HDMI Digital Video Interconnect Standard and Computers

HDMI connector

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With the rise of high-definition video content and 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 encouraged manufacturers to put together a new connector. From this, the High-Definition Multimedia Interconnect or HDMI standards were developed. HDMI has since become the defacto video connector.

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 added support for a smaller mini-HDMI connector which was useful for the extremely thin laptops and smaller consumer electronics like cameras. With HDMI version 1.4, the micro-HDMI connector was added with an even smaller connector that was useful for the growing use of tablet and smartphone devices.

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 possibly up to three mini-jack cables to run audio from it to the speakers, the HDMI cable simplifies the number of cables required to carry the audio signal to the monitor. In the original HDMI implementations of graphics cards, audio passthrough connectors were used to add the audio stream to the graphics cards but most now also feature sound drives to handle both audio and video at the same time.

While audio and video on a single cable was unique when HDMI was first introduced, this feature was also implemented into the DisplayPort video connector. Since that has occurred, the HDMI group has worked on expanding the support for additional multi-channel audio. This includes 7.1 audio in the HDMI version 1.4 and now up to a total of 32 audio channels with the latest HDMI version 2.0.

Increased Color Depth

Analog and digital color for PC computers have long been restricted to the 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 the 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 with version 1.3 color depths of 30, 36 and even 48-bit were added. This greatly increases the overall quality of the color that can be displayed, but both the graphics adapter and monitor must support the HDMI version 1.3 or higher. In contrast, the DisplayPort also introduced expanded color depth support up to the 48-bit color depth.

Backward 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 an HDMI graphics port on the computer, an HDMI monitor cannot connect to a DVI graphics port on the computer.

DisplayPort does not have as much flexibility in this area. In order to use DisplayPort with other video connectors, an active dongle connector is required to convert the video signal from the Displayport standard to HDMI, DVI or VGA. These connectors can be quite expensive and is a major drawback to the DisplayPort connector.

Version 2.0 Additions

With the rise of UltraHD or 4K Displays, there are some major bandwidth requirements in order to carry all of the data necessary for such a high-resolution display. The HDMI version 1.4 standards were able to go up to the 2160p resolutions required but only at 30 frames per second. This was a major shortcoming compared to the DisplayPort standards. Thankfully, the HDMI working group released version 2.0 before the bulk of 4K displays reached the market. In addition to the high frame rates at the UltraHD resolutions, it also supports:

  • Ability to have two (1080p) video streams carried over a single cable.
  • Improved audio sampling rates for improved sound fidelity.
  • Ability to carry four audio streams to multiple users on a single cable.
  • Support for 21:9 aspect ratio video for wider screen displays.
  • Dynamic audio to video synchronization.
  • Support for command and control extensions for multiple device control through a single device.

Most of these features have yet to be integrated into home consumer electronics or computer systems but they do have significant potential for users that may need to share a computer device, display or audio setup.

Should You Look at HDMI on a Computer System?

At this point, all consumer laptop and desktop computers should come with an HDMI port standard. This makes it very easy to use them with your standard digital computer monitors and HDTVs. It should be noted that there are still a few budget class computers on the market that do not feature this connector. We would avoid these computers as it can become a liability in the future. In addition to this, some corporate class computers may not feature the HDMI port but instead, come with a DisplayPort. This is a suitable alternative but you need to make sure you have a monitor that can support that connector.

The issue with HDMI support is more for tablet computers and smartphones. This is not something that is standard to them but you may want support for a micro or mini-HDMI connector so that it can be hooked up to an HDTV for streaming or playback of video content. This need has largely been bypassed by the advent of wireless screencast applications which use WiFi to connect smaller devices to larger screens.