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HDTV (High Definition Television)

HDTV (High Definition Television). HDTV History. Early 1980’s: Japan created analog HDTV Mid-1980s: US, trying to stay competitive, decided to go digital

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HDTV (High Definition Television)

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  1. HDTV(High Definition Television)

  2. HDTV History • Early 1980’s: • Japan created analog HDTV • Mid-1980s: • US, trying to stay competitive, decided to go digital • Congress gave stations a separate channel for transition to digital broadcast with the goal of all stations using digital broadcasts by 2006.

  3. Currently... • Less than 1% of US homes have HDTV capabilities • Approximately 11% of stations have digital broadcasts

  4. Digital Broadcasts • Digital TV is not necessarily HDTV • FCC only mandates transmission of digital television, not HDTV • Several broadcasters use multicasting instead of transmitting HDTV

  5. Multicasting • By using lower-definition signals, one channel can be split into several channels • Extra channels used for: • information services (datacasting) • music • Internet services

  6. HDTV Standards • 8-VSB (vestigial side band) • US, Canada, South Korea, Taiwan, Argentina • DVB-T (digital video broadcasting-terrestrial) • Europe, Australia • Japan uses a system similar to DVB-T

  7. HDTV Features • Provides up to 60 frames/sec screen writing rate • Uses MPEG-2 data compression • source info data rate is 1.2Gbps • broadcast data rate is 20Mbps • Square pixels 1/4 the size of analog TV’s pixels

  8. High definition studio videotoOver-the-air broadcast form • Two stages of processing needed: • MPEG-2 encoding • 8-VSB modulation

  9. MPEG-2 Encoding • Discrete cosine transform • Run length encoding • Bi-directional motion prediction • Multiplexes compressed video information together with pre-coded Dolby AC-3 audio

  10. 8-VSB Source: www.broadcast.harris.com/customer-service/8-vsb.html

  11. HDTV Types • HDTV or Digital-ready TV • 16:9 aspect ratio (width:height) • Displays: • 720-line progressive scan signal OR • 1080-line interlaced signal

  12. Interlaced • TV camera captures an image of 480 lines every 1/60th of a second • Allocated broadcast spectrum isn’t wide enough, so signal is compressed by discarding 1/2 of the lines • Transmits at 30 frames/sec with 2 fields/frame • Fields alternate every other resolution line

  13. Progressive • Lines of picture transmitted consecutively one line after another rather than 2 overlapping fields • Like computer monitor

  14. Digital Cable • Conventional cable broadcasts analog signal • Digital cable broadcasts digital signal to provide higher quality picture/sound • Digital cable is incompatible with digital signal used for HDTV • HDTV signal received through satellite dish, conventional cable, or antenna

  15. Future of Digital TV • May 2002: All commercial stations must begin digital broadcasts • May 2003: All stations (commercial & non-commercial) must begin digital broadcast • May 2006: Analog TV signals completely eliminated

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