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ADVANCED DIGITAL SIGNAL PROCESSING

Dr Mohammad Faiz Liew bin Abdullah

Department of Communication

Faculty of Electrical & Electronic Engineering University Tun Hussien Onn Malaysia

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Contents

What is DSP? What is DSP used for?

Speech & Audio processing Image & Video processing Adaptive filtering

DSP Devices and Architectures Summary & Conclusions

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INTRODUCTION

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What is DSP?

Digital Signal Processing the processing or manipulation of signals using digital techniques

ADC DACDigital Signal

ProcessorAnalogue to Digital Converter

Digital to Analogue Converter

Input Signal

Output Signal

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DSP

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WHY PROCESS SIGNAL?

Signals are corrupted by interference due to noise.

Signals are distorted due to the transmission medium.

Recover information present in the signal. Perform algorithm such as compression.

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HISTORICAL CONTRIBUTORS

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SIGNAL PROCESSING

Signal Processing

Analog Digital

V1(t) V2 (t)

i(t)

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ADVANTAGES & DISADVANTAGES OF DSP

Advantages:

Programmability. Stability.

Repeatability.

Easier implementation of adaptive algorithms.

Disadvantage:

Bandwidth limitation related to the processor cycle and algorithm complexity.

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PROCESSING METHODOLOGY

HARDWARE SOFTWARE

PC

FPGA DSP PROCESSOR

ASIC MICROPROCESSOR MICROCONTROLLER

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What is DSP Used For?

And much more!And much more!

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APPLICATION OF DSP

MULTIMEDIA

COMMUNICATION SPEECH

POWER BIOMEDICAL

OCEONOGRAPHIC SEISMIC APPLICATION DSP

SONAR IMAGE/VIDEO

RADAR AEROSPACE

INDUSTRIAL

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Speech Processing

Speech coding/compression Speech synthesis Speech recognition

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Some Properties of Speech

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

oo in blueo in spotee in keye in agains in spotk in key

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Some Properties of Speech

ee in keyo in spotoo in blue e in again

Vowels

s in spot k in key

Consonants

Quasi-periodic

Relatively high signal power

Non-periodic (random)

Relatively low signal power

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Speech Coding

BTS

BSC

MSC

TRAU

64 kbits/s

13 kbits/s

22.8 kbits/s

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Speech Coding Linear Prediction

A(z)

s(n)+ d(n)

se(n)

d(n)

A(z)

++

se(n)

sr(n)

Try to predict the current sample value; Transmit the prediction error.

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Speech Coding Vocoder

G

Pulse Train

Random Noise

Vocal TractModel

V/U

Synthesized Speech

Decoder

Original Speech

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

Signal PowerPitch

Period

Encoder

LPC-10:

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To be ornot to bethat is thequestion

Textnormalizationexpandsabbreviationsdates, times,money..etc

Parsing Pronunciation

Prosodyrules

Tu bee awrnawt tu beedhat iz dhekwestchun

semantic &syntactic partsof speechanalysis of text

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

Waveformgeneration

Synthesized speech

Apply wordstress, durationand pitch

Phonetic-to-acoustictransformation

phonetic formInputtext

Text-to-Speech Synthesis

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

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Speech Synthesis Applications

Speaking clocks Spoken (variable) announcements Talking emails + talking heads for mobile Synthesis of location-based information

(e.g. traffic information) 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 for a particular persons voice.

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

Speaker Recognition Who has spoken? Not easy

Sometimestherearenogapsbetweenwords.Sometim esthereareg aps inthe mid dleofwords.

Accents, dialects and Stress eggsist.

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Speech Recognition System

Featureextractionspeech

Phoneme recognition

Phonememodels

Sentencerecognition

Wordrecognition

Wordpronunciation

Semanticknowledge

decision

Syntacticknowledge

Dialogueknowledge

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Digital Audio

Standard music CD: Sampling Rate: 44.1 kHz 16-bit samples 2-channel stereo Data transfer rate = 21644,100 = 1.4 Mbits/s 1 hour of music = 1.43,600 = 635 MB

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Audio Coding (Contd)

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

used in DAB, DVD

Dolby AC3, Dolby Digital, Dolby Surround. Typical bit rates for 2-channel stereo:

64kbits/s to 384 kbits/s. Subband- or transform-based, making use

of perceptual masking properties.

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Audio Coding (Contd)

5.1 channels (3/2) with LFE channel: 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.

Typical 3/2 multichannel stereo configuration:Right Surround Right

Surround Left

Centre

Left

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Audio Coding Masking Auditory Masking:

Spectral: Strong frequency components mask weaker neighbouring frequency components.

Temporal: Strong temporal events mask recent and future events.

SPL/dB

10ms 160ms

Temporal Masking

timefreq/kHz1

SPL/dB

Spectral Masking

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200 300 400 500 600 700 80010

20

30

40

50

60

Hz

dB

Masking Example

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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, Interframe and intraframe prediction, Motion estimation.

Applications: Digital TV, DVD, etc.

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JPEG ExampleOriginal

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

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Adaptive Filtering

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

W(z) +x(n)

y(n)e(n)

d(n)

)()(2)()1( nnenn xww +=+

Filter update: Least Mean Squares (LMS) algorithm

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Adaptive Filtering Applications

Echo cancellation (telephone lines) Used in modems (making Internet access possible!!)

Acoustic echo cancellation Hands-free telephony

Adaptive equalization Active noise control Medical signal processing

e.g. foetal heart beat monitoring

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Some Other Application Areas Image analysis, e.g:

Face recognition, 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.); 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) Motorola (http://www.motorola.com) Analog Devices (http://www.analog.com)

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Typical DSP Operations

Filtering Energy of Signal Frequency transforms

==

1

0)()(

L

ii inxany

for (n=0; n

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Traditional DSP Architecture

X RAM Y RAM

Multiply/Accumulate

Accumulator

x(n-i) ai

y(n)

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

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SDC Core Skills

System Integration

System modelling

DSP

Speech Testing

Speech enhancement

Speech synthesis

Speech Recognition

Speech

PerformanceAssessment

MP3

Audio

Channel coding

Baseband processing

Mobile

Computer &

Networking

CAD Tools

Administration

Services

System on Chip (SoC)

Firmware design

AMR Coding

Speech compression

CPU (Oak, ARM)

H/w & S/w Co-design

Other digital audio

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SDC Firmware DevelopmentAlgorithm Definition

Floating-point and

Fixed-pointCo-Simulation

Co-Design

Implementation Co-Verification

COSSAPMatlab ...

Product Development

Behavioural, RTL, Logic ...

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.); RADAR/SONAR; Data transmission and reception; And many more..!!