Fixed code book with embedded adaptive code book
View Patent ↗A system including an adaptive code book and a fixed code book for code excited linear prediction coding of speech signals is provided. The invention includes an embedded adaptive code book in the fixed code book and the selection procedure for selecting excitation vector parameters. A code book update system updates the fixed code book with embedded adaptive code book based on the long term processing excitation vector parameters with previous synthesized excitation.
1. A system for code excited linear prediction coding of speech signals comprising:
a fixed code book with an embedded adaptive code book that is configurable to select excitation vector parameters, wherein the fixed code book includes both fixed codes and adaptive codes;
an adaptive code book that is configurable to select long term processing excitation vector parameters; and
a code book update system that is configurable to update the fixed code book with the embedded adaptive code book based on the long term processing excitation vector parameters;
wherein the system is configurable to determine whether the long term processing excitation vector parameters from the adaptive code book are suitable for coding of the speech signals, and if suitable, the system is configurable to use the long term processing excitation vector parameters from the adaptive code book for coding of the speech signals, and if not suitable, the system is configurable to use long term processing excitation vector parameters from the fixed code book with the embedded adaptive code book for coding of the speech signals;
wherein adaptive codes of the adaptive codebook have a different pitch lag search range than the adaptive codes of the fixed codebook.
2. The system of claim 1 wherein the code book update system further comprises an embedded adaptive code book interface system that is configurable to receive the long term processing excitation vector parameters from the adaptive code book or from past synthesized excitation.
3. The system of claim 1 wherein the code book update system further comprises an adaptive code book entry monitor that is configurable to determine whether the long term processing excitation vector parameters from the adaptive code book are different from the long term processing excitation vector parameters in the fixed code book with the embedded adaptive code book.
4. The system of claim 1 wherein the code book update system further comprises a fixed code book interface system that is configurable to determine best excitation vector parameters in the embedded adaptive code book.
5. The system of claim 1 wherein the code book update system further comprises a fixed code book update system that is configurable to replace old excitation vector parameters with new ones in the embedded adaptive code book.
6. The system of claim 1 wherein the fixed code book with the embedded adaptive code book further comprises a fixed and adaptive code search system that is configurable to locate the excitation vector parameters in the fixed code book and in the embedded adaptive code book.
7. The system of claim 1 wherein a first code book gain is applied to the fixed codebook with the embedded adaptive code book, and wherein a second code book gain is applied to the adaptive code book.
8. The system of claim 1 wherein the system determines that the long term processing excitation vector parameters from the adaptive code book are not suitable for coding of the speech signals due to a substantial change in spectrum of the speech signal.
9. The system of claim 1 wherein the system determines that the long term processing excitation vector parameters from the adaptive code book are not suitable for coding of the speech signals due to a substantial change in pitch lag of the speech signal.
10. The system of claim 1 wherein the adaptive codes of the adaptive codebook have a limited pitch lag search range compared to the adaptive codes of the fixed codebook.
11. A method for code excited linear prediction coding of speech signals comprising:
searching an adaptive code book for long term processing excitation vector parameters;
searching a fixed code book with an embedded adaptive code book for excitation vector parameters, wherein the fixed code book includes both fixed codes and adaptive codes;
determining whether the long term processing excitation vector parameters from the adaptive code book are suitable for coding of the speech signals;
if suitable, selecting the long term processing excitation vector parameters from the adaptive code book for coding of the speech signals
if not suitable, selecting long term processing excitation vector parameters from the fixed code book with the embedded adaptive code book for coding of the speech signals; and
using the excitation vector parameters and the selected long term processing excitation vector parameters to generate an excitation signal;
wherein adaptive codes of the adaptive codebook have a different pitch tag search range than the adaptive codes of the fixed codebook.
12. The method of claim 11 further comprising updating the fixed code book with the embedded adaptive code book with the long term processing excitation vector parameters from the adaptive code book.
13. The method of claim 11 further comprising:
determining whether an entry in the fixed code book with the embedded adaptive code book is optimal; and
updating the fixed code book with the embedded adaptive code book with the long term processing excitation vector parameters from the adaptive code book.
14. The method of claim 11 wherein searching the fixed code book with the embedded adaptive code book for the excitation vector parameters further comprises using a fixed and adaptive code search system.
15. The method of claim 11 wherein searching the fixed code book with the embedded adaptive code book for the excitation vector parameters further comprises:
determining a previous entry type; and
searching the fixed code book with the embedded adaptive code book based on the previous entry type.
16. The method of claim 11 wherein searching the fixed code book with the embedded adaptive code book for the excitation vector parameters further comprises using a search algorithm that applies different weightings to fixed code book entries and to embedded adaptive code book entries.
17. The method of claim 11 further comprising adjusting a size of the embedded adaptive code book.
18. The method of claim 11 further comprising:
applying a first code book gain to the fixed codebook with the embedded adaptive code book; and
applying a second code book gain to the adaptive code book.
19. The method of claim 11 the determining determines that the long term processing excitation vector parameters from the adaptive code book are not suitable for coding of the speech signals due to a substantial change in spectrum of the speech signal.
20. The method of claim 11 the determining determines that the long term processing excitation vector parameters from the adaptive code book are not suitable for coding of the speech signals due to a substantial change in pitch lag of the speech signal.
21. The method of claim 11 wherein the adaptive codes of the adaptive codebook have a limited pitch lag search range compared to the adaptive codes of the fixed codebook.