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DIGITAL TELEVISION

DIGITAL TERRESTRIAL TELEVISION BROADCASTINGThis process produces much clearer picture and sound quality than analog systems, similar to the difference between a compact disc recording (using digital technology) and an audiotape or long-playing record. A device that receives, decodes, and displays digital video broadcasts (in both high-definition and standard-definition formats) for consumer viewing. Digital television uses technology that records, transmits, and decodes a signal in digital formthat is, as a series of ones and zeros. It also permits additional features to be embedded in signals including program and consumer information as well as interactivities. Digital TelevisionPrimary Advantages consistent service quality with improved immunity from noise and near-error-free, perfect picture and sound propagation within the range of performance

Primary Advantageslower operating costs through the use of compression technology and improved system reliability

Primary Advantagesincreased programme diversity, the ability to provide multiple services in an existing single broadcasting service channel

The main problem is resolution. The resolution of the TV controls the crispness and detail in the picture you see. The resolution is determined by the number of pixels on the screen.

Main Problem with Analog TV

AnalogDigitalAn analog TV has a 4:3 aspect ratio, meaning that the screen is 4 units wide and 3 units high. For example, a "25-inch diagonal" analog TV is 15 inches high and 20 inches wide. The HD format for digital TV has a 16:9 aspect ratio, as shown below: Aspect Ratio

Each broadcaster has one digital TV channel, but one channel can carry multiple sub-channels if the broadcaster chooses that optionOn its digital channel, each broadcaster sends a 19.39-megabit-per-second (Mbps) stream of digital data. Broadcasters have the ability to use this stream in several different ways. A broadcaster can send a single program at 19.39 Mbps.A broadcaster can divide the channel into several different streams (perhaps four streams of 4.85 Mbps each). These streams are called sub-channels, and this type of broadcasting is called multicasting.MulticastingThere are three types of broadcast digital television (DTV), each with progressively better picture and sound quality: Digital technology is being developed that will offer sharper pictures on wider screens, and HDTV with cinema-quality images. High-Definition TV (HDTV)Standard-Definition TV (SDTV)Enhanced-Definition TV (EDTV)Types of Digital Television480i 480 lines by 704 pixels wide, displayed in interlaced format. Committee established by the FCC to define new standards for publicly regulated broadcast television in the United States Advanced Television Systems Committee (ATSC)

It has a 4:3 or 16:9 aspect ratio, 29.97-Hz frame rate, as defined by the ATSC standard.Standard Definition Television High-definition television (HDTV) image that is 480 vertical lines by 704 horizontal pixels displayed in progressive format 480p

It has a 4:3 or 16:9 aspect ratio, 59.94 Hz, 29.97 Hz, and 23.98 Hz frame rates, as defined by the ATSC standardEnhanced Definition Television

High-definition video formats that have 16:9 aspect ratio. Generally refers to 1080i or 720p images. 1,080 vertical lines by 1,920 horizontal pixels wide, displayed in an interlaced format.

It has a 16:9 aspect ratio, 29.97 Hz frame rate, 1080i 720 vertical lines by 1,280 horizontal pixels wide, displayed in progressive format.

It has a 16:9 aspect ratio, 59.94 Hz, 29.97 Hz, and 23.98 Hz frame rates, 720p High Definition Television To compress the image for transmission, broadcasters use MPEG-2 compressionMPEG-2 allows you to pick both the screen size and bit rate when encoding the show. A broadcaster can choose a variety of bit rates within any of the suggested resolutions. If a station wants to broadcast a sporting event (where there is lots of movement in the scene) at 1080i, the entire 19.39 megabits per second is needed to get a high-quality image. On the other hand, a newscast showing a newscaster's head can use a much lower bit rate. A broadcaster might transmit the newscast at 480p resolution and a 3-Mbps bit rate, leaving 16.39 Mbps of space for other sub-channels. Digital CompressionATSC Advanced Television Systems Committee DVB-T Digital Video Broadcasting - TerrestrialISDB-T - Integrated Services Digital Broadcasting - Terrestrial DTV SystemsATSC is a set of standards developed by the Advanced Television Systems Committee for digital television transmission that replaced much of the analog NTSC television system on June 12, 2009 in the United States and will replace NTSC by August 31, 2011 in Canada and December 31, 2021 in Mexico.

The ATSC System

The ATSC SystemFeatureswide screen 16:9 images up to 19201080 pixels in size supports a number of different display resolutions, aspect ratios, and frame rates different resolutions can operate in progressive scan or interlaced mode "theater quality" audio depends on numerous interwoven standards

Audio5.1 Audio Format

DVB-T is an abbreviation for Digital Video Broadcasting Terrestrial; it is the DVB European-based consortium standard for the broadcast transmission of digital terrestrial television that was first broadcast in the UK in 1997. This system transmits compressed digital audio, video and other data in an MPEG transport stream.DVB-T

The DVB-TFeaturesdesigned with built-in flexibility permits service flexibility robust against interference from delayed signals DVB-T compliant signals can also be carried over cables it can accommodate a large range of carrier to noise ratio and channel behavior

Audio3/2 Stereo Format

Integrated Services Digital Broadcasting (ISDB) is a Japanese standard for digital television (DTV) and digital radio used by the country's radio and television stations. ISDB replaced the previously used MUSE "Hi-vision" analogue HDTV system.ISDB-T(terrestrial) has adopted the MPEG-2 video and audio compression system.

ISDB-TISDB-T uses UHF 470MHz-770MHz, bandwidth of 300MHz, allocate 50 channels, namely ch.13-ch.62, each channel is 6MHz width (actually 5.572MHz effective bandwidth and 430kHz guard band between channels). ISDB-T allows to switch to two or three SDTV channels instead of one HDTV channel (multiplexing SDTV channels). Each channel is further divided into 13 segments. 1seg uses only single segment, and the remainder can be allocated as (1) one 12-segments HDTV program, (2) three 4-segments SDTV programs, or (3) one 8-segments (Medium Definition) program and one 4-segments SDTV program, broadcasted from a single TV station as the multiple-program arrangement

ISDB-TDigital-ready sets - They should be identified as standard definition (SDTV) sets. These TVs are normally 480p displays with a digital tuner built in. The problem with these sets is that their maximum resolution is the low 480p SD resolution, so if you want to watch high-definition TV, you won't be able to use these sets. HDTV-ready sets - These sets are essentially monitors able to display 1080i/p resolution in the 16:9 aspect ratio. They may or may not have tuners built in. Integrated HDTV sets - These sets have a digital tuner for broadcast DTV signals integrated into an HDTV display. With the standards changing so much, you may end up paying for an integrated tuner that becomes obsolete.

Buying A Digital TV SetThe preferred way to handle HDTV is to purchase the components separately: A 16:9 HDTV display capable of 720p and 1080i/p resolution A digital receiver An antenna Since the HDTV display will be the most expensive piece and will likely last 10 years or more, buying the components in this way allows you to change the receiver if you need to. There are currently three types of receivers: You can purchase a set-top box and a Yagi antenna to receive broadcast HDTV signals.

Buying A Digital TV SetYou can purchase a set-top box and a small satellite dish to receive HDTV signals from a satellite. You can purchase a board for your computer that lets you use your hard disk as an HDTV storage device, along with a Yagi antenna, and use it to receive signals on both your computer monitor and your HDTV display.

Buying A Digital TV SetA set-top box (STB) or set-top unit (STU) is a device that connects to a television and an external source of signal, turning the signal into content which is then displayed on the television screen.

Special digital set-top boxes are available for receiving digital television broadcasts on TV sets that do not have a built in digital tuner

Set-top Box

Many flat panel TVs use liquid-crystal display (LCD) screens that make use of a special substance that changes properties when a small electric current is applied to it.

LCD technology has already been used extensively in laptop computers.

LCD television screens are flat, use very little electricity, and work well for small, portable television sets.

Flat Panel Television Flat panel TVs made from gas-plasma displays can be much larger.

In gas-plasma displays, a small electric current stimulates an inert gas sandwiched between glass panels, including one coated with phosphors that emit light in various colors.

While just 8 cm (3 in) thick, plasma screens can be more than 150 cm (60 in) diagonally.

Flat Panel Television Digital television transition in the Philippines started its planning stage in 2006 after the National Telecommunications Commission (NTC) have released a memorandum on what DTV broadcast standard to be used for the countryThe commission has decided to have UHF TV channels 14-51 at frequency spectrum