HDMI

If you've shopped for an HDTV, a PlayStation 3, or an HD-DVD
or Blu-ray pla­yer, you've probably heard about HDMI. It can
seem like just one of many connections on televisions or
home-theater receivers. But HDMI is more than a port on the
back of a TV (and the often expensive cable that fits inside).
It's a set of rules for allowing high-definition electronic
devices to communicate. ­­

Before the development of high-definition televisions, most
TVs displayed pictures in what is now known as standard
definition. The picture was roughly square -- its aspect
ratio was 4:3. Its resolution, or the number of dots that
make up the picture on the screen, was about 704 x 480 pixels.
The picture was interlaced -- each piece of the moving image
was really half a picture, but the pictures changed quickly
enough that the human brain didn't really notice. Finally,
older TVs relied on analog signals, which travel as
a constantly varying electrical current.

HDTVs, on the other hand, are digital. They use information
in the form of ones and zeros. This information travels
through cables as distinct electrical pulses. HDTVs have
an aspect ratio of 16:9, so the picture is rectangular. They
also have a higher resolution -- current HDTV standards allow
for resolutions of up to 1920 x 1080 pixels. HDTV signals can
also be progressive, meaning that the each frame of the
moving image is a whole picture rather than half of one.

So, compared to standard TVs, HDTVs have a wider screen, more
pixels and a faster refresh rate. Often, HDTVs can display
more colors than older sets. This means that HDTVs need more
data and need it a lot faster than standard-definition TVs
do. If an HDTV can receive this information digitally, it
also doesn't have to spend time or processing power
converting the signal from an analog format.

This leads us to HDMI. Created by a group of electronics
manufacturers, the HDMI standard is a set of guidelines for
creating high-bandwidth connections between digital devices.
With the right setup, HDMI can make a significant difference
in a home-theater system. The current standard can carry
1080p high-definition signals, and it supports eight channels
of uncompressed audio, enough for a 7.1 surround-sound
system. HDMI can cut down on the number of cables required to
connect components, and it can even reduce the number of
remote controls needed to watch a movie.

­But there's a catch. In order to take advantage of
everything HDMI has to offer, all of the components of a home
theater have to be compatible with them. Some of the features
HDMI touts also don't yet exist in the consumer marketplace.
In addition, there's a limit to how long an HDMI cable can
be, and some users complain that the limit is too short to
support convenient setups.