Wednesday, June 8th 2022
HDMI 2.1a Specifications Updated to Include Cable Power Option
HDMI 2.1a, Amendment 1 adds a new feature: HDMI Cable Power. With this feature, active HDMI Cables can now be powered directly from the HDMI Connector, without attaching a separate power cable. This makes attaching and using active HDMI Cables as easy as using passive, wired HDMI Cables. To use the HDMI Cable Power feature, it is necessary to have an HDMI Cable which supports the HDMI Cable Power feature, and also an HDMI Source device which supports the HDMI Cable Power feature. This combination ensures that the active HDMI Cable can safely draw sufficient current from the HDMI Connector to power its internal circuitry.
In the case of the Ultra High Speed HDMI Cable, performance requirements are so high, it is likely that the only way to meet the Ultra High Speed HDMI requirements in cables longer than a few meters is through powered, active HDMI Cables. Therefore, HDMI Cable Power was added to help support the HDMI 2.1a specification's higher speeds by providing power to those active cables which may need it to function correctly. While active HDMI Cables have previously been used extensively in professional markets, their use will now increase in the home whenever consumers need longer-length Ultra High Speed HDMI Cables.
Connection is the same as attaching an ordinary, "wired" HDMI Cable, except that active cables can only be attached in one direction: One end of the cable is specifically labeled for attachment to the HDMI Source (transmitting) device, and the other end of the cable must be attached to the HDMI Sink (receiving) device. If the cable is attached in reverse, no damage will occur, but the connection will not work.
HDMI Cables with HDMI Cable Power include a separate power connector for use with source devices that do not support the HDMI Cable Power feature. Typically, these connectors will be USB Micro-B or USB Type-C, but different power connector types may be used. As more and more source devices add support for HDMI Cable Power, these longer cables will deliver convenience in the living room along with reliable, high performance home theater audio video.
Source:
HDMI
In the case of the Ultra High Speed HDMI Cable, performance requirements are so high, it is likely that the only way to meet the Ultra High Speed HDMI requirements in cables longer than a few meters is through powered, active HDMI Cables. Therefore, HDMI Cable Power was added to help support the HDMI 2.1a specification's higher speeds by providing power to those active cables which may need it to function correctly. While active HDMI Cables have previously been used extensively in professional markets, their use will now increase in the home whenever consumers need longer-length Ultra High Speed HDMI Cables.
HDMI Cables with HDMI Cable Power include a separate power connector for use with source devices that do not support the HDMI Cable Power feature. Typically, these connectors will be USB Micro-B or USB Type-C, but different power connector types may be used. As more and more source devices add support for HDMI Cable Power, these longer cables will deliver convenience in the living room along with reliable, high performance home theater audio video.
14 Comments on HDMI 2.1a Specifications Updated to Include Cable Power Option
If they had included 2-3 dummy/reserved pins we could have had HDMI power a lot earlier on.
PoE gets around this to a large degree by being choosy with the conductors used for power and earth/return, as well as much lower switching rates for the differential signals (excepting >10GBASE-T).
Edit: being that this appears to be extremely low current strictly for the active circuitry in a cable, I think my concern is moot. Also, it makes sense that the HDMI standard eschewed the concept entirely. Who in their right mind would've thought a (consumer-oriented cost-optimized) serial interconnect should have its own processor?
Optional standards are a big issue, since it's a huge pain in the ass to add support in later
edit for clarity:
What others said that it should have been HDMI 2.2 or something, HDMI 2.1 has so many optional features you dont even really know what you're buyingBecause HDMI has money behind it, with all its proprietary dolby technology support
It's so you can do exactly what some people here surmised, have a really long optical HDMI cable without it needing an external power connector
According to cablematters, HDMI 2.1 passive cables can only reach 3M /10 feet, with standard active cables maxing at 7.5M / 25 feet.
That's pretty damn short, and explains why they needed an official standard to help fix it
Passive DP 1.4 can do 2M or 6 feet 6 inches at 4K, they didnt list active DP cables, but they list and sell 10M/33 feet ones on their store - and it draws power from the displayport source