the copies of the film on DVD, BD, or even UHD.
I was extremely disappointed - especially since I originally saw it 13 times starting with the original theatrical release, then the Special Edition release. Those were prints and look much better.
I complained to the theater and was given free passes to another show. They explained they simply downloaded the file and screened it.

[HD Goofnut]

[David M]

Originally Posted by bhampton

Does anyone know by the numbers how UHD BD compares with the files used in movie theaters?

I have heard many theaters get encrypted hard drives containing movie releases.

I have also heard (but I do not know for sure) that digital movie theater projectors are 4K.

UHD BD claims theater quality sound and video at home and seems to deliver. I wonder if actual theaters still have higher bit rates. I know some theaters have higher frame rates.

-Brian

There's a lot more to it than just bitrates, but:

In terms of the image: Digital Cinema uses JPEG2000 compression at a max bitrate of 250mbps. That max rate goes for both 2K and 4K DCPs, so a 2K DCP will actually be less compressed than a 4K one. At a bitrate this high, DCP compressed images can afford not to rely on inter-frame compression at all. Each frame is intra coded, meaning that it is its own standalone entity. The frames don't refer to each other at all, which basically eliminates compression-related motion artefacts. Beyond that bitrate ceiling, DCPs are (as far as I'm aware) limited only by the maximum size of hard disk drive available, in theory, unlike a UHD BD where you have to get your entire disc into 66 or 100gb.

By comparison, UHD BD uses HEVC at a max video bitrate of 120mbps. Average bitrates are typically quite a bit lower for practical considerations. Crucially, like all consumer formats, it relies heavily on temporal redundancy, in other words, only storing the differences between frames, as Fjodor pointed out above. On UHD BD, as with standard BD, only one frame each second is stored in full. The other 23 in a 24fps film are approximated by the codec, which tries to store only the parts of the picture that change between frames. This is what can cause textures like film grain to swarm and swim around if there's too much compression, or not good compression.

For audio, Digital Cinema should have the edge if we're comparing Dolby Atmos (the home version operates at reduced bandwidth). Otherwise, they're comparable.

Taking that out of the equation, you then have to consider the hardware. Not all digital cinema presentations will be good (projectors not properly maintained, etc.), but for the average user, going into a theater and watching a DCP will give you much better quality than your home TV, simply because most home TVs haven't been properly set up.

Purely on image quality, a UHD BD, or in some cases even a standard BD, on a really good home display, could give a theatrical presentation a run for its money under the right conditions (if the disc is encoded well and the display properly set up). Even then though, you're comparing two very different experiences. I can forgive a lot to see a movie on the big screen with an audience.

[professorwho]

Originally Posted by brian9229

Some theaters download the files from satellites, through whatever studio.

I've experienced that several times. Mostly with regards to Fathom Events limited runs of classic films and anime titles. It's pretty easy to tell if it was downloaded from a satellite with a low bitrate DCP, as the artifacting can get REALLY bad (anime films have a ton of banding, but the worst had to be when I saw King Kong- the amount of macroblocking was insane!).

[Dubstar]

Originally Posted by professorwho

I've experienced that several times. Mostly with regards to Fathom Events limited runs of classic films and anime titles. It's pretty easy to tell if it was downloaded from a satellite with a low bitrate DCP, as the artifacting can get REALLY bad (anime films have a ton of banding, but the worst had to be when I saw King Kong- the amount of macroblocking was insane!).

the couple of times I saw Fathom Event's satellite feeds were downright shit.

[David M]

Originally Posted by professorwho

I've experienced that several times. Mostly with regards to Fathom Events limited runs of classic films and anime titles. It's pretty easy to tell if it was downloaded from a satellite with a low bitrate DCP, as the artifacting can get REALLY bad (anime films have a ton of banding, but the worst had to be when I saw King Kong- the amount of macroblocking was insane!).

That's really upsetting to hear that compression issues are being allowed to stink up the theatrical experience.

[Fjodor2000]

Originally Posted by David M

On UHD BD, as with standard BD, only one frame each second is stored in full. The other 23 in a 24fps film are approximated by the codec, which tries to store only the parts of the picture that change between frames.

Isn’t it up to 23 approximated frames between each I frame (which is stored in full)?

See section 2.1.2 here which says that the max number of frames in a GOP (Group Of Pictures) is 24 for 23.976 Hz content:
http://blu-raydisc.com/Assets/Downlo...608a-clean.pdf
and I don’t see any minimum number of frames in a GOP specified.

And each GOP must start with a full I frame:
https://en.wikipedia.org/wiki/Group_of_pictures