Residential Audio & Video Systems Copyright © 2005 Heathkit Company, Inc. All Rights Reserved Presentation 17 – Digital Television (DTV) – Part 1

2 Objectives At the end of this presentation, you will be able to:

3 Define conventional TV, NTSC TV, PAL, SECAM, DTV, SDTV, EDTV, HDTV, ATV, and ATSC TV. List five advantages of DTV over NTSC TV. Describe the cliff effect and explain what causes it. Explain the difference between interlaced and progressive scan. Explain why 1080i and 720p produce about the same quality picture even though 1080i has over twice as many pixels per frame. Explain why the native resolution of the display is important in an HDTV monitor.

4 Conventional Television NTSC – The standard adopted by the United States, Canada, Mexico, and dozens of other countries. PAL – The standard adopted by most of Europe, Africa, and much of Asia and South America SECAM – The standard adopted by France, Russia, Greece, Saudi Arabia, and a dozen or so other countries.

5 Television Terms Conventional Television or NTSC TV. Digital Television (DTV) SDTV EDTV HDTV

6 EDTV SDTV NTSC Picture Quality Sound Quality NTSC DTV

7 Television Terms (Continued) Advanced TV or ATV Advanced Television Standards Committee (ATSC)

8 Brief History of DTV Late1980’s – Japan launches an analog HDTV system – Broadcaster petition FCC for HDTV spectrum – Four digital standards were proposed – FCC challenges competing forces to jointly develop a “best of the best” digital system forming the “Grand Alliance”.

9 Brief History of DTV (Continued) 1995 – The Grand Alliance recommends the ASTC system to the FCC – FCC adopts the ASTC standard. First HDTV commercial broadcast – First commercial HDTV sets are introduced – One millionth digital set sold. By late 2004, 16 million digital sets had shipped.

10 Advantages of Digital TV Resolution – Up to six times the resolution of NTSC TV. Clarity – No snow, no ghosts, no sparkles. Wide-screen – More natural aspect ratio. Audio – Dolby Digital Sound. Versatility – Picture quality versus bandwidth tradeoff. Flexibility – Unforeseen future features. Better use of spectrum.

11 The Over-The-Air (OTA) TV Spectrum VHF Channels MHz – 216 MHz UHF Channels MHz to 806 MHz

12 With NTSC Adjacent Channel Frequencies Interfere A city with an NTSC TV station broadcasting on channel cannot have another NTSC station broadcasting on channel 2 or channel 4. In effect, the single 6-MHz wide NTSC channel accounts for 18-MHz of the TV spectrum.

13 ATSC uses the spectrum more efficiently. ATSC plays well with adjacent channels. ATSC and NTSC must coexist for sometime. ATSC is often given the vacated adjacent channels left empty by the NTSC system.

14 The Cliff Effect DTV broadcast pictures do not slowly deteriorate with distance from the transmitter. The picture remains excellent right out to the border of the reception area. Beyond that border, the DTV receiving equipment can no longer distinguish between a zero and a one, and the picture disappears altogether as if it fell off a cliff.

15 Picture Quality Versus Distance from Transmitter (NTSC) Excellent Good Fair Poor Unusable

16 Picture Quality Versus Distance from Transmitter (ATSC) Excellent Unusable

17 NTSC versus ATSC Rasters Active lines Pixels per line Scanning technique Scan rate Aspect ratio

18 Number of Active Lines NTSC – 480 ASTC

19 Number of Pixels per line NTSC – Practical upper limit of about 720 pixels per line. ATSC

20 HDTV Versus NTSC 1920 by 1080 Pixels 720 by 486 Pixels

21 Scanning Technique NTSC – Interlaced ATSC Interlaced Progressive

22 Progressive Scan

23 Interlaced Scan

24 Frame Rate NTSC – 30 interlaced frames per second ATSC 60 frames per second 30 frames per second 24 frames per second

25 Aspect Ratio NTSC – 4:3 ATSC 16:9 4:3

26 16 to 9 4 to 3

27 Pillar-Boxing Stretching

28 Compacting Cropping

29 Letter Boxing Pan and Scan

30 Active Lines/ Picture Pixel Per Line Aspect Ratio Picture Rate :924p, 30p, 60i :924p, 30p, 60p :924p, 30p, 60i, 60p :324p, 30p, 60i, 60p :324p, 30p, 60i, 60p Picture Rate = Frames per second (progressive) or fields per second (interlaced) i = interlaced; p = progressive

31 HD Formats in Use 1080i – NBC, CBS, and many of the HD cable channels. 720p – Fox, ABC, and ESPN

i Versus 720p (Pixels per frame) 1080i 1080 x 1920 = 2,073,000 pixel per frame HD 720p 720 x 1280 = 921,600 pixels per frame

i Versus 720p (Pixels per Second) 1080i 1080 x 1920 = 2,073,000 pixel per frame 30 frames x 2,073,000 = 62.2 megapixels/second HD 720p 720 x 1280 = 921,600 pixels per frame 60 frames x 921,600 = 55.3 megapixels/second

34 Native resolution The resolution that the monitor displays without any conversion. A monitor with 1080i native resolution must down-convert to display a 720p signal. A monitor with 720p native resolution must up-convert to display a 1080i signal. Often, picture quality depends on how well the monitor handles the conversion.

Residential Audio & Video Systems Copyright © 2005 Heathkit Company, Inc. All Rights Reserved End