By Gabriel Torres on April 20, 2005
The digital TV system allows a higher resolution image broadcasting, raising the TV image quality a lot. However, to use the new resolutions allowed by digital television you need a high resolution TV set, known as HDTV (High Definition TeleVision).
Older analog TV sets can tune in digital broadcasting using a converter box, but they are limited to shows aired in the standard TV resolution of 480 lines using interlaced scanning (also known as 480i, see table below).
HDTV is a reality in developed countries and there you can watch some shows – even the whole progamming, in some channels – in higher resolution for those who have already HDTV sets. The resolution varies according with the TV station. In the USA, for example, some HBO and CBS shows are aired in 1080i resolution, while the format used by Fox in the shows that are aired in HDTV format is 480p, and on ESPN HD – which is a channel where all their transmitions are in HDTV format – the standard used is 720p.
HDTV sets can run basically in three resolutions: 480, 720 and 1080 lines. The screen scanning technique can be interlaced ("i") or non-interlaced ("p", for progressive). In the table below you can check all posible HDTV resolutions.
|480i||640 x 480||Interlaced||4:3 (1.33)|
|480p||640 x 480||Progressive||4:3 (1.33)|
|720i||1280 x 720||Interlaced||16:9 (1.78)|
|720p||1280 x 720||Progressive||16:9 (1.78)|
|1080i||1920 x 1080||Interlaced||16:9 (1.78)|
|1080p||1920 x 1080||Progressive||16:9 (1.78)|
The difference in image quality between interlaced scan and progressive scan is huge. The analog TV system uses interlaced scanning. In this method first the odd lines are drawn (line 1, line 3, line 5 and so on) then, after the screen is filled, the even lines are drawn (line 2, line 4, line 6 and so on), and the process starts all over again. In total 60 frames per second are drawn (i.e., the screen is filled 60 times per second), being 30 frames made of odd lines and 30 frames made of even lines, intercalated. So which frame displays only half of the lines the TV set can shown.
In non-interlaced scanning (or progressive scanning, as it is being called now) all lines are drawn. From the 60 frames per second each frame has all lines the TV set is capable of showing.
You have to be very careful when comparing different resolutions. For example, the 1080i resolution is not necessarily better than 720p resolution. Even though 1080i resolution has more pixels on the screen its scanning is interlaced, while 720p uses progressive scanning, making its image quality better (basically better sharpness) than 1080i.
The biggest problem is that HDTV panels, like LCD monitors, have a native resolution (for more information on this issue, please read our tutorial about LCD monitors).
In order to show images from a resolution different from its native resolution, the HDTV set has to convert the image, which can be well done or not, depending on the HDTV model. Let's pick a random example. 42" plasma TV Panasonic TH42PA20UP has a 848x480 (480 lines) native resolution. To show 720p images it has to convert the image, making its image quality not so good as compared with a HDTV set with a native resolution of 720 lines.
So, if you are an user worried about image quality, when buying a HDTV set pay attention to its native resolution. Preferably it should be equal to the resolution you will watch the most.
It is possible to connect HDTV panels to your PC to use them as video monitors. Let's see how this can be done.
HDTV panels can be connected to the PC using one of the following connection types, listed by image quality order, from best to worst:
DVI connection is the best because it uses digital transmittion, while the other connection types use analog transmittion. Thus, if your HDTV panel has DVI connector, use it. If it doesn't have one, use the VGA connector then. If your HDTV panel doesn't have DVI nor VGA connectors, then the solution is using video component.
Connecting your HDTV panel to your PC using DVI or VGA connectors is really simple: just plug one end of the cable on the corresponding video card output and the other cable end to the correct connector on the panel.
For more information on DVI connection, please read our tutorial on the subject.
The connetion using component video is more complicated. Let's talk about it.
If your HDTV panel doesn't have DVI nor VGA inputs, the solution to connect it to your PC is using its component video inputs. To use this type of connection your video card must have component video output. The problem, however, is that is not so easy to recognize if a video card has or not this kind of output because it shares the same connector used by Super Video (S-Video). Almost all video cards nowadays have one S-Video connector, but the majority don't have component video output available in this connector.
One way to detect if your S-Video connector has component video output or not is looking at it. If it has only four pins, this means it has only S-Video output and doesn't have component video output. If it has more than four pins, this may mean that it has component video output. Check in Figure 6.
Figure 6: Identifying the S-Video connector used by your video card.
Pay attention that we said "may". This happens because there are some video cards – specially 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, only reading the board manual and looking on its specs 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. So, if you 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 we show on Figures 7 and 8.
If you are sure that your video card has component video output, just connect it to your HDTV panel, following these directions:
You will need a component video cable. This cable has three plugs, one green, one red and one blue.
If your video card doesn't have component video output and your HDTV panel doesn't have DVI nor VGA inputs, then the only way to connect your HDTV set to your PC is through Separated Video (S-Video) connection, which has a low image quality – you won't get a very sharp image on the screen. Its connection is rather simple, just plug one end of your Super Video cable to the HDTV S-Video input and the other end to your video card S-Video output. You may need to activate your video card S-Video output, which is done by going to your PC video configuration screen. Because of its low image quality we do not recommend this kind of connection.
After connecting your HDTV panel to your PC you may need to change its video configuration. Let's talk about it.
After installing your HDTV panel to your PC, you may need to change the video input, through one of the panel's buttons in order to get you PC image on the HDTV screen. After this you will need to change the screen resolution. This can be done through the Video icon on Control Panel.
You will face some issues. First, as we explained, every HDTV panel has its own native resolution. So the image will be perfect only when you configure the video to use to use your HDTV panel native resolution.
Secondly, HDTV is wide screen (16:9 aspect ratio) and you will need to adjust the image position on the screen through Windows video properties.
Another problem you may face is if you try to configure your panel in a resolution it doesn't support and get the image all scrambled. If this happens, just choose another resolution.
Figure 14: Configuring the resolution that will be used by the HDTV panel.
Figure 15: Adjusting image position.
That's it. Enjoy!
Originally at http://www.hardwaresecrets.com/article/HDTV-Tutorial/123