Hacker News Reader

Comment by frereubu | Hacker News Reader

Slightly OT, but the one thing I hate about watching films on streaming services is the banding on the images. Any relatively dark scene with gradations of lighting in the background is a mess of shifting lines. I'd love to see something like this built in to a native Netflix client... although I realise hell will freeze over before that's a reality.

View on HN

I don't see why clever video post-processing couldn't help with this. Why do you say hell will freeze over? This seems like a much easier solution for them than to increase bitrates and thus, bandwidth

The issue is that Netflix would have to do it, and they'd have to get permission from the content owners to modify the stream. I suspect hell would freeze over before anyone could agree on the relevant licensing arrangement

They might agree to a compression format, and the format could define post-processing.

Third party desktop software could also do this were it not for HDCP. I'm pretty sure any attempt to front-run the stream with a full-screen image processor will blacken the display.

You can do it in Chrome on macos without the screen going black, if you disable hardware acceleration. I dunno how long that will last, though.

Every good chinese 10$ HDMI Splitter or Capture Card will just ignore HDCP entirely. It's actually refreshing, you just plug it in and it works fine.

FYI, they already do this by synthesizing film grain! https://waveletbeam.com/index.php/news/48-netflix-film-grain...

Interesting!

For each source, they must develop a "grain profile" (or, likely multiple profiles) so they're applying the right grain ""effect" when re-graining?

And on the re-graining: is this being done on the client side??? Like, is my Roku adding back the grain to my Paul Thomas Anderson films?

(Note: I'm only 5 min through the video, so these may be answered)

TVs can do that, Netflix doesn’t have to. Our new top of the line Sony (A95K) has a debanding image setting. (But I think pretty much all Sony TVs have that setting.)

However, it doesn’t seem extremely great and tends to smooth out things it shouldn’t. I have it turned off. It seems like debanding in realtime is still too big of a task even for the most expensive TVs.

Which is why Netflix are the ones who should do it. Even on low-powered devices, they could stream some pre-computed debanding data for each pixel in the video (e. g. as a separate channel encoded with video).

No that's in the decoder step which is up to the shared library that's used for it on your system - likely doing a hardware call to your graphics card which is the perfect place to do this stuff.

The solution is a drop in decoder replacement. Heck it might already exist, it's a pretty obvious, easy and direct application.

Even the Apple TV 4K’s UI suffers from banding, such as when they generate blurred backgrounds in the Music app to match album artwork. They need to bring back their 1980s dithering algorithms or something.

Interesting. I don't see this with my Dolby Vision-capable setup, presumably because it stays in 10-bit mode for both UI rendering and video playback.

This may be due to how Netflix’s VMAF metric judges frame quality and prefers images with more edges, even when these are false edges caused by banding:

https://mobile.twitter.com/jonsneyers/status/157337162413241...

Moving to higher bit depths than 8-bit will also help a bit - it's not helped by agressive compression, but even with lossless compression (PNG) 8-bit gradients like skies still suffer from the problem...

AI based compression is under current research https://www.youtube.com/watch?v=dVa1xRaHTA0

Netflix has strong history of optimizing their streams. I bet they will be first to deploy.

You don’t need AI for this. The problem is that dark areas are fundamentally harder to code (they need more bits), and how much the artifacts are visible depends strongly on how your TV and viewing environment are set up.

It’s possible they’re viewing in a too bright setup and are seeing things they weren’t supposed to.

Netflix has the originals though. They would sooner just start streaming better quality.

Reply on news.ycombinator.com