arm_biquad_cascade_df1_q31.c
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r71 | /* ---------------------------------------------------------------------- | |||
* 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_q31.c | ||||
* | ||||
* Description: Processing function for the | ||||
* Q31 Biquad cascade filter | ||||
* | ||||
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0 | ||||
* | ||||
* 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 0.0.5 2010/04/26 | ||||
* incorporated review comments and updated with latest CMSIS layer | ||||
* | ||||
* Version 0.0.3 2010/03/10 | ||||
* Initial version | ||||
* -------------------------------------------------------------------- */ | ||||
#include "arm_math.h" | ||||
/** | ||||
* @ingroup groupFilters | ||||
*/ | ||||
/** | ||||
* @addtogroup BiquadCascadeDF1 | ||||
* @{ | ||||
*/ | ||||
/** | ||||
* @brief Processing function for the Q31 Biquad cascade filter. | ||||
* @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 | ||||
* The function is implemented using an internal 64-bit accumulator. | ||||
* The accumulator has a 2.62 format and maintains full precision of the intermediate multiplication results but provides only a single guard bit. | ||||
* Thus, if the accumulator result overflows it wraps around rather than clip. | ||||
* In order to avoid overflows completely the input signal must be scaled down by 2 bits and lie in the range [-0.25 +0.25). | ||||
* After all 5 multiply-accumulates are performed, the 2.62 accumulator is shifted by <code>postShift</code> bits and the result truncated to | ||||
* 1.31 format by discarding the low 32 bits. | ||||
* | ||||
* \par | ||||
* Refer to the function <code>arm_biquad_cascade_df1_fast_q31()</code> for a faster but less precise implementation of this filter for Cortex-M3 and Cortex-M4. | ||||
*/ | ||||
void arm_biquad_cascade_df1_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 */ | ||||
q63_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 */ | ||||
uint32_t shift = 32u - ((uint32_t) S->postShift + 1u); /* Shift to be applied to the output */ | ||||
uint32_t sample, stage = S->numStages; /* loop counters */ | ||||
#ifndef ARM_MATH_CM0 | ||||
/* Run the below code for Cortex-M4 and Cortex-M3 */ | ||||
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 variable acc 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 = (q63_t) b0 *Xn; | ||||
/* acc += b1 * x[n-1] */ | ||||
acc += (q63_t) b1 *Xn1; | ||||
/* acc += b[2] * x[n-2] */ | ||||
acc += (q63_t) b2 *Xn2; | ||||
/* acc += a1 * y[n-1] */ | ||||
acc += (q63_t) a1 *Yn1; | ||||
/* acc += a2 * y[n-2] */ | ||||
acc += (q63_t) a2 *Yn2; | ||||
/* The result is converted to 1.31 , Yn2 variable is reused */ | ||||
Yn2 = (q31_t) (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 = (q63_t) b0 *Xn2; | ||||
/* acc += b1 * x[n-1] */ | ||||
acc += (q63_t) b1 *Xn; | ||||
/* acc += b[2] * x[n-2] */ | ||||
acc += (q63_t) b2 *Xn1; | ||||
/* acc += a1 * y[n-1] */ | ||||
acc += (q63_t) a1 *Yn2; | ||||
/* acc += a2 * y[n-2] */ | ||||
acc += (q63_t) a2 *Yn1; | ||||
/* The result is converted to 1.31, Yn1 variable is reused */ | ||||
Yn1 = (q31_t) (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 = (q63_t) b0 *Xn1; | ||||
/* acc += b1 * x[n-1] */ | ||||
acc += (q63_t) b1 *Xn2; | ||||
/* acc += b[2] * x[n-2] */ | ||||
acc += (q63_t) b2 *Xn; | ||||
/* acc += a1 * y[n-1] */ | ||||
acc += (q63_t) a1 *Yn1; | ||||
/* acc += a2 * y[n-2] */ | ||||
acc += (q63_t) a2 *Yn2; | ||||
/* The result is converted to 1.31, Yn2 variable is reused */ | ||||
Yn2 = (q31_t) (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 = (q63_t) b0 *Xn; | ||||
/* acc += b1 * x[n-1] */ | ||||
acc += (q63_t) b1 *Xn1; | ||||
/* acc += b[2] * x[n-2] */ | ||||
acc += (q63_t) b2 *Xn2; | ||||
/* acc += a1 * y[n-1] */ | ||||
acc += (q63_t) a1 *Yn2; | ||||
/* acc += a2 * y[n-2] */ | ||||
acc += (q63_t) a2 *Yn1; | ||||
/* The result is converted to 1.31, Yn1 variable is reused */ | ||||
Yn1 = (q31_t) (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 = (q63_t) b0 *Xn; | ||||
/* acc += b1 * x[n-1] */ | ||||
acc += (q63_t) b1 *Xn1; | ||||
/* acc += b[2] * x[n-2] */ | ||||
acc += (q63_t) b2 *Xn2; | ||||
/* acc += a1 * y[n-1] */ | ||||
acc += (q63_t) a1 *Yn1; | ||||
/* acc += a2 * y[n-2] */ | ||||
acc += (q63_t) a2 *Yn2; | ||||
/* 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 = (q31_t) acc; | ||||
/* Store the output in the destination buffer. */ | ||||
*pOut++ = (q31_t) 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); | ||||
#else | ||||
/* Run the below code for Cortex-M0 */ | ||||
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]; | ||||
/* The variables acc holds the output value that is computed: | ||||
* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] | ||||
*/ | ||||
sample = blockSize; | ||||
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 = (q63_t) b0 *Xn; | ||||
/* acc += b1 * x[n-1] */ | ||||
acc += (q63_t) b1 *Xn1; | ||||
/* acc += b[2] * x[n-2] */ | ||||
acc += (q63_t) b2 *Xn2; | ||||
/* acc += a1 * y[n-1] */ | ||||
acc += (q63_t) a1 *Yn1; | ||||
/* acc += a2 * y[n-2] */ | ||||
acc += (q63_t) a2 *Yn2; | ||||
/* 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 = (q31_t) acc; | ||||
/* Store the output in the destination buffer. */ | ||||
*pOut++ = (q31_t) 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); | ||||
#endif /* #ifndef ARM_MATH_CM0 */ | ||||
} | ||||
/** | ||||
* @} end of BiquadCascadeDF1 group | ||||
*/ | ||||