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Displayport: A Better Video Interface

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Re: Displayport: A Better Video Interface

#301

Post by nyanpasu64 »

stephenr wrote: post #67
binkHN wrote: post #58

I didn’t realize Multi-Stream Transport (MST) requires OS support, and I was surprised to find out MacOS, with its great Thunderbolt support, does not support this. “Even” ChromeOS can do MST.

Technically macOS does support MST. But it only supports it to stitch together for a single display. It does not support daisy chaining two displays. Thankfully, every Mac for the last 7 years has Thunderbolt3 at least, so getting dual-4K-display from a single port/cable is still very doable, you just need a TB3 to dual DisplayPort or HDMI adapter.

Doesn't MST merely chop up the bandwidth of the lanes you have? So why would you update different parts of a single display using MST (each stream only getting part of the bandwidth of the link), rather than using the whole link to update the display from top to bottom at the same pixel depth and clock?

Re: Displayport: A Better Video Interface

#302

Post by nyanpasu64 »

CameronNemo wrote: post #300
nyanpasu64 wrote: post #295

Earlier quoted context omitted.

Did you decrease the USB ALSA period to the lowest practical value (eg. 128 or so)? In theory this provides finer-grained position updates and better stability at any given latency, but I'm not sure how it interacts with USB's polling rate.

Yes, the latency increases, the audio quality worsens, and I see the following messages in Pipewire's logs: [W][30498.719355] spa.alsa | [ alsa-pcm.c: 2478 spa_alsa_read()] steinberg_ur44_mono_in:UR44,0,2: follower delay:4042 target:4832 thr:256, resync (374 missed)

Ouch that's unfortunate :(

Re: Displayport: A Better Video Interface

#303

Post by stephenr »

deergomoo wrote: post #271
stephenr wrote: post #67

Earlier quoted context omitted.

Technically macOS does support MST. But it only supports it to stitch together for a single display. It does not support daisy chaining two displays. Thankfully, every Mac for the last 7 years has Thunderbolt3 at least, so getting dual-4K-display from a single port/cable is still very doable, you just need a TB3 to dual DisplayPort or HDMI adapter.

You can daisy chain the Studio Display and Pro Display, and you could daisy chain the old Thunderbolt Display. Is that using some custom thing over Thunderbolt rather than MST?

Yes that’s Thunderbolt daisy chaining.

Re: Displayport: A Better Video Interface

#304

Post by nyanpasu64 »

> If you see a DisplayPort interface on your board where you’d usually expect HDMI, that might just be because the company decided to avoid HDMI’s per-device royalties, and do firmly believe that this is a good thing.

Wikipedia says DP 1.3 requires "mandatory Dual-mode for DVI and HDMI adapters". Does this mean that all DP 1.3 ports must output HDMI (and presumably pay HDMI licensing fees) as well?

Re: Displayport: A Better Video Interface

#305

Post by ShadowBanThis01 »

throwawaymobule wrote: post #225
ShadowBanThis01 wrote: post #198

Earlier quoted context omitted.

It wasn't that short-lived. All DV cameras had FireWire. Although Sony, per its mania for undermining industry standards, created a bastardized version (called I-Link, ugh) whose connector lacked power and required a physical adapter. External FireWire drives (like LaCie's) were popular for quite a long time, since they required no extra power source.

I think the 4 pin version was also standard, it's just that Sony didn't own the trademark on FireWire, Apple did. Sony was actually one of the companies that developed the spec, according to Wikipedia. I had a HP laptop with that connector, but it was labelled IEEE- . Bought a 4 to 6 cable to connect it to an old iMac, but never bothered enough to use it.

I think it was more that Sony couldn't call its bullshit plug FireWire because it lacked a required FireWire feature.

Re: Displayport: A Better Video Interface

#306

Post by stephenr »

nyanpasu64 wrote: post #301
stephenr wrote: post #67

Earlier quoted context omitted.

Technically macOS does support MST. But it only supports it to stitch together for a single display. It does not support daisy chaining two displays. Thankfully, every Mac for the last 7 years has Thunderbolt3 at least, so getting dual-4K-display from a single port/cable is still very doable, you just need a TB3 to dual DisplayPort or HDMI adapter.

Doesn't MST merely chop up the bandwidth of the lanes you have? So why would you update different parts of a single display using MST (each stream only getting part of the bandwidth of the link), rather than using the whole link to update the display from top to bottom at the same pixel depth and clock?

From memory they use it on things like the Pro Display XDR (possibly some 5K’s too?) where the display supports DP1.2;

My understanding is, the spec doesn’t allow for 5K/6K at 60hz but does allow for MST to send two streams at up to 4K/60, so it’s a creative use of what the spec supports to allow a higher resolution than envisaged when the spec was published.

Re: Displayport: A Better Video Interface

#307

Post by ShadowBanThis01 »

dylan604 wrote: post #207
ShadowBanThis01 wrote: post #198

Earlier quoted context omitted.

It wasn't that short-lived. All DV cameras had FireWire. Although Sony, per its mania for undermining industry standards, created a bastardized version (called I-Link, ugh) whose connector lacked power and required a physical adapter. External FireWire drives (like LaCie's) were popular for quite a long time, since they required no extra power source.

Sony also gave us a professional studio DVCam deck that was SDI based that allowed you to connect to of them to get 4x dubbing speeds. Not once did it ever get used at the studio I was working. Nothing else in the shop used that format, so it was always just realtime SDI work. ahh, sony

Well, if we're going to review Sony's litany of standards-undermining horseshit, we'd be remiss to omit S/PDIF, which was a bastardization of the existing AES/EBU digital standard. Apparently it differs just enough to make interconnectivity unreliable... creating a pain in the ass for studios the world over.

Sony also briefly attempted to undermine Thunderbolt, by issuing a laptop that crammed Thunderbolt connections into a regular USB-A port.

I'm sure I'm forgetting (or unaware of) several others.

Then there was their ridiculous clinging to MemoryStick for what, a decade after the rest of the world had standardized on SD?

Re: Displayport: A Better Video Interface

#308

Post by mr_toad »

vel0city wrote: post #12
jsheard wrote: post #8

Earlier quoted context omitted.

It also allows the transmission of HDMI over USB-C, so you still have two competing standards

It allows it, but can you actually buy any products for it? https://www.notebookcheck.net/The-demise-of-HDMI-over-USB-C-... > True USB-C to HDMI adapters are no longer going to be a thing. The HDMI Alt Mode is more or less history, and DisplayPort has won. Notebookcheck spoke to HDMI LA and the USB-IF about it. > HDMI LA said that it doesn't know of a single adapter that has ever been produced. Similarly, at the USB…

> have yet to see a true USB-C to HDMI adapter

Not sure what this article means. I have a USB-C to HDMI adapter (made by Apple) and a USB-C to HDMI cable and both work.

Re: Displayport: A Better Video Interface

#309

Post by tormeh »

LelouBil wrote: post #283

A friend of mine had problems with his monitor, it would go into standby randomly when running certain games. I asked him for details about his setup and I was pretty confused when he said the connector at the back of his monitor had screws but I saw the Nvidia control panel reporting HDMI. Turns out he was using an HDMI to VGA adapter ! (GPU was outputting HDMI and screen consumed VGA). I just told him to go buy a d…

Huh, I have the same issue with pure HDMI. No clue what the reason is.

Re: Displayport: A Better Video Interface

#310

Post by somat »

The article missed the most important advantage of display port over hdmi, you can get locking connectors.

I joke of course, but of the two standards bodies vesa always feels like they were less interested in playing the drm game and more interested in making a useful standard.

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