DTV

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DTV
Roy Walker WA5YZD
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Do You Remember These?
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History

• In the United States, the National Television
  System Committee (for which the NTSC standard is
  named) standardized on 525 lines at 30 fps in
  1940, with regular broadcasts starting on July 1,
  1941.
• NTSC standard was updated to include first a
  non-compatible 441-line color standard in 1950,
  which was replaced by a compatible 525-line,
  29.97fps color standard approved in 1953 and used
  to this day.
• Current high definition video standards were
  developed during the course of the advanced
  television process initiated by the Federal
  Communications Commission in 1987 at the request
  of American broadcasters
• FCC process, led by the Advanced Television
  Systems Committee (ATSC) adopted a range of
  standards from interlaced 1080 line video with a
  maximum frame rate of 30 fps, and 720 line video,
  progressively scanned, with a maximum frame rate
  of 60 fps. The FCC officially adopted the ATSC
  transmission standard (which included both HD and
  SD video standards) in 1996, with the first
  broadcasts on October 28, 1998.

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Who is Affected by Change to DTV?

• Consumers who receive over-the-air television
  signals through antennas on television sets that
  are equipped with analog tuners and who do not
  subscribe to cable, satellite or a telephone
  company television service provider will be
  affected by the transition.
• At least 19.6 million households receive
  over-the-air signals exclusively in their homes,
  and 14.9 million households have secondary
  over-the-air television sets in their bedrooms or
  kitchens. Overall, nearly 70 million television
  sets are at risk of losing their signals on
  February 17, 2009, if consumers do not make the
  transition to DTV.

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Analog vs. Digital Television

• Analog TV AM vestigial sideband
• 6 MHz of bandwidth per channel plus the audio
• High power transmitters for coverage 45 to 75KW
  Avg. Out
• 300KW to 5MW ERP
• Noise and multi-path interference common
• Digital TV 8VSB MPEG-2 Stream
• 6 Mhz Channel can produce multiple programs
  viewable with ATSC tuner (multicasting)
• 5 to 7.5 KW Average Transmitter Output Power
• Austin Broadcasters - 98 KW to 1.5 MW ERP
• Received picture is either perfect or not at all
• 5.1 Surround Sound
• UHF Channel Spectrum

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Why the Change to Digital TV ?

• Increase number of programs local broadcasters
  can provide
• Improve the Quality of Picture and Sound
• Converting to DTV will also free up parts of the
  scarce and valuable broadcast airwaves.  Those
  portions of the airwaves can then be used for
  other important services, such as advanced
  wireless and public safety services (for example,
  police, fire departments, and rescue squads,
  commercial wireless).

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Transition to Digital Television

• TV stations serving all markets in the United
  States are airing digital television programming
  today, most will continue to provide analog
  programming through February 17, 2009.
• Full-power TV stations will cease broadcasting on
  their current analog channels, and the spectrum
  they use for analog broadcasting will be
  reclaimed and put to other uses.
• The Commission's digital tuner rule specifies
  that as of March 1, 2007, all new TVs must
  include digital tuners.

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Converter Box Coupon Program

• Between Jan. 1, 2008, and March 31, 2009, all
  U.S. households will be eligible to request up to
  two coupons, worth 40 each, to be used toward
  the purchase of up to two, digital-to-analog
  converter boxes.
• The National Telecommunications and Information
  Administration (NTIA) has responsibility for
  administering the coupon program. More
  information can be found at www.ntia.doc.gov/otiah
  ome/dtv/dtvcoupon.html.

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Digital Television Quality Levels

• Standard Definition TV (SDTV) - SDTV is the basic
  level of quality display and resolution for both
  analog and digital. Transmission of SDTV may be
  in either the traditional (43) or wide screen
  (169) format.
• Enhanced Definition TV (EDTV) - EDTV is a step up
  from Analog Television. EDTV comes in 480p wide
  screen (169) or traditional (43) format and
  provides better picture quality than SDTV, but
  not as high as HDTV.
• High Definition TV (HDTV) - HDTV in wide screen
  format (169) provides the highest resolution and
  picture quality of all digital broadcast formats.
  Combined with digitally enhanced sound
  technology, HDTV sets new standards for sound and
  picture quality in television. (Note HDTV and
  digital TV are not the same thing -- HDTV is one
  format of digital TV.)

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What You Should Know Before You Buy

• Compare DTV picture quality.  Go to the showroom
  and look at what you are paying for. Contrast
  and compare the cost with the picture quality and
  features within a brand you are considering.
  Look at the next brand and repeat the comparison.
• Image Processor Engines make the difference in
  picture quality.
• Bravia
• DLP  
• Make sure you have all the DTV equipment you
  need.  DTV equipment can be purchased as an
  integrated set or as separate components. 
  Integrated digital televisions have built-in
  tuners and a monitor to display the programming. 
  If you buy a DTV monitor (without an integrated
  tuner), you will need a stand-alone tuner, cable
  set-top box, or satellite set-top box to watch
  DTV.
• HDTV is the Top End Quality of DTV.  HDTV
  requires special equipment, so make sure to ask
  about HDTV-capable equipment and talk to your
  cable or satellite provider to verify you have
  the proper set-top box to view HDTV.

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Can You See the Difference?

• Is 720p vs. 1080i worth being concerned about?
  Yes and no. If you're a consumer looking for a
  new TV, you can happily ignore the 720p vs. 1080i
  debate because every TV which is described as
  HDTV or HDTV Ready is required to support both
  formats.
• You should be aware that lots of TVs which
  support 1080i have fewer than 1080 lines on their
  display and so scale the 1080 signal down. That's
  not a huge issue as even scaled down 1080i is far
  ahead of a regular NTSC picture. It is worth
  bearing in mind that more expensive HDTVs tend to
  have better scalers than cheaper ones, and this
  may be an issue

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720p vs. 1080i

• 720p signal is made up of 720 horizontal lines.
  Each frame is displayed in its entirety on-screen
  for 1/30th of a second. This is know as
  progressive scan (hence the 'p'). The quality is
  like watching 30 photographic images a second on
  TV.
• A 1080i signal comprises 1080 horizontal lines
  but all the lines are not displayed on-screen
  simultaneously. Instead, they are interlaced
  (hence the 'i'), i.e. every other lines is
  displayed for 1/60th of a second and then the
  alternate lines are displayed for 1/60th of a
  second. So the frame rate is still 30 frames per
  second, but each frame is split into two fields,
  which your brain then puts together
  subconsciously.

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Interlacing

• Most of the time interlacing works fine, but for
  fast moving images such as sports like baseball
  and hockey it can cause problems which manifest
  themselves as a 'stepping' effect on-screen.
  Progressive scan signals don't have this problem
  and so are better suited to sports.
• ESPN puts it like this 'Progressive scan
  technology produces better images for the fast
  moving orientation of sports television. Simply
  put, with 104 mph fastballs in baseball and 120
  mph shots on goal in hockey, the line-by-line
  basis of progressive scan technology better
  captures the inherent fast action of sports. For
  ESPN, progressive scan technology makes perfect
  sense.'

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Screen Technologies

• Cathode ray tube (CRT) screens traditional
  color television screens updated for digital
• Rear Projection TVs rear projection TVs can
  create brilliant, wide angle pictures on
  ever-larger screens (Its the Mirrors DLP)
• LCD screens - are very thin and produce extremely
  clear pictures, but are currently expensive and
  limited in size
• Plasma screens - create a bright, clear picture
  up to enormous sizes while remaining very thin.
  Cause high rf noise that interfere with HF
  communications.

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Aspect Ratio

• 4 X 3 Traditional TV aspect ratio, that is,
  the screens width as compared to its height. 
  For example, a 32 inch TV screen would be 25 ½
  inches wide and 19 inches tall.
• 16 X 9 Wide screen TV aspect ratio that is
  more like a movie screen than a traditional TV.
  For example, a 32 inch TV screen would be 28
  inches wide and 16 inches tall.
• Most new sets allow you to stretch or zoom the
  picture to fill the screen. Some do a smart
  zoom that maintains linearity of the picture.
  Cheaper set let you watch a distorted picture and
  most people never notice how bad it looks.

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Austin DTV Allocations
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Spectra Comparison
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Data Formatting for 8-VSB
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Questions