ATSC tuner
From Wikipedia, the free encyclopedia
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.
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[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, 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 a TV set can use to produce quality images and 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 a 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.
- There is a subsection in the ATSC standard (ATSC-E) that allows broadcasters to add extra (and variable types) of error correction to their broadcast streams.
- This error correction service is not mandatory in the US, nor is it mandatory in Canada.
- It is not known how many HDTV receivers support this error correction standard.
- For the transmission of HDTV at 720 or 1080, and extra 1% to 3% added error correction codes will help reduce some of ATSC's poorer performance with weak signals under adverse multipath conditions.
AV Synchronization
AV synchronization is the coordination of audio and video signals being displayed on a digital TV in proper time. AV synchronization ensures that the audio does not lag behind the video that is being displayed on the TV set or vice versa, so that both audio and video are in sync.
Media Reformatting
Media reformatting is extremely important because the formatting of images on TV sets differs significantly according to the technology employed. For instance, some televisions have an interlaced picture, whereas others have a progressive-scan picture.
Different televisions have a different aspect ratio.
[edit] U.S Government mandates
The FCC has issued the following mandates for devices entering the US:[1][2][3]
- 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 full power 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.
The US switch-off will make millions of non-Cable and non-Satellite connected TV sets to "go dark". Viewers who do not upgrade, either to a television with a digital tuner or a set-top box, will end up losing their only source of television. A Congressional bill has authorized subsidizing converter boxes in a way that would allow viewers 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.
[edit] References
- ^ FCC INTRODUCES PHASE-IN PLAN FOR DTV TUNERS (PDF). FCC (2002-08-08). Retrieved on 2006-06-05.
- ^ Requirements for Digital Television Receiving Capability (PDF). FCC (2005-11-08). Retrieved on 2006-06-05.
- ^ FCC Moves Up DTV Tuner Date, Broadens Scope. TWICE (2005-11-21). Retrieved on 2006-08-30.
- ^ CFR Title 47: Telecommunication; PART 15—RADIO FREQUENCY DEVICES; § 15.117 TV broadcast receivers (PDF). FCC (2006-10-01). Retrieved on 2007-02-11.
- ^ Pub. L. No. 109-171, 120 Stat. 4 (Feb. 8, 2006).
- ^ Senate approves 2009 for end of analog TV. MSNBC (2005-11-04). Retrieved on 2006-06-05. Section 3002 of the Act amends 47 U.S.C. section 309(j)(14) to provide for the February 17, 2009 deadline.
- ^ Commerce Department Issues Final Rule To Launch Digital-to-Analog Converter Box Coupon Program. NTIA (2007-03-12). Retrieved on 2007-03-12.
- ^ Canadian Radio-television and Telecommunications Commission (2007-05-17). "The Commission establishes a new approach for Canadian conventional television". Press release. Retrieved on 2007-05-17.
- ^ Broadcasting Public Notice CRTC 2007-53 (HTML). Sections 50 to 80. Canadian Radio-television and Telecommunications Commission (2007-05-17). Retrieved on 2007-05-17.
[edit] See also
- ATSC DVD recorders
- Digital terrestrial television
- Digital broadcasting
- Digital switchover
- High-definition television in the United States
- QAM tuner
- Tuner (radio)
- Virtual channel
[edit] External links
- The FCC's DTV information site
- 5th generation ATSC Receiver review (2006-12-17). Retrieved on 2006-12-17.
- Over the air digital television reception FAQ. AVS forum. Retrieved on 2006-06-05.
- Patent and royalty info 2006-12-27
- Understanding broadband silicon tuners for broadband cable and TV apps: A Tutorial. Digital TV Designline (2006-05-17). Retrieved on 2006-06-05.
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