HDTV (High Definition Television)

1
HDTV(High Definition Television)
2
HDTV History

• Early 1980s
• 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 TVs 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
• 169 aspect ratio (widthheight)
• 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 isnt 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