HDMI licensing administrator says the obscure HDMI Alt Mode specs are dead

Alfonso Maruccia

Posts: 912   +280
Staff
Why it matters: HDMI Alt Mode was designed to provide an efficient and flexible bridge between two different connection technologies. But HDMI Alt Mode promises never came to fruition, and the potential standard is now essentially dead, as officially confirmed by HDMI LA.

According to Notebookcheck, which spoke with HDMI Licensing Administrator (LA) representatives at CES 2023, HDMI Alt Mode will not be updated to the latest audiovisual standards. The technology was never adopted by manufacturers of end users, and it was essentially dead on arrival because of new market trends and DisplayPort competition.

As explained on the official page of the standard, HDMI Alt Mode would allow "HDMI-enabled source devices" to use a USB-C connection to deliver HDMI signal and features over a simpler cable with no need for additional protocols or adapters. This way, the "small form factor, reversible, and multi-purpose USB Type-C connector" could work together with the "leading display interface" (I.e. HDMI) on smartphones, tablets and PCs.

The latest version of the HDMI Alt Mode standard supports the full range of HDMI 1.4b features, including resolutions up to 4K, surround sound, Audio Return Channel, 3D (4K and HD), HDMI Ethernet Channel, Consumer Electronic Control, Deep Color, and HDCP DRM tech (1.4 and 2.2). "It's up to manufacturers," the specs say, "to choose which HDMI features they support on their products with USB Type-C."

And manufacturers clearly chose to avoid HDMI Alt Mode support altogether. The HDMI LA, which manages license agreements for commercial use of the most recent HDMI specifications, said that the technology simply has no place in the modern market. Companies like Apple have started adding HDMI ports on their products again, HDMI LA said, and HDMI Alt Mode offers no actual benefits when compared to DisplayPort Alt Mode.

Just like HDMI Alt Mode, DisplayPort Alt Mode was designed to use a USB-C port and cable combo to connect DisplayPort-compatible displays or TV sets. Furthermore, DisplayPort Alt Mode supports higher refresh rates (4K at 60Hz, uncompressed), 24-bit colors, and more. DisplayPort Alt Mode can even support HDMI 2.0 signals, and it was officially released 2 years before HDMI Alt Mode (in 2014), which clearly helped its wider adoption.

The HDMI LA admitted at CES they don't even know any actual manufacturer which produced an HDMI Alt Mode-compatible product. The same goes for the USB Implementers Forum, where people "familiar with the certification process" don't know if any HDMI Alt Mode adapter is available for purchase. So goodbye HDMI Alt Mode; we hardly knew you.

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As I see it, part of the problem with a "standard" like this is leaving it up to the manufacturers to pick and choose which features to support. If the manufacturers decide not to include certain features in their products, I don't see how they can claim that their product is compliant with the "standard."

Even with the mainstream HDMI connectors, it still seems up to the manufacturer to support, or not, all the features of the current "standard". I surveyed AVRs and not all of them support the 48Gbps speed and all of the features of the HDMI 2.1 "standard".

For me as someone who relies on HDMI for A/V reasons, HDMI is nothing more than a pseudo-standard that the consumer has to chase in order to get equipment that is compliant with the full range of features that are supposedly part of the current "standard." My solution to this is to not upgrade my equipment until the product(s) that I want support the full-range of features for the current "standard."

IMO, the HDMI LA should stop calling it a "standard" and instead, call it a pseudo-standard - but that would be bad marketing. :rolleyes:
 
HDMI is stupid. Displayport is a superior technology in nearly every aspect, and doesnt come with silly licensing shenanigans like HDMI does.

There's a very good reason HDMI alt never took off. Frankly I'd love to see it disappear altogether for AV and be replaced with displayport.
 
HDMI has CEC and ARC.

For everything else DisplayPort is usually a step ahead, and awesome.

Running 144hz 4K with Gsync out a standard USB C port over DP alt mode, and it just works. Even through a Thunderbolt hub. Open standards are powerful.
 
This is wild stupidity, tk. there are many laptops with only usb-c ports but no HDMI port. At the same time, DP Alt Mode only supports 2m lengths in UHBR modes. And HDMI 10 (and for a long time you need up to 50-100m in optics). Active HDMI adapters, those sold on the market, have chips inside that do not support the latest full HDMI 2.1 standards, but only 2.0b. What do you want to do to someone who bought a laptop with usb-c ports and who wants to connect a TV or monitor with HDMI 2.1 at 48Gbps?
 
This is wild stupidity, tk. there are many laptops with only usb-c ports but no HDMI port. At the same time, DP Alt Mode only supports 2m lengths in UHBR modes. And HDMI 10 (and for a long time you need up to 50-100m in optics). Active HDMI adapters, those sold on the market, have chips inside that do not support the latest full HDMI 2.1 standards, but only 2.0b. What do you want to do to someone who bought a laptop with usb-c ports and who wants to connect a TV or monitor with HDMI 2.1 at 48Gbps?

What resolution would a device need to be outputting which only has USB C on a TV with 2.1, which would be limited by 2.0? Does a use scenario even exist for that?
 
HDMI has CEC and ARC.

For everything else DisplayPort is usually a step ahead, and awesome.

Running 144hz 4K with Gsync out a standard USB C port over DP alt mode, and it just works. Even through a Thunderbolt hub. Open standards are powerful.

USB C have their own issues. Take a laptop - is it charging while it’s connected over that port? Is the monitor TB or USB C? Is the USB C port 3.0 or 3.2? Or my personal favourite I’ve encountered - “oh no that USB C port connects to the Intel iGPU not the nVidia one”

All standards have issues annoyingly!
 
4k@144Hz HDR 444
Regardless
All new OLED TV 120-144Hz HDR VRR. Many 4k monitors 144Hz HDR.
again, which monitors have this and only have HDMI? They all seem to have DP too…

All new OLED TVs do not have this - those that do are branded gaming TVs and have DP too.

You also ignored my other point too - what laptop would you connect to these which doesn’t already have native HDMI too?

And as I already posted in my last comment, HDMI 2.1 USB C adapters already exist:

 
Again… where’s the monitor which NEEDS. HDMI 2.1 and doesn’t have DP?

Once again, you’ve ignored my other point - where’s the laptop which only has USB C and can actually/needs to output this?

And once again, as I’ve linked twice now - your whole point is moot because USB C to HDMI 2.1 adapters already exist…
 
All monitors with 4k@144Hz HDR require full version HDMI 2.1 and DP2.0+.

No adapters from DP2.1 to HDMI 2.1. DP1.4b from TB4 not support bandwidth over 20Gbps.
 
USB C is great for mobile devices like laptop computers, tablets and mobile phones where dimensionally limited space. But owing to it's physical size it's also extremely fragile and prone to breakage. In that regard the DisplayPort and HDMI connectors are far more robust. There's nothing more annoying than breaking the plug tip on a cable, or worse damaging the plug socket.
 
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