AN2261 Freescale Semiconductor / Motorola, AN2261 Datasheet - Page 6

• Manufacturer Part Number: AN2261
• Description: ITU-T G.729AB Implementation on the StarCore SC140 Core
• Manufacturer: Freescale Semiconductor / Motorola

Implementation Process
2.1.2 Modifying the Channel Data
2.1.3 Adding the Annex B-Defined Tables
2.1.4 Verifying Bit Exactness Using Test Vectors
6
2
These test vectors are described in [5].
The modified channel data consists of global data used by both the encoder and decoder of the speech
codec to perform the following tasks:
• Decode the SID information
• Make the DTX decision
• Make the VAD decision
• Generate the comfort noise (CNG algorithm)
The changed functions necessitated additions of data to the global data for Linear Prediction Coding
(LPC), Linear Spectral Pair (LSP), and LSP quantization.
Table 6 presents the changes for some data tables from ITU-T G.729A required to integrate the ITU-T
G.729 Annex B Recommendation.
ITU provides a set of test vectors to verify the bit exactness of the encoder and decoder in the G.729AB
vocoder (see Table 7). Other internal Motorola test vectors are also used. In addition, the ITU test vectors
for the ITU-T G.729A optimized implementation maintain the bit exactness of the ITU-T G.729A
Recommendation when the VAD is disabled.
Word32 lag[]
Word16 table2[]
Word16 slope[]
Word16 freq_prev_reset[]
Encoder Input
Tstseq1.bin
Tstseq2.bin
Tstseq3.bin
Tstseq4.bin
Table Name
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
Table 7. ITU-T G.729AB Test Vectors
Table 6. Data Table Modifications
Two values added (8 bytes added)
Doubled size, thus removing the optimization from ITU-T G.729A
optimized implementation (64 bytes added)
Doubled size, thus removing the optimization from ITU-T G.729A
optimized implementation (64 bytes added)
New table (20 bytes added)
Encoder Output
Decoder Input
Tstseq1.bit
Tstseq2.bit
Tstseq3.bit
Tstseq4.bit
Tstseq5.bit
Tstseq6.bit
2
Comment
Decoder Output
Tstseq1.out
Tstseq2.out
Tstseq3.out
Tstseq4.out
Tstseq5.out
Tstseq6.out