Video

1. Video

2. Table of Content • Introduction • Types of video signal • Types of analog video signal • Computer-based digital video • Broadcast and video standards • Characteristics of digital video • Digital video data sizing • Ways to reduce video file size • Video file formats

3. Definition of Video • Video: • Technology of electronically • Capturing / recording (captured media) • Processing / storing • Transmitting a sequence of still images representing scenes in motion. Note: • Animation starts from discrete pictures and then process to illusion of continuous motion. • Discrete pictures  illusion of continuous motion

4. Types of Video signal • Two types of Video Signal • Analog video • Digital video

5. Analog Video Signal • Analog video is transferred by analog signal. • It contains the • luminance (brightness) and • chrominance (colour) of the image. • Most TV still sent and received video as an analog signal.

6. Types of Analog Video Signal • Three types of Analog Video Signal: • Component • Composite • S-Video

7. Component Video • Signals are split into 2 or more components; separates the: • Luminance: brightness (Y) • Chroma: colours (U and v) Advantage: Gives the best colour reproduction, since no “crosstalk” between the three different channels, unlike composite video and S-video. Disadvantages: Requires more bandwidth and good synchronization of the three components. Component Video

8. Composite Video • Composite video = two or more signals are mixed into a single carrier wave. Chroma (colours ) UV and Luminance (Brightness) Y = YUV • Video quality not as good as component video. Composite Video

9. S-Video • S-Video = separates into 2 signals : • Luminance • Chroma • S-Video is also known as Separate Video or Y/C. • Y  Luminance  Brightness • C  Chroma  Colour • The chroma or colour information is always combined into 1 signal. • Video quality better than composite video, worse than component video. S-Video

10. Aspect ratio • Aspect Ratio: ratio of the screen widthto the screen height. The aspect ratio of current television tubes is 4/3. For wide-screen television tubes the aspect ratio is 16/9

11. Digital Video Signal • Digital video is transferred by digital signal. • In most multimedia applications, the video signals need to be in a digital form in order to • store them in the memory of a computer and • to easily edit and integrate them with other media types.

12. Computer-based digital video • Three significant advantages: • It can be copied and reproduced without loss of quality • It can be manipulated easily – repositioned, resized, and recolor by a computer • It is easier to transmit over computer networks. • Three disadvantages: • It requires an enormous amount of computer storage space. • It requires high transfer rates. • Large file sizes and high transfer rates required for quality digital video, so the majority of the digital video currently available has made compromises that produce images lower in quality than those on VHS tapes.

13. Broadcast and Video Standards • NTSC • PAL • SECAM • HDTV

14. Characteristics of digital video • A framesingle image in a video sequence. • The frame is the basic feature of digital video: • height • width • color depth. (color resolution)

15. Characteristics of digital video • Frame rate • the number of images displayed within a specified amount of time to convey a sense of motion. • Frame rate per second.

16. Characteristics of digital video • Frame size • The VGA standard - monitors with resolutions of 640 x 480 pixels. • Need high image storage and processing power so usually frame sizes are less than 640 x 480 pixels. • Common frame sizes : • 640 x 480 for full screen VGA display • 320 x 240 quarter of a VGA display • 240 x 180 about a sixth of a VGA display • 160 x 120 sixteenth of a VGA display

17. Characteristics of digital video • Color depth or resolution • refers to the number of colors displayed on the screen at one time. • 1 bit for 2 colors to 8 bits/pixel (256 colors), 16 bits/pixel (65, 535 colors), and 24 bits/pixel (16.7 million colors).

18. Digital video data sizing • Digital video file size ( in bytes)= F * C * R * T Where • F = frame size (width x height) • C= colour depth (in bytes) • R= frame rate (frames per second) • T= time in seconds

19. Calculate Video File Size (Example 1) • Duration=10 mins • Frame rate=25 fps • Frame size=160 by 120 • Colour resolution=8-bit Video file size=600 sec x 25 fps x 160 x 120 x (8-bit/8) = 288,000,000 bytes = 288 MB

20. Calculate Video File Size (Example 2) • Duration=10 sec • Frame rate=30 fps • Frame size=VGA • Colour resolution=2 bytes • Sampling rate/Frequency=44.1 kHz • Sound resolution=8-bit • Channel=Stereo Video File Size: (10 sec x 30 fps x 640 x 480 x 2 bytes) + (10 sec x 44100 Hz x 8-bit/8 x 2) = 184,320,000 + 882,000 bytes = 185,202,000 bytes

21. Ways to reduce video file size • Reduce the size of the playback window - Internet - 160 x 120 pixels. • Decrease the number of colors, from 16 million to 256 or even 16 colors. • Reduce the frame rate from 30 down to 15 or less frames per second but more jerky. • Compress the file.

22. Video file formats • MPEG – most popular format • MOV – the Quicktime format(standard for Macintosh) • AVI – the MS- Windows • RealVideo - streaming

23. Summary • Video is the technology of electronically capturing, processing, and transmitting a sequence of still images representing scenes in motion. • 2 types of video signal: Analog video, Digital video • 3 types of analog video signal: Component, Composite, S-Video • Broadcast and video standards: NTSC, PAL, SECAM, HDTV

24. Summary • Video size = (Time(in sec)*Frame rate*Frame size*Colour resolution(in byte)) + (Time(in sec)*Frequency(in Hz)*Sound resolution(in byte)*Channel)