HDMI 2.1a Specifications Updated to Include Cable Power Option

[Uskompuf]

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.

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[Durvelle27]

I wish FireSticks had this from the jump. That would make cable management so easy

 

[Steevo]

I wish FireSticks had this from the jump. That would make cable management so easy

I have wondered why small displays and or other devices couldn’t have been HDMI powered as well, adding a set of larger power pins could have been so easy from the start.

 

[MrDweezil]

I wish FireSticks had this from the jump. That would make cable management so easy

I don't think that's what this is. This is power for the active cable itself, not the device on the other end.

 

[Panther_Seraphin]

I have wondered why small displays and or other devices couldn’t have been HDMI powered as well, adding a set of larger power pins could have been so easy from the start.

Considering HDMI was introduced nearly 20 years ago it probably wasnt something considered at the time and there wasnt much leeway put into the pin layout for expansion at a later date.

If they had included 2-3 dummy/reserved pins we could have had HDMI power a lot earlier on.

 

[LabRat 891]

Considering HDMI was introduced nearly 20 years ago it probably wasnt something considered at the time and there wasnt much leeway put into the pin layout for expansion at a later date.

If they had included 2-3 dummy/reserved pins we could have had HDMI power a lot earlier on.

I'm no EE, but I always assumed the switching noise and 'antenna-like' nature of untwisted unshielded SMPS-source LVDC power lines 'complicated' signal integrity on serial digital links. It wasn't until USB-C that we saw >0.9A @5V, and early USB 3 had an entire 'debacle' with WiFi and BT co-existance due to it effectively sharing the same 2.4ghz baseband.
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?

 

[trsttte]

I don't think that's what this is. This is power for the active cable itself, not the device on the other end.

Yes, but this new revision is also about increasing the amount of power available, previously 50mA and now 300mA with cable power. Still not enough to run a firestick or similar dongle but seems like a missed opportunity to not implement an higher limit for that purpose.

 

[Broken Processor]

I'm wondering why power through the cable is necessary to send the signal over longer distances when you can buy hdmi to fiber cables quiet cheap.

 

[chrcoluk]

There should be a hdmi 2.2 for this, so now we have hdmi 2.1 that might or might not include this feature.

 

[trsttte]

I'm wondering why power through the cable is necessary to send the signal over longer distances when you can buy hdmi to fiber cables quiet cheap.

It's not power through the cable (not on fiber cables anyway), it's power for the fiber converter built into the connector. Some (like really long distance) require an external adaptor (usb or something), this solves that.

 

[JAB Creations]

There should be a hdmi 2.2 for this, so now we have hdmi 2.1 that might or might not include this feature.

Exactly this.

 

[Minus Infinity]

Is there still a need for HDMI going forward. Can USB4 which incorporates DP2.0 be the only cable we need going forward. We just settled on a single USB-C port for charging, why not get rid of HDMI and get all in on USB4? Obviously I have very little knowledge of the intricacies of this but given USB 4 supports very high res 8K monitors why not use it for TV's and HT Amps. Obviously this would take a lot of time and all new devices going forward so it's longer term plan.

 

[Mussels]

This kind of thing makes displayport/USB-C seem so much better

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 buying

Is there still a need for HDMI going forward. Can USB4 which incorporates DP2.0 be the only cable we need going forward. We just settled on a single USB-C port for charging, why not get rid of HDMI and get all in on USB4? Obviously I have very little knowledge of the intricacies of this but given USB 4 supports very high res 8K monitors why not use it for TV's and HT Amps. Obviously this would take a lot of time and all new devices going forward so it's longer term plan.

Because HDMI has money behind it, with all its proprietary dolby technology support

 

[R-T-B]

I'm wondering why power through the cable is necessary to send the signal over longer distances when you can buy hdmi to fiber cables quiet cheap.

Not hdmi 2.1 ones.

Exactly this.

This is almost exclusively for active boosted cables. Not all hdmi 2.1 cables need or even want this.

 

[Mussels]

I read up more on this, the purpose is to let you run longer HDMI cables - nothing else

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