LPAS speech coder using vector quantized, multi-codebook, multi-tap pitch predictor
View Patent ↗A method and apparatus for reducing the complexity of linear prediction analysis-by synthesis (LPAS) speech coders. The speech coder includes a multi-tap pitch predictor having various parameters and utilizing an adaptive codebook subdivided into at least a first vector codebook and a second vector codebook. The pitch predictor removes certain redundancies in a subject speech signal and vector quantizes the pitch predictor parameters.
1. A method for performing multi-tap pitch predictor vector quantization, the method comprising:
determining a vector by combining at least a first subvector of a first codebook and a second subvector of a second codebook; and
vector quantizing pitch predictor parameters by applying the vector to the pitch predictor parameters.
2. The method of claim 1 , further comprising:
providing an adaptive codebook; and
dividing the adaptive codebook into the at least first and second codebooks.
3. The method of claim 1 , wherein determining the vector includes sequentially searching the at least first and second codebooks.
4. The method of claim 1 , wherein determining the vector includes considering all possible combinations of the at least first and second subvectors.
5. The method of claim 4 , wherein considering all possible combinations includes searching the at least first and second codebooks in analysis-by-synthesis fashion.
6. The method of claim 1 , wherein the at least first and second codebooks are equal in size.
7. The method of claim 1 , wherein determining the vector includes:
selecting at least a first index of the first codebook in a first stage and a second index of the second codebook in a second stage.
8. The method of claim 7 , further including performing the at least first and second stages sequentially.
9. The method of claim 7 , wherein selecting the indices includes selecting the indices using a perceptually weighted mean square error distortion criterion.
10. A pitch predictor for performing multi-tap pitch predictor vector quantization, comprising:
at least a first codebook, a second codebook, and a vector including at least a first subvector of the first codebook and a second subvector of the second codebook, configured to vector quantize pitch predictor parameters.
11. The pitch predictor of claim 10 , further comprising:
an adaptive codebook, wherein the at least first and second codebooks together form the adaptive codebook.
12. The pitch predictor of claim 10 , further including at least one searching unit to search the at least first and second codebooks in a sequential manner.
13. The pitch predictor of claim 10 , further including at least one searching unit to consider all possible combinations of the at least first and second subvectors.
14. The pitch predictor of claim 13 , wherein the searching unit performs analysis-by-synthesis searching.
15. The pitch predictor of claim 10 , wherein the at least first and second codebooks are equal in size.
16. The pitch predictor of claim 10 , further comprising:
a selection unit to select at least a first index of the first codebook in a first stage and a second index of the second codebook in a second stage.
17. The pitch predictor of claim 16 , wherein the selection unit is configured to select the at least first and second indices in a sequential manner.
18. The pitch predictor of claim 16 , wherein the selection unit is configured to select the at least first and second indices using a perceptually weighted mean square error distortion criterion.
19. A computer readable medium having computer readable program codes embodied therein for performing multi-tap pitch predictor vector quantization, the computer readable medium program codes including instructions that, when executed by a processor, cause the processor to:
determine a vector by combining at least a first subvector of a first codebook and a second subvector of a second codebook; and
vector quantize pitch predictor parameters by applying the vector to the pitch predictor parameters.