An HDMI switch (also known as HDMI switcher, HDMI selector) receives HDMI signals from multiple HDMI sources and sends the signals from one of them to your HDTV. This way, it serves as an agent to accept many HDMI signals for your HDTV, even if your HDTV has only 1 or 2 HDMI port(s).

You can connect multiple HD sources to your HDTV, such as your:

• Blu-Ray player, HD-DVD player, DVD player with HDMI output;

• PS3, Xbox360, Wii with HDMI output;

• HTPC, or computers with HDMI ports;

• HDTV box, satellite dish network, HDTV recorder;

• HD camera, or HD Cam recorder;

• Any other devices that are capable of outputting HDMI signals.

There are a few things you should consider before you buy an HDMI switch.

1. How Many Ports Do You Need?

An n-port HDMI switch receives HDMI signals from n HDMI sources.

A 100-port HDMI switch might be the best one in the world, but if you don't have 100 HDMI devices to be plugged in, it's a waste. Know how many devices you have that outputs HDMI videos, and buy the ones that best suit your needs.

It turns out that the most common, and therefore most affordable, ones are 3-port HDMI switches, maybe because most people only need 3 ports.

2. Supported Video and Audio Specifications

An HDMI switch has to support 1080i/p, 720p and all the standard-definition (for example, DVD) resolutions.

It has to support DTS / DTS-HD, Dolby Digital/Dolby TrueHD, Linear PCM (LPCM).

These are the basics of the basics, because these formats are frequently used in HDTV broadcast, HD gaming, and HD-DVD and Blu-Ray players. If an HDMI switch doesn't support any of these specs, it is not worth buying at all.

Also, it should not convert, upscale, downscale any video/audio contents at all, because any conversion probably brings loss of quality.

Now let's move on to some more advanced features that you should consider.

3. Automatic v.s. Manual HDMI Switching

A good HDMI switch should have both automatic and manual switching functions.

Automatic switching. Each time you turn on an HDMI source, the HDMI switch will automatically select this source. If you decide to turn on another one, the HDMI switch will switch to this second source. If you turn on another, it'll jump to this third device.

In most cases, this is intelligent enough to work out just fine and take care of most, if not all, of your switching needs.

Manual switching. Auto-switching may not always work when there is one or more HDMI sources "always on", such as an HDTV recorder (HD PVR) or a satellite network box, which you probably don’t turn off that often, and is, therefore, always turned-on in the background.

In that case, you will need to manually choose your desired HDMI source.

An HDMI switch with manual overriding function would usually have a button on it, which allows you to manually choose your desired HD source by pressing it.

For example, if the switch is currently on Input 1, your pressing the button once will let you choose Input 2, pressing it again allows you to jump to Input 3.

4. Is HDMI v1.3b Good Enough?

The short answer is yes, because 99% of the products out there in the market are compliant with HDMI 1.3b or earlier standards, such as HD-DVD players, PS3, Xbox360 and most Blu-Ray players.

Although HDMI v1.4 (released in May 2009) does bring in some exciting features such as 3D Over HDMI and resolutions up to 4k x 2k, there are very few products or cables supporting this new standard. Because of this, there appears to be no HDMI switches currently in the market that support HDMI 1.4 yet, although it should be a matter of time for the switches to adopt HDMI 1.4 as well in the future.

5. Is It HDCP-compliant?

HDCP is a copy protection to prevent copy-righted contents from traveling across HDMI / DisplayPort / DVI freely, unless the connected devices are HDCP-compliant.

A good HDMI Switch should support HDCP v1.0 / 1.1 pass-through.

If a device supports HDCP pass-through, it means that it is handing over the digital contents to the next device without even touching it at all (hence "pass-through").

It means that if your Blu-Ray, for example, works with your HDTV when they are connected directly by an HDMI cable, then they should also work with an HDMI switch that supports HDCP pass-through, because the switch simply passes the HDCP encryption to your HDTV without changing anything.

So do I need HDCP pass-through? Yes, you do. HDCP pass-through is a must-have feature. The higher supported version the better. The most commonly supported versions are v1.0 and v1.1.

Summary

A decent HDMI switch should have the following features:

• The right number of ports you need;

• As many video/audio formats supported as possible;

• Both automatic and manual switching;

• HDMI 1.3b compliant or above;

• HDCP v1.0/1.1 pass-through.

If you have checked all these features when deciding which HDMI switch to buy, you should be in good shape.