Table of Contents
EVRC for CDMA Systems
What is EVRC?
Where does EVRC fit in?
Bit Allocation in EVRC vs. VSELP
Performance with Sub-optimal Signals
General Description of EVRC
Bit Allocations by Packet Type
High-level Block Diagram
Codec Profile
Encoding at Rates 1/2 &1
Encoding at Rate 1/8
Encoding Profilefor Rate 1/8, 1/2, & 1
Presentation Outline
MODEL PARAMETERS ESTIMATION
Overview
Formant Filter Parameter Calculation
LINE SPECTRAL PAIRS(LSP)
Features and Comparison
Simulations On LSP
Observations
Voiced CASE
Unvoiced Signal
Band-pass signal
Perturbing LPC
Resolution Limit
Generation of Short-Term Prediction Residual
LSP INTERPOLATION
LSP to LPC Conversion
Generation of Residual
Quantization of LSP Parameters
LSP Parameter Splits Encoding at Rate 1
LSP Parameter Splits Encoding at Rate 1/2
LSP Parameter Splits Encoding at Rate 1/8
Typical Codebook
Computation of Weight
Error Matrix Computation
Adjustment of Quantization Error
Quantization Search
Generation of Quantized LSP
Fixed Codebook Excitation(Andrej Stefanov)
Outline
What type of codebook does the standard use ?
The Gain-Shape approach
Sparse codebook
How does the fixed codebook interact with the rest
of the standard ?
How is the excitation determined ?
Description of the rate 1/2 codebook
Description of the Rate 1 codebook
Decoder & Post-filtering - Maya Tampi
High-level Block Diagram
Packet Formatting (contd.)
Codebooks for different rates
Packet formatting (contd.)
A HIGH LEVEL BLOCK DIAGRAM OF THE DECODER
Frame Error Detection
Rate 1 &1/2 Decoding
Rate 1 and 1/2 subframe decoding
Rate 1/8 Decoding
Structure of FGIDX(m)
Rate 1/8 Subframe Decoding
Adaptive Postfilter
Block Diagram of the Adaptive Postfilter
Adaptive Postfilters (contd.)
Tilt Compensation Filter
Tilted Speech and Synthesized Speech
Short - term Residual Filter
Long term Postfilter
Short term Postfilter & Gain Normalization
Postfiltered Speech
Simulation Results
Performance of the Coder under different Transmission
conditions
Noise Suppression
Rate Determination
Formant Filter Parameter Calculation
Fixed Codebook Search
High Level Block Diagram of RCELP Decoder |
Author: Russell
Henning, Hsu Shu Hsin, Andrej Stefanov, Maya Tampi
Home Page: http://www.eas.asu.edu/~spanias/e598_s98/cdma/e598_s98_cdma.html
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