Comment by mips_r4300i | Hacker News Reader

Comment by mips_r4300i | Hacker News Reader

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IMAX 70mm is still the absolute benchmark for film quality, and has been so for decades. A really rough estimate is you'd need a 15-20k digital projector to approach the resolution of the film.

However, IMAX tried to go mass-market around 2008 and that's why you see so many supposedly-IMAX theaters now. They typically use 2K DLP projectors. Yeah, basically the same res as a gaming PC from 2011.

My theater has the crummy 2k digital, and let em tell you, you can DEFINITELY see the pixels. I would call it passable but it's not really great at all. The only benefit of these IMAX locations is that normal digital cinema can be even worse!

There are newer 4k laser projectors that some theaters are retrofitting into their old huge IMAX locations, but these still aren't going to hold a candle. 4k still isn't even enough to really come close to 35mm.

The digital tech just isn't there yet.

Consider also that resolution is only one factor. Bandwidth is another. Digital movies are often full of compression artefacts, especially when there's a lot going on in the scene.

As far as I know, movie theaters do not compress video. Its seems like they have a digital surrogate for movie reals

https://en.wikipedia.org/wiki/Digital_Cinema_Package

That's true; with a cap of 250 Mbps for the DCP stream, and a 4K frame size of 4096 × 2160, that's ~28 bits per pixel (if the soundtrack is disregarded). There might be a small amount of subsampling or run length encoding going on, but it's entirely plausible to distribute and play an uncompressed film on a professional projector.

EDIT: Forgot to factor frame rate into the math. Divide that by 24 frames per second. That got me curious, so I looked into it and found they're using JPEG 2000 on each frame with no inter-frame deltas. Essentially like a constant stream of I-frames.

From that link, it looks like they do compress and use JPEG2000 for it, with a max bit-rate of 250 mbit/s. IIRC 4k blu rays don't do more than 100 mbit/s, so that's quite a bit better.

4K uses h265 though, so I’d bet it achieves quite a bit better quality per bit.

Good point, and personally I've never seen compression artifacts on well-produced blu rays.

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