/* ---------------------------------------------------------------------- * Copyright (C) 2010-2014 ARM Limited. All rights reserved. * * $Date: 19. March 2015 * $Revision: V.1.4.5 * * Project: CMSIS DSP Library * Title: arm_biquad_cascade_df1_fast_q15.c * * Description: Fast processing function for the * Q15 Biquad cascade 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 Q15 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. * * Scaling and Overflow Behavior: * \par * This fast version uses a 32-bit accumulator with 2.30 format. * The accumulator maintains full precision of the intermediate multiplication results but provides only a single guard bit. * Thus, if the accumulator result overflows it wraps around and distorts the 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). * The 2.30 accumulator is then shifted by postShift bits and the result truncated to 1.15 format by discarding the low 16 bits. * * \par * Refer to the function arm_biquad_cascade_df1_q15() for a slower implementation of this function which uses 64-bit accumulation to avoid wrap around distortion. Both the slow and the fast versions use the same instance structure. * Use the function arm_biquad_cascade_df1_init_q15() to initialize the filter structure. * */ void arm_biquad_cascade_df1_fast_q15( const arm_biquad_casd_df1_inst_q15 * S, q15_t * pSrc, q15_t * pDst, uint32_t blockSize) { q15_t *pIn = pSrc; /* Source pointer */ q15_t *pOut = pDst; /* Destination pointer */ q31_t in; /* Temporary variable to hold input value */ q31_t out; /* Temporary variable to hold output value */ q31_t b0; /* Temporary variable to hold bo value */ q31_t b1, a1; /* Filter coefficients */ q31_t state_in, state_out; /* Filter state variables */ q31_t acc; /* Accumulator */ int32_t shift = (int32_t) (15 - S->postShift); /* Post shift */ q15_t *pState = S->pState; /* State pointer */ q15_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ uint32_t sample, stage = S->numStages; /* Stage loop counter */ do { /* Read the b0 and 0 coefficients using SIMD */ b0 = *__SIMD32(pCoeffs)++; /* Read the b1 and b2 coefficients using SIMD */ b1 = *__SIMD32(pCoeffs)++; /* Read the a1 and a2 coefficients using SIMD */ a1 = *__SIMD32(pCoeffs)++; /* Read the input state values from the state buffer: x[n-1], x[n-2] */ state_in = *__SIMD32(pState)++; /* Read the output state values from the state buffer: y[n-1], y[n-2] */ state_out = *__SIMD32(pState)--; /* Apply loop unrolling and compute 2 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] * acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */ sample = blockSize >> 1u; /* First part of the processing with loop unrolling. Compute 2 outputs at a time. ** a second loop below computes the remaining 1 sample. */ while(sample > 0u) { /* Read the input */ in = *__SIMD32(pIn)++; /* out = b0 * x[n] + 0 * 0 */ out = __SMUAD(b0, in); /* acc = b1 * x[n-1] + acc += b2 * x[n-2] + out */ acc = __SMLAD(b1, state_in, out); /* acc += a1 * y[n-1] + acc += a2 * y[n-2] */ acc = __SMLAD(a1, state_out, acc); /* The result is converted from 3.29 to 1.31 and then saturation is applied */ out = __SSAT((acc >> shift), 16); /* 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 */ /* x[n-N], x[n-N-1] are packed together to make state_in of type q31 */ /* y[n-N], y[n-N-1] are packed together to make state_out of type q31 */ #ifndef ARM_MATH_BIG_ENDIAN state_in = __PKHBT(in, state_in, 16); state_out = __PKHBT(out, state_out, 16); #else state_in = __PKHBT(state_in >> 16, (in >> 16), 16); state_out = __PKHBT(state_out >> 16, (out), 16); #endif /* #ifndef ARM_MATH_BIG_ENDIAN */ /* out = b0 * x[n] + 0 * 0 */ out = __SMUADX(b0, in); /* acc0 = b1 * x[n-1] , acc0 += b2 * x[n-2] + out */ acc = __SMLAD(b1, state_in, out); /* acc += a1 * y[n-1] + acc += a2 * y[n-2] */ acc = __SMLAD(a1, state_out, acc); /* The result is converted from 3.29 to 1.31 and then saturation is applied */ out = __SSAT((acc >> shift), 16); /* Store the output in the destination buffer. */ #ifndef ARM_MATH_BIG_ENDIAN *__SIMD32(pOut)++ = __PKHBT(state_out, out, 16); #else *__SIMD32(pOut)++ = __PKHBT(out, state_out >> 16, 16); #endif /* #ifndef ARM_MATH_BIG_ENDIAN */ /* 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 */ /* x[n-N], x[n-N-1] are packed together to make state_in of type q31 */ /* y[n-N], y[n-N-1] are packed together to make state_out of type q31 */ #ifndef ARM_MATH_BIG_ENDIAN state_in = __PKHBT(in >> 16, state_in, 16); state_out = __PKHBT(out, state_out, 16); #else state_in = __PKHBT(state_in >> 16, in, 16); state_out = __PKHBT(state_out >> 16, out, 16); #endif /* #ifndef ARM_MATH_BIG_ENDIAN */ /* Decrement the loop counter */ sample--; } /* If the blockSize is not a multiple of 2, compute any remaining output samples here. ** No loop unrolling is used. */ if((blockSize & 0x1u) != 0u) { /* Read the input */ in = *pIn++; /* out = b0 * x[n] + 0 * 0 */ #ifndef ARM_MATH_BIG_ENDIAN out = __SMUAD(b0, in); #else out = __SMUADX(b0, in); #endif /* #ifndef ARM_MATH_BIG_ENDIAN */ /* acc = b1 * x[n-1], acc += b2 * x[n-2] + out */ acc = __SMLAD(b1, state_in, out); /* acc += a1 * y[n-1] + acc += a2 * y[n-2] */ acc = __SMLAD(a1, state_out, acc); /* The result is converted from 3.29 to 1.31 and then saturation is applied */ out = __SSAT((acc >> shift), 16); /* Store the output in the destination buffer. */ *pOut++ = (q15_t) out; /* 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 */ /* x[n-N], x[n-N-1] are packed together to make state_in of type q31 */ /* y[n-N], y[n-N-1] are packed together to make state_out of type q31 */ #ifndef ARM_MATH_BIG_ENDIAN state_in = __PKHBT(in, state_in, 16); state_out = __PKHBT(out, state_out, 16); #else state_in = __PKHBT(state_in >> 16, in, 16); state_out = __PKHBT(state_out >> 16, out, 16); #endif /* #ifndef ARM_MATH_BIG_ENDIAN */ } /* The first stage goes from the input buffer to the output buffer. */ /* Subsequent (numStages - 1) occur in-place in the output buffer */ pIn = pDst; /* Reset the output pointer */ pOut = pDst; /* Store the updated state variables back into the state array */ *__SIMD32(pState)++ = state_in; *__SIMD32(pState)++ = state_out; /* Decrement the loop counter */ stage--; } while(stage > 0u); } /** * @} end of BiquadCascadeDF1 group */