ATSC tuner

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Multiple MPEG programs are combined then sent to a transmitting antenna. In the US broadcast digital TV system, an ATSC receiver then decodes the TS and displays it on your TV.

An ATSC tuner, often called an ATSC receiver or HDTV tuner, allows reception of ATSC digital television (DTV) signals broadcast over-the-air by TV stations in North America and South Korea. Such tuners may be integrated into the television, VCR, digital video recorder, and set-top box which provides audio/video output-connectors of various types.

1 Technical overview
2 How an ATSC Tuner Works
3 U.S Government mandates
- 3.1 Analog TV broadcast switch-off
4 References
5 See also
6 External links

[edit] Technical overview

The terms "tuner" and "receiver" are used loosely, and it is perhaps more appropriately called an ATSC receiver, with the tuner being part of the receiver (see Metonymy). The receiver generates the audio and video (AV) signals needed for television, and performs the following tasks: demodulation, error correction, transport stream demultiplexing, decompression, analog to digital conversion, AV synchronization, and media reformatting to match what is optimal input for one's TV. Examples of media reformatting include: interlace to progressive scan or vice versa, picture resolutions, aspect ratio conversions (16:9 to or from 4:3), frame rate conversion, even scaling. Zooming is an example of resolution change. It is commonly used to convert a low-resolution picture to a high-resolution display.

[edit] How an ATSC Tuner Works

An ATSC tuner works by generating audio and video signals that are picked up from over-the-air TV broadcasts. ATSC tuners provide the following functions: demodulation, transport stream demultiplexing, decompression, error correction, analog-to-digital conversion, AV synchronization and media reformatting to fit the specific type of TV screen optimally.

Demodulation

Demodulation means that the signal that is pulled off the airways is transformed into a usable signal that your TV set can use to display quality images and quality sound.

Transport Stream Demultiplexing

In the US, multiple digital signals are combined and then transmitted from one antenna source to create over the air broadcasts. An ATSC receiver then is able to decode the transport stream and display it on your TV set.

Decompression

Since digital signals that are broadcast over the air are compressed (packed smaller), once they are received by the ATSC tuner, these compressed packets of digital data are then unpacked to their original size, or using the proper term, decompressed.

Error Correction

Error correction is a technology that is used by the ATSC tuner to make sure that any data that is missing can be corrected. For instance, sometimes interference or a poor-quality signal will cause the loss of data information that the ATSC tuner receives. With error correction, the tuner has the ability to perform a number of checks and repair data so that a signal can be viewed on a TV set.

Analog-to-Digital Conversion

Analog-to-digital conversion, sometimes called ADC or A to D refers to a technology in which an analog signal is converted into a digital signal. In the context of an ATSC tuner, an analog TV broadcast that is broadcast over the air is received by the ATSC tuner and converted from its original analog signal to a new digital signal that can be viewed on a digital TV set.

AV Synchronization

AV synchronization is the coordination of audio and video signals being displayed on your digital TV in proper time. AV synchronization makes sure that your audio sound doesn't lag behind the video that is being displayed on your TV set or vice versa. This technology makes sure that both your audio and video are in synch.

Media Reformatting

Media reformatting is extremely important because different TV sets format their images significantly different and can use several different technologies. For instance, a standard TV has an interlaced picture, whereas a digital TV has a progressive-scan picture.

"Interlaced" means that while there are 30 image frames being shown per second on a standard TV, every 1/60th second the TV refreshes only half the image. With progressive scan, the entire image is refreshed 60 times per second.

TVs can come in different aspect ratios. An aspect ratio is the shape of the TV screen. For example, a standard TV is boxy in shape with a 4:3 ratio, while digital TV's come in aspect ratios more in the shape of a 16:9 rectangle.

[edit] U.S Government mandates

The FCC has issued the following mandates for devices entering the US:^[1]^[2]^[3]

By July 1, 2005 all televisions with screen sizes over 36" must include a built-in ATSC DTV tuner

By March 1, 2006 all televisions with screen sizes over 25" must include a built-in ATSC DTV tuner

By March 1, 2007 all televisions regardless of screen size, and all interface devices which include a tuner (VCR, DVD player/recorder, DVR) must include a built-in ATSC DTV tuner.

It should be noted that devices manufactured before these dates can still be sold without a built-in ATSC DTV tuner.

The current regulations are specified in the U.S. Code of Federal Regulations (CFR).^[4]

[edit] Analog TV broadcast switch-off

In early 2006 the Deficit Reduction Act of 2005^[5] became law, which calls for over-the-air television stations to cease their analog broadcasts by February 17, 2009^[6] (this cut-off date had been moved several times previously). Following that date, TVs and other equipment with legacy NTSC tuners would be unable to receive over-the-air broadcasts. This switch-off would cause tens of thousands of TVs to go dark and would cut off many lower-income viewers from their only source of television. A Congressional bill has authorized subsidizing converter boxes that would allow people to receive the new digital broadcasts on their old TVs. The final plan^[7] is to make two $40 coupons available from January 1, 2008 through March 31, 2009 for all households with the initial $990 million allocated, after which an additional $510 million in coupons will be available for each household that relies exclusively on over-the-air television reception. In Canada, the Canadian Radio-television and Telecommunications Commission (CRTC), has set August 31, 2011 as the date that over-the-air analog TV transmission service will cease in most parts of the country except in parts of the far North.^[8] ^[9] But unlike the United States, there is currently no plan to provide ATSC receivers at a discount to low-income households as of January 1, 2007.