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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  • Klober - Monday, January 17, 2005 - link

    I agree with archcommus87, even if they integrate audio and video onto a single card in the PC, my monitor and 5.1 speakers are still two separate pieces of equipment. So where is the cable supposed to plug in - the monitor or my sub? If it plugs into the monitor, then I still need the current cable I have running from my sound card to my sub. If it plugs into my sub, then I still need the cable running from my video card to my monitor. The integration makes sense for home theatre systems where everything goes to the receiver, but it sounds like a downright stupid idea for PCs. Either way though, I really can't stand the "secure" crap they're trying to push on us in order to take away our law given rights. They force us to crack the schemes to use our systems the way we should be able to according to the laws, and then they prosecute us for it. Just doesn't seem right to me. It's my equipment, I paid good money for it, and I'll use it how I like within the current laws. Reply
  • Googer - Monday, January 17, 2005 - link

    I am an analogue fan, I love my CRT! Does HDMI support analogue? Reply
  • archcommus87 - Monday, January 17, 2005 - link

    mcveigh: I'm talking about for a PC setup. I also don't understand the purpose of combining video and audio into one cable. No matter what future technologies ever come out, the sound system and monitor will ALWAYS be separate! Reply
  • epiv - Monday, January 17, 2005 - link

    I do not get the idea of combining audio and video signal into the same interface. Currently audio and video come from different component in a pc and is sent to different device too. Are they going to combine the Monitor and speaker into one package too? Reply
  • Brian23 - Monday, January 17, 2005 - link

    This is all crap. I don't even own a TV and I don't plan on getting one. The only shows I watch are the ones I play on DVD and the ones I download on the internet. Reply
  • stanmuffin - Monday, January 17, 2005 - link

    Bleh. The trend toward manufacturing devices that disobey their owners continues. It won't be long before we're not allowed to change the channel without watching 10 minutes of commercials first. Reply
  • ceefka - Monday, January 17, 2005 - link

    #15 Maybe they think you'll use your THX or AC3 capable receiver for the sound and the TV as a display. You're not listening to your TV when you play a DVD, do you?

    Intergrating Dolby Surround 5.1, 6.1, 7.1, DTS and or THX in your PCI-E graphicscard: Nice idea. With the size of the HDMI-plug you'd even have room for the optical/coax digital out, 2nd display and ViVo. It could also save us from any crappy on board solutions.
  • Koing - Monday, January 17, 2005 - link

    #12 KHysiek

    DVI suports 1920x1200. A Dual Link (DL) one will go up to the 30" 4MP display.

    The HDMI will go to a 'reciever' first then from the receiver to whatever you want. One run to the tv and speaker cable from the reciever.

    If you don't have a receiver you just go straight to the tv. BUT this crews the people who's receiver does not have HDMI :P

  • Noli - Monday, January 17, 2005 - link

    Totally agree #16
    Many people who have just or are just about to buy expensive plasma/lcd tvs will be truly p*ssed off when they find out that their swanky dvi/hdmi connection is not HDCP compliant and so can't watch the content they've paid for! (only some of the latest models are HDCP compliant).

    Not sure yet if the panasonic AE700 projector I bought (has hdmi) a couple of months ago is HDCP compliant but it will be annoying if it isn't. (Anyone know?)

    Here in the UK it is not so bad - the BBC said that they won't be broadcasting in HDTV modes (a strong candidate for hdcp protection I think) until 2010, though some sports events in 2005/6 maybe HDTV resolution and some dramas in 2007/8. By then, plasma/lcd tvs should be even cheaper but i still don't see how you can force a nation *and* manufacturers to force the changeover.

    All this will do is force the knowledgeable and the keen to hack HDCP and everyone else will suffer...
  • R3MF - Monday, January 17, 2005 - link

    oh well, their loss.

    we will crack it, just like we always have when vendor lock-in ensues.

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