| /* ---------------------------------------------------------------------- |
| * Project: CMSIS DSP Library |
| * Title: arm_biquad_cascade_df1_fast_q31.c |
| * Description: Processing function for the Q31 Fast Biquad cascade DirectFormI(DF1) filter |
| * |
| * $Date: 18. March 2019 |
| * $Revision: V1.6.0 |
| * |
| * Target Processor: Cortex-M cores |
| * -------------------------------------------------------------------- */ |
| /* |
| * Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved. |
| * |
| * SPDX-License-Identifier: Apache-2.0 |
| * |
| * Licensed under the Apache License, Version 2.0 (the License); you may |
| * not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an AS IS BASIS, WITHOUT |
| * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #include "arm_math.h" |
| |
| /** |
| @ingroup groupFilters |
| */ |
| |
| /** |
| @addtogroup BiquadCascadeDF1 |
| @{ |
| */ |
| |
| /** |
| @brief Processing function for the Q31 Biquad cascade filter (fast variant). |
| @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 |
| |
| @par Scaling and Overflow Behavior |
| 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. |
| @remark |
| Refer to \ref arm_biquad_cascade_df1_q31() 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 \ref arm_biquad_cascade_df1_init_q31() to initialize the filter structure. |
| */ |
| |
| void arm_biquad_cascade_df1_fast_q31( |
| const arm_biquad_casd_df1_inst_q31 * S, |
| const q31_t * pSrc, |
| q31_t * pDst, |
| uint32_t blockSize) |
| { |
| const q31_t *pIn = pSrc; /* Source pointer */ |
| q31_t *pOut = pDst; /* Destination pointer */ |
| q31_t *pState = S->pState; /* pState pointer */ |
| const q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ |
| q31_t acc = 0; /* Accumulator */ |
| q31_t b0, b1, b2, a1, a2; /* Filter coefficients */ |
| q31_t Xn1, Xn2, Yn1, Yn2; /* Filter pState variables */ |
| 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 pState values */ |
| Xn1 = pState[0]; |
| Xn2 = pState[1]; |
| Yn1 = pState[2]; |
| Yn2 = pState[3]; |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Apply loop unrolling and compute 4 output values simultaneously. */ |
| /* 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] |
| */ |
| |
| /* Loop unrolling: Compute 4 outputs at a time */ |
| sample = blockSize >> 2U; |
| |
| 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) b1 * Xn1) >> 32);*/ |
| mult_32x32_keep32_R(acc, b1, Xn1); |
| /* acc += b1 * x[n-1] */ |
| /* acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b0 * (Xn))) >> 32);*/ |
| multAcc_32x32_keep32_R(acc, b0, Xn); |
| /* acc += b[2] * x[n-2] */ |
| /* acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn2))) >> 32);*/ |
| multAcc_32x32_keep32_R(acc, b2, Xn2); |
| /* acc += a1 * y[n-1] */ |
| /* acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn1))) >> 32);*/ |
| multAcc_32x32_keep32_R(acc, a1, Yn1); |
| /* acc += a2 * y[n-2] */ |
| /* acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn2))) >> 32);*/ |
| multAcc_32x32_keep32_R(acc, a2, Yn2); |
| |
| /* The result is converted to 1.31 , Yn2 variable is reused */ |
| Yn2 = acc << shift; |
| |
| /* Read the second input */ |
| Xn2 = *(pIn + 1U); |
| |
| /* Store the output in the destination buffer. */ |
| *pOut = Yn2; |
| |
| /* 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);*/ |
| mult_32x32_keep32_R(acc, b0, Xn2); |
| /* acc += b1 * x[n-1] */ |
| /* acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn))) >> 32);*/ |
| multAcc_32x32_keep32_R(acc, b1, Xn); |
| /* acc += b[2] * x[n-2] */ |
| /* acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn1))) >> 32);*/ |
| multAcc_32x32_keep32_R(acc, b2, Xn1); |
| /* acc += a1 * y[n-1] */ |
| /* acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn2))) >> 32);*/ |
| multAcc_32x32_keep32_R(acc, a1, Yn2); |
| /* acc += a2 * y[n-2] */ |
| /* acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn1))) >> 32);*/ |
| multAcc_32x32_keep32_R(acc, a2, Yn1); |
| |
| /* The result is converted to 1.31, Yn1 variable is reused */ |
| Yn1 = acc << shift; |
| |
| /* Read the third input */ |
| Xn1 = *(pIn + 2U); |
| |
| /* Store the output in the destination buffer. */ |
| *(pOut + 1U) = Yn1; |
| |
| /* 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);*/ |
| mult_32x32_keep32_R(acc, b0, Xn1); |
| /* acc += b1 * x[n-1] */ |
| /* acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn2))) >> 32);*/ |
| multAcc_32x32_keep32_R(acc, b1, Xn2); |
| /* acc += b[2] * x[n-2] */ |
| /* acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn))) >> 32);*/ |
| multAcc_32x32_keep32_R(acc, b2, Xn); |
| /* acc += a1 * y[n-1] */ |
| /* acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn1))) >> 32);*/ |
| multAcc_32x32_keep32_R(acc, a1, Yn1); |
| /* acc += a2 * y[n-2] */ |
| /* acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn2))) >> 32);*/ |
| multAcc_32x32_keep32_R(acc, a2, Yn2); |
| |
| /* The result is converted to 1.31, Yn2 variable is reused */ |
| Yn2 = acc << shift; |
| |
| /* Read the forth input */ |
| Xn = *(pIn + 3U); |
| |
| /* Store the output in the destination buffer. */ |
| *(pOut + 2U) = Yn2; |
| pIn += 4U; |
| |
| /* 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);*/ |
| mult_32x32_keep32_R(acc, b0, Xn); |
| /* acc += b1 * x[n-1] */ |
| /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn1))) >> 32);*/ |
| multAcc_32x32_keep32_R(acc, b1, Xn1); |
| /* acc += b[2] * x[n-2] */ |
| /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn2))) >> 32);*/ |
| multAcc_32x32_keep32_R(acc, b2, Xn2); |
| /* acc += a1 * y[n-1] */ |
| /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn2))) >> 32);*/ |
| multAcc_32x32_keep32_R(acc, a1, Yn2); |
| /* acc += a2 * y[n-2] */ |
| /*acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn1))) >> 32);*/ |
| multAcc_32x32_keep32_R(acc, a2, Yn1); |
| |
| /* Every time after the output is computed state should be updated. */ |
| /* The states should be updated as: */ |
| /* Xn2 = Xn1 */ |
| Xn2 = Xn1; |
| |
| /* The result is converted to 1.31, Yn1 variable is reused */ |
| Yn1 = acc << shift; |
| |
| /* Xn1 = Xn */ |
| Xn1 = Xn; |
| |
| /* Store the output in the destination buffer. */ |
| *(pOut + 3U) = Yn1; |
| pOut += 4U; |
| |
| /* decrement loop counter */ |
| sample--; |
| } |
| |
| /* Loop unrolling: Compute remaining outputs */ |
| sample = (blockSize & 0x3U); |
| |
| #else |
| |
| /* Initialize blkCnt with number of samples */ |
| sample = blockSize; |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| 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);*/ |
| mult_32x32_keep32_R(acc, b0, Xn); |
| /* acc += b1 * x[n-1] */ |
| /* acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn1))) >> 32);*/ |
| multAcc_32x32_keep32_R(acc, b1, Xn1); |
| /* acc += b[2] * x[n-2] */ |
| /* acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn2))) >> 32);*/ |
| multAcc_32x32_keep32_R(acc, b2, Xn2); |
| /* acc += a1 * y[n-1] */ |
| /* acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn1))) >> 32);*/ |
| multAcc_32x32_keep32_R(acc, a1, Yn1); |
| /* acc += a2 * y[n-2] */ |
| /* acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn2))) >> 32);*/ |
| multAcc_32x32_keep32_R(acc, 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 = acc; |
| |
| /* Store the output in the destination buffer. */ |
| *pOut++ = acc; |
| |
| /* decrement 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 |
| */ |