There are several types of video connections that you can find on PC and consumer electronics (“CE”) products such as TVs, DVD/Blu-Ray players, video game consoles, cable TV receptors (“set-top boxes”), and video projectors. Even though they all serve the same purpose – to connect video signals from one device to another – the video quality obtained by each type of connection and/or the number of features available are completely different. Since you probably want to get the best video quality from your equipment, we’ve written this tutorial to explain the differences between each kind of connection and when to use each of them, with many tips on how to improve the video quality generated by your equipment.
The connection types we’ll cover are the following, listed from the worst video quality (the lowest number of features, as in the case of analog connections) to the best video quality (the highest number of features, as in the case of digital connections):
- Radio Frequency (RF) (analog)
- Composite Video (RCA) (analog)
- Separated Video (S-Video) (analog)
- Component Video (analog)
- Red, Green and Blue (RGB) (analog)
- Video Graphics Adapter (VGA) (analog)
- Digital Video Interface (DVI) (analog or digital)
- High-Definition Multimedia Interface (HDMI) (digital)
- DisplayPort (digital)
In a nutshell, you should use the best connection that is supported by both your TV set and the device you want to connect to it.
[nextpage title=”Radio Frequency (RF)”]
RF is the oldest way to transmit video signals. It is used on older TVs, VCRs, cable TV receptors, and video game consoles (think of the Atari 2600 and the Nintendo Entertainment System) where you have to tune the TV to channels 3 or 4 to get the image being generated by these devices. This kind of connection can be used to connect your VCR or cable TV box to your TV, but since nowadays all TVs have better video connections, you should use one of them in order to get a better image quality. In summary, use the RF connection only if you are hooking up a 1980’s video game console to your TV; otherwise, use one of the video connections described in the following pages.
There are two types of RF cables: 75-ohm coaxial and 300-ohm parallel. This second type was used by old terrestrial broadcasting antennas, but even this kind of antenna uses the 75-ohm coaxial cable presently. You can install a 300-ohm cable/connector into a 75-ohm connector by using an adapter, as we show in Figure 6.
In Figure 1, you can see the RF input on a TV set. On this plug, you should connect your old cable TV receptor, a 1980’s video game console, or your antenna, if you still use analog terrestrial TV. (Currently, in the U.S., terrestrial broadcasting is done only in digital format, so you will need an adaptor box similar to a cable TV box to be able to watch terrestrial broadcasting if you have an analog TV. If your TV is still based on a cathode ray tube, i.e., it is not a flat-screen TV, it is analog.) If the device you want to hook up to the TV has a better type of connection, you should use it instead if both your TV set and the device support a better kind of connection.
In Figure 2, you can see RF input and output on a VCR. The input is used to connect the VCR to older cable TV boxes or a TV antenna. The output can be used to connect the VCR to the TV, but this connection shouldn’t be done nowadays, since you can use composite video to connect your VCR to your TV, which provides a better image quality.
On computers, RF connectors are only used on TV cards or video capture cards to allow you to watch and record live TV shows on your computer, connecting the RF input plug to a cable TV box or a TV antenna. If you have a video capture card, don’t use this connector to hook a VCR to your PC, since you can use the composite video connection, which is better.
In Figure 4, you can see a typical RF cable and connector, and in Figure 5 another kind of connector that also can be used on RF connections. The difference between them is that the cable connector in Figure 4 is meant to be screwed to the female connector on your TV, VCR or cable TV box, while the second connector, in Figure 5, doesn’t need to be screwed, just push it towards the female connector and it will fit.
[nextpage title=”Composite Video (RCA)”]
Composite video is one of the most popular video connection types, and it uses an RCA connector. (Older video projectors can use a BNC connector for this connection.) Composite video is used on the popular “video in” and “video out” connectors, found on VCRs, TVs, DVD/Blu-Ray players, video game consoles from the 1990’s on, and video projectors. On PCs, video capture cards and some older video cards can provide this output.
This is the best option to connect your VCR to your TV set, assuming that they don’t have an S-Video connector. (Usually, newer TV sets have this connector, but VCRs usually don’t have an S-Video output.) For other devices, such as DVD/Blu-Ray players, contemporary video game consoles, video projectors, and PCs, you should not use this connection, because other connection types offer better image quality, and these devices support at least S-Video.
In Figure 7, you can see the composite video input on a TV set, and in Figure 8, the composite video output on a VCR. Usually, the female RCA connector used by composite video is yellow in order to be differentiated from other commonly found RCA connectors, especially audio, where red indicates the right audio channel and white or black indicates the left audio channel. Notice that the TV set from Figure 7 also has an S-video input, which is our next subject.
Since a VCR allows you to record videos, it has two composite connectors, an input and an output. You should connect the VCR output to the input located on the TV set to make the proper connection. The VCR input should be used in case you want to record something from another video source, such as another VCR (for copying tapes) or even a PC with composite video output.
In Figure 9, you can see the outputs of a typical DVD player. Even though it has a composite video output, it shouldn’t be use to connect the player to your TV or videoprojector, since usually it has S-Video and/or video component outputs, which provide a better video quality. We only see two uses of the composite video output of a DVD player: if your TV set is very old or if you want to record on VHS tape the contents of a DVD.
Some older video cards have an RCA connector, thus providing composite video. This output can be used to connect your PC to a TV (so you can use your TV as a video monitor) or to a VCR, to record images and videos on a VHS tape. The image quality of an analog TV set, however, is far below any video monitor. There are two reasons. First, the screens of analog TV sets work at 640×480 resolution, lower than the most common screen resolutions nowadays. Second, analog TV sets work with interlaced scanning, while video monitors work with non-interlaced scanning (a.k.a. progressive scanning), which provides a far better video quality.
You can also connect your video card to your TV using S-Video, if both devices have this connector. Furthermore, S-Video output from video cards can be transformed into composite video by the use of an adapter, as we will explain on the next page.
However, with digital TV sets (flat-screen TVs) the situation is different, because digital TVs provide higher resolution than analog TVs and are able to use progressive scanning. If you have this kind of TV set, you must use a better connection type to attach your computer to it in order to get the best image quality possible.
You will also find composite video on video capture cards, allowing you to connect your VCR to your computer in order to transform VHS tapes into computer videos.
In Figure 11, you can see the famous RCA male connector used by the composite video connection. The cable on the picture has two more connectors for carrying analog audio (one cable using a white plug for the left channel and one cable using a red plug for the right channel). The composite video cable uses the yellow plug.
Since RCA connectors are used for several different purposes (take a look at Figure 9), they are usually colored. In order to help you, here is a small list of the most frequently used colors for RCA connectors and cables:
- Yellow: Composite video
- Red: Right channel (audio)
- White or black: Left channel (audio)
- Purple: Subwoofer (audio)
- Orange: Digital audio (a.k.a. SPDIF)
- Green: Component video
- Blue: Component video
- Red: Component video
[nextpage title=”Separated Video (S-Video)”]
S-Video provides better image quality than composite video. The composite video signal uses only two wires, one carrying the video signal and the other one being the ground. On S-Video, three wires are used: one for carrying the image in black-and-white, one for carrying the color information signal, and the third is the ground. Hence the name of this standard, separated video.
All current TV sets and video projectors have this connector, but you should use it only if your TV or video projector and the device you want to connect to it don’t offer a better connection option, such as component video, DVI or HDMI.
Some older video cards have an S-Video output, as you can see in Figure 14. On video cards with video capture function (a.k.a. VIVO) or with component video outputs, this very same connector is also used for these functions. The standard S-Video connector has four pins. If the S-Video connector from your video card has more than four pins, that means your video card has component video or video capture functions. We’ll talk more about this on the next page.
S-Video is the best way to connect your PC to an old analog TV set, provided your TV set and your video card don’t support component video (see next page). However, keep in mind that the image quality of CRT-based TV sets is far below any video monitor. There are two reasons. First, analog TVs work at 640×480 resolution (a.k.a. 480i or SDTV), lower than the most common screen resolutions nowadays. Second, analog TV sets work with interlaced scanning, while video monitors work with non-interlaced scanning (a.k.a. progressive scanning), which provides far better video quality. Therefore, for connecting PCs to TVs and video projectors, you should use the DVI or HDMI connectors, as we will explain later. (If your video projector doesn’t feature either of these connectors, then the option is to use the VGA connection, which is usually found on video projectors but not on TV sets.)
In Figure 15, we see the standard S-Video connector and cable. The S-Video signal can be transformed into composite video by using an adapter (shown in Figures 16 and 17). It is useful to connect a video source that only has S-Video output to a TV set that doesn’t have an S-Video input or vice versa.
[nextpage title=”Component Video”]
Component video offers far better quality than S-Video. It is the preferred video connection to use between your video source and your TV set or video projector, when they support this kind of connection and don’t have a better connectivity option, such as DVI or HDMI. It uses three cables that should be connected as follows:
- Green connector: green input or input labeled as Y
- Blue connector: blue input or input labeled as Pb or Cb or B-Y
- Red connector: red input or input labeled as Pr or Cr or R-Y
The Y connector transmits video information (black-and-white image) while the color information is transmitted on the other connectors.
On the PC, some video cards have this kind of output, which should be used if you want to connect your PC to your TV set, but your TV doesn’t have a better kind of connection, i.e., VGA, DVI or HDMI.
The problem, however, is that it is not easy to recognize whether or not a video card has this kind of output, because it shares the same connector used by Separated Video (S-Video). If your video card has an S-Video output, it may or may not have support for component video.
One way to detect if your S-Video connector has component video output is by looking at it. If it has only four pins, this means it has only S-Video output and doesn’t support component video. If it has more than four pins, this may mean that it has component video. See Figure 19.
Notice that we said “may.” This happens because there are some video cards, especially those with video capture (VIVO) function, that have more than four pins on their S-Video connector, but these extra pins are used by another feature, not by component video.
In summary: If the S-Video connector from your video card has four pins, it doesn’t have component video output. If it has more than four pins, it may have component video output. To be sure, read the card’s manual to see if it has this feature.
To use the component video output from your video card, you will need an adapter. This adapter usually comes with video cards that have component video output. Therefore, if your video card came with a component video adapter, this means it has component video output!
The aspect of this adapter can vary; the two most common models are shown in Figures 20 and 21.
If your video card does not have component video output, you can still convert the VGA or DVI output of your video card into component video using an adapter. It is worth noticing that this connection is not just an electrical connection; it needs electronic components to make the conversion from the RGB standard to the YPbPr one used by the component video adapter. That is why this adapter cannot be easily made at home. Be careful, because there is a USD 15 cable on the market that claims to convert the VGA output into component video, but this cable doesn’t work correctly.
ATI (now AMD) used to sell an adapter for video cards that used this company’s chip for USD 30, called “DVI-to-HDTV Adapter” (ATI part number 151-V01093). This adapter didn’t work on video cards with chips from other manufacturers. (This occurred because boards with ATI chips already had support for the component video as a standard feature.) Click here for more information on this adapter.
Other manufacturers produce VGA or DVI converters for component video compatible with any video card, but their price is higher (up to USD 150, depending on the manufacturer and the functionalities). Be careful, as the cheapest converters may not generate a component video signal at the best resolution or quality that your TV may support. That is why you have to check the resolutions and modes your TV supports and the resolutions and modes the adapter is capable of generating before buying it. The two most popular adapters among enthusiasts are the Digital Key KD-VTCA3 and the Audio Authority 9A60.
[nextpage title=”Red, Green and Blue (RGB)”]
The RGB connection is an old standard used by workstation video monitors. It uses the same signals as VGA, but instead of using a single cable carrying all the wires together and using a single connector with all signals, it uses a separated cable for each signal. With separate cables, each signal has its own shielding, protecting it from electromagnetic interference, which does not occur on the standard VGA cable. Because of that, RGB connection offers better image quality than VGA at the same resolution.
However, since this connection can only be used with old analog video monitors, the image quality is limited by the age of the video monitor (newer video monitors offer a far better image quality than older video monitors because the technology used) and the screen resolution. Also, most of these old RGB video monitors run at a different scanning frequency than VGA, making it impossible to connect older video monitors that use this standard directly to your video card, using the VGA connector.
So, we put this kind of connection here just as a reference, since you probably won’t see it around anymore. Anyway, if you are curious about this standard or happen to have an old RGB video monitor, take a look at this link, you will find it very useful: http://www.epanorama.net/documents/vga2rgb.
Actually there are three different RGB cabling standards:
- RGB5: The one we mentioned on first paragraph; it uses five cables: red, green, blue, horizontal sync (Hsync), and vertical sync (Vsync)
- RGB4: Uses four cables: red, green, blue, and composite sync (Csync)
- RGB3: Uses three cables: red, green + Csync, and blue, also known as sync on green
Each one of these cables uses a BNC connector.
In summary, the RGB connection type is better than VGA, but because of its age, modern video monitors offer a far better image quality than these old RGB monitors.
[nextpage title=”Video Graphics Adapter (VGA)”]
VGA is the traditional plug used to connect your PC to video monitors. It is also one option to connect your PC to video projectors and digital TV sets (HDTVs). This connection offers a better video quality than component video, S-Video, and composite video because it uses an independent wire for each video signal: red, green, blue, horizontal sync, and vertical sync. It uses a 15-pin connector known as D-Sub, D-Shell or HD15. On this connection, information is transmitted using analog signals, while on DVI, HDMI, and DisplayPort, information is transmitted digitally, thus providing better quality. Therefore, if your video monitor, video projector or digital TV set (HDTV) has a DVI, an HDMI or a DisplayPort connector (which will be the case with current models available on the market), you should use one of them instead of the traditional VGA connector to hook up your PC to your monitor, projector or HDTV.
[nextpage title=”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.
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.
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).
[nextpage title=”High-Definition Multimedia Interface (HDMI)”]
HDMI is, today, the connection of choice for consumer electronics products, such as DVD and Blu-Ray players, digital cable/satellite receivers, video game consoles and, of course, computers. This is the connection you should use to hook up your video source (including your computer) to your TV if both support it. If you are connecting your PC to your TV, don’t forget to configure the video resolution to your TV’s maximum resolution after you connect the two in order to get the best image quality. Follow the table below.
|TV’s Maximum Resolution||Video Resolution|
|720p or 720i||1280 x 720|
|1080p or 1080i||1920 x 1080|
This connection works 100% in digital mode, is capable of transferring higher resolutions than DVI, features a copy-protection mechanism called HDCP (High-bandwidth Digital Copy Protection), and transfers digital audio signals on the same cable (up to eight channels with 24-bit resolution and 192 kHz sampling rate), eliminating the need of an extra cable for connecting audio if your devices support this feature. Version 1.4 of the HDMI connection also added support for Fast Ethernet networking (100 Mbps) on the same cable. In the table below, we summarize the main differences between the HDMI versions available.
|Version||HDMI 1.0-1.2||HDMI 1.3||HDMI 1.4|
|Maximum Resolution||1920 x 1200 at 60 Hz||2560 x 1600 at 75 Hz||4096 x 2160 at 24 Hz (“4K”)|
|Color Depth||24-bit||30-, 36-, and 48-bit||30-, 36-, and 48-bit|
|Dolby TrueHD and DTS-HD Master Audio||No||Yes||Yes|
We have already written a tutorial explaining in-depth how HDMI works, so you may want to read it if you are interested in HDMI. Also, our tutorial on SPDIF audio connection will give you a few more usage examples.
In the pictures below, you can see some examples of HDMI use.
As we mentioned on the previous page, you can easily convert DVI-D and DVI-I connectors to HDMI through a cable or adapter, which should be used if your video source (your computer, for example) has a DVI-D or DVI-I output but not HDMI.
DisplayPort is a connection similar to the HDMI in the respect that it can also carry, on a single cable, digital video and digital audio, supports eight channels, has 24-bit resolution and a 192 kHz sampling rate, just like HDMI. While HDMI is targeted more towards consumer electronics, DisplayPort is targeted more to computers. Another important difference between the two is that the DisplayPort is a royalty-free standard, while manufacturers that want to use the HDMI connection must pay a royalty fee for each product sold. It supports its own copy-protection protocol, DPCP (DisplayPort Content Protection), and since its 1.1 version, also supports the HDCP protocol. It supports 4K resolution (4096 x 2160) and 3D video, just like HDMI 1.4. DisplayPort is very similar to HDMI 1.4, except that HDMI 1.4 supports a Fast Ethernet connection. On the other hand, DisplayPort has a bandwidth of up to 21.6 Gbps, while the bandwidth of HDMI 1.3 and 1.4 is 10.2 Gbps, leaving “space” for future features and resolutions.
One advantage of DisplayPort over HDMI is that it allows the installation of up to three video monitors to each port. In order to do that, you will need to use a DisplayPort hub connected to the video card, and the video monitors will be connected to the hub. Optionally, you can use a video monitor that has this component embedded, so you connect this monitor to the video card and the other two monitors to the ports available on the first monitor.
There is a miniature version of the DisplayPort connector, called Mini DisplayPort or simply Mini DP.