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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

by crote 3y ago

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 is that all those Alt Mode specifications are proprietary. USB-C itself is a completely open spec and anyone can download the PDFs from their website - but the Alt Modes require you to join the VESA / HDMI consortium, with an associated member fee and NDA.

nyanpasu64 3y ago
It's not the real deal, but https://www.quantumdata.com/assets/essentials_displayport_usb-c_dp_alt_mode_protocols_webinar.pdf https://www.quantumdata.com/assets/essentials_displayport_us... looks to be quite useful for understanding DP Alt Mode. I've used their DP regular protocol PDFs, though because this is a transcript of an animated webinar, there are images covering text which you'll need to remove in a PDF editor or LibreOffice Draw (which can import PDFs).
MBCook 3y ago
> 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 common add-in GPUs are making implementing TB harder?
- hocuspocus 3y ago
  > Then it seems to have been HDMI for a while (?) Not really. HDMI is basically DVI++ but it's first and foremost a TV and video interface. Once DVI started to be limiting, both PCs and high-end monitors adopted DP. HDMI came to PCs and monitors later, sometimes with limitations, for instance my Dell U2711 couldn't run at its native resolution over HDMI. A few years later UHD 4:4:4 was literally impossible from a PC GPU before HDMI 2.0, while not a problem even on older DP 1.2.
  - kjadslkjdsjd 3y ago
    Also DP can do cool things like carrying the signals for multiple monitors (daisy chaining)... I have one usb type c cable that does power display and usb for my 2 dell monitors... it is awesome... sadly Apple never implemented DP daisy chaining this and when you try it with their hardware you only get a mirrored output.
    - lxgr 3y ago
      Yes, it’s a pity they never implemented that. Presumably some deal with Intel to push Thunderbolt :/ It’s an open spec now, but at the time Apple was pushing Thunderbolt hard, only Intel was building the chips for it, both for computers and peripherals (ie monitors, docks etc.)
- yyyk 3y ago
  DisplayPort is royalty-free while HDMI charges licensing per unit. Additionally, Intel strongly supported DP so many boards came with support even if there was nothing to connect it to, and Intel ensured support in USB specs. Eventually enough display manufacturers added support* and DP became common enough, this generated demand and we ended with a self-reinforcing system. There's still a lot of HDMI, so I wouldn't say the computer world is standardized. In my experience, people just use whatever port is available... * Display turnaround time is significant. Displays can survive a decade comfortably. A few people brag about their 10000K display with 10000Hz refresh rates, but many people just keep their display until it drops or until they buy a new system. So DP took a long time to be universally supported and that hampered adoption for a long time.
- crote 3y ago
  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.
usernew 3y ago
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 chromecast the screen from that one. I connect them all to TVs. With HDMI on the TV end. So literally your dead on arrival example is not even present in the life of my household, while what's talked about in the article is widely used.
- seba_dos1 3y ago
  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.
  - usernew 3y ago
    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-Alt-Mode-and-more-power-in-cables.680552.0.html https://www.notebookcheck.net/The-demise-of-HDMI-over-USB-C-...
    - 3y ago
ianburrell 3y ago
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.

by crote 3y ago

nyanpasu64 3y ago

It's not the real deal, but https://www.quantumdata.com/assets/essentials_displayport_usb-c_dp_alt_mode_protocols_webinar.pdf https://www.quantumdata.com/assets/essentials_displayport_us... looks to be quite useful for understanding DP Alt Mode. I've used their DP regular protocol PDFs, though because this is a transcript of an animated webinar, there are images covering text which you'll need to remove in a PDF editor or LibreOffice Draw (which can import PDFs).

MBCook 3y ago

> 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 common add-in GPUs are making implementing TB harder?

hocuspocus 3y ago
> Then it seems to have been HDMI for a while (?) Not really. HDMI is basically DVI++ but it's first and foremost a TV and video interface. Once DVI started to be limiting, both PCs and high-end monitors adopted DP. HDMI came to PCs and monitors later, sometimes with limitations, for instance my Dell U2711 couldn't run at its native resolution over HDMI. A few years later UHD 4:4:4 was literally impossible from a PC GPU before HDMI 2.0, while not a problem even on older DP 1.2.
- kjadslkjdsjd 3y ago
  Also DP can do cool things like carrying the signals for multiple monitors (daisy chaining)... I have one usb type c cable that does power display and usb for my 2 dell monitors... it is awesome... sadly Apple never implemented DP daisy chaining this and when you try it with their hardware you only get a mirrored output.
  - lxgr 3y ago
    Yes, it’s a pity they never implemented that. Presumably some deal with Intel to push Thunderbolt :/ It’s an open spec now, but at the time Apple was pushing Thunderbolt hard, only Intel was building the chips for it, both for computers and peripherals (ie monitors, docks etc.)
yyyk 3y ago
DisplayPort is royalty-free while HDMI charges licensing per unit. Additionally, Intel strongly supported DP so many boards came with support even if there was nothing to connect it to, and Intel ensured support in USB specs. Eventually enough display manufacturers added support* and DP became common enough, this generated demand and we ended with a self-reinforcing system. There's still a lot of HDMI, so I wouldn't say the computer world is standardized. In my experience, people just use whatever port is available... * Display turnaround time is significant. Displays can survive a decade comfortably. A few people brag about their 10000K display with 10000Hz refresh rates, but many people just keep their display until it drops or until they buy a new system. So DP took a long time to be universally supported and that hampered adoption for a long time.
crote 3y ago
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.

usernew 3y ago

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 chromecast the screen from that one. I connect them all to TVs. With HDMI on the TV end. So literally your dead on arrival example is not even present in the life of my household, while what's talked about in the article is widely used.

seba_dos1 3y ago
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.
- usernew 3y ago
  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-Alt-Mode-and-more-power-in-cables.680552.0.html https://www.notebookcheck.net/The-demise-of-HDMI-over-USB-C-...
  - 3y ago

ianburrell 3y ago

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.