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Concepts of Multimedia Concepts of Multimedia Processing and TransmissionProcessing and Transmission
IT 481, Lecture 3Dennis McCaughey, Ph.D.
5 February, 2007
01/23/2006Dennis McCaughey, IT 481, Spring 20072
Signal properties: (a) time-varying analog signal;
(b) sinusoidial frequency components;
01/23/2006Dennis McCaughey, IT 481, Spring 20073
Signal properties: (c) signal bandwidth examples; (d) effect of a limited bandwidth transmission channel.
01/23/2006Dennis McCaughey, IT 481, Spring 20075
Signal Encoder Design: Associated Waveform Set
Analog Signal
Low Pass Filtered Version
Clock
Output from Sample & Hold
Quantizer Output
01/23/2006Dennis McCaughey, IT 481, Spring 20078
Quantization Procedure: Source of Errors
bits ofnumber where2
2
intervalon quantizati
max nV
q
q
n
dBlog20
Decibelsin Range Dynamic
minmax10 VVD
D
01/23/2006Dennis McCaughey, IT 481, Spring 200713
Example character sets to produce unformatted text: the basic ASCII character set
m=1101101
M=1001101
01/23/2006Dennis McCaughey, IT 481, Spring 200717
(b) some simple object examples; (c) effect of changing position attribute; (d) solid objects.
01/23/2006Dennis McCaughey, IT 481, Spring 200718
AttributesAttributes
Shape: line, circle square, etc. Size Color Shadow Shape can be open or closed 3D through rendering
01/23/2006Dennis McCaughey, IT 481, Spring 200719
Facsimile Machine Principles: (a) Schematic; (b) Digitization format
01/23/2006Dennis McCaughey, IT 481, Spring 200720
Color Derivation Principles: Additive Color Mixing
01/23/2006Dennis McCaughey, IT 481, Spring 200721
Color Derivation Principles: Subtractive Color Mixing
01/23/2006Dennis McCaughey, IT 481, Spring 200722
Color principlesColor principles
Gamut: Range of colors produced by combinations of the three primaries
Additive Color Mixing– Black is produced when all three primaries are
zero– Display applications
Subtractive Color Mixing– White is produced when all three primaries are
missing– Printing applications
01/23/2006Dennis McCaughey, IT 481, Spring 200724
Television/Computer Monitor Principles: Raster-Scan Principles
Progressive Scan
01/23/2006Dennis McCaughey, IT 481, Spring 200725
Television/Computer Monitor Principles: Pixel Format on Each Scan Line
01/23/2006Dennis McCaughey, IT 481, Spring 200727
Some ParametersSome Parameters
Phosphor Triad: Primary colors used– Different for NTSC and PAL
Typical spot size: 0.025 in Flicker: if the frame rate is too low
– NTSC: 60 fields/sec => 30 frames/sec– PAL 50 frames/sec
01/23/2006Dennis McCaughey, IT 481, Spring 200728
Example Display Resolutions and Memory
Standard Resolution Number of Colors
Memory Required/Frame
(Bytes)
VGA 640x480x8 256 307.2kB
XGA640x480x161024x768x8
64K256
614.4kB786.432kB
SVGA800x600x161024x768x8
1024x768x24
64K25616M
960kB786.432kb
2359.296kB
01/23/2006Dennis McCaughey, IT 481, Spring 200729
Screen Resolutions: (a) Visible Lines Per Frame; (b) Digitization Spatial Resolution
01/23/2006Dennis McCaughey, IT 481, Spring 200732
Color Image Capture: RGB Signal Generation Alternatives
01/23/2006Dennis McCaughey, IT 481, Spring 200734
PCM Principles: Signal Encoding and Decoding Schematic
01/23/2006Dennis McCaughey, IT 481, Spring 200735
PCM Principles: CompandingPCM Principles: Companding
International Standard: – ITU-T Recommendation G.711
Companding employs a non-linear or un-equal set of quantization steps– Linear quantization produces quantization noise
that is independent of signal level– Ear is more sensitive to noise on quiet signals
than on– Finer quantization at lower levels provides an
increased signal quality, especially 8-Bit PCM
01/23/2006Dennis McCaughey, IT 481, Spring 200738
CD-Quality AudioCD-Quality Audio
Music Bandwidth = 15Hz-20KHz– Minimum sampling rate=20ksps– Actual sampling rate = 44.1ksps– 16bis/sample– Total Bit rate = 44.1x103x16 1.411Mbps– Stereo means that the total bit rate is 2.822Mbps
Much greater than the 64kbps of a PCM telephone channel and twice that of a T1 at1.54Mbps
01/23/2006Dennis McCaughey, IT 481, Spring 200741
Interlaced Scanning Principles
•NTSC employs interlaced scanning
•Due to bandwidth limitations in the first half of the 20th century
01/23/2006Dennis McCaughey, IT 481, Spring 200742
Color Source PropertiesColor Source Properties
Brightness– The amount of energy that hits the eye
Hue– The actual Color of the source
Saturation– Vividness of the color– Pastels have a lower saturation. e.g. pink has a
lower saturation level than red Television transmission does not employ an
RGB color space
01/23/2006Dennis McCaughey, IT 481, Spring 200743
Luminance and ChrominanceLuminance and Chrominance
To transmit RGB requires three times the bandwidth of a Black & White video
Transform the RGB to a Luminance-Chrominance color space as most of the bandwidth is in the Luminance plane– Driven by limited bandwidth available– A B&W TV can receive and display directly on a color
composite video signal broadcast– Very Clever
Two Analog Luminance-Chrominance color spaces– NTSC (YIQ)– PAL (YUV)– Computer (YCbCr) (digital)
01/23/2006Dennis McCaughey, IT 481, Spring 200744
Color TransformationsColor Transformations
YBYRQ
YBYRI
BGRY
NTSC
YRV
YBU
BGRY
PAL
41.048.0
27.074.0
114.0587.0299.0
:
877.0
493.0
114.0587.0299.0
:
Transformations are different as the PAL & NTSC primaries are not the same
01/23/2006Dennis McCaughey, IT 481, Spring 200746
Baseband Spectrum of Color Television Signals: NTSC System
In NTSC, theeye is more sensitive to I than Q, hence more bandwidth
I & Q are modulated in quadrature to occupy the same spectrum
01/23/2006Dennis McCaughey, IT 481, Spring 200747
Baseband Spectrum of Color Television Signals: PAL System
01/23/2006Dennis McCaughey, IT 481, Spring 200749
CCIR-601CCIR-601
4:2:2 is the original digitization format used in CCIR-601
RGB bandwidths each up to 6MHz Sampling Rates
– Minimum of 12Msps for Y and 6Msps for Cb and Cr
– 13.5Msps for Y and 6.75Msps for Cb and Cr
13.5Msps is the nearest 12Msps resulting in a whole number of samples/line
– 625 line system 62microsec sweep - 12 microsec blank (62-12)x106x13.5x106=702 samples/line
01/23/2006Dennis McCaughey, IT 481, Spring 200752
HDTV Formats: SIFHDTV Formats: SIF
Source Intermediate Format: SIF Source quality comparable to VCRs Resolutions
– 525-line system: Y = 360x240 Cb=Cr = 180x120
– 625-Line system: Y = 360x288 Cb=Cr = 180x114
Worst case bit rate– 6.75x106X8+2(1.6875x106x8) = 81Mbps
01/23/2006Dennis McCaughey, IT 481, Spring 200753
HDTV Formats: CIFHDTV Formats: CIF
Common Intermediate Format: CIF– Y = 360x288– Cb = Cr = 180x144– Progressive Scan– 30 Hz
4CIF– Y = 720x576– Cb = Cr = 360x288
16CIF– Y = 1440x1152– Cb = Cr = 720x576
01/23/2006Dennis McCaughey, IT 481, Spring 200754
HDTV Formats: CIFHDTV Formats: CIF
Quarter CIF: QCIF– Y = 180x144– Cb = Cr = 90x72
Data Rate– 3.375x106X8+2(0.84375x106x8) = 81Mbps
01/23/2006Dennis McCaughey, IT 481, Spring 200755
Multimedia CommunicationsMultimedia CommunicationsStandards and ApplicationsStandards and Applications
Slide: Courtesy, Hung Nguyen