Hacker News Reader

Comment by 83457 | Hacker News Reader

"I can send an IP packet to Europe faster than I can send a pixel to the screen. How f’d up is that?" - John Carmack

I had a hard time believing that quote at the time. John ended up answering the question I asked about it on SuperUser [1] with details about his setup. His writeup is impressive: he actually set up a high-speed camera to record the actual latency.

[1] https://superuser.com/q/419070/2269

I used to work for Philips' TV branch, they used a similar setup. Instead of a camera they mounted a light sensor to the display and measured end-to-end delay for various color transitions (white-to-black, black-to-white, ...). All other manufacturers and many serious reviewers perform similar tests.

Of course, these tests are always performed with all built-in image processing disabled, those can easily add 2 frames of delay on modern televisions. MPEG deblocking and noise removal are performed by most TV brands to improve image quality at a cost of latency.

Right, the issue is that 60Hz is ridiculously slow. Ethernet hardware is multiple orders of magnitude faster. It's just because of broadcast TV and CRT legacy. G-Sync / FreeSync allow up to 240Hz, which is ~4ms latency.

60Hz is 16.7ms between each picture. However, that only gives you a lower bound on the latency. The actual time from GPU sending picture, to picture being on screen, can be a lot more. See the John Carmack answer above.

No, the issue was that he was using a display with a crazy amount of buffering because they were doing so much filtering and doing it poorly.

It's not just monitors even keyboards can have 40+ms worth of delay and it all adds up.

I don't think that was what he was referring to

"I video record showing both the game controller and the screen with a 240 fps camera" https://superuser.com/q/419070/2269

So, it's total response times from key press on a game controller to screen that is important not individual components. Sure, 0.04 seconds on it's own is not a big deal, but when 5 or six things take 0.04 seconds you hit noticeable delays.

G-Sync and FreeSync have nothing to do with the available maximum refresh rate on any monitor. That is a property of the display interface.

Solution: send the pixel to the screen over IP!

(joking, but with a tiny serious element)

this reminds me of the argument that instead of going to USB C 3.1 as the grand unifying connector for all peripherals (including video), we should have instead migrated to Ethernet cables for everything.

ethernet over multimode fiber, I want to be able to have accessories hundreds of meters away from my computer

Just make sure those cables are never bent beyond the minimum bend radius.

It's amazing how much you can bend fiber. Fiber is really hard to break just by bending it, assuming it is well insulated. You can have performance loss with bends and kinks though.

Just use bend-insensitive fiber. It's not like copper cables like being kinked, either.

Careful, multi-mode fiber is near its scaling limits. 10GBASE-SR and 25GBASE-SR exist, but that's about it. (By contrast, 40GBASE-LR and 100GBASE-LR work over single-mode fiber, and DWDM + coherent optics can push the medium much further.) Wouldn't want to be stuck at 25 gbps forever ;-)

Yeah, some of us can type pretty fast. And for mice, some of us take clicker games seriously.

in all seriousness, why not?

The obvious ones: Ethernet cables are big (imagine one on a phone), and aren't designed to be plugged and unplugged the massive number of times that USB cables are (spring contacts wear out, little clips break).

USB cables have little to do with the question of sending pixels via IP

Outside HDMI and some DisplayPort cables, all display connectors click or screw in

And we’re talking about desktop OS and displays

I'm not even sure about sending it as IP, rather as raw Ethernet frames (or simply just using the cables).

well maybe the actual plug could be modified into a small form, while still being pin-compatible with cat 5/5e/6.

The little plastic bits always snap off. Ethernet is great for semipermanent wires but not very good for peripherals like portable hard drives that are constantly disconnected and reconnected.

What’s that to do with displays which aren’t unplugged frequently?

I plug/unplug from my display several times daily, since the MBP connected to it travels with me. Granted, the end of the cable in the monitor typically doesn't move¹

¹well, one of them. The crap LG monitors we have constantly forget about the peripherals that are attached, and one easy way to fix this is to detach/reattach the peripheral. I suspect that the company is never going to RMA these devices, sadly.

USB-C is used for all sorts of devices many of which are unplugged frequently.

That problem is largely solved if you use 8P8C connectors with a rubber boot protecting the latching tab.

https://info.pcboard.ca/wp-content/uploads/2017/04/RJ45-Conn...

Even with the protective guard the little plastic tabs inevitably break on me. I can't even say those have fared any better than the unprotected versions.

My main complaint is that the protective rubber often gets stiff as it ages, which can make it pretty dang hard to remove old cables (until you resort to pliers).

You can't tell me that's better than the USB-C connector.

Even HDMI is better.

My MacBook Pro’s USB-C connectors glitch if you move them slightly. I like the data rate but I’m not happy with RAM-pack wobble in 2017.

Yeah, live hinges (that is, plastic bits that intentionally bend, not rotate on pins) are always going to break eventually. They're just so easy to make that it's a trade off that doesn't fall in the consumer's favor.

Living hinges can have lifespan in the millions of cycles with the correct materials and design. I'm sure it's possible to make an Ethernet connector that doesn't break easily, but it would cost more, and people aren't willing to pay.

Actually not a bad idea. Ethernet speed is one gigabit per second.

And there are high throughput devices like LIDARs (eg Velodyne LiDAR known from Google/Waymo self-driving cars) that are connected via Ethernet rather than USB.

Having 1 GBit Ethernet LAN network since 2004, I would prefer the possibility to upgrade to 10Gbit home Ethernet in near future.

It's a terrible idea. USB-3 is faster than 1Gbit/s. and there's no way you can drive a 5K monitor with any current or near future Ethernet standard, the bandwidth demands are too punishing.

Ethernet isn't optimized around short-haul signals, like computer to screen over a few metres at most, it's for 100m+ runs in datacentres. The signals have to be a lot more durable.

> "USB-3 is faster than 1Gbit/s"

But Cat 6 Ethernet is 10 Gbit/s.

Still not as fast as USB-3+Thunderbolt which is already 40Gbit/s and intended to be pushed to at least 80Gbit/s to support 8K screens.

> there's no way you can drive a 5K monitor with any current or near future Ethernet standard, the bandwidth demands are too punishing.

Really? You need more than 100gbit for 5k monitor? Because there is an 40/100gbit ethernet phy standard right now (has been for a while, since 2011). And work is being done on up to 200gbit (due to be ratified in late 2018).

5120 * 2880 * 32bits * 60FPS is only 28.3 Gbit and both 40Gbit and 100Gbit are well established standards.

Granted 40GB cards are running 50$ and 100Gbit cards are running ~700$, but that's most from the low volumes involved.

Really though the larger issue is Ethernet connectors are not designed to be plugged in and removed regularly.

> "Ethernet connectors are not designed to be plugged in and removed regularly"

Well could easily use a smaller and easier plug while still being pin compatible with ethernet.

Currently ethernet doesn't look cheap enough for video to me.

Even a simple 1920x1080 60Hz monitor needs 3 Gb/s, a 2560*1440 144Hz monitor 13 Gb/s, a 4k 60Hz 12 Gb/s.

DisplayPort 1.2 offers 17 Gb/s and DisplayPort 1.3 offers 26 Gb/s.

40 Gbps and 100 Gbps Ethernet standard was defined in 2010 [1]. Google "buy 100 Gbps Ethernet" and you will find it is real, although currently is geared primarily for datacenters.

[1] wikipedia.org/wiki/100_Gigabit_Ethernet

Some people tried, most went out of business. Either chapter 11 or bought for assets and IP. OnLive was the biggest one.

people working on compositors should have that printed out and hung above their coffee machines.

Reply on news.ycombinator.com