Video Adapters Explained

Video Adapters

What is a Video Adapter?
The term "video adapter" used to mean the card in a desktop PC that connected a monitor to the computer and allowed the computer to output text or images to a screen. This usage has largely been replaced by "graphics card." Nowadays, "video adapter" refers to a small device that attaches to a port on a PC or laptop and converts one video protocol to another, such as DisplayPort to HDMI. A video adapter may also come in the form of an adapter cable, which performs the video protocol conversion and has a cable built in.

HDMI to VGA Adapter

HDMI to VGA Adapter Cable

Video Signal Conversion
Video interfaces and standards have evolved over the years so it's not uncommon for computers, video equipment and peripherals to "talk different languages" and support different features. You may want to use an older monitor as a second screen but your laptop doesn't support the video interface, or the only available laptop port is incompatible with your monitor. An inexpensive video adapter may be a lot cheaper than buying a new monitor.

Video signal conversion is similar to translating from one language to another. It is easy if both languages have a rich vocabulary but consider the case where one language has more words than another. For example, the latest edition of the Oxford English Dictionary contains more than 170,000 words but Chinese has only 83,000. Even for the most gifted translator, interpreting the precise meaning of an English conversation in Chinese would be challenging, and the reverse would require some creativity! Converting an audio video signal from a feature-rich protocol to a less functional format means discarding information and capabilities. For example, converting a DisplayPort 4K signal for display on a VGA monitor will typically yield a resolution of 1920 x 1080 (1080p) at 60 Hz. Note that most video adapters or adapter cables work in one direction only (e.g. from a DP port to a VGA monitor but not the reverse).

Video Adapter Matrix

Converting a DisplayPort Signal

DisplayPort to HDMI Adapters
HDMI and DisplayPort are functionally similar video interfaces, but they use different methods of transmission (TMDS vs. LVDS). It is possible to connect a DisplayPort port on a laptop or PC to an HDMI monitor with no loss of image quality using a DP to HDMI adapter or adapter cable. If you use a passive cable, make sure the port on the video source is a DP++ (DisplayPort ++) dual mode port. If your graphics card does not support DP++, use an active cable such as Eaton's P582-006-HD-V2A.

Cables   Adapters

Converting an HDMI Signal

High Definition Multimedia Interface (HDMI) is a standard for transmitting uncompressed audio and video between a source and a receiver or display. HDMI has been widely adopted and can be found on almost all televisions and computer monitors.

HDMI connectors are available in three sizes: standard, mini and micro. There are also different types of HDMI cable (Standard, High Speed, Premium High Speed and Ultra High Speed), each designed to support a specific video resolution.

HDMI to VGA (or VGA to HDMI) Adapters

HDMI to VGA Adapter Cable
(P566-010-VGA)

HDMI to VGA with Audio
(P566-010-VGA-A)

VGA and Audio to HDMI
(P116-006-HDMI-A)

When converting to and from VGA, remember that it is a video-only interface. If you want audio, you will need to handle that separately via a 3.5 mm jack or USB connection. Also, keep in mind that a high-resolution HDMI signal will be downgraded to 1920 x 1200 (WUXGA) at 60 Hz.

Converting DVI Video

Developed in 1999, Digital Visual Interface (DVI) is a video-only interface for transmitting uncompressed digital video to displays at resolutions as high as 2560 x 1600 (WQXGA).

The DVI standard supports analog and digital signaling. Digital connectors come in two varieties: single link and dual link. A single link DVI connector uses a single transmitter. A dual link connector has six additional pins and a second transmitter that allows it to support higher resolutions. Some DVI connectors also support analog signaling. The small analog pins are clustered around the flat blade on DVI-A and DVI-I connectors.

DVI-A
17-pin analog only

DVI-D Single Link
19-pin digital only

DVI-D Dual Link
25-pin digital only

DVI-I Single Link
23-pin analog/digital

DVI-I Dual Link
29-pin analog/digital

Converting to and from VGA

The 15-pin Video Graphics Array (VGA) connector first appeared on the IBM PS/2 personal computer in 1987 and was subsequently adopted by most PCs, as well as many monitors, projectors, game consoles and instrumentation. The connector is variously referred to as D-Sub 15-pin, HD15 or DB-15.

Even though the analog VGA interface has been largely replaced by digital interfaces like DVI, HDMI and DisplayPort, there is still a large number of older devices with VGA ports still in use. An adapter is required to convert to and from the VGA format.

Converting USB-C or Thunderbolt™ 3 Video

Thunderbolt 3 to HDMI
You can connect a Thunderbolt 3 port to an HDMI display, but not directly. Thunderbolt 3 has native support for DisplayPort and from DP you can get to HDMI by way of an adapter. You can also use an adapter cable like Eaton's U444-006-H4K6BE to convert DP Alt Mode to HDMI.

USB Type-C® to HDMI via Alt Mode
USB Alt Mode allows a USB-C port to transmit non-USB signals, making it extremely versatile. For example, a laptop, Chromebook or Android phone with a USB-C port might use Alt Mode to output video to an HDMI TV or monitor without the need for an adapter. This is an important feature because the new, thinner laptops and tablets have a USB-C port but no HDMI port.

Odd as it may sound, you will need a USB-C port that supports USB Power Delivery to take advantage of USB HDMI Alt Mode, because it is the PD handshake that establishes an Alt Mode connection. You will also need a cable with a USB-C connector on one end and a USB-C or HDMI connector on the other. Older USB-A cables do not support Alt Mode. Another option is to use an adapter cable supporting DisplayPort Alt Mode, such as Eaton's U444-006-HDR4BE, to connect a USB-C port to an HDMI display.

USB Type-C to VGA
An adapter or adapter cable can convert video from a USB-C or Thunderbolt 3 port to an older VGA monitor by using DisplayPort Alt Mode as an intermediate format. DisplayPort signaling is converted to VGA by a chip in the adapter. The resulting resolution of 1920 x 1200 at 60Hz is the maximum supported by the VGA interface.

When buying a USB-C to VGA adapter, keep in mind that not all USB-C ports support DisplayPort Alt Mode. Check your laptop or PC manufacturer's website or the owner's manual to make sure it supports USB-C Alt Mode prior to purchasing.

Adapter cables like the U444-016-V can transmit a VGA signal up to 16 ft.

Video Adapter Q&A

What's the Difference between TMDS and LVDS Signaling?
When digital data is transmitted, especially over long distances, it is susceptible to noise and signal loss. Differential Signaling is a way to protect it from interference as it travels from source to receiver. It works like this:

• The sending device transmits two copies of the signal over different internal wires, including an "out-of-phase" version of the actual signal.
• The receiving device puts the out-of-phase signal back in phase and compares it to the actual signal, ignoring any differences (noise) between the two.

Low Voltage Differential Signaling (LVDS) is a widely used method of transmitting digital data. Its low-voltage, high-quality signal makes it ideal as an internal display interface for laptops, tablets and flat-panel displays. LVDS data is not encoded.

Transition Minimized Differential Signaling (TMDS) is a form of LVDS used in DVI and HDMI interfaces. TMDS signals are encoded so they have an equal number of ones and zeros, reducing the chance that the signal will degrade.

What is the difference between an active cable and a passive cable?
A passive cable simply passes the signal from one end to the other. The further the signal has to travel, the more it degrades, a process known as attenuation. That's why passive cables have a limited length. Active cables on the other hand include a signal booster that enables video and audio to be transmitted over longer distances. Active cables sometimes require a power supply to support signal conditioning.

Passive DisplayPort to HDMI Cable
(P582-003-V2)

Active DisplayPort to HDMI Cable
(P582-003-V2-ACT)

How can I tell if a cable is passive or active?
Active cables have larger and slightly longer connectors to accommodate the circuitry necessary to convert and boost the signal.

What is DisplayPort Dual Mode (DP++)?
DisplayPort uses Low Voltage Differential Signaling (LVDS), which is not compatible with the Transition Minimized Differential Signaling (TMDS) used by DVI or HDMI. However, DisplayPort dual mode ports can transmit a single link DVI or HDMI TMDS signal using a simple passive adapter or adapter cable. Devices supporting dual mode will detect a DVI or HDMI adapter and send TMDS instead of LVDS signals. Note that dual mode is an optional feature and is not implemented by all device manufacturers, so check for DP++ support before purchasing. If your graphics card does not support DP++, use an active cable. Also keep in mind that DP++ is not bidirectional and does not support dual link DVI.

Thunderbolt™ is a trademark of Intel Corporation or its subsidiaries in the U.S. and/or other countries. USB Type-C® and USB-C® are registered trademarks of USB Implementers Forum. All other trademarks are the property of their respective owners. Eaton has a policy of continuous improvement. Specifications are subject to change without notice. Images may differ slightly from actual products. Eaton uses primary and third-party agencies to test products for compliance with standards. Go to Tripp Lite by Eaton's website for more information, including complete warranty terms and conditions.