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A project seminar

on

performance analysis & implementation of

AMR- WIDEBAND SPEECH CODEC

PERFORMED BY

(1) Kapadia Kunal R. (6229) (2) Desai Chintan B. (6211)

(3) Desai Jaimin B. (6212) (4) Chopra Dhikant R. (6208)

GUIDED BY

(Prof. Ninad S. Bhatt)

(Mr. Vijayendra A. Desai)

ELECTRONICS & COMMUNICATION ENGINEERING DEPARTMENT

OF

C.K.PITHAWALA COLLEGE OF ENGINEERING & TECHNOLOGY,

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Problem statement:To design &implement AMR-WB.

We are going to implement AMR WIDEBAND USINGMATLAB. We have started our work with AMR & VAD. IN our project we will used following ALGORITHM :

I. LPC (LINEAR PREDICTIVE CODING)II. CELP (CODE EXITED LINEAR PREDICTIVE CODING)III. ACELP (ALGEBRIC CODE EXITED LINEAR PREDICTIVE

CODING )

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speech coding is a procedure to represent a digitized speech signal using

as few bits as possible, maintaining at the same time a reasonable level ofspeechquality.

SPEECHCODERS

ccording to bit rate according to coding technique

High bit rate >15kbpsMedium bit rate 5 to 10kbpsLow bit rate 2 to 5kbpsVery low bit rate < 2kbps

Waveform codersParametric codersHybrid coders

Requirements of speech coders

Low bit rateHigh speech qualityRobustness across different speakersRobustness in the presence of channel errorGood performance on non speech signals

Low memory size & low computational complexityLow coding delay

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asic block diagram of speech coding :

FILTER SAMPLERA/D

CONVERTER

SOURCEENCODE

R

CHANNEL

ENCODER

CHANNEL

CHANNELDECODER

SOURCEDECODE

R

D/ACONVETER

FILTER

SPEECH

OUTPUTSPEECH

Limitation of other basic speech coders SORCE CODER & CHANNEL CODER WORK SEPARETELY.

SolutionIN AMR, THIS LIMITATION OVERCOME THE PROBLEM OF SOURCE CODER & CHA

CODER WORKING SIMULTANEOUSLY.

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AMR(ADAPTIVE MULTI RATE ):

AMR is a technique to maintain good voice quality invarious conditions of channel.

It is a technique which increases voice quality andboosted channel error robustness and capacity.

Why AMR is used?

IN CELLULAR COMMUNICATION, quality of voice is mostimportant.It depends on channel condition.Bad channel condition produces many error.TO maintain voice quality in different channel condition AMR

is required.

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BASIC DIAGRAM OF AMR CODECSYSTEM :

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OPERATION OF AMR :

AMR FULL RATE:[BIT RATE22.8kbps]

Total 8 modes of operation From 12.2 kbps to 4.75kbps In worst channel conditio:4.75kbps In best channel condition: 12.2kbps

AMR HALF RATE:[BIT RATE11.4kbps]

Total 6 modes of operation From 7.95 kbps to 4.75kbps In worst channel condition:4.75kb In best channel condition: 7.95kbp

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LINK ADAPTION & IN-BANDSINGALLING: IT CONSISTS OF CHANNEL QUALITY MEASUREMENT & CODEC MODEALGORITHM.

IT ADAPTS BIT PARTITIONING BETWEEN CHANNEL & SPEECH CODING.DEPENDING ON C/I, LINK ADAPTION SELECT THE OPTIMAL CODEC &CHANNEL MODE. C/I

(dB)AMR

MODE(kb/s)

>=8 12.2

>=5

7.95

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VAD (VOICE ACTIVITYDETECTION):IT IS A TECHNIQUE USED IN SPEECH PROCESSING WHEREIN

THE PRESENCE OR ABSENCE OF HUMAN SPEECH IS

DETECTED IN REGION OF AUDIO. Features of VAD:

LINE SPECTRAL FREQUENCIES FULL-BAND ENERGY

LOW-BAND ENERGY(

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FILTERBANK &

COMPUTATION OF SUB

BANDLEVELS

PITCHDETECTION

TONEDETECTION

COMPLEXSIGNAL

ANALYSIS

VADDECESION

S(i)

T_OP[n]

T0,t1

OL-LTPCorrelati

on vector

level[n]

pitch

tone

Complexwarning

Complextimer

VADFLAG

BLOCK DIAGRAM VADALGORITHM:

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A. NOISE REDUCTION, e.g. via spectral subtraction.B. FEATURES OR QUANTITIES ARE CALCULATED FROM A SECTION OF

SIGNAL INPUT.C. DETECT WHETHER SPEECH IS TRANSMITTED OR NOT.

DESIGN OF VAD ALGORITHM:

FILTER BANK: Input signal is divided into frequency band usinga 9 band filter bank.

PITCH DETECTION: IT detects vowel sounds & other periodicsignal.TONE DETECTION: IT detects information tone.COMPLEX SIGNAL ANALYSIS: It detects correlated signals inthe high pass filtered weighted speech domain.

VAD DECESION: After comparing with threshold value it givesVAD output.

OVERVIEW OF VAD BLOCK DIAGRAM:

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WEB SUPPORT:

En.wikipedia.org www.vocal.com www.3gpp.org

REFERENCES:

BOOK SUPPORT

Speech Coding Algorithms Foundation and Evolution ofStandardizatied Coders by Wai C. Chu,A John Wiley &Sons,2003 Wireless Communication Principle and Practice by Theodore S.Rappaport, 2005

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HANK YOU!!!