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The Technology of Home Theater Projectors and Systems - A Guide to Multiple HDMI Sources

By Art Feierman
Index of Home Theater Projector Questions

Dealing With HDMI and Multiple HDMI Sources

Well, let's start off with the obvious: HDMI can really be a pain!

The cables tend to be from fairly expensive to twilight zone expensive.

Theoretically, HDMI was spec'd to work over short distances - about 20 feet. Fortunately thanks to superior (and expensive) cable technology, runs of 20 meters (about 66 feet) and even slightly longer are possible.

For beyond those lengths, there are a host of solutions - extenders (some using CAT5 or CAT6), repeaters, fibre-optics, and so on. Depending on what you need, you can extend HDMI for thousands of feet, if not longer - budget allowing. Even wireless HDMI is on the horizon, with several relatively affordable products announced, and intended to ship by now 5/08, but delayed. We should see soon, wireless HDMI from Gefen, Belkin, possibly Philips, and others, hit the market over the next few months to a year.

But, this article isn't going to get into the finer points of getting an HDMI signal from point A to point B, but rather, is about choosing among your switching options.

Overview: Most of today's home theater projectors have two HDMI inputs, a few have three (I'm including DVI inputs that are fully HDMI compliant). Rarely you'll find a projector with four or more, and if you do, it is probably using an external processor box (those tend to be loaded with inputs).

On the other end, your DVD or Blu-ray DVD player will normally have one HDMI output, as will your Cable box, or Satellite Dish tuner. Then there's your PC should you want to output digitally to your projector. And you might have a game machine such as the X-Box with HDMI output. (If you have a Sony PS3, it is probably also your Blu-ray player.)

And over the next couple of years, there may be other digital devices that you might want to interface, including a home video server, or a room controller.

The bottom line is that if you have only two digital inputs on your projector, you can find your self short rather quickly, as a cable or satellite box, plus a Blu-ray player now uses up all your inputs.

And some of us also have HD-DVD players, and standard DVD players that have digital outputs.

You may ask, why bother going digital (HDMI) with a standard DVD player - why not just use component video - another high quality signal alternative. The answer is - "why not?" if you can feed all your high and low resolution display sources over HDMI, then you don't have to run additional cables at significant expense.

The assumption, therefore, is that if possible for the maximum future proofing, you probably want to use HDMI where ever possible.

The next assumption is, that if your projector only has 2 HDMI inputs, you will almost certainly, in the long run, find yourself needing more.

AV Receivers:

The good news is that most over $300 AV receivers now offer HDMI switching. The bad news - most of these receivers seem to have either two, or three HDMI inputs, again, not enough for anyone with a full complement of devices.

In the grand scheme of things switching for four inputs should be standard on AV receivers, and switching for four, should be standard on projectors.

Otherwise, without one or the other, as more devices go to digital (HDMI), people who wire up now, will likely find themselves coming up short in the future.

HDMI Switchers

And that means you may need a switcher.

The biggest problem is figuring out your entire layout. If you have an AV Receiver, but are short HDMI switching, and buy a switcher, do you bypass the AV Receiver altogether, or use it for most of your devices, and use the switcher just to bring in the extra devices?

And here's another key issue if you find yourself needing a switcher. This is a problem I ran into. Ultimately, my Marantz AV receiver switches only two DVI (HDMI) inputs, so I decided, especially since I'm frequently changing out equipment, to let the receiver only handle audio, and have the switchers feed the projector (or projectors directly).

The first thing that became a problem was audio. Remember, HDMI carries audio. That's not an issue for a projector since traditionally, home theater projectors don't have audio.

The problem, the 4-to-1 switcher (four inputs, one output) that I was looking at (as well as several others I looked at), has just HDMI switching - no way to separate out the audio, to send it to the receiver.

I ended up solving my problem by buying two switchers - the 4 to 1, where I input all my devices, and a 2-to-1, chosen because it also happens to have a separate digital optical output.

My wiring path:

4 Sources
v v v v
4-1 switcher
2-1 switcher
HDMI out . Dig Optical Out
v . . . . . . . . . . v
projector . AV Receiver

And that leaves me a spare (5th) HDMI input.

Lastly, if you are going switcher, or, for that matter, AV receiver, be sure to ask if the switching will fully support HDMI 1.3a and Deep Color. Since these are just switchers, and not extenders, it shouldn't be a problem, but it can't hurt to check!

Index of Home Theater Projector Questions

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