Flexible and scalable combined innovation codebook for use in CELP coder and decoder
In a CELP coder, a combined innovation codebook coding device comprises a pre-quantizer of a first, adaptive-codebook excitation residual, and a CELP innovation-codebook search module responsive to a second excitation residual produced from the first, adaptive-codebook excitation residual. In a CELP decoder, a combined innovation codebook comprises a de-quantizer of pre-quantized coding parameters into a first excitation contribution, and a CELP innovation-codebook structure responsive to CELP innovation-codebook parameters to produce a second excitation contribution.
1. A Code-Excited Linear Prediction (CELP) codebook coding device for encoding sound into first, second, and third sets of encoding parameters, comprising:
at least one processor
a memory coupled to the processor and embodying instructions which cause the processor to implement:
a Linear Prediction (LP) filter for processing an input sound signal and producing a first LP residual;
an adaptive-codebook search module adapted to, in response to the first LP residual, find an adaptive-codebook contribution and produce pitch parameters forming the first set of encoding parameters;
a first subtractor for producing a second, adaptive-codebook excitation residual by subtracting the adaptive-code book contribution from the first LP residual;
a pre-quantizer including a calculator of a transform of the second, adaptive-codebook excitation residual to produce quantized transform coefficients forming the second set of encoding parameters;
a second subtractor for producing a third excitation residual by subtracting an inverse-transformed version of the quantized transform coefficients from the adaptive-codebook contribution; and
a CELP innovation-codebook search module adapted to, in response to the third excitation residual, find an innovation-codebook contribution and produce innovation codebook parameters forming the third set of encoding parameters.
2. A CELP codebook coding device as defined in claim 1 , wherein the transform calculator of the pre-quantizer is a calculator of a Discrete Cosine Transform (DCT) of the second residual to produce DCT coefficients.
3. A CELP codebook coding device as defined in claim 1 , wherein the transform calculator produces transform coefficients, and the pre-quantizer comprises a quantizer of the transform coefficients to produce the quantized transform coefficients.
4. A CELP codebook coding device as defined in claim 3 , wherein the quantizer of the pre-quantizer is an algebraic vector quantizer to produce, in response to the transform coefficients from the transform calculator, algebraic-vector-quantized transform coefficients.
5. A combined innovation codebook coding device as defined in claim 3 , wherein the quantizer encodes transform coefficients related to lower frequencies only, depending on an available bit-budget.
6. A CELP codebook coding device as defined in claim 1 ,
wherein the pre-quantizer comprises a pre-emphasis filter of the second, adaptive-codebook excitation residual to produce a pre-emphasized second residual prior to calculating the transform.
7. A CELP codebook coding device as defined in claim 6 , wherein the pre-emphasis filter emphasizes low frequencies of the second, adaptive-codebook excitation residual.
8. A CELP codebook coding device as defined in claim 6 , comprising a calculator of an inverse transform of the quantized transform coefficients, and a de-emphasis filter of the inverse-transformed coefficients to produce a time-domain contribution forming the inverse-transformed version of the quantized transform coefficients, and wherein the second subtractor subtracts the time-domain contribution from the adaptive-codebook contribution to produce the third residual.
9. A CELP codebook coding device as defined in claim 1 , wherein the CELP innovation-codebook search module is an Algebraic CELP (ACELP) innovation-codebook search module.
10. A CELP codebook coding device as defined in claim 1 , wherein the pre-quantizer quantizes only transform coefficients having an energy exceeding a specified threshold, so that spectral dynamics of the third residual are reduced or maintained within a desired range.
11. A CELP coder comprising the Code-Excited Linear Prediction (CELP) codebook coding device as defined in claim 1 .
12. A Code-Excited Linear Prediction (CELP) codebook decoding device for decoding sound in response to pitch parameters, pre-quantized coding parameters and innovation-codebook parameters, comprising:
at least one processor
a memory coupled to the processor and embodying instructions which cause the processor to implement:
an adaptive codebook structure for producing an adaptive codebook contribution in response to the pitch parameters;
a de-quantizer of the pre-quantized coding parameters into a first innovation excitation contribution, the de-quantizer comprising an inverse transform calculator responsive to the coding parameters;
a CELP innovation-codebook structure responsive to the innovation-codebook parameters to produce a second innovation excitation contribution;
an adder of the adaptive codebook contribution, the first innovation excitation contribution and the second innovation excitation contribution to form a total excitation signal; and
a Linear Prediction (LP) synthesis filter for processing the total excitation signal and producing a synthesis signal representing a synthesis of said sound.
13. A CELP codebook decoding device as defined in claim 12 , wherein the de-quantizer comprises a decoder for de-quantizing the pre-quantized coding parameters.
14. A CELP codebook decoding device as defined in claim 13 , wherein the decoder comprises an Algebraic Vector Quantizer (AVQ) decoder.
15. A CELP codebook decoding device as defined in claim 13 , wherein the inverse transform calculator is responsive to the de-quantized coding parameters.
16. A CELP codebook decoding device as defined in claim 15 , wherein the inverse transform is an inverse Discrete Cosine Transform (DCT).
17. A CELP codebook decoding device as defined in claim 13 , wherein the de-quantizer comprises a de-emphasis filter supplied with the inverse-transformed, de-quantized coding parameters to produce the first innovation excitation contribution.
18. A CELP decoder comprising the Code-Excited Linear Prediction (CELP) codebook decoding device according to claim 12 .
19. A Code-Excited Linear Prediction (CELP) codebook coding method for coding sound into first, second and third sets of encoding parameters, comprising:
producing a first Linear Prediction (LP) residual using a sound signal;
searching an adaptive codebook in response to the first LP residual to find an adaptive-codebook contribution and produce pitch parameters forming the first set of encoding parameters;
producing a second, adaptive-codebook excitation residual by subtracting the adaptive codebook contribution from the first LP residual;
pre-quantizing the second, adaptive-codebook excitation residual, the pre-quantizing comprising calculating a transform of the second, adaptive-codebook excitation residual to produce quantized transform coefficients forming the second set of encoding parameters;
producing a third excitation residual by subtracting an inverse-transformed version of the quantized transform coefficients from the adaptive-codebook contribution; and
searching a CELP innovation-codebook in response to the third excitation residual to find an innovation-codebook contribution and produce innovation codebook parameters forming the third set of encoding parameters.
20. A CELP codebook coding method as defined in claim 19 , wherein the transform is a Discrete Cosine Transform (DCT).
21. A CELP codebook coding method as defined in claim 19 , wherein the pre-quantizing comprises calculating the transform of the second, adaptive-codebook excitation residual to produce transform coefficients, and quantizing the transform coefficients to produce the quantized transform coefficients.
22. A CELP codebook coding method as defined in claim 21 , wherein quantizing the transform coefficients comprises algebraic vector quantizing said transform coefficients.
23. A CELP codebook coding method as defined in claim 21 , wherein quantizing the transform coefficients comprises encoding transform coefficients related to lower frequencies only, depending on an available bit-budget.
24. A CELP codebook coding method as defined in claim 19 , wherein pre-quantizing the second, adaptive-codebook excitation residual comprises pre-emphasis filtering the second, adaptive-codebook excitation residual prior to calculating the transform of the second, adaptive-codebook excitation residual.
25. A CELP codebook coding method as defined in claim 24 , wherein pre-emphasis filtering comprises emphasizing low frequencies of the second, adaptive-codebook excitation residual.
26. A CELP codebook coding method as defined in claim 19 , comprising calculating an inverse transform of the quantized transform coefficients, and de-emphasis filtering the inverse-transformed coefficients to produce a time-domain contribution forming the inverse-transformed version of the quantized transform coefficients, wherein producing the third excitation residual comprises subtracting the time-domain contribution from the adaptive-codebook contribution.
27. A CELP codebook coding method as defined in claim 19 , wherein the CELP innovation-codebook search is an ACELP innovation-codebook search.
28. A CELP codebook coding method as defined in claim 19 , wherein pre-quantizing the second, adaptive-codebook excitation residual comprises pre-quantizing only transform coefficients having an energy exceeding a specified threshold, so that spectral dynamics of the third excitation residual are reduced or maintained within a desired range.
29. A Code-Excited Linear Prediction (CELP) codebook decoding method for decoding sound in response to pitch parameters, pre-quantized coding parameters and innovation-codebook parameters, comprising:
applying the pitch parameters to an adaptive codebook structure for producing an adaptive codebook contribution;
de-quantizing the pre-quantized coding parameters into a first innovation excitation contribution, wherein de-quantizing the pre-quantized coding parameters comprises calculating an inverse transform of the coding parameters; and
applying the innovation-codebook parameters to a CELP innovation-codebook structure to produce a second innovation excitation contribution;
adding the adaptive codebook contribution, the first innovation excitation contribution and the second innovation excitation contribution to form a total excitation signal; and
processing the total excitation signal through a Linear Prediction (LP) synthesis filter to produce a synthesis signal representing a synthesis of said sound.
30. A CELP codebook decoding method as defined in claim 29 , wherein de-quantizing the pre-quantized coding parameters comprises decoding the pre-quantized coding parameters to produce de-quantized coding parameters.
31. A CELP codebook decoding method as defined in claim 30 , wherein decoding the pre-quantized coding parameters comprises Algebraic Vector Quantizer (AVQ) decoding said pre-quantized coding parameters.
32. A CELP codebook decoding method as defined in claim 29 , wherein calculating an inverse transform of the coding parameters comprises calculating the inverse transform of the de-quantized coding parameters.
33. A CELP codebook decoding method as defined in claim 32 , wherein the inverse transform is an inverse Discrete Cosine Transform (DCT).
34. A CELP codebook decoding method as defined in claim 32 , comprising de-emphasis filtering the inverse-transformed, de-quantized coding parameters to produce the first innovation excitation contribution.