ANALOG AND DIGITAL VIDEO Henning Schulzrinne Columbia University - - PowerPoint PPT Presentation

▶
analog and digital video
SMART_READER_LITE
LIVE PREVIEW

ANALOG AND DIGITAL VIDEO Henning Schulzrinne Columbia University - - PowerPoint PPT Presentation

Oct 22, 2023 958 likes •1.13k views

ANALOG AND DIGITAL VIDEO Henning Schulzrinne Columbia University COMS 6181 - Spring 2015 with material from Mark Handley 2 Video & image sources VGA video (computer video output) component video R, G, B + H (horizontal sync),

slide-1
SLIDE 1

ANALOG AND DIGITAL VIDEO

Henning Schulzrinne Columbia University

COMS 6181 - Spring 2015 with material from Mark Handley

slide-2
SLIDE 2

Video & image sources

  • VGA video (computer video output)
  • component video
  • R, G, B + H (horizontal sync), V (vertical sync)
  • Analog video from cameras
  • NTSC or PAL coded color
  • composite or component video
  • Digital images
  • scanners, copiers and fax machines
  • digital cameras
  • Images = still pictures
  • Video = motion pictures

2

slide-3
SLIDE 3

Example: DVI connector

3

analog RGB + Hsync

DD C

DRe d1 DGr Dred 2

video only (no audio)

slide-4
SLIDE 4

Example: HDMI connector

4

  • fully digital signal
  • audio
  • video (similar to DVI)
  • remote control signals
  • no closed captioning
slide-5
SLIDE 5

Analog TV: CRT

5

howstuffworks.com

cathode conductive coating anode phosphor-coated screen shadow mask

slide-6
SLIDE 6

TFT LCD

6

slide-7
SLIDE 7

Analog TV

7

vertical retrace scan lines

slide-8
SLIDE 8

How many frames?

  • Movies use 24 fps
  • Not scanned – just photographs
  • Flicker, with undersampling (stroboscopic) problems
  • dark environment à less sensitivity to flicker
  • TV
  • scanned
  • fairly bright environment
  • à use interlacing to reduce flicker

8

Mark Handley

slide-9
SLIDE 9

Interlacing

9

slide-10
SLIDE 10

Interlacing artifacts

10

www.100fps.com

motion scene change

slide-11
SLIDE 11

Composite video

11

horizontal retrace vertical: 400-500 µs black white

howstuffworks.com Wikipedia

slide-12
SLIDE 12

Color

12

slide-13
SLIDE 13

Color

13

rods cones

Wikipedia TeXample.net

additive metamerism: tristimulus values

slide-14
SLIDE 14

Subtractive color: printing

14

magenta (complement of green) cyan (complement of red) yellow (complement of blue)

slide-15
SLIDE 15

Color representation

  • Luminance (Y) = brightness
  • Chrominance
  • RGB (red, green, blue)
  • basic analog components
  • YPbPr (Y, B-Y, R-Y)
  • color space for component video
  • YUV
  • YCbCr
  • digital representation

15

slide-16
SLIDE 16

Color mapping

  • True color
  • RGB in 8 bits each (common) à 16.7 million colors
  • RGB in 16 bits each à 281 trillion
  • Eye: 10 million colors
  • Indexed color
  • color table
  • 8 bit index à RGB 24 bit
  • approximate using dithering
  • see “web safe colors”

16