Digital Media Primer YueLing Wong Copyright c2013 by
"Digital Media Primer" Yue-Ling Wong, Copyright (c)2013 by Pearson Education, Inc. All rights reserved. 1
Chapter 6 Fundamentals of Digital Video Part 1 The Properties of Broadcast Video 2
In this lecture, you will learn: • the basic terminology of broadcast standards that will prepare you to learn digital video terminology and standards 3
Video motion a sequence of pictures 4
Video motion a sequence of pictures frames 5
Frame Rate • How fast the pictures are captured • How fast the frames are played back is determined by • Frames per second (fps) 6
Broadcast Standards • • Digital video resolution Color spaces Frame rate Influenced by analog TV broadcast standards 7
Standards for Analog Color TV • NTSC: – designated by U. S. 's National Television Systems Committee – U. S. , Japan, Taiwan, parts of the Carribean, South America • PAL: – Phase Alternating Line – Australia, New Zealand, Western Europe, Asian • SECAM: – Séquentiel Couleur avec Mémoire – France, former Soviet Union, Eastern Europe 8
Frame Rates of Different Broadcast Standards Video Type Frame Rate (frames per second) NTSC (black-and-white) 30 NTSC (color) 29. 97 PAL 25 SECAM 25 Motion-picture film 24 9
How CRT Monitors and TVs Display Pictures • Picture displayed on CRT is made up of horizontal lines – NTSC: 525 lines (about 480 lines are picture) – PAL and SECAM: 625 lines (about 576 lines are picture) • Lines are traced across the screen – one line at a time – from top to bottom 10
Ways of Tracing Lines From Top to Bottom • Progressive scan: – from top to bottom in one pass • Interlaced scan: – in two passes: 1. even-numbered lines 2. odd-numbered lines 11
Also see the interactive tutorial: VIDEO DISPLAY: INTERLACED SCAN VERSUS PROGRESSIVE SCAN AN INTERACTIVE ANIMATION THAT ILLUSTRATES TWO-PASS SCANNING IN INTERLACED SCAN AND ONE-PASS SCANNING IN PROGRESSIVE SCAN. 12
Field • Set of lines in the same pass • 2 fields in interlaced scan: – even-numbered lines – odd-numbered lines • Upper field: the field that contains the topmost scan line • Lower field: – the other field 13
Undesirable Side Effects of Interlaced Scan • The two fields in a frame are captured at a slightly different moment in time • Discontinuities will become apparent for fast moving objects in video shot in the interlaced mode • Comb-like artifacts 14
Comb-like Artifacts 15
Upper Field 16
Lower Field 17
Also see the interactive tutorial: VIDEO RECORDING: INTERLACED MODE VERSUS PROGRESSIVE MODE AN INTERACTIVE ANIMATION THAT ILLUSTRATES HOW THE INTERLACE ARTIFACT MAY BE PRODUCED IN FAST-ACTION VIDEOS. 18
Also see the interactive tutorial: UPPER FIELD AND LOWER FIELD AN INTERACTIVE DEMO SHOWS THE UPPER FIELD AND THE LOWER FIELD OF A VIDEO FRAME. 19
Also check out the video: FAST-ACTION DIGITAL VIDEO SHOWING THE INTERLACE ARTIFACT THE SOCCER PRACTICE VIDEO CLIP FROM WHICH THE EXAMPLE IS USING HERE TO SHOW THE COMB-LIKE INTERLACE ARTIFACT. 20
Interlace Artifacts • Not visible during normal playback of most videos 21
Deinterlace • To remove the interlace artifact • Common method: – discard one field – fill in the gaps by duplicating or interpolating the other field 22
Deinterlaced Result 23
Color Format for Videos • Luminance-chrominance color models • Luminance: brightness Chrominance: color or hue 24
Luminance-chrominance Color Model Examples • YUV: – Y: luminance component – U and V: chrominance components – used for PAL • YIQ: – Y: luminance component – I and Q: chrominance components – used for NTSC 25
Review Questions Note to instructor: Depending on your preference, you may want to go over the review questions at the end of this lecture as an instant review or at the beginning of next lecture to refresh students' memory of this lecture. 26
Review Question Which of the following is the television broadcast standard for the U. S. and Japan? A. NTSC B. PAL C. SECAM 27
Review Question Which of the following is the television broadcast standard for most of the Asian countries? A. NTSC B. PAL C. SECAM 28
Review Question In the YUV color model, the Y-component is ___, the U-component is ___, and V-component is ___. A. luminance; chrominance B. luminance; chrominance; luminance C. luminance; chrominance D. chrominance; luminance E. chrominance; luminance 29
Review Question The frame rate for the NTSC system is ___ fps. A. 24 B. 25 C. 28. 9 D. 29. 97 E. 30 30
Review Question The frame rate for the PAL system is ___ fps. A. 24 B. 25 C. 28. 9 D. 29. 97 E. 30 31
Review Question The frame rate for the motion-picture film is ___ fps. A. 24 B. 25 C. 28. 9 D. 29. 97 E. 30 32
Review Question The scan mode of a CRT computer monitor is ___. A. interlaced B. progressive 33
Review Question The scan mode of a CRT television set is ___. A. interlaced B. progressive 34
Review Question Interlaced scan displays the frame by scanning the lines of a frame ___. A. in one pass from top to bottom B. in two passes: even-numbered lines in one pass and odd-numbered lines in the second 35
Review Question Progressive scan displays the frame by scanning the lines of a frame ___. A. in one pass from top to bottom B. in two passes: even-numbered lines in one pass and odd-numbered lines in the second 36
Review Question The comb-like artifact in a digital video, as shown here, occurs in the ___ video. A. interlaced B. progressive C. both A and B 37
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