arm_biquad_cascade_df1_fast_q31.c
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r41 | /* ---------------------------------------------------------------------- | ||
* Copyright (C) 2010 ARM Limited. All rights reserved. | ||||
* | ||||
* $Date: 15. July 2011 | ||||
* $Revision: V1.0.10 | ||||
* | ||||
* Project: CMSIS DSP Library | ||||
* Title: arm_biquad_cascade_df1_fast_q31.c | ||||
* | ||||
* Description: Processing function for the | ||||
* Q31 Fast Biquad cascade DirectFormI(DF1) filter. | ||||
* | ||||
* Target Processor: Cortex-M4/Cortex-M3 | ||||
* | ||||
* Version 1.0.10 2011/7/15 | ||||
* Big Endian support added and Merged M0 and M3/M4 Source code. | ||||
* | ||||
* Version 1.0.3 2010/11/29 | ||||
* Re-organized the CMSIS folders and updated documentation. | ||||
* | ||||
* Version 1.0.2 2010/11/11 | ||||
* Documentation updated. | ||||
* | ||||
* Version 1.0.1 2010/10/05 | ||||
* Production release and review comments incorporated. | ||||
* | ||||
* Version 1.0.0 2010/09/20 | ||||
* Production release and review comments incorporated. | ||||
* | ||||
* Version 0.0.9 2010/08/27 | ||||
* Initial version | ||||
* | ||||
* -------------------------------------------------------------------- */ | ||||
#include "arm_math.h" | ||||
/** | ||||
* @ingroup groupFilters | ||||
*/ | ||||
/** | ||||
* @addtogroup BiquadCascadeDF1 | ||||
* @{ | ||||
*/ | ||||
/** | ||||
* @details | ||||
* | ||||
* @param[in] *S points to an instance of the Q31 Biquad cascade structure. | ||||
* @param[in] *pSrc points to the block of input data. | ||||
* @param[out] *pDst points to the block of output data. | ||||
* @param[in] blockSize number of samples to process per call. | ||||
* @return none. | ||||
* | ||||
* <b>Scaling and Overflow Behavior:</b> | ||||
* \par | ||||
* This function is optimized for speed at the expense of fixed-point precision and overflow protection. | ||||
* The result of each 1.31 x 1.31 multiplication is truncated to 2.30 format. | ||||
* These intermediate results are added to a 2.30 accumulator. | ||||
* Finally, the accumulator is saturated and converted to a 1.31 result. | ||||
* The fast version has the same overflow behavior as the standard version and provides less precision since it discards the low 32 bits of each multiplication result. | ||||
* In order to avoid overflows completely the input signal must be scaled down by two bits and lie in the range [-0.25 +0.25). Use the intialization function | ||||
* arm_biquad_cascade_df1_init_q31() to initialize filter structure. | ||||
* | ||||
* \par | ||||
* Refer to the function <code>arm_biquad_cascade_df1_q31()</code> for a slower implementation of this function which uses 64-bit accumulation to provide higher precision. Both the slow and the fast versions use the same instance structure. | ||||
* Use the function <code>arm_biquad_cascade_df1_init_q31()</code> to initialize the filter structure. | ||||
*/ | ||||
void arm_biquad_cascade_df1_fast_q31( | ||||
const arm_biquad_casd_df1_inst_q31 * S, | ||||
q31_t * pSrc, | ||||
q31_t * pDst, | ||||
uint32_t blockSize) | ||||
{ | ||||
q31_t *pIn = pSrc; /* input pointer initialization */ | ||||
q31_t *pOut = pDst; /* output pointer initialization */ | ||||
q31_t *pState = S->pState; /* pState pointer initialization */ | ||||
q31_t *pCoeffs = S->pCoeffs; /* coeff pointer initialization */ | ||||
q31_t acc; /* accumulator */ | ||||
q31_t Xn1, Xn2, Yn1, Yn2; /* Filter state variables */ | ||||
q31_t b0, b1, b2, a1, a2; /* Filter coefficients */ | ||||
q31_t Xn; /* temporary input */ | ||||
int32_t shift = (int32_t) S->postShift + 1; /* Shift to be applied to the output */ | ||||
uint32_t sample, stage = S->numStages; /* loop counters */ | ||||
do | ||||
{ | ||||
/* Reading the coefficients */ | ||||
b0 = *pCoeffs++; | ||||
b1 = *pCoeffs++; | ||||
b2 = *pCoeffs++; | ||||
a1 = *pCoeffs++; | ||||
a2 = *pCoeffs++; | ||||
/* Reading the state values */ | ||||
Xn1 = pState[0]; | ||||
Xn2 = pState[1]; | ||||
Yn1 = pState[2]; | ||||
Yn2 = pState[3]; | ||||
/* Apply loop unrolling and compute 4 output values simultaneously. */ | ||||
/* The variables acc ... acc3 hold output values that are being computed: | ||||
* | ||||
* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] | ||||
*/ | ||||
sample = blockSize >> 2u; | ||||
/* First part of the processing with loop unrolling. Compute 4 outputs at a time. | ||||
** a second loop below computes the remaining 1 to 3 samples. */ | ||||
while(sample > 0u) | ||||
{ | ||||
/* Read the input */ | ||||
Xn = *pIn++; | ||||
/* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */ | ||||
/* acc = b0 * x[n] */ | ||||
acc = (q31_t) (((q63_t) b0 * Xn) >> 32); | ||||
/* acc += b1 * x[n-1] */ | ||||
acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn1))) >> 32); | ||||
/* acc += b[2] * x[n-2] */ | ||||
acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn2))) >> 32); | ||||
/* acc += a1 * y[n-1] */ | ||||
acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn1))) >> 32); | ||||
/* acc += a2 * y[n-2] */ | ||||
acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn2))) >> 32); | ||||
/* The result is converted to 1.31 , Yn2 variable is reused */ | ||||
Yn2 = acc << shift; | ||||
/* Store the output in the destination buffer. */ | ||||
*pOut++ = Yn2; | ||||
/* Read the second input */ | ||||
Xn2 = *pIn++; | ||||
/* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */ | ||||
/* acc = b0 * x[n] */ | ||||
acc = (q31_t) (((q63_t) b0 * (Xn2)) >> 32); | ||||
/* acc += b1 * x[n-1] */ | ||||
acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn))) >> 32); | ||||
/* acc += b[2] * x[n-2] */ | ||||
acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn1))) >> 32); | ||||
/* acc += a1 * y[n-1] */ | ||||
acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn2))) >> 32); | ||||
/* acc += a2 * y[n-2] */ | ||||
acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn1))) >> 32); | ||||
/* The result is converted to 1.31, Yn1 variable is reused */ | ||||
Yn1 = acc << shift; | ||||
/* Store the output in the destination buffer. */ | ||||
*pOut++ = Yn1; | ||||
/* Read the third input */ | ||||
Xn1 = *pIn++; | ||||
/* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */ | ||||
/* acc = b0 * x[n] */ | ||||
acc = (q31_t) (((q63_t) b0 * (Xn1)) >> 32); | ||||
/* acc += b1 * x[n-1] */ | ||||
acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn2))) >> 32); | ||||
/* acc += b[2] * x[n-2] */ | ||||
acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn))) >> 32); | ||||
/* acc += a1 * y[n-1] */ | ||||
acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn1))) >> 32); | ||||
/* acc += a2 * y[n-2] */ | ||||
acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn2))) >> 32); | ||||
/* The result is converted to 1.31, Yn2 variable is reused */ | ||||
Yn2 = acc << shift; | ||||
/* Store the output in the destination buffer. */ | ||||
*pOut++ = Yn2; | ||||
/* Read the forth input */ | ||||
Xn = *pIn++; | ||||
/* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */ | ||||
/* acc = b0 * x[n] */ | ||||
acc = (q31_t) (((q63_t) b0 * (Xn)) >> 32); | ||||
/* acc += b1 * x[n-1] */ | ||||
acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn1))) >> 32); | ||||
/* acc += b[2] * x[n-2] */ | ||||
acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn2))) >> 32); | ||||
/* acc += a1 * y[n-1] */ | ||||
acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn2))) >> 32); | ||||
/* acc += a2 * y[n-2] */ | ||||
acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn1))) >> 32); | ||||
/* The result is converted to 1.31, Yn1 variable is reused */ | ||||
Yn1 = acc << shift; | ||||
/* Every time after the output is computed state should be updated. */ | ||||
/* The states should be updated as: */ | ||||
/* Xn2 = Xn1 */ | ||||
/* Xn1 = Xn */ | ||||
/* Yn2 = Yn1 */ | ||||
/* Yn1 = acc */ | ||||
Xn2 = Xn1; | ||||
Xn1 = Xn; | ||||
/* Store the output in the destination buffer. */ | ||||
*pOut++ = Yn1; | ||||
/* decrement the loop counter */ | ||||
sample--; | ||||
} | ||||
/* If the blockSize is not a multiple of 4, compute any remaining output samples here. | ||||
** No loop unrolling is used. */ | ||||
sample = (blockSize & 0x3u); | ||||
while(sample > 0u) | ||||
{ | ||||
/* Read the input */ | ||||
Xn = *pIn++; | ||||
/* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */ | ||||
/* acc = b0 * x[n] */ | ||||
acc = (q31_t) (((q63_t) b0 * (Xn)) >> 32); | ||||
/* acc += b1 * x[n-1] */ | ||||
acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn1))) >> 32); | ||||
/* acc += b[2] * x[n-2] */ | ||||
acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn2))) >> 32); | ||||
/* acc += a1 * y[n-1] */ | ||||
acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn1))) >> 32); | ||||
/* acc += a2 * y[n-2] */ | ||||
acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn2))) >> 32); | ||||
/* The result is converted to 1.31 */ | ||||
acc = acc << shift; | ||||
/* Every time after the output is computed state should be updated. */ | ||||
/* The states should be updated as: */ | ||||
/* Xn2 = Xn1 */ | ||||
/* Xn1 = Xn */ | ||||
/* Yn2 = Yn1 */ | ||||
/* Yn1 = acc */ | ||||
Xn2 = Xn1; | ||||
Xn1 = Xn; | ||||
Yn2 = Yn1; | ||||
Yn1 = acc; | ||||
/* Store the output in the destination buffer. */ | ||||
*pOut++ = acc; | ||||
/* decrement the loop counter */ | ||||
sample--; | ||||
} | ||||
/* The first stage goes from the input buffer to the output buffer. */ | ||||
/* Subsequent stages occur in-place in the output buffer */ | ||||
pIn = pDst; | ||||
/* Reset to destination pointer */ | ||||
pOut = pDst; | ||||
/* Store the updated state variables back into the pState array */ | ||||
*pState++ = Xn1; | ||||
*pState++ = Xn2; | ||||
*pState++ = Yn1; | ||||
*pState++ = Yn2; | ||||
} while(--stage); | ||||
} | ||||
/** | ||||
* @} end of BiquadCascadeDF1 group | ||||
*/ | ||||