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Displayport: A Better Video Interface

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Re: Displayport: A Better Video Interface

#131

Post by gs17 »

hot_gril wrote: post #82

"We’ve all gotten used to HDMI." Well that's it then, I don't need another less common way to do the same thing. There's always that theory that low-end devices will opt for DP to avoid royalties, but the cheapest laptops and monitors tend to be HDMI-only if anything because DP is more of a special feature. Similar story with H.264/5 vs VP8/9.

> There's always that theory that low-end devices will opt for DP to avoid royalties, but the cheapest laptops and monitors tend to be HDMI-only if anything because DP is more of a special feature.

Yeah, when I needed a new laptop dock, one of my annoyances was having to pay extra for a DP one because our lab's IT refuses to stock adapters or cables "because people keep using them instead of returning them" and they "spent extra" to get monitors which have a single DP port.

Re: Displayport: A Better Video Interface

#132

Post by Aaargh20318 »

hot_gril wrote: post #116
Aaargh20318 wrote: post #83

Earlier quoted context omitted.

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…

Makes sense to move the windows if you close a laptop lid, but not if you turn off a monitor. You can't disconnect the laptop screen, but you can easily disconnect the monitor. I have a cheap laptop that doesn't understand a turned-off monitor as unusable, and it's actually way nicer that way.

Why is it nicer? What is the use case for having unreachable windows?

Re: Displayport: A Better Video Interface

#134

Post by jamestanderson »

mvid wrote: post #84
tivert wrote: post #77

Are there any KVM switches that do Displayport well (i.e. where switching between inputs does not look like a display disconnect to the PC)? I'm still using HDMI because I like to share my home multi-monitor setup between my personal machine and my work laptop, and the KVM switches are able to fool the PCs into thinking the monitor are always connected. Years ago I tried a Displayport switch, but it could not -- I as…

https://store.level1techs.com/?category=Hardware This is what I use. It appears to disconnect, but also doesnt seem to be an issue. My machines re-organize instantly.

I got their 10gbps displayport switch to use with switching a single monitor between a Windows desktop PC and an M1 MacBook Pro. I have a 4k@144hz monitor and can get the full framerate and resolution with this setup. I've never had any problems, would highly recommend.

Re: Displayport: A Better Video Interface

#135

Post by tverbeure »

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,…

Latency is limited to the amount of buffering that's present in the interface logic (on sides). In the case of regular DP, there's just a few FIFOs and pipeline stages, so the latency is measured in nanoseconds.

When using display stream compression (DSC), there's a buffer of 1 line, and a few FIFOs to handle rate control. At the resolution for which DSC is used (say, 4K/144Hz), the time to transmit a single line is around 3us. So that's the maximum additional latency you can expect.

Re: Displayport: A Better Video Interface

#136

Post by tverbeure »

remix2000 wrote: post #23

With HDMI, I have both video and audio traveling over a single cable. That is _extremely_ convenient. DP _theoretically_ supports audio too, but AFAIK that's not widely implemented.

All modern GPUs and monitors (that's have a speaker) support audio-over-DP. They have for over a decade.

It's widely implemented.

Re: Displayport: A Better Video Interface

#137

Post by pxc »

jchw wrote: post #121
tivert wrote: post #77

Are there any KVM switches that do Displayport well (i.e. where switching between inputs does not look like a display disconnect to the PC)? I'm still using HDMI because I like to share my home multi-monitor setup between my personal machine and my work laptop, and the KVM switches are able to fool the PCs into thinking the monitor are always connected. Years ago I tried a Displayport switch, but it could not -- I as…

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 USB hubs or Thunderbolt docks, etc.).

The Level1Techs KVM switches don't meet GP's criterion for hotplugging behavior, unfortunately. Switching between devices is just an unplug and replug for them.

Like you, I've found that macOS and Windows don't handle hotplugging monitors well, but Linux desktops (in my case, KDE Plasma) consistently do the right thing and don't require a repeater to lie to them about monitors always being plugged in.

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

Re: Displayport: A Better Video Interface

#138

Post by NavinF »

londons_explore wrote: post #64
pid-1 wrote: post #48

Sorry if that sounds stupid, but why isn't Ethernet used for this sort of high bw signaling?

It should be. As soon as video data is in packets, it should be routable over a network like any other data. Give up the custom connectors, custom cables, etc. Need a wireless display? No worries, we can route the data over wifi too. Need 5 displays? Thats what an ethernet switch is for. Screen mirroring? We have multicast. Need a KVM? Well you can probably write a few scripts to change which computer your screen get…

Naw it's because >=40G Ethernet never saw much consumer adoption. QSFP DACs and optics are also kinda bulky by consumer standards so a lot of people would want a new connector. Even LC connectors would be too large for laptops.

Re: Displayport: A Better Video Interface

#139

Post by hot_gril »

tshaddox wrote: post #123

> However, I’d like to tell you that you probably should pay more attention to DisplayPort – it’s an interface powerful in a way that we haven’t seen before. Lines like that really show just how long it can take for standards to get on the radar of mainstream tech culture. I remember hearing about and being excited about DisplayPort's move to packetized digital video in college in 2008, and seeing the first Macs with…

That, and a similar line might've been said about FireWire, which didn't really make it.

Re: Displayport: A Better Video Interface

#140

Post by c-hendricks »

jamestanderson wrote: post #134
mvid wrote: post #84

Earlier quoted context omitted.

https://store.level1techs.com/?category=Hardware This is what I use. It appears to disconnect, but also doesnt seem to be an issue. My machines re-organize instantly.

I got their 10gbps displayport switch to use with switching a single monitor between a Windows desktop PC and an M1 MacBook Pro. I have a 4k@144hz monitor and can get the full framerate and resolution with this setup. I've never had any problems, would highly recommend.

Nice, I'll check these out. I went with an HDMI KVM and am worried about updates to HDMI making it obsolete.
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