Video Connectors Tutorial

Digital Video Interface (DVI)

All of the connection types we’ve seen so far use analog signals. HDMI and DisplayPort connections use digital signals. DVI, on the other hand, can carry both analog and digital signals. Here are the types of DVI connectors available:

• DVI-A: Analog connection
• DVI-D: Digital connection; usually when we say “DVI” we are referring to DVI-D
• DVI-I: Cable or connector that can carry both DVI-A and DVI-D signals; DVI-A cables can carry only DVI-A signals and DVI-D cables can carry only DVI-D signals
• Single Link: Allows screen resolutions up to 1920 x 1080 pixels at 60 frames per second (60 Hz)
• Dual Link: Allows screen resolutions up to 2048 x 1536 pixels at 60 frames per second (60 Hz)

In Figure 26, you can see the differences between these connectors.

Figure 26: DVI connector types

So, what is that all about? If you have a device that produces an analog signal, it will have a DVI-A connector and you can only connect it to a display that has a DVI-A connector. You can use a DVI-A cable or a DVI-I cable to make this connection. The same idea holds true for digital devices. If your device has a DVI-D connector, you can only connect it to a display that also has a DVI-D connector. You will have to use a DVI-D or DVI-I cable to make such a connection. You cannot connect a DVI-A device to a DVI-D display and vice versa.

If your device has a DVI-I connector (which is the case with video cards), this means that it produces both analog and digital signals. You should use a cable (DVI-A or DVI-D) according to the kind of connection your display supports: analog or digital. Or use a DVI-I cable, which supports both.

Of course, using a digital connection is best, but you are limited as to what kind of connection your product offers. You should not worry too much about these several different kinds of available connections. Today, almost all consumer electronics products feature a digital connection, so you will find either a DVI-D or a DVI-I connector. You will probably be using a DVI-D or DVI-I cable, which fits both connectors, so you have nothing to worry about. See the examples below.

Since computers, digital cable/satellite converters, DVD/Blu-Ray players, and video game consoles are digital equipment, when transmitting video signals using analog media such as VGA or component video outputs, they must first convert the signals from digital to analog. On the other end of the cable, the LCD monitor, HDTV set (flat-screen TV) or video projector must convert the analog signal back to digital, since these devices are also digital. There is image quality drop in this process of converting the signal from digital to analog and then back to digital.

The advantage of using a DVI-D, HDMI or DisplayPort connection is that you skip these digital/analog/digital conversions, thus improving image quality.

All PC video cards nowadays offer at least one DVI output (usually a dual-link DVI-I connector, allowing you to connect displays with analog or digital connection), as you can see in Figure 27. You can also find DVI connectors (usually a DVI-D connector) on LCD monitors, digital cable/satellite converters, HDTV sets (i.e., flat-screen TVs), video projectors, and some DVD players. If they don’t have a DVI connector, they will have an HDMI connector, which is even better.

DVI-D and DVI-I connectors can be easily converted into HDMI, as HDMI is fully compatible with DVI-D. We will talk more about this on the next page.

To connect your PC to your video monitor, video projector or HDTV, you should use the DVI connection instead of the traditional VGA connector, as it will provide the best image quality possible. Of course, if both the device and your TV have an HDMI connector, then simply use an HDMI cable as explained on the next page. However, if your HDTV has an HDMI connector and your PC or video source (e.g., cable TV decoder) has a DVI connector, you can connect your PC to it using a DVI-to-HDMI converter or cable, as we will show on the next page. In our tutorial “Everything You Need to Know About the SPDIF Connection,” we present a few practical examples of usage of the DVI connection. 

Figure 27: DVI output (DVI-I dual link connector) on a video card

 Figure 28: DVI output (DVI-D dual link connector) on a digital cable TV box

Figure 29: DVI input (DVI-D single link connector) on an HDTV set

Figure 30: DVI-D single link cable

It is very interesting to note that DVI-I outputs can be transformed into VGA outputs by the use of an adapter that usually comes with the video card (see Figure 31). Thus, you can transform DVI-I connectors on your video card on a VGA output, allowing you to connect the PC to older video monitors that don’t have a DVI connector. This connection, however, will be analog, not digital, since the VGA connection uses analog signals, and you are using the DVI-A signals from the connector to generate this output.

Converting a VGA to a DVI connector with a simple connector, however, is not possible, as the VGA output uses analog signals. Video monitors featuring a DVI input usually require digital signals (i.e., a DVI-D connector).

Figure 31: DVI to VGA adapters