Concepts of Multimedia Processing and Transmission IT 481, Lecture 3 Dennis McCaughey, Ph.D. 5 February, 2007.

Concepts of Multimedia Concepts of Multimedia Processing and TransmissionProcessing and Transmission

IT 481, Lecture 3Dennis McCaughey, Ph.D.

5 February, 2007

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Signal properties: (a) time-varying analog signal;

(b) sinusoidial frequency components;

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Signal properties: (c) signal bandwidth examples; (d) effect of a limited bandwidth transmission channel.

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Signal Encoder Design: Circuit Components

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Signal Encoder Design: Associated Waveform Set

Analog Signal

Low Pass Filtered Version

Clock

Output from Sample & Hold

Quantizer Output

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Alias Signal Generation Due to Under Sampling

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Example 2.1Example 2.1

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Quantization Procedure: Source of Errors

bits ofnumber where2

2

intervalon quantizati

max nV

q

q

n

dBlog20

Decibelsin Range Dynamic

minmax10 VVD

D

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Quantization Procedure: Noise Polarity

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Example 2.2Example 2.2

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Signal Decoder Design: Circuit Components

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Signal Decoder Design: Associated Waveform Set

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Example character sets to produce unformatted text: the basic ASCII character set

m=1101101

M=1001101

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Supplementary Set of Mosaic Characters

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Example Videotex/ Teletext Characters

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Graphics Principles: Example Screen Format

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(b) some simple object examples; (c) effect of changing position attribute; (d) solid objects.

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AttributesAttributes

Shape: line, circle square, etc. Size Color Shadow Shape can be open or closed 3D through rendering

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Facsimile Machine Principles: (a) Schematic; (b) Digitization format

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Color Derivation Principles: Additive Color Mixing

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Color Derivation Principles: Subtractive Color Mixing

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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

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Television/Computer Monitor Principles: Schematic

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Television/Computer Monitor Principles: Raster-Scan Principles

Progressive Scan

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Television/Computer Monitor Principles: Pixel Format on Each Scan Line

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Raster-Scan Display Architecture

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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

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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

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Screen Resolutions: (a) Visible Lines Per Frame; (b) Digitization Spatial Resolution

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Example 2.3Example 2.3

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Color Image Capture: Schematic

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Color Image Capture: RGB Signal Generation Alternatives

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Example 2.4Example 2.4

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PCM Principles: Signal Encoding and Decoding Schematic

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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

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PCM Principles: Compressor Characteristic

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PCM Principles: Expander Characteristic

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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

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Example 2.5Example 2.5

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Audio/Sound Synthesizer Schematic

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Interlaced Scanning Principles

•NTSC employs interlaced scanning

•Due to bandwidth limitations in the first half of the 20th century

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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

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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)

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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

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Example 2.6Example 2.6

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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

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Baseband Spectrum of Color Television Signals: PAL System

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Sample Positions with 4:2:2 Digitization Format

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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

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Example 2.7Example 2.7

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Sample Positions in 4:2:0 Digitization Format

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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

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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

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HDTV Formats: CIFHDTV Formats: CIF

Quarter CIF: QCIF– Y = 180x144– Cb = Cr = 90x72

Data Rate– 3.375x106X8+2(0.84375x106x8) = 81Mbps

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Multimedia CommunicationsMultimedia CommunicationsStandards and ApplicationsStandards and Applications

Slide: Courtesy, Hung Nguyen

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Sample Positions for SIF and CIF

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Sample Positions for QCIF