Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Displayport: A Better Video Interface

hackaday.com

Post reply on HN
Print view View original

181–190 of 426 posts

Re: Displayport: A Better Video Interface

#181

Post by xxpor »

drbawb wrote: post #167
AlotOfReading wrote: post #156

Earlier quoted context omitted.

I use one, so I can confirm they work extremely well, subject to some caveats: * The total cable length is important, both between the host / KVM and the KVM / monitor, as well as any daisy chained displays you have. I had to use certified cables to get everything working reliably with my setup. * There's a weird interaction with BIOS power on. The boot display drivers I have freak out if they aren't the active displ…

>There's a weird interaction with BIOS power on. The boot display drivers I have freak out if they aren't the active display and fail. I solve this by switching the KVM before I turn the computer on. After everything is booted into an OS, it works fine to switch. Do you have an AMD GPU by any chance? I have the level1tech 2-head DP 1.4 KVM, with an AMD RX 560 on a Linux host, and after updating to kernel 6.4 recently…

I have a similar issue with a Nvidia 1080Ti on my old desktop. It's related to the UEFI deciding if the iGPU or the Nvidia GPU should be primary and to disable the iGPU or if the iGPU should stay enabled.

Re: Displayport: A Better Video Interface

#182

Post by green-salt »

spearman wrote: post #165

> A carefully shaped money-backed lever over the market is absolutely part of reason you never see DisplayPort inputs on consumer TVs, where HDMI group reigns supreme What does this actually mean?

HDMI is licensed, Displayport doesn't need one. I'm sure there's money changing hands in the TV sector of most display manufacturers.

Re: Displayport: A Better Video Interface

#183

Post by qubitcoder »

LoveMortuus wrote: post #10

I personally prefer HDMI or DVI, I don't like DisplayPort because on the display that I have, when I turn off the display the computer detects it as if I've physically disconnected the display, which then moves all the windows that I had open around and breaks my macros...

While not specific to DisplayPort, I've been really impressed with the AV Access 8K KVM Switch [1]. 4K at 120Hz without chroma subsampling was a hard requirement.

I use it with macOS Ventura and a Windows 11 desktop. It works nicely in conjunction with a Dell Thunderbolt 3 dock to power an LG OLED and support additional accessories. And it has EDID emulation, which is crucial for maintaining consistent display arrangement.

I've tried other DisplayPort KVM switches with mixed success. This is the first one that's worked out of the box.

[1] https://www.avaccess.com/products/8ksw21-kvm/

[2] https://www.amazon.com/dp/B0BPRZPFM6?

Re: Displayport: A Better Video Interface

#184

Post by samtho »

crazygringo wrote: post #119

> Just like most digital interfaces nowadays, DisplayPort sends its data in packets. This might sound like a reasonable expectation, but none of the other popular video-carrying interfaces use packets in a traditional sense – VGA, DVI, HDMI and laptop panel LVDS all work with a a stream of pixels at a certain clock rate. Funny, a stream of data at a constant rate makes much more sense to me intuitively than packets,…

> Funny, a stream of data at a constant rate makes much more sense to me intuitively than packets, specifically for uncompressed video.

There is a data rate floor for how fast the device that outputs must meet. We’ve surpassed this (due to optimization at the silicon level, designing hardware who’s sole job it is to send bursts of data) and we end up running out of data in the buffer periodically because it’s just so fast. Because analog is real time, you can squeeze much else in that data stream but with digital, we are afforded the luxury of packet switching instead of that line being idle, we can pump even more down the linen.

> Are there any downsides to packetization, like increased latency or dropped frames or anything? Or not really, is it all upsides in being able to trivially combine multiple data streams or integrate easily into hubs?

If I recall correctly, the timing and data rates is all prearranged based on reported capacity and abilities of the receiving device and it won’t even attempt to support multiple streams if it is incapable of doing so or the data channel established cannot fully support the bandwidth required.

Re: Displayport: A Better Video Interface

#185

Post by drbawb »

Aaargh20318 wrote: post #83
Perz1val wrote: post #65

Earlier quoted context omitted.

It's not an OS problem, that's how DP is supposed to work and that's in fact stupid

It’s an OS problem for not handling monitors being disconnected and reconnected properly. What is stupid is having half your windows unreachable because they are on a monitor that is turned off. How does that help anyone? Imagine how annoying it would be on a laptop? I use my laptop in a meeting, and have a few windows open on its screen, then I arrive at my desk and plug in my 2 external monitors and keep my laptop…

>Imagine how annoying it would be on a laptop?

>That would be an absolutely brain dead way of working.

For starters: the experience I want on my laptop is not the same as the experience I want on my desktop. I have two monitors at home, sometimes I like to turn off the wing-monitor when I am watching a movie on the center screen. (To avoid distraction, and also minimize glare, etc.) That doesn't mean I want those windows rearranged: that's probably going to interfere w/ the movie that is playing, fuck up my desktop wallpapers, icons, window sizes, etc. The whole point of turning off the monitor is to hide those distractions.

Also not all window managers suck as badly as Mac OS and Windows. By default I have odd-numbered virtual desktops go to the left montior, and even-numbered virtual desktops go to the right monitor. If I want to move a viewport to another monitor, I renumber it accordingly, and all the windows move to that monitor: complete w/ their proportional positions and sizes.

The idea that _a device hotplug event_ would change how my virtual desktops are laid out is so absurd to me that I switched operating systems to avoid the default Windows behavior. So maybe consider that paradigms and workflows other than "a docked laptop" exist before calling people braindead?

Re: Displayport: A Better Video Interface

#186

Post by ender341341 »

pxc wrote: post #137
jchw wrote: post #121

Earlier quoted context omitted.

None of them are perfect, but I've heard good things about the DP switch from Level1techs. The thing is, all of them are a little tricky, but they mostly differ in how quirky they are, and I suspect the reason why people like the Level1techs DP switch is that they seem to at least try to alleviate some of the issues DP switches tend to get into. https://store.level1techs.com/products/14-kvm-switch-dual-mo... The star…

The Level1Techs KVM switches are rebranded Startech switches with 'dumber' firmwares whose dumbness affords better compatibility with niche DisplayPort features. I have a bunch of them and I like them pretty well, but getting a bunch of computers all plugged in turns out to be a bit of a nightmare, especially when you need some long-ish cable runs or you are daisy-chaining devices (e.g., multiple KVM switches, adding…

> FWIW, I don't get the 'Apple computers just refuse to work' issue with any of my L1T KVMs.

My work intel macbook worked great on it for like a year once I got a high quality usb-c -> displayport cable, but an os update borked it... though it's definitely the mac that's the problem as it also has problems sometimes with just strait to the monitor too (on the other hand 49" ultrawide is pushing the bandwidth near it's limits).

My personal arm macbook has always worked great on it with even a crappy usb-c -> displayport

my windows desktop also always worked great on it.

Re: Displayport: A Better Video Interface

#187

Post by AlotOfReading »

drbawb wrote: post #167
AlotOfReading wrote: post #156

Earlier quoted context omitted.

I use one, so I can confirm they work extremely well, subject to some caveats: * The total cable length is important, both between the host / KVM and the KVM / monitor, as well as any daisy chained displays you have. I had to use certified cables to get everything working reliably with my setup. * There's a weird interaction with BIOS power on. The boot display drivers I have freak out if they aren't the active displ…

>There's a weird interaction with BIOS power on. The boot display drivers I have freak out if they aren't the active display and fail. I solve this by switching the KVM before I turn the computer on. After everything is booted into an OS, it works fine to switch. Do you have an AMD GPU by any chance? I have the level1tech 2-head DP 1.4 KVM, with an AMD RX 560 on a Linux host, and after updating to kernel 6.4 recently…

Nvidia on both, one consumer and one workstation. Neither CPU has built-in graphics iirc, nor do the motherboards expose the ports.

Re: Displayport: A Better Video Interface

#188

Post by hiatus »

xxpor wrote: post #181
drbawb wrote: post #167

Earlier quoted context omitted.

>There's a weird interaction with BIOS power on. The boot display drivers I have freak out if they aren't the active display and fail. I solve this by switching the KVM before I turn the computer on. After everything is booted into an OS, it works fine to switch. Do you have an AMD GPU by any chance? I have the level1tech 2-head DP 1.4 KVM, with an AMD RX 560 on a Linux host, and after updating to kernel 6.4 recently…

I have a similar issue with a Nvidia 1080Ti on my old desktop. It's related to the UEFI deciding if the iGPU or the Nvidia GPU should be primary and to disable the iGPU or if the iGPU should stay enabled.

Curious how you went about determining that was the source of the issue.

Re: Displayport: A Better Video Interface

#189

Post by someplaceguy »

chx wrote: post #168

> However, if you don’t need the full bandwidth that four lanes can give you, a DP link can consist of only one or two main lanes resulting in two This is how many USB C docks operate. The USB C connector also has four high speed lanes and there's a mode where two are assigned to carry DisplayPort data and two are assigned to be TX and RX respectively for USB. Until DP 1.4 appeared, this meant you were quite limited…

What is the benefit of adding compression here? Does that mean that the bandwidth might or might not be sufficient depending on which pictures are being shown on the screen?

If so, that doesn't seem very reliable and if not, what's the point of compression?

Re: Displayport: A Better Video Interface

#190

Post by pxc »

ender341341 wrote: post #186
pxc wrote: post #137

Earlier quoted context omitted.

The Level1Techs KVM switches are rebranded Startech switches with 'dumber' firmwares whose dumbness affords better compatibility with niche DisplayPort features. I have a bunch of them and I like them pretty well, but getting a bunch of computers all plugged in turns out to be a bit of a nightmare, especially when you need some long-ish cable runs or you are daisy-chaining devices (e.g., multiple KVM switches, adding…

> FWIW, I don't get the 'Apple computers just refuse to work' issue with any of my L1T KVMs. My work intel macbook worked great on it for like a year once I got a high quality usb-c -> displayport cable, but an os update borked it... though it's definitely the mac that's the problem as it also has problems sometimes with just strait to the monitor too (on the other hand 49" ultrawide is pushing the bandwidth near it'…

> on the other hand 49" ultrawide is pushing the bandwidth near it's limits

One of the things I've learned too late is that using DisplayPort (and maybe HDMI, idk) anywhere near its bandwidth limits is not worth it for me. Having to think about cable run lengths as well as cable quality and peripheral quirks and internal Thunderbolt dock bandwidth allocation and so on and so on just fucking sucks.

It'll probably take until the next/latest (2.1) generation of DisplayPort propagates before using multiple monitors with specs similar to my current ones (high refresh rate and HDR, but not even HiDPI) isn't painful, cumbersome, and finicky.

I probably won't be able to use them by then anyway. Ugh.

Post reply on HN