Table of Contents
SBC/ADPCM
Introduction
Three classes of Acoustic Signals
Wideband Speech Coding
Improvements of Wideband Speech over Telephone
Speech
Outline
Applications
SB-ADPCM Block Diagram
Transmit audio part - Functional Description
Receive audio part - Functional Description
Quadrature Mirror Filters - Functional Description
PPT Slide
Basic possible modes of operation
LSB uses embedded encoding
PPT Slide
Performance of the Inverse Adaptive Quantizer
PPT Slide
Reported Mean Opinion Score (MOS)
Simulated Sound files
Profile of G.722 SBC/ADPCM
Profile of Encoder and Decoder
Lower Sub Band encoder - profile
Lower Sub Band encoder - profile Basic overview
Higher Sub Band encoder - profile
Lower Sub Band decoder - profile
Higher Sub Band decoder - profile
Real-time implementation considerations
Outline for QMF
Encoder block diagram of SBC-ADPCM
Decoder block diagram of SBC-ADPCM
QMF-Description
QMF-theory block diagram
QMF-theory - sub-band filters spectra
Motivation
Simulation - noise on different sub-bands
QMF - Transmitter- the filter given in the standards
QMF Transmitter- low pass filter
QMF coefficients
QMF transmitter- higher sub-band filter H1
QMF transmitter- higher sub-band filter H1
Frequency responses of the QMF filters
QMF transmitter output computation
What does it mean computationwise?
QMF Transmitter- how to match theory with equations
Explanation of the transmitter equations
Explanation of the transmitter equations-cont..
Explanation of the transmitter equations-cont.
Mutiplexer (MUX)
Demultiplexer
Receiver - output computation
What does it mean ?
Explanation of equation from theory
Steps to obtain the receiver’s equations:
Explanation of equation from theory
Explanation of equation from theory Fitting input
variable in theoretical equation
Explanation of equation from theory Transforming
equation into time domain
Explanation of equation from theory Transforming
equation into time domain
Explanation of equation from theory Relating rl’
and rh’ with rl and rh
Explanation of equation from theory separating
odd and even, introducing rl and rh
QMF receiver - Explanation from Theory
Receiver- Theory
Summary of QMF receiver filters
Explanation of equation from theory replacing filter
coefficients
Explanation of equation from theory replacing filter
coefficients and simplify
Explanation of equation from theory replacing filter
coefficients and simplify
Explanation of equation from theory replacing filter
coefficients and simplify
Perfect Reconstruction ?
Simulations
Plot for male voice in time domain
Plot for male voice in frequency domain
ADAPTIVE QUANTIZER
OUTLINE
INTRODUCTION
Functional Description
Variables
LOWER SUB-BAND
HIGHER SUB-BAND
Decision Levels and Output Codes
Decision Levels and Output Codes
Calculations
Calculations
Quantizer Adaptation Algorithm
Encoder Details
BLOCK 1L
QUANTL INPUT/OUTPUT
WD and MIL
BLOCK 3L
LOGSCL
DELAYA
SCALEL
DELAYL
LSB Encoder Normal Operation
LSB Encoder Normal Operation
LSB Encoder with DELT fixed at reset value of 32.
LSB Encoder with DELT fixed at a very high number
LSB Encoder with Adaptive Predictor output fixed
at zero
INTRODUCTION
OUTLINE
PREDICTOR
BASIC IDEA
ADPCM-DELAY REPLACED BY PREDICTOR BLOCK
PREDICTION IN DPCM
DELAYA
PARREC
RECONS
UPZERO
PPT Slide
UPPOL1
FILTEZ
FILTEP
Why pole order = 2 and zero order = 6 ?
PARAMETERS WHICH EFFECT ADAPTIVE PREDICTOR
GRADIENT ALGORITHM VS KALMAN ALGORITHM
INPUT SPEECH
LMS ALGORITHM FOR ADAPTIVE PREDICTION IN ADPCM
THE PREDICTOR
Stability Condition
Gradient Algorithm
The LMS Algorithm
SIGN LMS
Simulations for different gains
Log scaling Tandeming and distortion
More detail ...
u - law scaling
Shortened u-law scale table
u - law Transform
Tandeming
Tandeming Sound Files
Sound Files
Tandeming Plot (48kbps)
Perceptual Quality
Backward Adaption Distortion
Algorithm
Algorithm
Sound Files |