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5/17/2012 1 Digital Signal Processing: Digital Signal Processing: An Introduction and Some Examples of its Everyday Use Dr D. H. Crawford EPSON Scotland Design Centre Contents What is DSP? What is DSP used for? What is DSP used for? – Speech & Audio processing – Image & Video processing – Adaptive filtering DSP Devices and Architectures Slide 2 DSP at EPSON Scotland Design Centre Summary & Conclusions
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Page 1: Digital Signal Processing:Digital Signal Processingfeihu.eng.ua.edu/NSF_TUES/w7_1.pdf · Digital Signal Processing:Digital Signal Processing: ... – Speech & Audio processing –

5/17/2012

1

Digital Signal Processing:Digital Signal Processing:An Introduction and Some Examples of its

Everyday Use

Dr D. H. Crawford

EPSON Scotland Design Centre

Contents

• What is DSP?

• What is DSP used for?What is DSP used for?– Speech & Audio processing

– Image & Video processing

– Adaptive filtering

• DSP Devices and Architectures

Slide 2

• DSP at EPSON Scotland Design Centre

• Summary & Conclusions

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What is DSP?

• Digital Signal Processing – the processing or manipulation of signals using digital p g g gtechniques

ADC DACDigital Signal

ProcessorA l Di it l t

Input Signal

Output Signal

Slide 3

ProcessorAnalogue to Digital Converter

Digital to Analogue Converter

What is DSP Used For?

Slide 4

…And much more!…And much more!

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Speech Processing

• Speech coding/compression

Slide 5

• Speech synthesis

• Speech recognition

Some Properties of Speech

The blue--- s---p--o---------t i-s--on--the-- k--ey a---g--ai----n------

Slide 6

“oo” in “blue”“o” in “spot”“ee” in “key”“e” in “again”“s” in “spot”“k” in “key”

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Some Properties of Speech

Vowels

“ee” in “key”“o” in “spot”“oo” in “blue” “e” in “again”

Consonants

•Quasi-periodic

•Relatively high signal power

Slide 7

“s” in “spot” “k” in “key”

•Non-periodic (random)

•Relatively low signal power

Speech Coding

TRAU

BSC

MSC64 kbits/s

13 kbi /

22.8 kbits/s

Slide 8

BTS

13 kbits/s

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Speech Coding – Linear Prediction

• Try to predict the current sample value;

• Transmit the prediction error.

A(z)

s(n)+

– d(n)

se(n)… d(n)

A(z)

++

se(n)

sr(n)

Transmit the prediction error.

Slide 9

e( )

Speech Coding – Vocoder

Original Speech

Analysis:

Encoder

Pulse Train V/U

Decoder

Analysis:• Voiced/Unvoiced decision• Pitch Period (voiced only)• Signal power (Gain)

Signal PowerPitch

Period

Slide 10

G

Pulse Train

Random Noise

Vocal TractModel

V/U

Synthesized SpeechLPC-10:

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To be ornot to bethat is thequestion

Tu bee awrnawt tu beedhat iz dhekwestchun

phonetic formInputtext

Text-to-Speech Synthesis

Textnormalization

expandsabbreviationsdates, times,money..etc

Parsing Pronunciation

kwestchun

semantic &syntactic ‘partsof speech’ analysis of text

phonetic descriptionof each word, dictionarywith letter-to-sound rules as a back up

Slide 11

Prosodyrules

Waveformgeneration

Synthesized speech

Apply wordstress, durationand pitch

Phonetic-to-acoustictransformation

Text-to-speech synthesis sounds very natural these days.

Speech Synthesis Applications

• Speaking clocks

S k ( i bl ) t• Spoken (variable) announcements

• Talking emails + talking heads for mobile

• Synthesis of location-based information (e.g. traffic information)

• Interactive systems (e g catalogue ordering

Slide 12

• Interactive systems (e.g. catalogue ordering, Yellow Pages, ...)

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Speech/Speaker Recognition• Speech Recognition – What has been spoken?

– Speaker dependent – Recognition system trained f ti l ’ ifor a particular person’s voice.

– Speaker independent – Recognition system expected to deal with a wide variety of speakers.

• Speaker Recognition – Who has spoken?

• Not easy…

Slide 13

ySometimestherearenogapsbetweenwords.Sometim esthereareg aps inthe mid dleofwords.

Accents, dialects and Stress eggsist.

Speech Recognition System

Featureextractionspeech Phoneme

recognition

Phonememodels

Sentencerecognition

Wordrecognition

Wordpronunciation

Semanticknowledge

decision

Dialogue

Slide 14

Syntacticknowledge

Dialogueknowledge

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Digital Audio

• Standard music CD:• Standard music CD:– Sampling Rate: 44.1 kHz

– 16-bit samples

– 2-channel stereo

– Data transfer rate = 21644,100 = 1.4 Mbits/s

Slide 15

– 1 hour of music = 1.43,600 = 635 MB

Audio Coding (Cont’d)

• Key standards:– MPEG: Layers I, II, and III (MP3); AAC.y , , ( );

• used in DAB, DVD

– Dolby AC3, Dolby Digital, Dolby Surround.

• Typical bit rates for 2-channel stereo:– 64kbits/s to 384 kbits/s.

Slide 16

• Subband- or transform-based, making use of perceptual masking properties.

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Audio Coding (Cont’d)• Typical 3/2 multichannel stereo configuration:

RightSurround

Right

• 5.1 channels (3/2) with LFE channel:Left Right Centre

Surround Left

Centre

Left

Slide 17

– Left, Right, Centre,– Left Surround, Right Surround,– Low Frequency Effects (LFE) (Reduced Bandwidth).

• LFE loudspeaker can, in general, be placed anywhere in the listening room.

Audio Coding – Masking

• Auditory Masking:– Spectral: Strong frequency components mask weaker

neighbo ring freq enc componentsneighbouring frequency components.

– Temporal: Strong temporal events mask recent and future events.

SPL/dB

Temporal Masking

SPL/dB

Spectral Masking

Slide 18

10ms 160ms timefreq/kHz1

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Masking Example

30

40

50

60

dB

Slide 19

200 300 400 500 600 700 800

10

20

Hz

Image/Video

• Still Image Coding:– JPEG (Joint Photographic Experts Group):

• Discrete Cosine Transform (DCT) based

– JPEG2000: Wavelet Transform based

• Video Coding:– MPEG (Moving Pictures Experts Group):

• DCT-based,

I t f d i t f di ti

Slide 20

• Interframe and intraframe prediction,

• Motion estimation.

– Applications: Digital TV, DVD, etc.

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JPEG ExampleOriginal

JPEG (100:1)JPEG (4:1)

Slide 21

Adaptive Filtering

• Self-learning: Filter coefficients adapt in response to training signal.

W(z) +

–x(n)y(n)

e(n)

d(n)

Slide 22

)()(2)()1( nnenn xww

• Filter update: Least Mean Squares (LMS) algorithm

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Adaptive Filtering Applications

• Echo cancellation (telephone lines)U d i d ( ki I t t ibl !!)– Used in modems (making Internet access possible!!)

• Acoustic echo cancellation– Hands-free telephony

• Adaptive equalization

• Active noise control

Slide 23

• Medical signal processing– e.g. foetal heart beat monitoring

Some Other Application Areas

• Image analysis, e.g:– Face recognition,

O ti l Ch t R iti (OCR)– Optical Character Recognition (OCR);

• Restoration of old image, video, and audio signals;• Analysis of RADAR data;• Analysis of SONAR data;• Data transmission (modems, radio, echo

cancellation channel equalization etc );

Slide 24

cancellation, channel equalization, etc.);• Storage and archiving;• Control of electric motors.

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DSP Devices & Architectures

• Selecting a DSP – several choices:– Fixed-point;

– Floating point;

– Application-specific devices(e.g. FFT processors, speech recognizers,etc.).

• Main DSP Manufacturers:– Texas Instruments (http://www.ti.com)

M l (h // l )

Slide 25

– Motorola (http://www.motorola.com)

– Analog Devices (http://www.analog.com)

Typical DSP Operations

• Filtering

• Energy of Signal

1

0

)()(L

ii inxany

• Frequency transforms 0i

for (n=0; n<N; n++){s=0;for (i=0; i<L; i++)

Pseudo C code

Slide 26

( ; ; ){s += a[i] * x[n-i];

}y[n] = s;

}

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Traditional DSP Architecture

X RAM Y RAMx(n-i) ai

Multiply/Accumulate

Accumulator

x(n i) i

Slide 27

y(n)

N.B. Most modern DSPs have more advanced features.

DSP at EPSON

EPSON S tl d D i C t d l

“Energy-saving Firmware”

Slide 28

EPSON Scotland Design Centre develops a broad range of technologies to minimize power consumption and maximize cost

effectiveness in mobile DSP applications.

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SDC Core Skills

System modelling

DSP Speech

MP3

Audio

Baseband processing

Mobile

Administration

Services

Speech compression

System Integration

Speech Testing

Speech enhancement

Speech synthesis

Speech Recognition

PerformanceAssessment

MP3

Channel coding

Computer &

Networking

CAD Tools

Administration

Firmware design

AMR Coding

CPU (Oak, ARM)

H/w & S/w Co-design

Other digital audio

Slide 29

System on Chip (SoC)

SDC Firmware Development

Algorithm Definition

Fl ti i tFloating-point and

Fixed-pointCo-Simulation

Co-Design

COSSAPMatlab ...

Behavioural, RTL, Logic ...

Slide 30

Implementation Co-Verification

Product Development With Barcelona and TokyoDesign Centres

MCU, DSP ...

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Summary & Conclusions

• DSP used in a wide range of everyday applications

• Looked at:– Speech coding; Speech synthesis & recognition;

– Image/Video;

– Adaptive filtering.

• Other areas include:– Image analysis (e.g. face recognition, OCR, etc.);

Slide 31

– RADAR/SONAR;

– Data transmission and reception;

– And many more…..!!