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Diffstat (limited to 'platform/CMSIS/DSP_Lib/Source/FilteringFunctions/arm_fir_decimate_fast_q31.c')
| -rw-r--r-- | platform/CMSIS/DSP_Lib/Source/FilteringFunctions/arm_fir_decimate_fast_q31.c | 351 |
1 files changed, 351 insertions, 0 deletions
diff --git a/platform/CMSIS/DSP_Lib/Source/FilteringFunctions/arm_fir_decimate_fast_q31.c b/platform/CMSIS/DSP_Lib/Source/FilteringFunctions/arm_fir_decimate_fast_q31.c new file mode 100644 index 0000000..33813dc --- /dev/null +++ b/platform/CMSIS/DSP_Lib/Source/FilteringFunctions/arm_fir_decimate_fast_q31.c @@ -0,0 +1,351 @@ +/* ---------------------------------------------------------------------- +* Copyright (C) 2010-2014 ARM Limited. All rights reserved. +* +* $Date: 12. March 2014 +* $Revision: V1.4.4 +* +* Project: CMSIS DSP Library +* Title: arm_fir_decimate_fast_q31.c +* +* Description: Fast Q31 FIR Decimator. +* +* 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 FIR_decimate + * @{ + */ + +/** + * @brief Processing function for the Q31 FIR decimator (fast variant) for Cortex-M3 and Cortex-M4. + * @param[in] *S points to an instance of the Q31 FIR decimator 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 input 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 log2(numTaps) bits (where log2 is read as log to the base 2). + * + * \par + * Refer to the function <code>arm_fir_decimate_q31()</code> for a slower implementation of this function which uses a 64-bit accumulator to provide higher precision. + * Both the slow and the fast versions use the same instance structure. + * Use the function <code>arm_fir_decimate_init_q31()</code> to initialize the filter structure. + */ + +void arm_fir_decimate_fast_q31( + arm_fir_decimate_instance_q31 * S, + q31_t * pSrc, + q31_t * pDst, + uint32_t blockSize) +{ + q31_t *pState = S->pState; /* State pointer */ + q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ + q31_t *pStateCurnt; /* Points to the current sample of the state */ + q31_t x0, c0; /* Temporary variables to hold state and coefficient values */ + q31_t *px; /* Temporary pointers for state buffer */ + q31_t *pb; /* Temporary pointers for coefficient buffer */ + q31_t sum0; /* Accumulator */ + uint32_t numTaps = S->numTaps; /* Number of taps */ + uint32_t i, tapCnt, blkCnt, outBlockSize = blockSize / S->M; /* Loop counters */ + uint32_t blkCntN2; + q31_t x1; + q31_t acc0, acc1; + q31_t *px0, *px1; + + /* S->pState buffer contains previous frame (numTaps - 1) samples */ + /* pStateCurnt points to the location where the new input data should be written */ + pStateCurnt = S->pState + (numTaps - 1u); + + /* Total number of output samples to be computed */ + + blkCnt = outBlockSize / 2; + blkCntN2 = outBlockSize - (2 * blkCnt); + + while(blkCnt > 0u) + { + /* Copy decimation factor number of new input samples into the state buffer */ + i = 2 * S->M; + + do + { + *pStateCurnt++ = *pSrc++; + + } while(--i); + + /* Set accumulator to zero */ + acc0 = 0; + acc1 = 0; + + /* Initialize state pointer */ + px0 = pState; + px1 = pState + S->M; + + /* Initialize coeff pointer */ + pb = pCoeffs; + + /* Loop unrolling. Process 4 taps at a time. */ + tapCnt = numTaps >> 2; + + /* Loop over the number of taps. Unroll by a factor of 4. + ** Repeat until we've computed numTaps-4 coefficients. */ + while(tapCnt > 0u) + { + /* Read the b[numTaps-1] coefficient */ + c0 = *(pb); + + /* Read x[n-numTaps-1] for sample 0 sample 1 */ + x0 = *(px0); + x1 = *(px1); + + /* Perform the multiply-accumulate */ + acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32); + acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32); + + /* Read the b[numTaps-2] coefficient */ + c0 = *(pb + 1u); + + /* Read x[n-numTaps-2] for sample 0 sample 1 */ + x0 = *(px0 + 1u); + x1 = *(px1 + 1u); + + /* Perform the multiply-accumulate */ + acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32); + acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32); + + /* Read the b[numTaps-3] coefficient */ + c0 = *(pb + 2u); + + /* Read x[n-numTaps-3] for sample 0 sample 1 */ + x0 = *(px0 + 2u); + x1 = *(px1 + 2u); + pb += 4u; + + /* Perform the multiply-accumulate */ + acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32); + acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32); + + /* Read the b[numTaps-4] coefficient */ + c0 = *(pb - 1u); + + /* Read x[n-numTaps-4] for sample 0 sample 1 */ + x0 = *(px0 + 3u); + x1 = *(px1 + 3u); + + + /* Perform the multiply-accumulate */ + acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32); + acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32); + + /* update state pointers */ + px0 += 4u; + px1 += 4u; + + /* Decrement the loop counter */ + tapCnt--; + } + + /* If the filter length is not a multiple of 4, compute the remaining filter taps */ + tapCnt = numTaps % 0x4u; + + while(tapCnt > 0u) + { + /* Read coefficients */ + c0 = *(pb++); + + /* Fetch 1 state variable */ + x0 = *(px0++); + x1 = *(px1++); + + /* Perform the multiply-accumulate */ + acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32); + acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32); + + /* Decrement the loop counter */ + tapCnt--; + } + + /* Advance the state pointer by the decimation factor + * to process the next group of decimation factor number samples */ + pState = pState + S->M * 2; + + /* The result is in the accumulator, store in the destination buffer. */ + *pDst++ = (q31_t) (acc0 << 1); + *pDst++ = (q31_t) (acc1 << 1); + + /* Decrement the loop counter */ + blkCnt--; + } + + while(blkCntN2 > 0u) + { + /* Copy decimation factor number of new input samples into the state buffer */ + i = S->M; + + do + { + *pStateCurnt++ = *pSrc++; + + } while(--i); + + /* Set accumulator to zero */ + sum0 = 0; + + /* Initialize state pointer */ + px = pState; + + /* Initialize coeff pointer */ + pb = pCoeffs; + + /* Loop unrolling. Process 4 taps at a time. */ + tapCnt = numTaps >> 2; + + /* Loop over the number of taps. Unroll by a factor of 4. + ** Repeat until we've computed numTaps-4 coefficients. */ + while(tapCnt > 0u) + { + /* Read the b[numTaps-1] coefficient */ + c0 = *(pb++); + + /* Read x[n-numTaps-1] sample */ + x0 = *(px++); + + /* Perform the multiply-accumulate */ + sum0 = (q31_t) ((((q63_t) sum0 << 32) + ((q63_t) x0 * c0)) >> 32); + + /* Read the b[numTaps-2] coefficient */ + c0 = *(pb++); + + /* Read x[n-numTaps-2] sample */ + x0 = *(px++); + + /* Perform the multiply-accumulate */ + sum0 = (q31_t) ((((q63_t) sum0 << 32) + ((q63_t) x0 * c0)) >> 32); + + /* Read the b[numTaps-3] coefficient */ + c0 = *(pb++); + + /* Read x[n-numTaps-3] sample */ + x0 = *(px++); + + /* Perform the multiply-accumulate */ + sum0 = (q31_t) ((((q63_t) sum0 << 32) + ((q63_t) x0 * c0)) >> 32); + + /* Read the b[numTaps-4] coefficient */ + c0 = *(pb++); + + /* Read x[n-numTaps-4] sample */ + x0 = *(px++); + + /* Perform the multiply-accumulate */ + sum0 = (q31_t) ((((q63_t) sum0 << 32) + ((q63_t) x0 * c0)) >> 32); + + /* Decrement the loop counter */ + tapCnt--; + } + + /* If the filter length is not a multiple of 4, compute the remaining filter taps */ + tapCnt = numTaps % 0x4u; + + while(tapCnt > 0u) + { + /* Read coefficients */ + c0 = *(pb++); + + /* Fetch 1 state variable */ + x0 = *(px++); + + /* Perform the multiply-accumulate */ + sum0 = (q31_t) ((((q63_t) sum0 << 32) + ((q63_t) x0 * c0)) >> 32); + + /* Decrement the loop counter */ + tapCnt--; + } + + /* Advance the state pointer by the decimation factor + * to process the next group of decimation factor number samples */ + pState = pState + S->M; + + /* The result is in the accumulator, store in the destination buffer. */ + *pDst++ = (q31_t) (sum0 << 1); + + /* Decrement the loop counter */ + blkCntN2--; + } + + /* Processing is complete. + ** Now copy the last numTaps - 1 samples to the satrt of the state buffer. + ** This prepares the state buffer for the next function call. */ + + /* Points to the start of the state buffer */ + pStateCurnt = S->pState; + + i = (numTaps - 1u) >> 2u; + + /* copy data */ + while(i > 0u) + { + *pStateCurnt++ = *pState++; + *pStateCurnt++ = *pState++; + *pStateCurnt++ = *pState++; + *pStateCurnt++ = *pState++; + + /* Decrement the loop counter */ + i--; + } + + i = (numTaps - 1u) % 0x04u; + + /* copy data */ + while(i > 0u) + { + *pStateCurnt++ = *pState++; + + /* Decrement the loop counter */ + i--; + } +} + +/** + * @} end of FIR_decimate group + */ |