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Inside HDBaseT Technology: A Better HDMI Extender

HDBaseT delivers 4K x 2K video, audio, control, Ethernet and up to 100 watts of power over a single Cat 5 cable up to 100 meters ... without degrading the signal. How'd they do that?


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HDBaseT: One Cat 5 cable for 100 meters of uncompressed video, audio, control, Ethernet, power, HDMI pass-through

Rx0, Rx1, and Rx2 on the left-hand side correspond to the three red, blue, and green TMDS color channel outputs from the HDMI chip (note that they are viewed as receiving the HDMI TMDS data from the perspective of the HDBaseT chip). The +/- designates that that it is two “wires” that normally make up one of the differential twisted pairs within an HDMI cable. The RxC is the associated TMDS Clock line. These signals also carry the audio that is multiplexed over the video lines the in same way as an HDMI cable.

The important sets of pins are on the right-hand side of the diagram. The top set of pins corresponds to the four PHY-layer HDBaseT twisted pair wires to the RJ-45 jack (HDBT0 through 3). The HDBaseT chip simply acts as a pass-through for the HDMI TMDS signals that then get modulated using the HDBaseT coding scheme mentioned previously.

The other set of pins on the bottom right connect to a standard HDMI Type A connector. It will be up to the vendors to decide if they want to include that connector in their devices or to just use the RJ-45 instead.

This is a clear illustration of how HDBaseT augments HDMI instead of replacing it, as some have suggested.

Some other pins of note are the additional lines normally run individually within an HDMI cable. These include the Consumer Electronics Control (CEC) line and the Display Data Channel (DDC) line. Since these also are passed through from the associated HDMI chip, all of the functionality for CEC, HDCP, EDID discovery, Content Type Signaling, and things like the HDMI 3D_Structures embedded in the video stream work as they would if it were an HDMI cable.

While there is no dedicated wire in the HDBaseT cable for Hot Plug Detect (HPD) like there is with HDMI, there is logic built into the chips at both ends that raises a flag on the source side whenever a new device is plugged in. This logic is used for initiating the process for obtaining the EDID information from the new device and initiating the HDCP key exchange, just as it would with an HDMI cable.

HDMI 1.4 Integration Unclear


Notice that the Link Layer Ethernet channel is independent of the HDMI 1.4 chipset interface.

While this works for sending Ethernet across the HDBaseT cable, will it have the capability to bridge to the Ethernet channel on newer HDMI 1.4 chipsets that offer HDMI Ethernet Channel (HEC) capabilities.

Perhaps integration will be up to the vendor?

Similarly, there does not appear to be any capability to interface with the HDMI 1.4 Reverse Audio Channel feature. While this currently may not be a mass market requirement, it could impact how well this version of the technology integrates with these newer features of the HDMI 1.4 platform moving forward.

HDBaseT Distance: Going the Extra .12 Mile


For the maximum video resolution over HDBaseT, the length of a point-to-point Cat 5 wire run should remain under 100 meters. Cat 6, as always, will do even better.

You can extend the overall source to sink length to 200 meters using an HDBaseT switch.

Additionally, you potentially could daisy chain switches to increase that distance if required. This could be a big plus when using the technology for commercial installations or for digital signage applications.

HDBaseT: The Whole Picture
I. HDBaseT Cat 5 Technology is Useful, but No 'HDMI Killer'
II. Inside HDBaseT Technology: A Better HDMI Extender
III. Is HDBaseT a Game Changer? (coming soon)
The distance limitations, however, have less to do with the technology than with Hollywood.

The studios want to limit the distribution of premium content to a single household. Apparently, 100 meters is long enough to cover most homes.

Therefore, HDBaseT has a built-in capability to impose a “logical” limitation on the end-to-end length of an HDBaseT infrastructure to 100 Meters. HDBaseT has a built-in mechanism for accurately detecting the maximum source to sink distance.

Limiting the maximum distribution distance can be enabled by the content providers for certain types of material. Just don’t tell them about it.

5Play: Breaking it Down


Before it was HDBaseT, Valens Semiconductor marketed the technology as 5Play (white paper .pdf). Here are those five “plays.”

1. Uncompressed HD Video
It should be apparent by now that the video implementation is a simple pass-through from an HDMI chipset.

All of the same resolutions incorporated into the HDMI 1.4 specifications appear to be supported; however, there currently is no public information available on how deep the bit depth will go for Deep Color, nor is there any information about support for the new Color Spaces introduced with 1.4.

HDBaseT does support 2K x 4K resolution at the same frame rates as HDMI, in addition to the new mandatory 3D formats.

There currently is no integration with DisplayPort, but there is talk of being able to work with dual port versions (DisplayPort ++) via the HDMI interface.

Since the DDC line, which carries the HDCP encryption handshaking, is passed through, playback of premium content is consistent with HDMI. It actually may end up being more reliable since the HDBaseT coding scheme is not as susceptible to the resistive, capacitive, and crosstalk-related electrical problems that a normal HDMI cable may experience. Coding schemes tend to have less degradation over longer distances than strictly sending out high-speed binary ones and zeros.

2. Audio
Audio is passed through the same as video, so all standard formats are included. Once again, protected audio content will work as well. At some point, we may see HDBaseT used for audio-only distribution, but the costs may prohibit its wide use.





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Article Topics

News · Product News · Video · Multiroom Video · Wire and Cable · HDMI · Hdbaset · Hdmi Extender · All topics

About the Author

DrFlick, Play
I provide consulting and implementation services for manufacturers and consumer electronics installation companies on new technologies, products, and strategies related to standards-based Distributed Audio, Video, Communications, and Control (DAVCC) systems for the home and consumer market spaces. My long-term goal is to be instrumental in the development and deployment of entertainment systems on space stations and space colonies.

10 Comments (displayed in order by date/time)

Posted by CaW  on  07/19  at  02:47 PM

They might not want you to think its a replacement, but its a replacement.  As a tech savvy consumers and a DIY, I sure as heck like the idea of being able to create my own video distribution with standard user terminated Cat6 cables instead of relying on some kludgy after market add-on.  Building it on HDMI/making it backwards compatible, etc, just reduces the chance of litigation against the companies behind it.

Posted by deathtohdmi  on  07/19  at  04:48 PM

Death to HDMI wink I wonder what the poor “audiophile” companies are going to think of this when we finally swith over.

Posted by DrFlick  on  07/19  at  06:07 PM

CaW,

Yes, from a cabling perspective, this seems like a great solution for point-to-point runs.  However, I still caution you when you start adding multiple sink devices without some good EDID and CEC management tools (and an infrastructure to support them).

  =D-

Posted by jbrown  on  07/20  at  09:34 AM

I think everyone universally hates HDMI, and with good reason. It has suffered from three main issues from the beginning. 1. ridiculous distance limitations unless you spend a fortune. 2. insane copy protection lockdowns for no good reason. 3. possibly the 2nd worst A/V connector design ever (s-video is still the worst). Hopefully this addresses at least two of them.

Jason Brown
http://www.asktheadvisors.com

Posted by Clint DeBoer  on  07/20  at  10:13 AM

No offense to Julie & Derek, but the article is a bit misleading. You are drawing from the existing chipset to make a statement that “Contrary to overzealous reports, HDBaseT is not a replacement for HDMI—and will not be a replacement anytime soon.” (which you then contradict with the statement from Micha Risling, VP of sales and marketing for Valens Semiconductor.) Let me be clear, HDBaseT is certainly NOT an enhancement… not in the long view.

Had you spoken to the president of HDBaseT (as I have) you would have found that this is INDEED designed to be an eventual replacement/competitor to HDMI. What you have observed is simply that: 1) the EXISTING chip technology is designed, necessarily, to interface with HDMI, since it was designed as an HDMI balun; and 2) of COURSE it’s not going to replace HDMI right away as it will need to be rolled out as a concurrent technology until the AV equipment supporting it hits critical mass and HDMI can be phased out…

HDMI is a connection and spec, nothing more. There is no magic, and certainly no reason that it has to stay around in order for HDBaseT to function. This is only based on an existing chipset that has been on the market since WELL before the specification for HDBaseT was finalized.

So the real question is how quickly can it be rolled out? My guess is VERY quickly based on the desire for AV receiver manufacturers to be the “hub” of the home theater. HDMI didn’t allow for this, but HDBaseT does.

Posted by DrFlick  on  07/20  at  11:09 AM

Clint,

No offense to you, but your article at http://www.audioholics.com/news/industry-news/hdmi-dead-hdbaset is about as misleading as it gets.  In fact, that specific article is one of the primary reasons I wanted to write something that factually describes the technology behind HDBaseT, not just publish some overzealous headline making statements that obviously are just designed to attract hits on a web site.  If you had said that we finally have a potential solution that could replace the dreaded HDMI connectors and cables, then I could agree with the concept of what you were trying to say.  However and maybe it is just me, releasing a technology that claims to be killing off the exact technology it REQUIRES to run makes no sense.  You allude to their potentially licensing the HDMI and HDCP technologies to include into a single chip of their own sometime in the future, but all that does is reduce the form factor and cost.  It still keeps HDMI very much alive – it just changes the connection media and connector.  Additionally, with their chipset still directly supporting pass-through to an HDMI connector the entire CE industry has pretty much decided to embrace, my view is that the only thing they are delivering is a standardized alternative for connecting HDMI devices together – an HDMI Extender with some additional optional (and in some cases potentially incompatible) features.  Further, you neglected to mention the additional cost of including their technology into devices already being gouged by low profits and prices when it actually is less expensive to continue using the current HDMI connector for non-long distance connections.  Add on top of that your blatant acceptance of how the power distribution possibly could be delivered and all you have done is confuse the readers even more.

I believe it would have been more beneficial if you actually had done some research into how the technology works, presented the pros, presented the cons, presented things to look out for when selecting it as an alternate connectivity solution, and then made a case for why it might become an interconnection standard if and when others in the industry can justify embracing it.  I also am curious why you missed out on stating some of the positive features like “rolling back” to Ethernet that eliminates some of the interoperability confusion in the market – I guess that part was not in their marketing brochure.  You also missed highlighting an ugly feature like forced distance limitations as a form of DRM enforcement – I guess that was not in their marketing brochure either.  All you printed was the hype given to you by the company.  If we relied on that for all of our purchasing decisions, we would own one of everything.  We have yet to see how it pans out in real life installations and with real products.  Either way, it will be a good alternative to the current HDMI connectors, but it definitely is not an HDMI killer.

I will stand by what I wrote over pushing the Fear, Uncertainty, and Doubt that you are so willing to propagate.  My goal is to provide clarity, not regurgitate marketing confusion.

  =D-

Posted by Julie Jacobson  on  07/20  at  12:18 PM

sorry, Clint, didn’t meant to pick on you ... your article was great and you guys do an awesome job. AND ..... We use sensationalist headlines all the time.

In fact, we did interview Ariel as well. Naturally, they would LOVE to replace HDMI with their technology ... so did 1394 and so did every other technology.  But it won’t even be a consideration for a hugely long time.

Posted by DrFlick  on  07/29  at  02:48 PM

If anyone is interested in a more technically-detailed analysis of HDBaseT, I have posted a more in-depth version of this article at my blog site http://thedigitallifestyle.com/cs/TDL/b/custom/archive/2010/07/25/Clearing-up-the-HDBaseT-Technical-FUD-_2D00_-Installment-031.aspx.

  =D-

Posted by DrFlick  on  08/07  at  10:22 AM

Clint,

I appreciate your public apology at about 32 minutes into your recent podcast at http://www.avrant.com/?p=1460.  As mentioned, if we believ all of the sensationalism, hype, and FUD from vendors’ marketing departments without taking the time to understand how all of these new technologies actually work “on the wire,” we would own one of everything – and be disappointed in 90% of them once we have them.

  =D-

Posted by UKHDMi  on  09/25  at  08:51 AM

Just launched HDbaseT Solution http://www.youtube.com/watch?v=DkT0AOBeVAc

Any feedback?

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