3 ms·

> This is usually visible as ugly banding or blocking in dark scenes. I was just complaining about this a couple weeks ago with some friends after the “Dark” e

by zaroth 7y ago

> This is usually visible as ugly banding or blocking in dark scenes. I was just complaining about this a couple weeks ago with some friends after the “Dark” episode of GoT. I was saying the codecs don’t seem to have caught up or they are just being fed at too low a bit rate to really excel at dark scenes. It’s hard to imagine this is just a scaling issue with the color ranges, and if so, how could it possibly not have been fixed?! I have a high end OLED screen in a very dark room, and I was very disappointed by the picture quality. Enough to wish I hadn’t watched it through HBO Go and that I had a better source. I would love to see some before/after scenes showing the effect of the patch.

brigade 7y ago
It's not; full-range YCbCr doesn't exist anywhere in the "pro" or broadcast pipelines that would have been used for GoT. I think he meant to say that the limited dynamic range of 8-bit video manifests most obviously in dark scenes, since that's where standard gamma curves are the most imprecise relative to our vision (which was fine back when TVs couldn't reproduce that range anyway.) The 14% from full-range doesn't help that much; really you need the 4x finer precision you get from 10bit.
brokenmachine 7y ago
>I have a high end OLED screen in a very dark room, and I was very disappointed by the picture quality. Unfortunately for you, high end OLED in a very dark room is literally the most likely conditions under which you'd be annoyed by these problems... :-) HDR is the way to go.
- zaroth 7y ago
  It’s Dolby Vision from the ATV to the set, it’s the source encoding I assume that just couldn’t live up to material. Perhaps bitrate compromises have to be made when you’re streaming to so many people at once, but it’s not usually so glaring.
  - brokenmachine 7y ago
    Oh, that's surprising. If it is truly Dolby Vision then the dynamic metadata should cope very well with darker scenes, so it must be either the source material or the compression for streaming. It will be interesting to see if it looks better when a higher-quality Bluray version comes out.
stevenwoo 7y ago
The Amazon 720P version had noticeable banding several times during that episode that was distracting even the day after so it's probably not a bandwidth issue, the Dothraki charge into the dark might have been a cool idea on paper but what a disappointment in execution. I think the director and cinematographer are just ignorant of how stuff gets delivered to consumers. https://news.avclub.com/was-game-of-thrones-the-long-night-too-dark-to-see-t-1834416256 https://news.avclub.com/was-game-of-thrones-the-long-night-t...
- zaroth 7y ago
  From a tweet linked from that article: https://pbs.twimg.com/media/D5SmDG7WwAAMhdf.jpg:large https://pbs.twimg.com/media/D5SmDG7WwAAMhdf.jpg:large I think that particular screenshot makes it look even worse than it was, but it was definitely sub-par. I assume that a hardcopy 4K Bluray would not exhibit the same effects?
zbobet2012 7y ago
A) Having a different color space is a violation of spec (H.264 profile's Baseline, Main, and High all define yuv420p). Don't expect your decoder to present these properly. B) The issues you're seeing with background banding are _not_, primarily colorspace issues. While having a larger colorspace helps, these are largely related to the way quantization is done for the macro blocks in h.264. The original h.264 spec (which is baseline and main profiles) only had a exponential quantization matrix. During quantization we are "rounding" to the nearest integer for pixels. If we imagine each macroblock only had _one_ frequency coefficient. Dark scenes would have a low coefficient, say 1.4 If we round to 1 that's a 28.5% error in the rounding. A brighter scene which is at 9.4 has a rounding error of only 4.3%. Custom quantization matrices and non linear quantization matrices(which are available in newer codecs) help deal with this. Advanced h264 encoders have variance adaptive quantization technologies to help choose what level of quantization to apply to a block. In short: h264 has technological limitations that are not caused by colorspace and the encoder doing this encode doesn't have strong AQ.

by zaroth 7y ago

brigade 7y ago

It's not; full-range YCbCr doesn't exist anywhere in the "pro" or broadcast pipelines that would have been used for GoT. I think he meant to say that the limited dynamic range of 8-bit video manifests most obviously in dark scenes, since that's where standard gamma curves are the most imprecise relative to our vision (which was fine back when TVs couldn't reproduce that range anyway.) The 14% from full-range doesn't help that much; really you need the 4x finer precision you get from 10bit.

brokenmachine 7y ago

>I have a high end OLED screen in a very dark room, and I was very disappointed by the picture quality. Unfortunately for you, high end OLED in a very dark room is literally the most likely conditions under which you'd be annoyed by these problems... :-) HDR is the way to go.

zaroth 7y ago
It’s Dolby Vision from the ATV to the set, it’s the source encoding I assume that just couldn’t live up to material. Perhaps bitrate compromises have to be made when you’re streaming to so many people at once, but it’s not usually so glaring.
- brokenmachine 7y ago
  Oh, that's surprising. If it is truly Dolby Vision then the dynamic metadata should cope very well with darker scenes, so it must be either the source material or the compression for streaming. It will be interesting to see if it looks better when a higher-quality Bluray version comes out.

stevenwoo 7y ago

The Amazon 720P version had noticeable banding several times during that episode that was distracting even the day after so it's probably not a bandwidth issue, the Dothraki charge into the dark might have been a cool idea on paper but what a disappointment in execution. I think the director and cinematographer are just ignorant of how stuff gets delivered to consumers. https://news.avclub.com/was-game-of-thrones-the-long-night-too-dark-to-see-t-1834416256 https://news.avclub.com/was-game-of-thrones-the-long-night-t...

zaroth 7y ago
From a tweet linked from that article: https://pbs.twimg.com/media/D5SmDG7WwAAMhdf.jpg:large https://pbs.twimg.com/media/D5SmDG7WwAAMhdf.jpg:large I think that particular screenshot makes it look even worse than it was, but it was definitely sub-par. I assume that a hardcopy 4K Bluray would not exhibit the same effects?

zbobet2012 7y ago

A) Having a different color space is a violation of spec (H.264 profile's Baseline, Main, and High all define yuv420p). Don't expect your decoder to present these properly. B) The issues you're seeing with background banding are _not_, primarily colorspace issues. While having a larger colorspace helps, these are largely related to the way quantization is done for the macro blocks in h.264. The original h.264 spec (which is baseline and main profiles) only had a exponential quantization matrix. During quantization we are "rounding" to the nearest integer for pixels. If we imagine each macroblock only had _one_ frequency coefficient. Dark scenes would have a low coefficient, say 1.4 If we round to 1 that's a 28.5% error in the rounding. A brighter scene which is at 9.4 has a rounding error of only 4.3%. Custom quantization matrices and non linear quantization matrices(which are available in newer codecs) help deal with this. Advanced h264 encoders have variance adaptive quantization technologies to help choose what level of quantization to apply to a block. In short: h264 has technological limitations that are not caused by colorspace and the encoder doing this encode doesn't have strong AQ.