HDMI stands for High Definition Multimedia Interface, and was designed to be a backwards-compatible replacement for the DVI interface commonly found on computer monitors. The standard called for a single cable that could carry a high-definition video stream, up to eight channels of digital audio and a single Consumer Electronics Control Signal. Its primary purpose was to become the standard connection between all consumer AV devices and computer displays. Today, all new projectors and televisions will come with at least one HDMI connection and usually more to receive hi-definition video.

Perhaps the most significant part of the HDMI specification is the support for HDCP, High-bandwidth Digital Copy Protection. HDCP-protected content such as Blu-Ray movies can only be decoded by licensed HDCP players, and any devices that connect to the player, must also be HDCP certified, or the player will only output a standard-definition signal. For this reason, when buying high-definition projectors, televisions or other devices, it’s best to make sure they have HDMI connections and are HDCP certified.

Be careful when hooking up your home theatre system. It is not possible to have a HDMI connection to your amplifier, and then a component connection to your projector, as the HDCP protocol will prevent the player from sending a hi-def video signal due to the final connection not being via HDMI. It is possible, however, to connect your blu-ray player or cable box to your TV by HDMI and use a separate connection, such as a digital optical cable, to send audio to your amplifier.

HDMI carries both audio and video. This means only a single cable is required to connect a TV to your Blu-ray player or cable box. If you use a separate Home Theatre amplifier, then the player and cable box can first be connected to the amplifier, which is then connected by another HDMI cable to your TV. In this setup, the amplifier uses the audio channels and passes the video channel on to the TV. If you use the approach, look for a high-quality Home Theatre amplifier, with several HDMI inputs for all your sources, which also support HDCP.

Finally, a few words on buying HDMI cables. The prices of HDMI cables can vary enormously, with certain branded cables costing 10x the price of the same length unbranded cable. In practice, HDMI cable quality has very little impact on the quality of the audio and video transmitted through it. Unlike previous home video cable standards, HDMI is an all-digital connection, so the signals are much more resistant to interference and noise. For short cable lengths, almost any HDMI cable will be fine. Longer lengths can be more susceptible to connection dropouts due to HDCP signal loss, so consider spending a little extra on these, but keep away from the most expensive brands as they offer very little extra benefit.

To begin with, you will need a hi-def source. Many cable and satellite packages offer hi-def channels, but many channels use large amounts of compression to squeeze multiple high-def channels into a limited amount of bandwidth. This causes images to have compression artefacts, such as macro blocking, mosquito noise or banding. Audio can also be affected, with very low or high frequencies clipped and complex parts of the soundtrack sounding “muddy”.

The same problem is present on the new “download” services that allow you to download and watch a film for a fixed price. Although less noticeable, the problems of compression are still visible. Lastly, some DVD players will provide “up-scaling” of standard DVD’s, and while this can be an improvement on letting your TV upscale the image, it’s not a true high-definition signal, and will appear soft and blurred.

The best source for Hi-Definition content is from a Blu-Ray disc, where there is enough space to store the image without introducing noticeable compression artefacts, and to hold completely lossless sound. Look for a player with an internet connection for easy updates to the firmware, or alternatively consider a Sony Playstation 3 console, which is also a very high-quality Blu-Ray player.

With a hi-def system, only one cable, HDMI, is required to transmit both picture and sound. A HDMI cable is a digital connection, so there are fewer problems from noise or interference. Beware overpriced cables; the digital signal means expensive multi-layered insulation is not necessary. Pay no more than you would for good computer DVI cable, on which the HDMI standard is based.

The hi-def signal will first go into your home-cinema amplifier, which will need a HDMI input. The amplifier needs to be capable of decoding the sound formats used by the Blu-Ray disc. The most common formats are Dolby Digital Plus and DTS-HD, these are updates of the formats used on DVD’s, and all modern home cinema amps should decode them. Look out for Dolby True HD and DTS-HD Master Audio support, these are new formats for maximum-quality lossless sound, but only the latest or more expensive amps have support for these right now. Lastly you may see LPCM audio tracks. These are lossless and uncompressed, so no decoding is required and all amps can play them.

Your amp should have a HDMI output that will allow you to connect it to your TV or Projector. With the amp handling the audio, the video signal is fed back out and into your display. To properly function your display will need to be “HDCP compliant”, HDCP stands for HD “Copy Protection”, and only HDMI inputs with the built in HDCP technology can decode HD video. All newer displays have this, but some early TV’s and projectors had HDMI sockets that missed out the HDCP chip.

There are several different resolutions that can be called High Definition. 720p and 1080i are used by some TV channels and also hi-def video games. The highest standard is 1080p, and is used by Blu-Ray movies. Most new displays will handle all three formats, but when buying a TV or projector, check the native resolution, the number of physical lines of picture it can display. TV’s that only have a native resolution of 720 will be forced to scale a 1080p signal down, which will reduce the picture detail and may introduce artefacts.

When most consumers go down to the store and pick up a big new flat screen plasma or LCD TV, they may think that they are all set and ready to go. In fact, the sound provided by even an expensive top-of-the-range TV is incredibly limited, providing little or no low-frequency response, producing only a flat, distorted version of the movies music, and generating little or no directionality. If they are good at anything, it is producing clear, audible dialogue, but that’s pretty much it.

Modern movie soundtracks contain so much more information; they contain multiple channels so the viewer perceives the sound to be coming from a particular direction, such as a plane flying overhead, or dialogue coming from left or the right. They also contain low-frequency information, to reproduce deep bone-shaking sounds such as explosions or rumbling engines. To be able to access and hear all this extra information you need a dedicated home theatre audio system.

The basic home theatre audio system consists of an amplifier and multi-channel speaker set. The job of the amplifier is to decode and then amplify the multiple audio tracks present on the disc. To do this, it needs to be connected to the DVD or Blu-Ray player by a data-cable. A fiber-optic digital audio cable (also known as a TOS-link cable) will be needed for DVD’s, but to decode next-generation hi-def audio will require a HDMI cable connection. The HDMI cable also carries the video stream, so most amplifiers will have a HDMI out socket, allowing the video information to continue on to the TV or projector.

In terms of power, a quality separate amplifier be marked somewhere in the 80-100 watt range, which is plenty for watching a movie in the average family home.  Beware amplifiers that are built into DVD players, or into a speaker set, they are usually underpowered and will perform poorly. The most demanding audio signals to reproduce are the low-frequency type; so many speaker-sets will have “active” sub-woofers, which have small dedicated amplifiers built in.

Speakers for home-cinema can be purchased in packages of matched sets, or individually, allowing you to mix fronts from one manufacturer with rears from another. In general, purchasing a set of matched speakers is the best option for beginners and will produce a very good sound. Unlike regular stereo speakers, home cinema speaker-sets are generally split into dedicated low and mid/high frequency speakers, with the sub-woofer speaker handling the low-frequency sounds by itself. This works because it is very difficult to detect the direction of low-frequency sounds, so it does not matter where in the room the sub-woofer is placed. By contrast the direction of mid and high frequency sounds is easier to detect, so speaker-placement is key, with left/ right speakers best positioned level with the screen and widely spaced apart, the central speaker positioned directly beneath the screen, and the rear speakers positioned diagonally facing the viewer from behind. This setup is for a 5.1 speaker set, which is all that is really required for proper directionality, although 6.1 and 7.1 sets are available.

When it comes to budgeting for your home theatre, you have some big choices to make. It’s possible to spend anything from $1000 to $1,000,000 on a home cinema, although typically a good setup will cost no more than $3000. The key is to budget wisely, don’t spend all your money on a Projector while buying cheap speakers or your experience will suffer!

Typically, a Home Theatre setup will consist of a DVD (or nowadays a Blu-Ray) player, a Home Theatre Amplifier, a set of surround sound speakers, and a Projector and screen. Some people prefer to use an LCD or Plasma TV, but while these are good enough for TV programs, sports or video gaming, nothing less than a proper projector and screen setup will give you the real “big screen” feel you get at a movie theatre. When budgeting, don’t forget to include the cost of extras like cables, and seating, and even dedicated lighting and remote controls if you want them.

With the death of HD-DVD, Blu-Ray is now the only hi-def movie format, so the heart of you system should be a good quality Blu-Ray player. There are now plenty to choose from, with prices starting from around $300, but surprisingly, one of the best Blu-Ray players is a the Sony Playstation 3. Not only is it a very capable video games machine, but it’s video output is of a very high quality, and it benefits from very speedy menus and loading due to it’s powerful processors.

Your next purchase should be a Home Theatre Amplifier (Amp). Home Theatre amplifiers are different from Stereo Amplifiers, in that they can decode the sound formats used by DVD’s and Blu-Rays, and have outputs for 6, 7, or 8 channels. A good amplifier is a must, look for one that is powerful enough for your room, and can also decode the latest sound formats. Some amplifiers will also switch your video between multiple inputs and outputs, which can be useful if you want to hook up several sources to your projector and speakers.

Speakers should be chosen to match your amplifier. For home cinema the most popular setup is 5.1, where there are 5 main speakers, and 1 “subwoofer”, a speaker dedicated to producing very low “booming” sounds. If you want to feel every explosion or gunshot of a film, buy a speaker package with a high-quality subwoofer! The 5 normal speakers are placed around your seating position; one in front, one each to the front left and front right, and one each to the rear left and rear right. 6.1 and 7.1 systems are available with even more speakers, but 5.1 is good enough for most rooms.

Lastly, you will want a projector and screen. The models that are right for you will depend on your room size and the level of ambient light when you watch your films. In general, look for the brightest, most high-contrast model you can afford, and buy a model that produces at least a 720p image, although preferably 1080p.

To begin with, you will need to consider brightness and contrast. Most projectors have their brightness stated in two ways, Lumens and foot-Lamberts. Sadly the Lumen rating is not a really useful gauge of brightness, as it often does not take into account the viewing size of the final image or reduction due to normal rather than max usage. In dark conditions such as a dedicated home theatre room, look for a brightness rating of around 40 fL, and increase it depending on how much extra ambient light your viewing room will have.

Contrast is often a more useful measure of projector quality than brightness. A high-quality projector will have a contrast ratio of 5,000:1 or more, all though check to see if the projector uses a “dynamic iris” to help boost its contrast range. These work by restricting the light output in dark scenes, allowing the projector to produce “blacker blacks”. Many such projectors will also just quote “on/off” contrast, which is the difference between a full black and full white screen. A better measure is ANSI contrast, which uses a chequered test pattern, and measures the difference between the light and dark squares. This value will be unaffected by any dynamic iris, and is usually a lower value.

Next you need to think about the supported resolutions you want to display. The very best is 1080p,so called “full HD”, and will allow you to display Blu-Rays and other high-definition content properly. Most games and computer presentations will only need 720p or 1024×768 resolution, so if you won’t be primarily watching movies, save some money and go for a lower-spec model. 1080p and 720p are both 16:9 widescreen resolutions, whereas 1024×768 is 4:3, which is a more square standard used by many computer monitors and older TV’s. Consider the screen you will be displaying on. To get full use of the screen, make sure it’s resolution matches that of your projector.

Finally, make note of the “throw distance” of the projector. “Short Throw” projectors are designed to be placed closer to the screen and still produce a big image, whereas “long throw” projectors are the opposite. Also quoted will be the amount of zoom available, which will allow you to grow or shrink the image somewhat. Another useful feature on most projectors is lens-shift. This will allow you more flexibility in placing the projector relative to the screen by enabling you to move the image up and down or left and right by a certain amount without distorting the image.