How Does HDTV Work?

HDTV stands for High Definition TV. HDTV makes it possible to see movies at your home with a satellite TV signal and experience the same crystal clear image without going to the theatre. Before discussing about HDTV, it is important to understand how a traditional TV works.

The much higher resolution in a HDTV produces clarity and vibrant colour, which was not seen from a traditional TV. The usual analog TV screen has 525 scan lines for each image, with 480 actually visible. The traditional TV has an effective picture resolution of about 210,000 pixels. In the highest resolution digital TV formats, each picture contains about 2 million pixels, which means about 10 times more picture detail on the HDTV screen. With digital television, the transmission of the signal is from the satellite dish directly to the satellite receiver that decodes the signal and broadcasts it to your TV set.

Another difference between the traditional TV and HDTV is the difference between a progressive and interlaced signal. The differences between the two can be characterized by the way the image is displayed on the screen. With interlaced format in case of HDTV, the information is filled in first with the odd lines on the screen and then the even lines. While the movement on the screen is so fast it's not easily detectable to a human eye, you may have experienced a 'flicker' quality with interlacing.

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HDTV or High-Definition Television usually works in the flowing way. The MPEG-2 is the most common format of codec used for HDTV digital broadcast. Formats like MPEG-2 also supports up to 4:2:2 YCbCr chroma sub sampling and 10 bit quantization. The HD transmitters use 4:2:0 and a 8-bit quantization to save on bandwidth.

Some broadcasters are also planning to apply and use the MPEG-4 AVC, like the BBC which has been working on such a method through satellite broadcast, this method saves a huge amount of bandwidth as compared to MPEG-2 systems.

A few broadcasters in Germany have already applied the use of MPEG-4 along with DVB-S2. Even though MPEG-2 is most commonly used it currently seems that in near future that all the European HDTV convert to MPEG-4.

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