HDMI and Computers

Introduction

With the rise of high definition video content with the adoption of HDTV, the need for a standard unified connector was needed. The DVI interface was originally developed for computer systems and was placed on early HDTV units, but there are a number of limitations with it that manufacturers looked to put together a newer connector. From this, the High Definition Multi-media Interconnect or HDMI standards were developed.

This article looks at some of the features of the HDMI interface in relation to the older DVI interface and what it can mean for personal computer systems.

Smaller Standardized Connectors

One of the big advantages of the HDMI interface over the DVI interface is the size of the connector. The DVI interface is similar in size to the older VGA interface at roughly 1.5 inches in width. The standard HDMI connector is roughly one third the size of the DVI connector. The HDMI version 1.3 specification also includes a new mini-HDMI connector that is even smaller, a key feature for notebook PCs and small consumer devices such as camcorders.

Audio and Video on a Single Cable

The cable advantages of HDMI become even more pronounced over DVI because HDMI also carries digital audio. With most home computers using at least one and possible up to three mini-jack cables to run audio from it to the speakers, the HDMI cable simplifies the number of cables require to carry the audio signal to the monitor. For PCs, the hardware must be designed with some sort of pass-through connector to run the audio signal from the audio processor to the graphics card to combine the digital video and audio into a single stream.

Increased Color Depth

Analog and digital color for PC computers has long been restricted to 24-bit color producing roughly 16.7 million colors. This is generally considered true color because the human eye can't distinguish between the shades easily. With the increased resolution of HDTV, the human eye can tell a difference in overall quality of color between 24-bit color depth and higher levels, even if it can't distinguish the individual colors.

DVI is limited to this 24-bit color depth. Early HDMI versions are also limited to this 24-bit color, but the newer 1.3 version allows colors depths of 30, 36 and even 48-bit color depths. This greatly increases the overall quality of the color that can be displayed, but both the graphics adapter and monitor must support the newer HDMI version 1.3.

HDCP

One of the big requirements for the high definition DVD and TV signals is a digital rights management signal. This allows the rights holder to ensure that a digital copy of the material cannot be capture before it reaches the video display. At this point, Blu-ray and HD-DVD do not require this, but in the future they may enable it such that the video quality is degraded down to standard definition or potentially blank out the screen. This has huge implications for computer users.

The DVI video standard did not require that the HDCP or high definition copy protection signal be supported by the devices. As a result, many PC computers and monitors that feature the DVI connector may be locked out from the high definition content. Some video card and display manufacturers do support the HDCP signal with the DVI devices, but it can be hard to ensure that your hardware is compliant.

HDMI has this HDCP built into the standard. As a result, any HDMI capable graphics card and monitor must have this feature. This prevents the potential problem in the future of restricted or non-functional digital video from the PC.

Backwards Compatible

One of the most important features included with the HDMI standard is the ability for it to be used with DVI connectors. Through the use of an adapter cable, an HDMI plug can be attached to a DVI monitor port for the video signal. This is a very useful feature for those that do purchase a system with an HDMI compliant video output but their television or computer monitor only has a DVI input. It should be noted that this only uses the video portion of the HDMI cable so no audio can be used with it. In addition, while a monitor with a DVI connector can connect to a HDMI graphics port on the computer, a HDMI monitor cannot connect to a DVI graphics port on the computer.

Should You Look at HDMI on a Computer System?

For PCs that will be used solely as a computer to a standard computer monitor, it is not necessary to look for one with an HDMI connector. Those looking to use the computer in a home theater environment with a high definition TV set can greatly benefit from the single cable that can carry both the audio and the video. Of course, even though a computer may have an HDMI video connector, it may lack the internal connector inside to graph the PC audio into the HDMI video signal. If the TV uses the older DVI connector, a PC with the HDMI connector will still function with it through the HDMI to DVI adapters.