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Displayport: A Better Video Interface

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Re: Displayport: A Better Video Interface

#311

Post by sillywalk »

hot_gril wrote: post #139
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.

Apparently it's 1394b is used in some military applications, the F-35 for example.

Re: Displayport: A Better Video Interface

#312

Post by mr_toad »

privacyking wrote: post #272
emilyst wrote: post #177

Earlier quoted context omitted.

> Ps.: When I say Thunderbolt, I am well aware of how Thunderbolt 4 is just USB4 with optional features made mandatory. It's not relevant to the discuss at hand. Dear God, I hope this situation settles down in the near future. As it is I have years of USB-C-looking cables that all do different things but are visually indistinguishable.

If you get a thunderbolt 4 cable it can do everything, at least until the 80gbps one comes out

Be nice if they weren’t 10x the price of normal USB-C cables.

Re: Displayport: A Better Video Interface

#313

Post by ThatPlayer »

mr_toad wrote: post #308
vel0city wrote: post #12

Earlier quoted context omitted.

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.

The article talks about how adapters like yours use the DisplayPort Alt Mode protocol and then have a DP to HDMI adapter integrated. Rather than implementing the HDMI Alt Mode protocol which also works over USB-C.

Re: Displayport: A Better Video Interface

#314

Post by MBCook »

dylan604 wrote: post #276
hot_gril wrote: post #171

Earlier quoted context omitted.

Yeah, FireWire was a necessity at the time for certain use cases. Even basic consumer digital camcorders required FW400 to pull onto a PC.

I maybe mis-remembering, but was it possible to add FireWire to an existing PC with an expansion card? I know Thunderbolt was not possible from 3rd party vendors and only the mobo manufacturers could offer a card. I bought one to make a Hackintosh, but then a mobo firmware disabled the card because they didn't want to support it. I seem to recall Firewire being the same way

Yes it was. Still is. I almost bought a FireWire card so I could use an iPod with Windows before the USB model came out. I also remember an old Dell laptop I had having a FW port.

When FW400 came out we were on USB1 which was stuck at 12mbps. It wasn’t designed for hard drives and such. It was for floppies, keyboards, mice, printers, barcode scanners, etc. Low bandwidth. Not that that stopped manufacturers.

FireWire just wasn’t popular on the PC side outside of video editing (and perhaps other specialized uses).

USB got far more useful with USB2, which went to 480mbps, but IIRC you couldn’t achieve that and it had tons of CPU overhead. FW could max out its bandwidth and had low CPU overhead by design despite having a lower theoretical max.

But it was over. USB2 was cheaper and FAR FAR more common. FW800 existed for those who needed more bandwidth. But for most people USB2 was plenty and they already had it.

Thunderbolt took over for FW, and as of USB4 the two are basically the same (relative to FW vs USB’s differences).

Re: Displayport: A Better Video Interface

#315

Post by MBCook »

ShadowBanThis01 wrote: post #305
throwawaymobule wrote: post #225

Earlier quoted context omitted.

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.

The feature was the power pin. You couldn’t power a device from that tiny plug (on either side).

I do understand why they did it. Sony is the master of miniaturization and wanted things to be small as possible. So the idea of making one of their little tiny handheld camcorders noticeably bigger just for a single connector was probably a non-starter for them.

So they made up their own and then used their size to force it to become a part of the standard.

Re: Displayport: A Better Video Interface

#316

Post by willis936 »

rasz wrote: post #277
fanf2 wrote: post #221

Earlier quoted context omitted.

The important difference is that (like VGA) DVI and HDMI still dedicate particular physical wires to separate red, green, and blue channels. Display port does not shard individual pixels across multiple channels: all bits (all colours) of a pixel are sent on the same diffpair. If a DP link has multiple lanes then the bits of different successive pixels are sent on each lane.

This is great, but then they drop the ball by forcing garbage (“interspersed stuffing symbols”) between the packets instead of letting you use that BW.

You are not giving the full picture in this trade. The people making the spec knew the trade well. You add a lot of complexity to a receiver by forcing it to generate its own timing information from whatever video signal is sent. That work has to be done somewhere and it is most robust when done at the source.

Re: Displayport: A Better Video Interface

#317

Post by willis936 »

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,…

If you didn't packetize then the receiver would never recover line coding state when a single symbol is missed. The rest are incidental details.

Re: Displayport: A Better Video Interface

#318

Post by mr_toad »

fsh wrote: post #57
pid-1 wrote: post #48

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

The bandwidth is much too low.

Better compression would surely help.

The cloud gaming people are telling us they can deliver 4K 60fps video over 35Mbps.

Re: Displayport: A Better Video Interface

#319

Post by justusthane »

somat wrote: post #310

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.

It’s mentioned towards the beginning:

> Physically, desktop/laptop DisplayPort outputs come in two flavors – full-size DisplayPort, known for its latches that keep the cable in no matter what, and miniDisplayPort

But yeah, the latches are great.

Re: Displayport: A Better Video Interface

#320

Post by ShadowBanThis01 »

MBCook wrote: post #315
ShadowBanThis01 wrote: post #305

Earlier quoted context omitted.

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

The feature was the power pin. You couldn’t power a device from that tiny plug (on either side). I do understand why they did it. Sony is the master of miniaturization and wanted things to be small as possible. So the idea of making one of their little tiny handheld camcorders noticeably bigger just for a single connector was probably a non-starter for them. So they made up their own and then used their size to force…

Yes, I noted that: "whose connector lacked power and required a physical adapter."
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