This week, I explained what HDMI is and how it works with
content protection.  Let's continue with more on the appropriate times to use HDMI and how to overcome issues with older HDMI implementations.

When and Why to Use HDMI

From a practical standpoint, one inexpensive HDMI cable can
replace several expensive analog connections on a single device. In some cases,
a single device could require up to 11 cables for multi-channel audio and
high-resolution video; HDMI replaces them all as an efficient, unified
solution. More importantly, if you have a non-CRT digital television like an
LCD, DLP or LCoS set, using HDMI avoids several analog-to-digital
conversions.  When you use an analog
component connection between your digital source and digital display, the data
on the DVD is converted to analog and sent via component cable to the display,
which then converts the analog component signal back to digital so you can view
it.  But with a digital HDMI connection,
the information on the DVD is sent unchanged to your digital display for
viewing. While some people may not notice the conversions, you want to avoid
them where possible.

From a content standpoint, HD DVD and Blu-ray players have
to look for an Image Constraint Token (ICT) on all discs.  If the disc is equipped with an ICT and the
player isn’t connected to a HDCP capable display, it will down convert the
video from 1080p to 540p.  No titles
currently invoke the ICT, but the studios can start using it on a title by
title basis at any time.  The main reason
they haven’t used it yet is because so many people have older HDTVs that don’t
support HDCP.  Also, upconverting DVD
players with HDMI aren’t supposed to output higher than a 480p signal over
component video, and will only output an upconverted signal over HDMI (these
same rules apply to HD DVD and Blu-ray players when they are playing back
DVDs).

And from a resolution standpoint, HDMI maxes out at 1080p resolution, which makes it essential for larger TVs that support that maximum. Not all content supports 1080p, but for game systems and high-def disc players, HDMI is your best bet for transferring 1080p content to your screen.

HDMI Issues

While it seems like using HDMI should be as simple as
plugging in a wire and turning on your equipment, it doesn’t always work that
way.  While most new HDMI devices don’t
have interface problems,  some early
devices (mostly cable and satellite set top boxes) didn’t fully support the
standard.  They would work great when an
HDMI cable connected them directly to your display but wouldn’t work when you
connected them to a repeating device (like an A/V receiver).  If you have one of these boxes, try
contacting your cable or satellite provider to see if there is a software
update, if not a free hardware replacement. 
If not, I recommend that you try to use a digital audio cable to connect
the box to your receiver. In some cases this won’t work, and you may need to
resort to using an analog component video connection. Fortunately, many
receivers that support HDMI will allow you to convert component signals to
HDMI, so you can still connect a single cable from the receiver to the display. 

Another issue happens (also typically with early devices) when
users connect their source to their display using HDMI, and then run a digital
audio connection to their non-HDMI receiver for surround sound.  Since most displays can only support a two-channel
stereo signal, your source can limit the audio-out to stereo output or even
shutdown the digital connection to the receiver.  If you are using this configuration and are
only getting two channels sent to your receiver, look for an option in the
setup menu of your display or the source device to turn HDMI audio off.  Some issues can be easily remedied by checking
that all settings match up in your source, receiver, and display (which will
vary based on the make and model of each component).  If you are having problems, check your
owners’ manuals for specific settings and instructions on how to change
them.  Other issues may require firmware
updates from the manufacturer—a process that can be painful but will sometimes save
you from shipping the device back to the manufacturer.  In some rare instances, there may be no
workarounds due to limitations in how HDMI was implemented in your components,
and you may be forced to use component video.

If you are having problems and are using a HDMI switch,
repeater, or some type of booster, make sure you are using one that has an
external power supply.  Any product that derives
its power directly from an HDMI cable does more harm than good.

In the next installment, I’ll talk about the different
versions of HDMI, the optional features they support, and some purchasing
considerations. --Adam

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