CMSIS DSP library
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arm_biquad_cascade_df1_fast_q31.c
00001 /* ---------------------------------------------------------------------- 00002 * Copyright (C) 2010-2013 ARM Limited. All rights reserved. 00003 * 00004 * $Date: 17. January 2013 00005 * $Revision: V1.4.1 00006 * 00007 * Project: CMSIS DSP Library 00008 * Title: arm_biquad_cascade_df1_fast_q31.c 00009 * 00010 * Description: Processing function for the 00011 * Q31 Fast Biquad cascade DirectFormI(DF1) filter. 00012 * 00013 * Target Processor: Cortex-M4/Cortex-M3 00014 * 00015 * Redistribution and use in source and binary forms, with or without 00016 * modification, are permitted provided that the following conditions 00017 * are met: 00018 * - Redistributions of source code must retain the above copyright 00019 * notice, this list of conditions and the following disclaimer. 00020 * - Redistributions in binary form must reproduce the above copyright 00021 * notice, this list of conditions and the following disclaimer in 00022 * the documentation and/or other materials provided with the 00023 * distribution. 00024 * - Neither the name of ARM LIMITED nor the names of its contributors 00025 * may be used to endorse or promote products derived from this 00026 * software without specific prior written permission. 00027 * 00028 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 00029 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 00030 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 00031 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 00032 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 00033 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 00034 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 00035 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 00036 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 00037 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 00038 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 00039 * POSSIBILITY OF SUCH DAMAGE. 00040 * -------------------------------------------------------------------- */ 00041 00042 #include "arm_math.h" 00043 00044 /** 00045 * @ingroup groupFilters 00046 */ 00047 00048 /** 00049 * @addtogroup BiquadCascadeDF1 00050 * @{ 00051 */ 00052 00053 /** 00054 * @details 00055 * 00056 * @param[in] *S points to an instance of the Q31 Biquad cascade structure. 00057 * @param[in] *pSrc points to the block of input data. 00058 * @param[out] *pDst points to the block of output data. 00059 * @param[in] blockSize number of samples to process per call. 00060 * @return none. 00061 * 00062 * <b>Scaling and Overflow Behavior:</b> 00063 * \par 00064 * This function is optimized for speed at the expense of fixed-point precision and overflow protection. 00065 * The result of each 1.31 x 1.31 multiplication is truncated to 2.30 format. 00066 * These intermediate results are added to a 2.30 accumulator. 00067 * Finally, the accumulator is saturated and converted to a 1.31 result. 00068 * 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. 00069 * 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 00070 * arm_biquad_cascade_df1_init_q31() to initialize filter structure. 00071 * 00072 * \par 00073 * 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. 00074 * Use the function <code>arm_biquad_cascade_df1_init_q31()</code> to initialize the filter structure. 00075 */ 00076 00077 void arm_biquad_cascade_df1_fast_q31( 00078 const arm_biquad_casd_df1_inst_q31 * S, 00079 q31_t * pSrc, 00080 q31_t * pDst, 00081 uint32_t blockSize) 00082 { 00083 q31_t acc = 0; /* accumulator */ 00084 q31_t Xn1, Xn2, Yn1, Yn2; /* Filter state variables */ 00085 q31_t b0, b1, b2, a1, a2; /* Filter coefficients */ 00086 q31_t *pIn = pSrc; /* input pointer initialization */ 00087 q31_t *pOut = pDst; /* output pointer initialization */ 00088 q31_t *pState = S->pState; /* pState pointer initialization */ 00089 q31_t *pCoeffs = S->pCoeffs; /* coeff pointer initialization */ 00090 q31_t Xn; /* temporary input */ 00091 int32_t shift = (int32_t) S->postShift + 1; /* Shift to be applied to the output */ 00092 uint32_t sample, stage = S->numStages; /* loop counters */ 00093 00094 00095 do 00096 { 00097 /* Reading the coefficients */ 00098 b0 = *pCoeffs++; 00099 b1 = *pCoeffs++; 00100 b2 = *pCoeffs++; 00101 a1 = *pCoeffs++; 00102 a2 = *pCoeffs++; 00103 00104 /* Reading the state values */ 00105 Xn1 = pState[0]; 00106 Xn2 = pState[1]; 00107 Yn1 = pState[2]; 00108 Yn2 = pState[3]; 00109 00110 /* Apply loop unrolling and compute 4 output values simultaneously. */ 00111 /* The variables acc ... acc3 hold output values that are being computed: 00112 * 00113 * acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] 00114 */ 00115 00116 sample = blockSize >> 2u; 00117 00118 /* First part of the processing with loop unrolling. Compute 4 outputs at a time. 00119 ** a second loop below computes the remaining 1 to 3 samples. */ 00120 while(sample > 0u) 00121 { 00122 /* Read the input */ 00123 Xn = *pIn; 00124 00125 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */ 00126 /* acc = b0 * x[n] */ 00127 //acc = (q31_t) (((q63_t) b1 * Xn1) >> 32); 00128 mult_32x32_keep32_R(acc, b1, Xn1); 00129 /* acc += b1 * x[n-1] */ 00130 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b0 * (Xn))) >> 32); 00131 multAcc_32x32_keep32_R(acc, b0, Xn); 00132 /* acc += b[2] * x[n-2] */ 00133 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn2))) >> 32); 00134 multAcc_32x32_keep32_R(acc, b2, Xn2); 00135 /* acc += a1 * y[n-1] */ 00136 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn1))) >> 32); 00137 multAcc_32x32_keep32_R(acc, a1, Yn1); 00138 /* acc += a2 * y[n-2] */ 00139 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn2))) >> 32); 00140 multAcc_32x32_keep32_R(acc, a2, Yn2); 00141 00142 /* The result is converted to 1.31 , Yn2 variable is reused */ 00143 Yn2 = acc << shift; 00144 00145 /* Read the second input */ 00146 Xn2 = *(pIn + 1u); 00147 00148 /* Store the output in the destination buffer. */ 00149 *pOut = Yn2; 00150 00151 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */ 00152 /* acc = b0 * x[n] */ 00153 //acc = (q31_t) (((q63_t) b0 * (Xn2)) >> 32); 00154 mult_32x32_keep32_R(acc, b0, Xn2); 00155 /* acc += b1 * x[n-1] */ 00156 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn))) >> 32); 00157 multAcc_32x32_keep32_R(acc, b1, Xn); 00158 /* acc += b[2] * x[n-2] */ 00159 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn1))) >> 32); 00160 multAcc_32x32_keep32_R(acc, b2, Xn1); 00161 /* acc += a1 * y[n-1] */ 00162 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn2))) >> 32); 00163 multAcc_32x32_keep32_R(acc, a1, Yn2); 00164 /* acc += a2 * y[n-2] */ 00165 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn1))) >> 32); 00166 multAcc_32x32_keep32_R(acc, a2, Yn1); 00167 00168 /* The result is converted to 1.31, Yn1 variable is reused */ 00169 Yn1 = acc << shift; 00170 00171 /* Read the third input */ 00172 Xn1 = *(pIn + 2u); 00173 00174 /* Store the output in the destination buffer. */ 00175 *(pOut + 1u) = Yn1; 00176 00177 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */ 00178 /* acc = b0 * x[n] */ 00179 //acc = (q31_t) (((q63_t) b0 * (Xn1)) >> 32); 00180 mult_32x32_keep32_R(acc, b0, Xn1); 00181 /* acc += b1 * x[n-1] */ 00182 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn2))) >> 32); 00183 multAcc_32x32_keep32_R(acc, b1, Xn2); 00184 /* acc += b[2] * x[n-2] */ 00185 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn))) >> 32); 00186 multAcc_32x32_keep32_R(acc, b2, Xn); 00187 /* acc += a1 * y[n-1] */ 00188 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn1))) >> 32); 00189 multAcc_32x32_keep32_R(acc, a1, Yn1); 00190 /* acc += a2 * y[n-2] */ 00191 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn2))) >> 32); 00192 multAcc_32x32_keep32_R(acc, a2, Yn2); 00193 00194 /* The result is converted to 1.31, Yn2 variable is reused */ 00195 Yn2 = acc << shift; 00196 00197 /* Read the forth input */ 00198 Xn = *(pIn + 3u); 00199 00200 /* Store the output in the destination buffer. */ 00201 *(pOut + 2u) = Yn2; 00202 pIn += 4u; 00203 00204 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */ 00205 /* acc = b0 * x[n] */ 00206 //acc = (q31_t) (((q63_t) b0 * (Xn)) >> 32); 00207 mult_32x32_keep32_R(acc, b0, Xn); 00208 /* acc += b1 * x[n-1] */ 00209 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn1))) >> 32); 00210 multAcc_32x32_keep32_R(acc, b1, Xn1); 00211 /* acc += b[2] * x[n-2] */ 00212 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn2))) >> 32); 00213 multAcc_32x32_keep32_R(acc, b2, Xn2); 00214 /* acc += a1 * y[n-1] */ 00215 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn2))) >> 32); 00216 multAcc_32x32_keep32_R(acc, a1, Yn2); 00217 /* acc += a2 * y[n-2] */ 00218 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn1))) >> 32); 00219 multAcc_32x32_keep32_R(acc, a2, Yn1); 00220 00221 /* Every time after the output is computed state should be updated. */ 00222 /* The states should be updated as: */ 00223 /* Xn2 = Xn1 */ 00224 Xn2 = Xn1; 00225 00226 /* The result is converted to 1.31, Yn1 variable is reused */ 00227 Yn1 = acc << shift; 00228 00229 /* Xn1 = Xn */ 00230 Xn1 = Xn; 00231 00232 /* Store the output in the destination buffer. */ 00233 *(pOut + 3u) = Yn1; 00234 pOut += 4u; 00235 00236 /* decrement the loop counter */ 00237 sample--; 00238 } 00239 00240 /* If the blockSize is not a multiple of 4, compute any remaining output samples here. 00241 ** No loop unrolling is used. */ 00242 sample = (blockSize & 0x3u); 00243 00244 while(sample > 0u) 00245 { 00246 /* Read the input */ 00247 Xn = *pIn++; 00248 00249 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */ 00250 /* acc = b0 * x[n] */ 00251 //acc = (q31_t) (((q63_t) b0 * (Xn)) >> 32); 00252 mult_32x32_keep32_R(acc, b0, Xn); 00253 /* acc += b1 * x[n-1] */ 00254 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b1 * (Xn1))) >> 32); 00255 multAcc_32x32_keep32_R(acc, b1, Xn1); 00256 /* acc += b[2] * x[n-2] */ 00257 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) b2 * (Xn2))) >> 32); 00258 multAcc_32x32_keep32_R(acc, b2, Xn2); 00259 /* acc += a1 * y[n-1] */ 00260 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a1 * (Yn1))) >> 32); 00261 multAcc_32x32_keep32_R(acc, a1, Yn1); 00262 /* acc += a2 * y[n-2] */ 00263 //acc = (q31_t) ((((q63_t) acc << 32) + ((q63_t) a2 * (Yn2))) >> 32); 00264 multAcc_32x32_keep32_R(acc, a2, Yn2); 00265 00266 /* The result is converted to 1.31 */ 00267 acc = acc << shift; 00268 00269 /* Every time after the output is computed state should be updated. */ 00270 /* The states should be updated as: */ 00271 /* Xn2 = Xn1 */ 00272 /* Xn1 = Xn */ 00273 /* Yn2 = Yn1 */ 00274 /* Yn1 = acc */ 00275 Xn2 = Xn1; 00276 Xn1 = Xn; 00277 Yn2 = Yn1; 00278 Yn1 = acc; 00279 00280 /* Store the output in the destination buffer. */ 00281 *pOut++ = acc; 00282 00283 /* decrement the loop counter */ 00284 sample--; 00285 } 00286 00287 /* The first stage goes from the input buffer to the output buffer. */ 00288 /* Subsequent stages occur in-place in the output buffer */ 00289 pIn = pDst; 00290 00291 /* Reset to destination pointer */ 00292 pOut = pDst; 00293 00294 /* Store the updated state variables back into the pState array */ 00295 *pState++ = Xn1; 00296 *pState++ = Xn2; 00297 *pState++ = Yn1; 00298 *pState++ = Yn2; 00299 00300 } while(--stage); 00301 } 00302 00303 /** 00304 * @} end of BiquadCascadeDF1 group 00305 */
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