Talk about HDMI

So, more specifically, what is HDMI? HDMI - High Definition Multimedia Interface - is actually just a logical progression on top of DVI. The video segment of the HDMI signal is actually compatible pin for pin with DVI, but in a much different package. HDMI improves on DVI by transmitting digital audio on the same interface, adding support for HDCP and also better DDC options for manufacturers.

HDMI provides 5Gbps over copper interconnects up to 15 feet - that's enough headroom for a 1080p signal and 8 channel audio. For those who like to do the math, a 1080p raw video signal and eight 192kHz audio channels require less than 4Gbps. So, there is a significant portion of unused overhead built into the HDMI specification. We've seen demonstrations of hooking your DVD player, receiver, and PVR each with a single cable at shows like CES and the word is that adoption of HDMI is going even faster than originally planned.

Below, you can see a cross-section of what the 19-pin HDMI cable looks like. The smaller, sturdier cable was designed with laptops and slimmer devices in mind. The DVI cable on the right shows the large difference in size.

Click to enlarge.

Right now, HDMI cables, like the original DVI cables, are very expensive. High quality cables easily retail for more than $100 each, although middle of the pack HDMI cables in the one and two meter range can be had for less than $20.

Remember the interoperability and quality issues with older DVI connectors on video cards? Since DVI is a relatively loose protocol, manufacturers are not strictly enforced to adhere to design principles. Signal quality on DVI connectors hit a low point in 2001/2002, but fortunately, it seems that awareness of the problem has started to rectify these issues. Since Silicon Image had a significant influence on the original DVI and HDMI specifications, they have taken it upon themselves to set up their own quality control laboratories, PanelLink Cinema (PLC). New devices will go through a very stringent verification process to assure that the next generation interfaces don't have the same problems which plagued DVI. The lab also works directly with Intel's HDCP spinoff licensor, Digital Content Protection, to assure that HDMI-ready devices adhere to the HDCP guidelines. Copy protection is a large facet in the HDMI specification, so it only makes sense that Intel and Silicon Image have so much invested in building trust with the content providers.

Today, the largest factor that plagues HDMI in the living room is whether or not devices are actually taking advantage of 8 channel audio. Many of the first generation HDMI ready devices only utilized two channels with the thought that TVs in particular would not need anymore than 2 channels. As a result, many new devices still ship with separate stereo inputs just as they do with DVI, but obviously, the push will be for new devices to drop these inputs in favor of digitally-protected high fidelity capabilities built in the cable specification. Stereo would just be a fall back.

Significance on Desktop


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  • otemanu - Monday, January 17, 2005 - link

    By adopting HDCP we make it possible for the media producers to enable more restrictions than exist on DVD and digital broadcasts today. HDCP means to abandon most of the digital displays sold up to now. Virtually none of the computer screens and many older plasma-screens that support DVI but not HDCP/HDMI will not be allowed to show future BlueRay/HD-DVD movies or HDTV broadcasts. This will result in the same type of cracking that exists for DVD/Region/macromedia - not to copy - just to be able to buy and watch a movie on existing hardware/software. Were will it end? Should only certified "locked" media pc be allowed to display movies? Only certified companies be able to produce players. They are making the DVD/mp3 mistake again. Reply
  • shabby - Monday, January 17, 2005 - link

    Whats the point of carrying audio to the tv when its the reciever that needs it?
    But i wouldnt mind a geforce 6800 with soundstorm, that would be sweet.
  • Lonyo - Monday, January 17, 2005 - link

    I would guess that graphics card manufacturers, chipset mfs and soundcard mfrs could work together using PCIe to manage a way to direct the sound card output through the graphics card.
    Since you can hook up two graphics cards, I would guess you could route sound through a graphics card.
    Still, it does seem a little unecessary to have this at all.
    To me, it seems to assume a total lack of discrete speaker systems?
  • R3MF - Monday, January 17, 2005 - link

    agreed with 10 also.

    is there no way to strip out the content protection rubbish from what is a good connector?
  • KHysiek - Monday, January 17, 2005 - link

    I thought this interface was supposed to replace DVI, mainly cause DVI is too slow for high refresh/ high resolution displays. AFAIK DVI max is about 1600x1200/60Hz. Reply
  • elecrzy - Monday, January 17, 2005 - link

    agrees with 10. Reply
  • Woodchuck2000 - Monday, January 17, 2005 - link

    I'm sure there were rumours at one point that Soundstorm 2 might end up integrated into one of nVidia's graphics cards...

    That would make a lot of sense now, given this article!
  • mcveigh - Monday, January 17, 2005 - link

    Stefan as I see it right now it only affects the HTPC users. I would have it go out to my receiver which would then send one signal to my speakers and the hdmi video only to my TV.

    unless the come up with a hdmi monitor that outputs to speakers/receiver.
  • bersl2 - Monday, January 17, 2005 - link

    s/manage you/manage how you/ Reply
  • bersl2 - Monday, January 17, 2005 - link

    Uh, this "protection" crap is making me sick.

    And so is this vision of the future where I have even less control over my machines and the data in my possession.

    Media matter more than ever in culture, and you are going to hand over control to entities whose sole responsibility is to make money, in effect, giving up control of your culture? You are going to let someone who doesn't care what you believe in manage you make sense of the world?

    Think. Please. Think about what is going on. You choose what you want, but consider what it is you are slated to lose and how important that is to you.

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