Low Roller

HDCP and HDMI: What They Mean For You


Earlier this year, Silicon Image ended many months of speculation and long-standing rumors by officially announcing that HDMI (High Definition Multimedia Interface) will soon make its way into our PC’s. With the upcoming next-generation DVD formats, the increasing popularity of HTPC’s, the advent of Windows Media Center Edition, and Hollywood’s desire for copy protection, it was only a matter of time before HDMI found its way into the home computer.

The Basics

For those of you out of the loop, HDMI is the digital audio/video interface that is quickly becoming the standard in home theater products such as cable boxes, A/V receivers, and TV’s. Soon there may be one in your PC. With HDMI, both digital audio and digital video signals are carried on the same cable. This single connection packs enough punch to potentially carry full-blown 1080p high-definition video along with 8 channels of 192kHz audio. It seems nothing new in the world of digital entertainment can green-lighted these days without the approval of Hollywood, and that means copy protection. One of the most important elements of the HDMI specification is HDCP, or High-bandwidth Digital Content Protection.



HDCP was jointly developed by Intel, and is designed to protect digital audio/video connections between HDCP compliant sources and HDCP compliant displays. Using a two-way connection such as HDMI, an HDCP source (such as a DVD player) will send a signal to verify the display device is HDCP compliant. Once the source device gets a response verifying the display is HDCP compliant, the two devices will exchange keys and the source device will begin to transmit the digital video(and perhaps audio) to the display. If the source device does not get a signal back from the display verifying the display is HDCP compliant, the source will refuse to transmit any content. HDCP is found on all HDMI devices, as well as many, but not all, DVI devices.

HDMI is an evolution of the DVI (Digital Video Interface) standard, and is backward compatible DVI. While HDMI can carry both digital audio and digital video, DVI can only pass a digital video signal. For example, a DVD player’s DVI output can be plugged into the HDMI input of a television set. The only thing required is a DVI-to-HDMI adapter. In this case, the digital audio signal uses a separate S/PDIF connection (Toslink or Coax) from the DVD player to plug into an A/V receiver or a digital audio input of the TV. This is required because only the digital video signal is transmitted on the DVD player’s DVI output. Besides not carrying digital audio, standard DVI does not have the bandwidth capacity of the HDMI specification, nor does it have HDCP copy protection built in.

DVI-HDCP is nothing more than the standard DVI interface with HDCP copy protection. Most DVI connections on home theater equipment being sold today are DVI-HDCP. However, in the computer world, this is not the case. Currently, no DVI inputs on any computer monitor sold today are HDCP copy protected. Also, no video card being sold has an HDCP compliant DVI output. (ATI’s newer generation Radeon cards claim to be “HDCP Ready.” This is not the same as HDCP compliant.) The first fully HDCP compliant video outputs on PC’s should begin to appear on upcoming video cards and motherboards later this year.

This brings us to the significance of the announcement by Silicon Image back in March. If the PC is to become a keystone in the digital living room as Microsoft would like it to, it needs to be compatible with the connections of the latest generation A/V equipment. Similarly, if consumers are going to have the ability to watch next-generation media like HD-DVD and Blue-Ray on their PC, desktop equipment needs, for better or worse, to incorporate HDCP copy protection. With the announcement earlier this year, its official these things will soon come to pass.

Transition Pains

One certainty of the transition to HDMI, in both consumer electronics and PC industry, is that the price of being an early adopter will be high. This should come as no surprise. If you recently invested a large sum of money in your desktop or your home theater, you will most likely be sorely disappointed to learn at least some of that equipment is not quite as ‘future proof’ as you had hoped.

In the home theater world, many products have been shipping with HDMI. One glaring problem with these early HDMI connectors is the audio capability. While the HDMI spec can handle 8 channels of 192 kHz audio, almost all the current HDMI connectors are only capable of passing Dolby Digital 2.0. What does this mean? If you bought one of the newer DVD players with an HDMI output you will still need to connect a separate coax or Toslink S/PDIF connection between your DVD player and your receiver to enjoy 5.1 DD or DTS. This scenario holds true for just about every DVD player, cable/satellite box, A/V receiver, and HDTV currently on the market. While it can be expected that future A/V products will undoubtedly ship with HDMI connectors capable of multichannel audio, consumer needs to be aware of the current limitations of equipment being sold today.

As with audio, current HDMI connections are not capable of carrying the full blown 1080p video signals built into the HDMI spec. All products currently on the market with HDMI connectors are only capable of passing up to 1080i/720p video signals. This is true even of the 1080p TV’s that are entering the market this year. While there are no broadcast or DVD 1080p sources currently on the market other than a PC, technologies like HD-DVD and Blue-ray may very well bring full blown 1080p video into the home. So, before you hog wild and spend $13,000 on that eye-popping 70” 1080p 006 Qualia from Sony, be aware you will not be able to feed that TV a 1080p video source.(Qualia’s are said to be upgradeable, just be prepared to spend an extra few thousand dollars if you want 1080p over HDMI)

On many of today’s HDTV’s, there is another dirty little secret manufacturers don’t want you to know. One of the main attractions offered by digital connections such as HDMI is the potential to eliminate the digital-to-analog and analog-to-digital conversions that can degrade the image quality of the original source material. Keeping the signal in its digital form from the source media to the displaying of the image is generally desirable. Many of today’s TV’s take the incoming digital image signal from their HDMI or DVI inputs and convert it into the analog component pathway, before converting the signal back into digital format for display. The good news is most of today’s digital displays are very good at these D/A and A/D conversions, and the image does not seem to suffer much, if at all.

The Desktop

The adoption of HDMI and DVI-HDCP on the desktop PC environment could prove to be particularly painful. LCD flat panel monitors being sold today have vanilla DVI inputs. Since current DVI inputs on LCD monitors lack HDCP copy protection, it is a possibility that future video cards with HDMI or DVI-HDCP outputs will have limited functionality when connected to these devices. In all likelihood, future video cards will not transmit HD content such as the next generation DVD formats to non-HDCP copy protected digital inputs. While analog connections are not subject to HDCP copy protection, the playback resolution of HDCP protected media over an analog connection will likely be limited.

Final Thoughts

If you’re in the market for new home theater and/or computer equipment, keep in mind possible limitations of the current line of digital inputs and outputs. There are some great pieces of equipment out there, but it’s up to the consumer to do the necessary homework to make an informed purchase. Places around the web such as AV Science contain a wealth of information, and with a little effort, you can avoid unpleasant surprises that can accompany the purchase of bleeding edge technology.

Low Roller

I've been meaning to post something on HDMI for a while, but things keep changing so fast I desided to wait fot the dust to settle a little.

If anyone has any thoughts, suggestion, or corrections on my article above, please feel free to share. I'll try to clean it up a little in the coming days, and update it if needed.

MrDigital

Awesome post! I didn't know anything about this stuff.

-MrD