HDMI Alt Mode for USB Type-C Connector(hdmi.org) |
HDMI Alt Mode for USB Type-C Connector(hdmi.org) |
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.
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?
* 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.
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.
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.
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.
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.
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.
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.
If you're confused, read https://arstechnica.com/gadgets/2023/01/hdmi-to-usb-c-spec-a...
When you have a C-to-HDMI (eg https://frame.work/products/hdmi-expansion-card) it's more like .... C-to-DP(implicit in type C)-to-HDMI. If you have a monitor that has both DP and HDMI you probably want to get yourself a simple C-to-DP cable as there's no active conversion going on so it's more likely to work.
USB4 ports mandatorily have DisplayPort output, on each port. HDMI is not going to catch up. It is an expensive proprietary system & won't ever match the availability.
"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 features and also require converters and connector adapters to connect to HDMI-enabled displays. A simple HDMI to USB Type-C cable can be used to connect USB Type-C devices to native HDMI displays."
There is a similar situation with DP++ to HDMI adapters; they need to only shift voltage levels (3.3V for DP vs. 5V for HDMI) since the DP++ port can output “HDMI on DP wires”, but actual DP to HDMI conversion involves actually translating things at the pixel level.
Please tell me that this is not marketing speak for HDCP! What other "native HDMI" features are there that DisplayPort does not already support?
(Nor ARC/eARC, but I think those would be of limited utility for the USB-C alt mode.)
So there were two different ways to run DP over a cable with a USB-C connector.
Sounds like it’s good it’s dead.
Thunderbolt also doesn’t really natively send DP over USB; it encapsulates it (plus PCI express) in a custom wire format.
Only DP alt mode actually uses DisplayPort at the wire level over USB-C cables or ports.
USB-C cables can be garbage, so you probably need to get a better one.
Here is another example. A coworker came crying that her monitor is dropping connection. We’ve tried an HDMI cable (this is a full size monitor connected to a laptop), problem disappears.
It’s a difference between working reliably (like an HDMI cable) vs working sometimes, if you are lucky.
It depends much more on the combination of monitor, source, and cable, than on native DP vs USB-C, in my experience.
This is my “universal” cable;
https://www.amazon.com/dp/B093YVRHMB
- USB A and USB C on one end.
- USB C, micro USB and lightning on the other end.
- 100 W charging support
- 10Gbps data transfer
- supports video over USB-C
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.
The _only_ reason I want a linux based phone is so I can just use my phone like a normal device.
The software implementations (who remembers MTP?) for phones kills its usability as a general purpose device.
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.)
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-...
> 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)
It's just a screen, no touch capabilities or any real processing onboard.
This screen has 3 usbc ports and a mini hdmi port. It also has an audio out jack.
In theory, it can be driven with a usbc to usbc cable from a phone or computer, but I don't have a device that can drive it this way.
The second usbc port is auxiliary power for when your phone can't power the whole screen.
The third usbc port is for daisy chaining another device.
The way I use this thing is from my (fairly old) laptop that only has display port out. I have an adapter that changes the DP port on my laptop to full side hdmi and then use the hdmi to hdmi mini cable that came with the screen.
Unfortunately, this setup does not pass sound to the audio jack. I wish my laptop had an hdmi port instead.