Concepts of High Definition Television (HDTV)
October 8, 2008
What is High Definition Television?
A high definition television is a digital television broadcasting system that come with higher resolution compared to the traditional television systems. High Definition Television broadcasts signals digitally, and hence require less bandwidth if the video compression used is sufficient. The term high definition was once used for a series of television systems that were introduced in the year 1930s and 1940s. A HDTV compatible television does not improve the quality of the Standard Definition Television.
LCD TV manufacturers adopt the 16:9 aspect ratio that is compatible for HD Ready 1080p video standard, due to the increasing scale of manufacturing yield and the resolution of the VRAM and VGA that is 768 pixel format. HDTV display images in higher details than the DVD or analog television as it comes with double the linear resolution of SDTV(Standard Definition Television). A high resolution requires higher bandwidth to be transmitted in correct form.
A television or a radio receives signals through various media such as a satellite, cable or air medium and this signal is converted to the form the device is capable of displaying. This is made possible with the digital tuners. A tuner is a device that configures a device, no matter if it is an electronic device, mechanical device or a musical device. Tuners convert low frequency radio frequency signals to a form that is supported by the device. A tuner is also capable of receiving digital broadcasts through the satellite or any other medium and displaying it on the standard definition television or high definition television sets.
Sources of HD Signal Broadcast
HDTV require High Definition signals to display superior quality images. High Definition signals are broadcast by various sources such as:
1.Some internet connections such as Apple TV can broadcast HD signal for video games like Playstation 3 and Xbox 360. Some other services also offer movie trailers, HD movies, clips to download and more.
2.Satellite based TV companies such as Freesat and Sky digital offer HDTV. To receive HD content new satellite dish and New satellite receiver box are required.
3.Blu-ray disc can store up to 10 hours of HD video content based on the encoder settings.
4.HD signals are broadcast over the air and hence can be captured by the antenna. An HD tuner is required to receive this signal. Some HDTV models come with built-in HD tuner and other that do not have this facility would require a HD tuner box, which can be rented from a satellite company or a cable company.
5.Some computer graphics card either have DVI or HDMI interfaces to display images or video to an HDTV.
6.Some DVD-R disc provide 20 to 40 minutes of HD video content.
Parameters of HDTV
Three major parameters of HDTV broadcast systems are Scanning system, Frame rate and Frame size. Scanning system is identified with the letter ‘i’ for interlaced scanning and ‘p’ for progressive scanning. Frame rate is defined as the number of video frames that are produced per second. Frame size is defined as the number of pixels that are formed both horizontally and vertically. For example, 1920 x 1080. Whenever these parameters are used, it may be specified in the form as frame size scanning system frame rate. Frame rate can also specified without a resolution. In the case of a resolution, both the transmitted signal and the native resolution of the TV is considered. HDTV sets upconvert or upscale the transmitted signal to the native format. The video format resolution of high definition display is usually of 720 horizontal lines. The native resolution of HD Ready TV is 1366 x 768 pixels.
Advantages
Images that are formed in HDTV are of better quality as it has more number of lines of resolution. As the gaps between the scan lines are narrower, the images produced are more sharper. Sound track of HDTV video signal is Dolby Digital 5.1 surround sound that produces excellent surround sound capability.
Disadvantages
The best quality of HDTV is not achieved as the operators do not follow HDTV specification properly. They use lower resolutions and broadcast more channels with limited bandwidth. This reduces the quality of the video that is broadcast. Inappropriate cabling is also a factor that puts down the quality of the image. HDMI cables are more expensive than the component cables but provide best picture and sound quality. Though HDTV has some disadvantages one must consider its plus points and deal with this concept accordingly.
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