Transcript Text Encryption - PersonalWebIWayanSW

Video
Table of Content
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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
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
Types of Video signal
• Two types of Video Signal
• Analog video
• Digital video
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.
Types of Analog Video Signal
• Three types of Analog Video Signal:
• Component
• Composite
• S-Video
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 Svideo.
Disadvantages:
Requires more bandwidth and good
synchronization of the three components.
Component Video
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
S-Video
• S-Video = separates into 2 signals :
1. Luminance
2. 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
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
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.
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.
Broadcast and Video Standards
• NTSC
• PAL
• SECAM
• HDTV
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)
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.
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 :
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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
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).
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
Calculate Video File Size (Example 1)
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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
Calculate Video File Size (Example 2)
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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
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.
Video file formats
 MPEG – most popular format
 MOV – the Quicktime format(standard for
Macintosh)
 AVI – the MS- Windows
 RealVideo - streaming
Summary
1. Video is the technology of electronically capturing, processing,
and transmitting a sequence of still images representing scenes
in motion.
2. 2 types of video signal: Analog video, Digital video
3. 3 types of analog video signal: Component, Composite, S-Video
4. Broadcast and video standards: NTSC, PAL, SECAM, HDTV
Summary
5. Video size =
(Time(in sec)*Frame rate*Frame size*Colour resolution(in byte))
+
(Time(in sec)*Frequency(in Hz)*Sound resolution(in byte)*Channel)