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

HDMI Alt Mode for USB Type-C Connector

hdmi.org

Post reply on HN
Print view View original

41–50 of 53 posts

Re: HDMI Alt Mode for USB Type-C Connector

#41

Post by seba_dos1 »

usernew wrote: post #34
crote wrote: post #8

HDMI Alt Mode was basically dead on arrival. The computer world pretty much standardized on DisplayPort already, so USB-C devices would already have to support DisplayPort Alt Mode anyways. Why add support for yet another Alt Mode when DP-to-HDMI converter chips are dirt cheap, and pretty much all USB-C-to-HDMI cables will be using those anyways due to the aforementioned DP ubiquity. One thing which really bothers me…

So, maybe I'm missing something here, but who is talking about computers? Most things that need to be connected to with HDMI, are TVs. I have 5, none of them take display port or USB-C. The all take HDMI. I have no "monitors" because... Why would I need one (I only "game" things that have to run on dosbox)? But let's talk computers. And phones. All mine, only have USB-C. I have an old one that has micro, and I chrome…

It's not used at all. HDMI alt-mode is several years old and nothing implements it. Even HDMI LA considers it dead now, they closed their certification program for it.

In practice, video over USB-C uses either DP alt-mode, Thunderbolt or USB4 (and the latter ones encapsulate DP over their own protocols). All USB-C to HDMI cables and adapters actually use DisplayPort and converters. HDMI alt-mode was indeed dead on arrival.

Re: HDMI Alt Mode for USB Type-C Connector

#42

Post by crooked-v »

usernew wrote: post #34
crote wrote: post #8

HDMI Alt Mode was basically dead on arrival. The computer world pretty much standardized on DisplayPort already, so USB-C devices would already have to support DisplayPort Alt Mode anyways. Why add support for yet another Alt Mode when DP-to-HDMI converter chips are dirt cheap, and pretty much all USB-C-to-HDMI cables will be using those anyways due to the aforementioned DP ubiquity. One thing which really bothers me…

So, maybe I'm missing something here, but who is talking about computers? Most things that need to be connected to with HDMI, are TVs. I have 5, none of them take display port or USB-C. The all take HDMI. I have no "monitors" because... Why would I need one (I only "game" things that have to run on dosbox)? But let's talk computers. And phones. All mine, only have USB-C. I have an old one that has micro, and I chrome…

> while what's talked about in the article is widely used

Except it's not, because that functionality is basically nonexistent. All the USB-C to HDMI connectors out there are actually doing the USB-C DisplayPort mode with the equivalent of a DP->HDMI hardware dongle built in.

Re: HDMI Alt Mode for USB Type-C Connector

#43

Post by crote »

MBCook wrote: post #23
crote wrote: post #8

HDMI Alt Mode was basically dead on arrival. The computer world pretty much standardized on DisplayPort already, so USB-C devices would already have to support DisplayPort Alt Mode anyways. Why add support for yet another Alt Mode when DP-to-HDMI converter chips are dirt cheap, and pretty much all USB-C-to-HDMI cables will be using those anyways due to the aforementioned DP ubiquity. One thing which really bothers me…

> The computer world pretty much standardized on DisplayPort already Do you know why that is? I live in the Apple world do I didn’t follow the changes. Last time I had a PC it was VGA and DVI, which gives you a sense of the timeline. Then it seems to have been HDMI for a while (?) and now seems to be moving to DisplayPort. Is there a reason DisplayPort over Thunderbolt didn’t catch on? Maybe something about how commo…

HDMI was designed by the entertainment industry to connect HD televisions. Its initial version was electronically basically half of a DVI connector, with some audio data thrown into the video stream. Plenty for a 1080p 60Hz stream, but not much beyond that.

DisplayPort was developed by VESA for computer use. It supported a higher bandwidth than HDMI and rapidly gained support for features like variable refresh rates, compression, and feeding multiple monitors through a single cable.

Nowadays it doesn't really matter that much, and they both essentially have the same capabilities. It's now HDMI for televisions and DP for computers because History.

Re: HDMI Alt Mode for USB Type-C Connector

#44

Post by Aaron2222 »

dmitrygr wrote: post #25
eigen wrote: post #4

not a lot of details in this but I'm curious how the AC-coupled USB-C interface works with the DC-coupled HDMI. typically there would be a DP-to-HDMI convertor in the cable plug and just use DP alt-mode but this specifically says: "This allows native HDMI features and capabilities to be utilized in a source device and to be directly connected to any HDMI display. Other Alt Mode solutions do not enable HDMI-specific f…

> native HDMI features Please tell me that this is not marketing speak for HDCP! What other "native HDMI" features are there that DisplayPort does not already support?

DisplayPort supports HDCP, it's not HDMI-only.

Re: HDMI Alt Mode for USB Type-C Connector

#45

Post by teaearlgraycold »

lxgr wrote: post #38
teaearlgraycold wrote: post #13

Earlier quoted context omitted.

This has not been my experience at all with DP in lightning and USB ports.

Lightning doesn’t support DP, does it? There are lightning to HDMI adapters, but these fascinatingly run a full SoC that receives and decodes a compressed H.264 video stream over lightning, which I wouldn’t really call HDMI over lightning.

Oops. I meant Thunderbolt. Terrible naming decisions were made.

Re: HDMI Alt Mode for USB Type-C Connector

#46

Post by lxgr »

teaearlgraycold wrote: post #45
lxgr wrote: post #38

Earlier quoted context omitted.

Lightning doesn’t support DP, does it? There are lightning to HDMI adapters, but these fascinatingly run a full SoC that receives and decodes a compressed H.264 video stream over lightning, which I wouldn’t really call HDMI over lightning.

Oops. I meant Thunderbolt. Terrible naming decisions were made.

Never underestimate the amount of pain engineers will subject themselves and others to, all in service of a clever pun.

Re: HDMI Alt Mode for USB Type-C Connector

#47

Post by usernew »

seba_dos1 wrote: post #41
usernew wrote: post #34

Earlier quoted context omitted.

So, maybe I'm missing something here, but who is talking about computers? Most things that need to be connected to with HDMI, are TVs. I have 5, none of them take display port or USB-C. The all take HDMI. I have no "monitors" because... Why would I need one (I only "game" things that have to run on dosbox)? But let's talk computers. And phones. All mine, only have USB-C. I have an old one that has micro, and I chrome…

It's not used at all. HDMI alt-mode is several years old and nothing implements it. Even HDMI LA considers it dead now, they closed their certification program for it. In practice, video over USB-C uses either DP alt-mode, Thunderbolt or USB4 (and the latter ones encapsulate DP over their own protocols). All USB-C to HDMI cables and adapters actually use DisplayPort and converters. HDMI alt-mode was indeed dead on ar…

I'm not addressing the Alt-mode. Please read what was written, and reply to what was written. The comment to which I replied said you connect devices with display port, not HDMI, because all your devices are monitors. The real-world use case is USB-C to HDMI, to connect to a TV. I have no idea what my cables do, but they have USB-C on one end, and HDMI, not DP on the other, and I plug them into the TV.

The comment stated you don't need HDMI on the other end. I am not arguing for "Alt-mode" protocol, nor did I write "Alt-mode" anywhere in my comment. I am specifically replying to the wrong fact that most people use USB-C to connect to and HDMI port, not a DP port, on the other end of the cable.

From a quick google, the reason Alt mode is "dead" is because most devices natively support HDMI and you don't need alt-mode. https://www.notebookcheck.net/The-demise-of-HDMI-over-USB-C-...

Re: HDMI Alt Mode for USB Type-C Connector

#48

Post by ianburrell »

crote wrote: post #8

HDMI Alt Mode was basically dead on arrival. The computer world pretty much standardized on DisplayPort already, so USB-C devices would already have to support DisplayPort Alt Mode anyways. Why add support for yet another Alt Mode when DP-to-HDMI converter chips are dirt cheap, and pretty much all USB-C-to-HDMI cables will be using those anyways due to the aforementioned DP ubiquity. One thing which really bothers me…

Also, there is MHL alt mode which sends the signal over one pair like DP.mi don’t know if this gets used but at least it makes sense unlike HDMI mode.

The reason why HDMI alt mode is awful is that it uses most the wires for HDMI. That doesn’t leave any wires for other uses like USB3. It may even use USB2 wires. The UsB-C docks would be impossible. The only use is for passive adapters.

Re: HDMI Alt Mode for USB Type-C Connector

#49

Post by ianburrell »

usernew wrote: post #47
seba_dos1 wrote: post #41

Earlier quoted context omitted.

It's not used at all. HDMI alt-mode is several years old and nothing implements it. Even HDMI LA considers it dead now, they closed their certification program for it. In practice, video over USB-C uses either DP alt-mode, Thunderbolt or USB4 (and the latter ones encapsulate DP over their own protocols). All USB-C to HDMI cables and adapters actually use DisplayPort and converters. HDMI alt-mode was indeed dead on ar…

I'm not addressing the Alt-mode. Please read what was written, and reply to what was written. The comment to which I replied said you connect devices with display port, not HDMI, because all your devices are monitors. The real-world use case is USB-C to HDMI, to connect to a TV. I have no idea what my cables do, but they have USB-C on one end, and HDMI, not DP on the other, and I plug them into the TV. The comment st…

You are missing that there is a chip in HDMI side of the cable that converts DisplayPort to HDMI. DisplayPort is what goes over the cable and what the device knows about.

Re: HDMI Alt Mode for USB Type-C Connector

#50

Post by seba_dos1 »

usernew wrote: post #47
seba_dos1 wrote: post #41

Earlier quoted context omitted.

It's not used at all. HDMI alt-mode is several years old and nothing implements it. Even HDMI LA considers it dead now, they closed their certification program for it. In practice, video over USB-C uses either DP alt-mode, Thunderbolt or USB4 (and the latter ones encapsulate DP over their own protocols). All USB-C to HDMI cables and adapters actually use DisplayPort and converters. HDMI alt-mode was indeed dead on ar…

I'm not addressing the Alt-mode. Please read what was written, and reply to what was written. The comment to which I replied said you connect devices with display port, not HDMI, because all your devices are monitors. The real-world use case is USB-C to HDMI, to connect to a TV. I have no idea what my cables do, but they have USB-C on one end, and HDMI, not DP on the other, and I plug them into the TV. The comment st…

You seem pretty confused.

> From a quick google, the reason Alt mode is "dead" is because most devices natively support HDMI and you don't need alt-mode.

If you do video over USB-C, you need alt-mode. Everything uses DisplayPort alt-mode and converts it to HDMI if needed. These days most devices have no other form of video connectivity than USB-C.

You link to an article that literally states "DisplayPort has won".

> The real-world use case is USB-C to HDMI, to connect to a TV.

The real world use case is to connect a PC or phone to an external display. Usually that's going to be a PC monitor, where physical DisplayPort actually is ubiquitous these days. Personally, I don't even have a TV - I'm not exactly a gamer so I don't see why would I need one.

(I actually connect my laptop to a screen using HDMI connector on the screen side, but that's only because it's about 10 years old :P)

Post reply on HN