T12 GROUP 2

High Definition Technology
High Definition Technologies are those which have been developed to have a clearer quality and image when either viewed or utilized, as opposed to the technologies of the past.

HDTV
What is HDTV?

HDTV is defined as a television that is 720 or more pixels high. A pixel is a point of solid colour. Televisions change the colour of their pixels to produce an image, similar to the way a computer monitor works. Pixels within a television are of the same size,however, as the size of the television changes the size of the pixels change as well. Each pixel is three closely spaced dots of color (red, blue and green). HDTV pixels are square, smaller, and are more closely spaced than traditional televisions. This leads to at least 4 1/2 times more visual detail. A standard TV has 525 scanned lines for each image. There are two format for refreshing the image. Interlaced(i) which refreshes the image every 30th of a second, however, only half the image is refreshed. The full image is refreshed every 60th of a second. Progressive(p) format refreshes the entire image every 30th of a second. In an SDTV only 480 lines are visible on the TV and is referred to as 480i (480 lines of usable resolution, interlaced).

HDTV Resolution

There are four formats that can be seen on a High Definition TV, they are: 480i, 480p, 720p, and 1080p. The higher the number the higher the resolution, HDTV’s can play all four, Higher Definition are usually referred to as having either 720p and 1080p.All HDTV's signals are digital signals, SDTV’s rely on analog signals for broadcasts. HDTV signals require 19.39Mbps of bandwidth -- five times the bandwidth of SDTV signals.

HDTV Screen Ratio

The aspect ratio is the integer fraction that can be found when the number of pixels that a television has width wise is divided by the number of pixels height wise. SDTVs have an aspect ratio of 4:3 meaning that they are a rectangular, but quite similar to a square. HDTV’s have an aspect ratio of 16:9. This aspect means that they are wider and are closer to the proportions as seen by the human eye. Cinema screens usually have an aspect ratio of 16:9, which is the screen ratio of all HDTV. This means that most movies can be viewed on TV as they would be shown in the theater. SDTV's crop off the sides of movies and programming that does not fit the ratio, and results in approximately 1/3 of the picture to be missing. With HDTV, the entire image can be viewed without any cropping or letter boxes.

Plasma vs. LCD
In the market for High definition television watching there are hundreds of TV’s to choose from but for most people the choices boil down to Plasma and LCD. Flat panel TV’s are getting bigger and dropping in price, so the question stands: Which are better? The answer to this question all greatly depends on what you are using the TV for. We’ll go through some of the advantages of both high definition TV technologies.

Plasma Plasma displays panels use a matrix of tiny gas plasma cells that are charged by electrical voltages to emit light and create a picture image.

Liquid Crystal Displays (LCD) panels Trap a liquid crystal solution between 2 sheets of polarized glass. When an electric current passes through the crystals, they change the polarization of light passing through the polarized glass. LCD panels do not generate light but subtract light generated by a back-light source to create a picture image

Energy Consumption

Plasma screens are commonly believed to consume the most power in the energy efficiency debate between LCDs and Plasmas. This can be attributed to their construction. A plasma screen is made up of pixels, each of which have an individual light source which illuminates as needed. Conversely, an LCD has a backlight, illuminating the entire screen. LCDs create the picture not by illuminating the pixels, but by blocking light from getting through to certain pixels. The LCD backlight provides a steady source of power, while Plasma pixels are constantly switching off and on. This makes the energy consumption of each particular television to be rather subjective, depending on what is being viewed. In a recent test done by the Call for Help crew from TechTv, the crew took on the task of finding the television that consumed the most energy.

"As prevailing wisdom suspects, the plasma monitor consumed more energy under all of the different real-world viewing tests, but the Battlestar Galactica test showed the difference narrowing. Under the solid colour testing, the plasma ate up more energy than the LCD screen except when displaying a solid black screen, where the power consumption of the plasma screen plummeted to about a quarter of its usual use. The plasma screen used the most energy showing a screen with TV static on it, because there’s a lot of white, and it’s rapidly moving."

In this way, it has been shown that LCD screens do consume less power, however, that changed during certain conditions, such as when they displayed a solid color background on the screen or when there was static electricity. These situations taxed the LCD more heavily and resulted in more evenly matched results between LCD and plasma TVs.

Blu-ray vs. HD DVD
During the war to see which high definition DVD format would become the most popular, Warner Brothers, Apple, Dell, HP, and Samsung Electronics supported the use of Blu-ray, made by Sony, while Microsoft and Intel support supported HD DVD format, made by Toshiba (Unknown 2005). Both Blu-ray and HD DVD produce the same sharpness of image, however Blu-ray can hold 25 GB of information while HD DVD holds only 15 GB. This difference is due to HD DVD using “MPEG-4 data-compression scheme rather than the MPEG-2 scheme still used by Blu-ray”, in the end, blu-ray won out because it was able to hold more information.

Table 1: (Fischetti 2007)

A multi-layer blue ray disk can hold as much as 50 GB of data on it. This increase in holding capacity (in comparison to a standard DVD) is due to the fact that blue ray utilizes a blue-violet laser rather than a red one. The blue laser has a shorter wave length and therefore can be focused with greater precision, allowing “the data pits, which constitute the digital 1s and Os, [to] be smaller”, (Fischetti 2007). This allows for data to be stored closer together on the disk and thereby increases the storage capacity. Recent developments have added as many as 20 layers to the new discs, increasing the storage capacity to 500GB



From http://www.cd-writer.com/blu_ray_faq.html