AN2094 Freescale Semiconductor / Motorola, AN2094 Datasheet - Page 4

• Manufacturer Part Number: AN2094
• Description: ITU-T G.729 Implementation on StarCore SC140
• Manufacturer: Freescale Semiconductor / Motorola

G.729 Recommendation for Speech Compression
1.2.2 Decoding
The G.729 decoder synthesizes the output speech samples from the received bitstream as show in Figure 3.
First, parameter indices are extracted from the received bitstream and decoded to obtain the parameters
corresponding to a 10 ms speech frame. These parameters include:
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LSP coefficients
Two fractional pitch delays
Two fixed codebook vectors
Two sets of adaptive and fixed codebook gains.
LPC Info
ITU-T G.729 Implementation on the StarCore™ SC140/SC1400 Cores, Rev. 1
Codebook
Codebook
Parameter
Adaptive
Encoding
Fixed
.
Codebook
Codebook
Figure 3. Principle of the CS-ACELP Decoder
Adaptive
Fixed
.
Figure 2. CS-ACELP Encoding
Analysis
.
Pitch
Transmitted
Bitstream
Gc
Gp
Gp
Gc
Quantization
Gain
Speech
Input
Fixed CB
Search
.
Short-term
.
Filter
Preprocessing
Quantization
Interpolation
LP analysis
Synthesis
Perceptual
Weighting
Filter
LPC Info
Processing
Post-
Freescale Semiconductor
Speech Output