Cabling For Maximum HDTV Resolution
Cabling For Maximum HDTV Resolution
To understand how cabling relates to HDTV display quality a brief overview of HDTV basics is important. Once you understand the common resolutions that comprise "HDTV" you will see there are a variety of ways to connect video components for both HDTV and HDTV-equivalent video quality.
HDTV is usually defined as video resolutions of 720p, 1080i or 1080p, however you will see that WXGA at 768p is also HDTV. The "i" and "p" represent the method in which your video screen is filled with video frames. Although they are filled from top to bottom and left to right, "i" and "p" represent two methods of frame filling. Put simply, the "i" stands for interlaced where your video screen displays all the odd-numbered lines first and then all the even-numbered lines next. The "p" stands for progressive scan or de-interlaced where all the lines are filled from top to bottom in order repeatedly. This line filling occurs very rapidly to give viewers a smooth moving picture. Generally, "p" (progressive scan) is preferred over "i" (interlaced) as far as video quality is concerned. At the same resolution, say 1080p versus 1080i, progressive scan video offers better video quality than interlaced video for two primary reasons: First, in interlaced video something called the "persistence of vision" (the human eye's tendancy to retain an image in memory for a brief moment) causes the human eye to see "artifacts" which are perceived as flickering on the video screen. The second reason progressive scan is preferred over interlaced is that it has double the number of verticle lines of resolution, since each video frame is filled alternately (odd-numbered lines and then even-numbered lines), so you only see half of the current frame and half of the next frame repeatedly. Confusing perhaps but this is why 1080i offers half the resolution of 1080p, UNLESS the 1080i signal is de-interlaced to 1080p. Newer video displays, such as LCDs, micromirror (DLP) or plasma displays are inherently progressive scan only and will automatically up-convert 1080i to 1080p.
The numbers "720" or "1080" in 720p or 1080i represent the number of verticle lines of resolution on your video display. The "720" stands for 1280x720 (displaying 921,600 pixels/dots), and "1080" stands for 1920x1080 (displaying 2,073,600 pixels/dots). Generally, more pixels lead to higher resolutions, so 1920x1080 would offer better video quality than 1280x720 if both video screens fill frames the same way ("i" or "p" above).
1080p represents the final frontier of high-definition television offers the highest quality video available for the home theater environment. However, it is also important to note that the advantages of 1080p are usually not noticed in all video programs or on 40-inch and smaller screens. Also, tests have shown that you need to sit back from the screen 3 times the viewing height of your screen to notice the benefits of 1080p. For example, you would need to sit at least 11.5 feet away from a 46-inch screen to notice the benefits of 1080p. To achieve 1080p quality you will need a video source offering 1080i or 1080p and an HDTV that is 1080p capable. Video sources offering 1080p are Blu-ray disc players, HD-DVD players, Microsoft's XBox 360, SONY's PS3 as well as 1080i content that can be up-converted (de-interlaced) to 1080p. De-interlacing 1080i content to 1080p content is done using a process called "3:2 pulldown reversal" and will work as long as the original video signal was not overly filtered. The best cables used to connect these sources to your HDTV will depend on the product's features. For example, the Microsoft Xbox 360 requires a component video cable to view HDTV at 1080p, but SONY's PS3 requires an HDMI cable to view 1080p.
It is important to note that some HDTVs will only display certain HDTV resolutions (listed in its product manual) while others will display almost any video resolution provided to it by converting it to the best screen fit and resolution automatically. This also applies to whether an HDTV's input signal is interlaced or progressive scan. An HDTV may simply display the exact signal it receives (or a blank screen), or it may up-convert a signal by de-interlacing. Newer displays, such as LCDs, micromirror (DLP) or plasma displays are inherently progressive scan and will up-convert any interlaced video to progressive scan.
Ports In General: Ports that are HDTV-capable are component, DVI, HDMI and RGB/RGBHV. Due to space limitations on the back of video devices and/or computers many manufacturers are moving towards "switchable" ports. These ports allow two types of video signals to travel through the same connection. The following are examples of common switchable ports: 15-pin RGB & Component ports, DVI & RGB ports, DVI & Component ports. To activate port switchablility features you may need to change the settings of your video device or add a special adapter. Check your product manual to verify if any of your video ports are switchable. IMPORTANT NOTE: You can damage your HDTV if you do not properly match the vertical frequency (refresh rate) of your computer's video output with your HDTV's video input. Be sure to check your product documentation for optimal settings.
Computer to HDTV Connectivity: Computers often require special software that will allow you to match your computer's vertical frequency (refresh rate) with one your HDTV can accept. For PCs a popular program called PowerStrip can be used: http://www.entechtaiwan.com/util/ps.shtm. For Macs a popular program called DisplayConfigX can be used: http://www.3dexpress.de. IMPORTANT NOTE: You can damage your HDTV if you do not properly match the vertical frequency (refresh rate) of your computer's video output with your HDTV's video input. Be sure to check your product documentation for optimal settings. Again, check the documentation of both your computer's video graphics adapter and your HDTV to see which resolutions they support.
Component Video Ports: Component cables can carry all HDTV video resolutions (including 1080p) and have three RCA connections, three BNC connections, or a single 15-pin connection. A trend on many flat screen displays is to have a 15-pin port that is switchable between RGB signals and Component signals, however your hardware settings usually require changing to enable one or the other. Also, some computer graphics adapters feature component video outputs to plug directly into your HDTV. Although 15-pin "Component" or "Y-Pb-Pr" connections are physically the same as the 15-pin connections found on many computers and monitors, they are completely different signals. Be sure to check your product manual to verify if your 15-port is RGB/VGA or component/Y-Pb-Pr. To connect a computer's 15-pin RGB/VGA port to your HDTV's component-video port you will first need a VGA-to-Component video converter like this: http://store.a2zcable.com/rgbconv.html . You will then need a "component" video cable with the appropriate connectors. Also, some DVI ports are component-video-capable DVI ports. Although not very common, DVI-component ports are usually "switchable" and may require a change in your hardware settings or a special adapter to work. Again, check your product documentation. See also the Computer to HDTV section above. (To shop for component video cables click here.)
DVI & HDMI Ports: Both DVI cables and HDMI cables can carry all HDTV resolutions (including 720p, 1080i, 1080p and WXGA) and use the same type of digital video signal to plug seamlessly into each other. Although HDMI can carry both video and audio in the same cable, DVI transmits only the video signal. However, DVI is more backwards compatible than HDMI in that it can also transmit analog RGB and/or component video signals IF your DVI port is RGB video and/or component video capable AND your DVI cable is analog video capable. Also, the rules for connecting DVI & HDMI digital video (not analog) also apply to M1, EVC, DFP and P&D connections, as these connections use the same digital signals as DVI/HDMI. For optimal video performance over DVI or HDMI cables the maximum recommended cable distance is limited to about 15 feet, although heavy duty cables featuring thicker conductors can carry signals accurately beyond 15 feet. Success beyond 25 feet will often depend on the quality of the circuitry inside your video transmitting device. Maximum HDTV resolution is 1080p and this requires 4.4Gbps transfer rates. HDMI cables and single-link DVI cables carry 4.95Gbps, and dual-link DVI cables carry about 9.9Gbps, so any of these cables can carry maximum HDTV resolutions. One important note about DVI is this: Some DVI ports are analog-capable DVI ports (known as DVI-A or DVI-I ports) and can be connected to 15-pin RGB/VGA ports, 3-RCA component video ports (if component video enabled DVI ports) or other DVI ports with the appropriate cable and/or adapter. DVI ports that are "component video" enabled (see section) may require a change in your hardware or menu settings or a special adapter to work. See also the Computer to HDTV section above. (To shop for HDMI, DVI, M1, DFP video cables click here.)
RGB / RGBHV Ports: RGB (short for RGBHV) cables use the same signals used by most 15-pin computer video ports and can transmit all HDTV resolutions, including 1080p. Many HDTV tuners and especially computers feature RGB ports in the form of a single 15-pin connection, five BNCs or five RCAs. (Although 15-pin "RGB" connections are physically the same as 15-pin "Component" or "Y-Pb-Pr" connections, they are completely different signals.) Although HDTV tuners simply pass HDTV signals to your HDTV, computers may have other requirements. Depending on the resolutions supported by your computer's video display adapter and those supported by your HDTV, RGB cables can carry a variety of HD resolutions, including WXGA (at 1280x768, 1280x800 and/or 1366x768) and HDTV's 1280x720 or 1920x1080. To connect your computer's 15-pin RGB port to your HDTV's DVI port two things are required: an RGB-capable DVI port (known as DVI-A or DVI-I port, NOT DVI-D) and a 15-pin-to-DVI cable or adapter. The reverse of this scenario is also true (DVI to 15-pin RGB). To connect a computer's 15-pin RGB port to your HDTV's component-video port you will first need a VGA-to-Component video converter like this: http://store.a2zcable.com/rgbconv.html . You will then need a "component" video cable with the appropriate connectors. Also, computers usually need some additional software to match your computer's resolution output to your HDTV's resolution input. (To shop for RGB & RGBHV video cables click here.)
CABLE & SATELLITE BOX TO HDTV CABLES - To take advantage of HD cable television or HD satellite television, two things are first required: an HD-ready cable or satellite box (featuring component video and/or HDMI video ports) and a subscription to your cable or satellite provider's HD programming. If your HDTV or cable/satellite box has DVI instead of HDMI you will need an HDMI to DVI cable.
SONY PS3 - If the Playstation3 game, DVD disc or Blu-Ray Disc program content and your video display support it, the PS3's HDMI connection can provide 480i, 480p, 720p, 1080i or 1080p resolutions, and the PS3's component video connections can provide 480i, 480p, 720p or 1080i resolutions (but not 1080p).
Microsoft XBox 360 - If the Xbox 360 game, DVD disc or HD-DVD Disc program content and your video display support it, the Xbox 360's component video connection can provide 480i, 480p, 720p, 1080i or 1080p.
Blu-Ray Disc Players - Blu-Ray discs are recorded in 1080p and all Blu-Ray disc players provide 1080p source video. If your HDTV does not support 1080p, the signals would be down-converted to a resolution your video display supports (480i, 480p, 720p or 1080i).
HD-DVD Players - HD-DVD discs are recorded in 1080p and all HD-DVD disc players provide 1080p source video. If your HDTV does not support 1080p, the signals would be down-converted to a resolution your video display supports (480i, 480p, 720p or 1080i).
Notes On Using Adapters: Using adapters or extension cables (such as DVI-to-HDMI adapters, 15-Pin-to-3-RCA adapters, 15-Pin female/female couplers, RCA/RCA gender changers, 15-pin extension cables and such) increase overall signal degradation, especially when running longer distances. Whenever possible it is best to use a single cable with the appropriate connectors between your video devices for maximum video quality. (To shop for video adapters click here.)
Although component video, DVI/HDMI and RGB can carry a variety of HDTV resolutions, your video devices may "prefer" one over the other. So it is best to check your hardware manual for any port preferences.
As you can see, there are numerous ways to connect your video sources and displays to achieve HDTV quality video. With respect to cables, video quality may depend on which video ports are preferred by the manufacturer of your video devices, so always check your product documentation for cabling preferences. The quality of the cables used to connect your video devices may also effect video quality. Since most cable shoppers believe high prices and big brand names determine quality, several cable companies now focus on higher prices and flashy marketing to sell cables rather than on the electrical specifications of their cables. (See our Comparing Video Cable Quality article for details.) The quality of your picture may also be effected by your cabling distance (such as long DVI or HDMI cable runs) and/or the quality of the circuitry inside of your video components. For example, some HDTVs may use low grade HDMI circuitry while using high grade component-video circuitry. In this case component will likely appear better on your screen. However, the reverse could also happen. Once again, always check a video device's documentation to verify which HDTV capabilities your device may, or may not, have.
Enjoy the show!
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