1. Video

2. Table of Content Introduction Types of video signal
Types of analog video signal
Computer-based digital video
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
RGB: Red, Green, Blue
YUV: Y  luminance component (brightness / intensity)
U, V  chrominance component (colour)
Crosstalk: Any phenomenon by which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel.

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: separate video or super video
Humans are able to differentiate spatial resolution in greyscale images much better than for the colour part of colour images. Therefore colour information sent can be much less accurate than intensity information
S-Video

10. Aspect ratio
Aspect Ratio: ratio of the screen width to 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. 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)

14. 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.

15. 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

16. 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).

17. 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

18. 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

19. 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 Hz x 8-bit/8 x 2)
= 184,320, ,000 bytes
= 185,202,000 bytes

20. Ways to reduce video file size
Reduce the size of the playback window - Internet 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.

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