| /* ---------------------------------------------------------------------- |
| * Copyright (C) 2010-2014 ARM Limited. All rights reserved. |
| * |
| * $Date: 19. October 2015 |
| * $Revision: V.1.4.5 a |
| * |
| * 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 |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * - Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * - Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in |
| * the documentation and/or other materials provided with the |
| * distribution. |
| * - Neither the name of ARM LIMITED nor the names of its contributors |
| * may be used to endorse or promote products derived from this |
| * software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
| * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
| * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, |
| * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; |
| * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER |
| * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN |
| * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
| * POSSIBILITY OF SUCH DAMAGE. |
| * -------------------------------------------------------------------- */ |
| |
| #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 acc = 0; /* accumulator */ |
| q31_t Xn1, Xn2, Yn1, Yn2; /* Filter state variables */ |
| q31_t b0, b1, b2, a1, a2; /* Filter coefficients */ |
| 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 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) 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 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);*/ |
| 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 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 |
| */ |
