ITMA11 Introduction To Video

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ITMA11 Introduction To Video

  1. 1. Conventional “analog” TV • Commercially available since late 1930’ • Picture formed by sweeping an electrical signal ITMA 11 horizontally across the screen one line at a time. Introduction to Video and Film Krates Ng Fall 2008 from www.maxim-ic.com 1 2 Interlaced scanning • TV uses interlaced scanning • Each picture, referred to as a frame, is divided into two separate sub-pictures, referred to as fields. Two fields, odd and even, make up a frame. from www.maxim-ic.com 3 4 Progressive Scanning • Used in delivering computer signals. • Picture is painted on the screen by scanning all of the horizontal lines of the picture in one pass from the top to the bottom. from www.maxim-ic.com 5 6 1
  2. 2. Resolution Standard Video Resolution • Computer visual signals use pixel resolution. • Standardized computer display resolutions: Name Width Height QVGA 320 240 VGA 640 480 SVGA 800 600 XGA 1024 768 SXGA 1280 1024 WXGA 1366 768 UXGA 1600 1200 WUXGA 1920 1200 7 8 3 major world TV systems • TV uses lines • NTSC – National Television Systems Committee – e.g. 525 lines in NTSC, 625 lines in PAL – Used in USA and Japan • PAL – Phase Alternating Line – Used in UK and Asia • SECAM – Sequential Coleur Avec Memoire • Many sub systems under each major system. 9 10 Which country uses which? NTSC • Interlaced into two fields • 525 scan lines per frame ( 485 visible lines max.). • Ordinary TV has about 320 lines. • Vertical frame rate: 29.97 frame/sec. • Bandwidth 4.2MHz • Used to use YIQ color model (now YUV) 11 12 from wikipedia.org 2
  3. 3. PAL Visible raster area Vertical blanking period • Interlaced into two fields Horizontal blanking period • 625 scan lines per frame (≈ 575 visible max.) 525 lines (NTSC) • Vertical frame rate: 25 frame/sec. 625 lines (PAL) About 480 visible About 576 visible • Bandwidth 5.5MHz Visible raster area • Uses YUV color model 13 14 NTSC and PAL YUV Color Model • NTSC • YUV model defines a – Less flicker color space in terms of one luminance – Poorer resolution (brightness) and two • PAL chrominance (color) – Sharper resolution components. – More flicker • Models human color reception better than RGB. from wikipedia.org 15 16 YUV from RGB YUV • Y= 0.299R + 0.587G + 0.114B Original U • U= 0.492(B − Y) = − 0.147R − 0.289G + 0.436B • V= 0.877(R − Y) V Y = 0.615R − 0.515G − 0.100B 17 18 3
  4. 4. Advantages of YUV Digital TV in HK • Compatible with black & white analog TV • 31 Dec 2007: Digital Terrestrial Television sets: Transmit Y and ignore U and V. (DTT) • Can easily discard color information • Four major systems: according to the available bandwidth since – ATSC (adv. Tv systems committee): US, .kr, .ca humans are more sensitive to luminance. – DVB-T (digital video broadcasting – terrestrial): EU, .sg, .au, .nz – ISDB-T (integrated services digital broadcasting – terrestrial): JP – GB20600-2006: CN, HK 19 20 What do you need to get DTTV? References 1. Check your coverage • www.digitaltv.gov.hk 2. Check your building • www.hkdtt.tv 3. Set-top box or iDTV • Coverage in HK: – http://www.digitaltv.gov.hk/general/pdf/covera ge.pdf 21 22 Film to Video Transfer Film Squeezing 24 film frames into • Progressive scanning 30 video frames is achieved by • Run as 24 frame/sec. (fps) repeating fields • Film formats: in a 3:2 sequence (AKA – http://www.widescreenmuseum.com/widescree 3:2 pulldown) n/apertures.htm 23 24 4

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