analog and digital video
play

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

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),


  1. ANALOG AND DIGITAL VIDEO Henning Schulzrinne Columbia University COMS 6181 - Spring 2015 with material from Mark Handley

  2. 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

  3. 3 Example: DVI connector DRe DGr DD d1 C Dred analog 2 RGB + Hsync video only (no audio)

  4. 4 Example: HDMI connector • fully digital signal • audio • video (similar to DVI) • remote control signals • no closed captioning

  5. 5 Analog TV: CRT conductive coating cathode anode phosphor-coated screen shadow mask howstuffworks.com

  6. 6 TFT LCD

  7. 7 Analog TV scan lines vertical retrace

  8. 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 Mark Handley

  9. 9 Interlacing

  10. 10 Interlacing artifacts motion scene change www.100fps.com

  11. 11 Composite video white black horizontal retrace vertical: 400-500 µ s howstuffworks.com Wikipedia

  12. 12 Color

  13. 13 Color rods cones metamerism: tristimulus values additive Wikipedia TeXample.net

  14. 14 Subtractive color: printing yellow (complement of blue) magenta cyan (complement of green) (complement of red)

  15. 15 Color representation • Luminance (Y) = brightness • Chrominance • RGB (red, green, blue) • basic analog components • YP b P r (Y, B-Y, R-Y) • color space for component video • YUV • YCbCr • digital representation

  16. 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”

Download Presentation
Download Policy: The content available on the website is offered to you 'AS IS' for your personal information and use only. It cannot be commercialized, licensed, or distributed on other websites without prior consent from the author. To download a presentation, simply click this link. If you encounter any difficulties during the download process, it's possible that the publisher has removed the file from their server.

Recommend


More recommend