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Old 19th November 2019, 17:24   #7211  |  Link
benwaggoner
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Join Date: Jan 2006
Location: Portland, OR
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Quote:
Originally Posted by markiemarcus View Post
Was quite a treat to watch it again I must say. I wonder what the difference in process was, because it obviously wasn't an easy source to work with.

It's a nice encode too. I've noticed that a number of grainy UHD Blu-rays have issues from time-to-time in that regard. There are a handful of scenes in both Blade Runner and The Fog that completely fall apart. Seems inexcusable given how much space there is to play with. In the case of The Fog, the bit rate actually plummets in the affected scenes.
Grain is essentially uncompressible random noise. It's random spatially and temporally, includes chroma, and is typically very high frequency. So it can use the vast majority of bits encoding a frame, is sensitive to QP differences between I, P, B, and b frames, and is otherwise a worst-case nightmare.

While encoding 4K content might take only 2x the bitrate as 1080p, doing grain is much more linear. 80 Mbps 4K is only twice that of Blu-ray 1080p. There are cases of grain that is quite literally impossible to encode without perceptible artifacts. Heck, just encoding a flat gray slide with JUST grain on it can be very challenging.

And that grain, even in lossless, can be quite distracting to a viewer. There's certainly way more fine detail grain on the Blade Runner Blu-ray than Ridley Scott ever saw when he was working on it, due to perf screens, dimmer projectors, etcetera. And in HDR, it's also way brighter grain than would have been seen before. One risk with SMPTE 2100 HDR is that any filters that assume gamma instead of linear light will do weird high contrast things in high luma, since the code values have much bigger jumps in luma than 709 gamma had. Conversely, low luma might not get enough filtering if processed assuming 709.
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