ImpulseResponseTarget

Computes the impulse response and target signal required for the adaptive codebook search.

Syntax

IppStatus ippsImpulseResponseTarget_GSMAMR_16s(const Ipp16s* pSrcSpch, const Ipp16s* pSrcWgtLpc1, const Ipp16s* pSrcWgtLpc2, const Ipp16s* pSrcQLpc, const Ipp16s* pSrcSynFltState, const Ipp16s* pSrcWgtFltState, Ipp16s* pDstImpulseResponse, Ipp16s* pDstLpResidual, Ipp16s* pDstAdptTarget);

Parameters

pSrcSpch	Pointer to the 50-element input speech vector, where elements 0 - 9 are from the previous subframe, and elements 10 - 49 are from the current subframe.
pSrcWgtLpc1	Pointer to an eleven-element vector of weighted LP coefficients associated with `A(z/γ₁)` on the current subframe, represented using Q3.12.
pSrcWgtLpc2	Pointer to an eleven-element vector of weighted LP coefficients associated with `A(z/γ₂`) on the current subframe, represented using Q3.12.
pSrcQLpc	Pointer to an eleven-element vector of quantized LP coefficients for the current subframe, represented using Q3.12.
pSrcSynFltState	Pointer to the ten-element vector that contains the state of the synthesis filter, represented using Q15.0.
pSrcWgtFltState	Pointer to the ten-element vector that contains the state of the weighting filter, represented using Q15.0..
pDstImpulseResponse	Pointer to the 40-element vector that contains the impulse response, represented using Q3.12.
pDstLpResidual	Pointer to the 40-element vector that contains the LP residual, represented using Q15.0.
pDstAdptTarget	Pointer to the 40-element vector that contains the LP residual, represented using Q15.0.

Description

The function ippsImpulseResponseTarget_GSMAMR is declared in ippsc.h file. This function computes the impulse response and target signal required for the adaptive codebook search. This function is performed on a subframe basis using the following approach:

The impulse response h( n) of the weighted synthesis filter, H(z)W(z) = A(z/γ₁)/[ Â(z) A(z/γ₂) , is computed by applying the filters 1/Â(z) and 1/A(z/γ₂) to the zero-padded impulse response of the filter A(z/γ₁).
The target signal is then obtained by applying to the LP residual res_LP(n) the cascaded synthesis and weighting filters 1/Â(z) and A(z/γ₁)/A(z/γ₂) , respectively. The adaptive codebook search also uses the residual signal res_LP(n to update the history of past excitations. The LP residual is obtained by inverse filtering the input speech, that is

Return Values

ippStsNoErr	Indicates no error.
IppStsNullPtrErr	Indicates an error when one of the specified pointers is NULL.