arm_fir_interpolate_q15.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_fir_interpolate_q15.c    
00009 *    
00010 * Description:  Q15 FIR interpolation.    
00011 *    
00012 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
00013 *  
00014 * Redistribution and use in source and binary forms, with or without 
00015 * modification, are permitted provided that the following conditions
00016 * are met:
00017 *   - Redistributions of source code must retain the above copyright
00018 *     notice, this list of conditions and the following disclaimer.
00019 *   - Redistributions in binary form must reproduce the above copyright
00020 *     notice, this list of conditions and the following disclaimer in
00021 *     the documentation and/or other materials provided with the 
00022 *     distribution.
00023 *   - Neither the name of ARM LIMITED nor the names of its contributors
00024 *     may be used to endorse or promote products derived from this
00025 *     software without specific prior written permission.
00026 *
00027 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
00028 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
00029 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
00030 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 
00031 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
00032 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
00033 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
00034 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
00035 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
00036 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
00037 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
00038 * POSSIBILITY OF SUCH DAMAGE.    
00039 * ---------------------------------------------------------------------------*/
00040 
00041 #include "arm_math.h"
00042 
00043 /**    
00044  * @ingroup groupFilters    
00045  */
00046 
00047 /**    
00048  * @addtogroup FIR_Interpolate    
00049  * @{    
00050  */
00051 
00052 /**    
00053  * @brief Processing function for the Q15 FIR interpolator.    
00054  * @param[in] *S        points to an instance of the Q15 FIR interpolator structure.    
00055  * @param[in] *pSrc     points to the block of input data.    
00056  * @param[out] *pDst    points to the block of output data.    
00057  * @param[in] blockSize number of input samples to process per call.    
00058  * @return none.    
00059  *    
00060  * <b>Scaling and Overflow Behavior:</b>    
00061  * \par    
00062  * The function is implemented using a 64-bit internal accumulator.    
00063  * Both coefficients and state variables are represented in 1.15 format and multiplications yield a 2.30 result.    
00064  * The 2.30 intermediate results are accumulated in a 64-bit accumulator in 34.30 format.    
00065  * There is no risk of internal overflow with this approach and the full precision of intermediate multiplications is preserved.    
00066  * After all additions have been performed, the accumulator is truncated to 34.15 format by discarding low 15 bits.    
00067  * Lastly, the accumulator is saturated to yield a result in 1.15 format.    
00068  */
00069 
00070 #ifndef ARM_MATH_CM0_FAMILY
00071 
00072   /* Run the below code for Cortex-M4 and Cortex-M3 */
00073 
00074 void arm_fir_interpolate_q15(
00075   const arm_fir_interpolate_instance_q15 * S,
00076   q15_t * pSrc,
00077   q15_t * pDst,
00078   uint32_t blockSize)
00079 {
00080   q15_t *pState = S->pState;                     /* State pointer                                            */
00081   q15_t *pCoeffs = S->pCoeffs;                   /* Coefficient pointer                                      */
00082   q15_t *pStateCurnt;                            /* Points to the current sample of the state                */
00083   q15_t *ptr1, *ptr2;                            /* Temporary pointers for state and coefficient buffers     */
00084   q63_t sum0;                                    /* Accumulators                                             */
00085   q15_t x0, c0;                                  /* Temporary variables to hold state and coefficient values */
00086   uint32_t i, blkCnt, j, tapCnt;                 /* Loop counters                                            */
00087   uint16_t phaseLen = S->phaseLength;            /* Length of each polyphase filter component */
00088   uint32_t blkCntN2;
00089   q63_t acc0, acc1;
00090   q15_t x1;
00091 
00092   /* S->pState buffer contains previous frame (phaseLen - 1) samples */
00093   /* pStateCurnt points to the location where the new input data should be written */
00094   pStateCurnt = S->pState + ((q31_t) phaseLen - 1);
00095 
00096   /* Initialise  blkCnt */
00097   blkCnt = blockSize / 2;
00098   blkCntN2 = blockSize - (2 * blkCnt);
00099 
00100   /* Samples loop unrolled by 2 */
00101   while(blkCnt > 0u)
00102   {
00103     /* Copy new input sample into the state buffer */
00104     *pStateCurnt++ = *pSrc++;
00105     *pStateCurnt++ = *pSrc++;
00106 
00107     /* Address modifier index of coefficient buffer */
00108     j = 1u;
00109 
00110     /* Loop over the Interpolation factor. */
00111     i = (S->L);
00112 
00113     while(i > 0u)
00114     {
00115       /* Set accumulator to zero */
00116       acc0 = 0;
00117       acc1 = 0;
00118 
00119       /* Initialize state pointer */
00120       ptr1 = pState;
00121 
00122       /* Initialize coefficient pointer */
00123       ptr2 = pCoeffs + (S->L - j);
00124 
00125       /* Loop over the polyPhase length. Unroll by a factor of 4.        
00126        ** Repeat until we've computed numTaps-(4*S->L) coefficients. */
00127       tapCnt = phaseLen >> 2u;
00128 
00129       x0 = *(ptr1++);
00130 
00131       while(tapCnt > 0u)
00132       {
00133 
00134         /* Read the input sample */
00135         x1 = *(ptr1++);
00136 
00137         /* Read the coefficient */
00138         c0 = *(ptr2);
00139 
00140         /* Perform the multiply-accumulate */
00141         acc0 += (q63_t) x0 *c0;
00142         acc1 += (q63_t) x1 *c0;
00143 
00144 
00145         /* Read the coefficient */
00146         c0 = *(ptr2 + S->L);
00147 
00148         /* Read the input sample */
00149         x0 = *(ptr1++);
00150 
00151         /* Perform the multiply-accumulate */
00152         acc0 += (q63_t) x1 *c0;
00153         acc1 += (q63_t) x0 *c0;
00154 
00155 
00156         /* Read the coefficient */
00157         c0 = *(ptr2 + S->L * 2);
00158 
00159         /* Read the input sample */
00160         x1 = *(ptr1++);
00161 
00162         /* Perform the multiply-accumulate */
00163         acc0 += (q63_t) x0 *c0;
00164         acc1 += (q63_t) x1 *c0;
00165 
00166         /* Read the coefficient */
00167         c0 = *(ptr2 + S->L * 3);
00168 
00169         /* Read the input sample */
00170         x0 = *(ptr1++);
00171 
00172         /* Perform the multiply-accumulate */
00173         acc0 += (q63_t) x1 *c0;
00174         acc1 += (q63_t) x0 *c0;
00175 
00176 
00177         /* Upsampling is done by stuffing L-1 zeros between each sample.        
00178          * So instead of multiplying zeros with coefficients,        
00179          * Increment the coefficient pointer by interpolation factor times. */
00180         ptr2 += 4 * S->L;
00181 
00182         /* Decrement the loop counter */
00183         tapCnt--;
00184       }
00185 
00186       /* If the polyPhase length is not a multiple of 4, compute the remaining filter taps */
00187       tapCnt = phaseLen % 0x4u;
00188 
00189       while(tapCnt > 0u)
00190       {
00191 
00192         /* Read the input sample */
00193         x1 = *(ptr1++);
00194 
00195         /* Read the coefficient */
00196         c0 = *(ptr2);
00197 
00198         /* Perform the multiply-accumulate */
00199         acc0 += (q63_t) x0 *c0;
00200         acc1 += (q63_t) x1 *c0;
00201 
00202         /* Increment the coefficient pointer by interpolation factor times. */
00203         ptr2 += S->L;
00204 
00205         /* update states for next sample processing */
00206         x0 = x1;
00207 
00208         /* Decrement the loop counter */
00209         tapCnt--;
00210       }
00211 
00212       /* The result is in the accumulator, store in the destination buffer. */
00213       *pDst = (q15_t) (__SSAT((acc0 >> 15), 16));
00214       *(pDst + S->L) = (q15_t) (__SSAT((acc1 >> 15), 16));
00215 
00216       pDst++;
00217 
00218       /* Increment the address modifier index of coefficient buffer */
00219       j++;
00220 
00221       /* Decrement the loop counter */
00222       i--;
00223     }
00224 
00225     /* Advance the state pointer by 1        
00226      * to process the next group of interpolation factor number samples */
00227     pState = pState + 2;
00228 
00229     pDst += S->L;
00230 
00231     /* Decrement the loop counter */
00232     blkCnt--;
00233   }
00234 
00235   /* If the blockSize is not a multiple of 2, compute any remaining output samples here.        
00236    ** No loop unrolling is used. */
00237   blkCnt = blkCntN2;
00238 
00239   /* Loop over the blockSize. */
00240   while(blkCnt > 0u)
00241   {
00242     /* Copy new input sample into the state buffer */
00243     *pStateCurnt++ = *pSrc++;
00244 
00245     /* Address modifier index of coefficient buffer */
00246     j = 1u;
00247 
00248     /* Loop over the Interpolation factor. */
00249     i = S->L;
00250     while(i > 0u)
00251     {
00252       /* Set accumulator to zero */
00253       sum0 = 0;
00254 
00255       /* Initialize state pointer */
00256       ptr1 = pState;
00257 
00258       /* Initialize coefficient pointer */
00259       ptr2 = pCoeffs + (S->L - j);
00260 
00261       /* Loop over the polyPhase length. Unroll by a factor of 4.        
00262        ** Repeat until we've computed numTaps-(4*S->L) coefficients. */
00263       tapCnt = phaseLen >> 2;
00264       while(tapCnt > 0u)
00265       {
00266 
00267         /* Read the coefficient */
00268         c0 = *(ptr2);
00269 
00270         /* Upsampling is done by stuffing L-1 zeros between each sample.        
00271          * So instead of multiplying zeros with coefficients,        
00272          * Increment the coefficient pointer by interpolation factor times. */
00273         ptr2 += S->L;
00274 
00275         /* Read the input sample */
00276         x0 = *(ptr1++);
00277 
00278         /* Perform the multiply-accumulate */
00279         sum0 += (q63_t) x0 *c0;
00280 
00281         /* Read the coefficient */
00282         c0 = *(ptr2);
00283 
00284         /* Increment the coefficient pointer by interpolation factor times. */
00285         ptr2 += S->L;
00286 
00287         /* Read the input sample */
00288         x0 = *(ptr1++);
00289 
00290         /* Perform the multiply-accumulate */
00291         sum0 += (q63_t) x0 *c0;
00292 
00293         /* Read the coefficient */
00294         c0 = *(ptr2);
00295 
00296         /* Increment the coefficient pointer by interpolation factor times. */
00297         ptr2 += S->L;
00298 
00299         /* Read the input sample */
00300         x0 = *(ptr1++);
00301 
00302         /* Perform the multiply-accumulate */
00303         sum0 += (q63_t) x0 *c0;
00304 
00305         /* Read the coefficient */
00306         c0 = *(ptr2);
00307 
00308         /* Increment the coefficient pointer by interpolation factor times. */
00309         ptr2 += S->L;
00310 
00311         /* Read the input sample */
00312         x0 = *(ptr1++);
00313 
00314         /* Perform the multiply-accumulate */
00315         sum0 += (q63_t) x0 *c0;
00316 
00317         /* Decrement the loop counter */
00318         tapCnt--;
00319       }
00320 
00321       /* If the polyPhase length is not a multiple of 4, compute the remaining filter taps */
00322       tapCnt = phaseLen & 0x3u;
00323 
00324       while(tapCnt > 0u)
00325       {
00326         /* Read the coefficient */
00327         c0 = *(ptr2);
00328 
00329         /* Increment the coefficient pointer by interpolation factor times. */
00330         ptr2 += S->L;
00331 
00332         /* Read the input sample */
00333         x0 = *(ptr1++);
00334 
00335         /* Perform the multiply-accumulate */
00336         sum0 += (q63_t) x0 *c0;
00337 
00338         /* Decrement the loop counter */
00339         tapCnt--;
00340       }
00341 
00342       /* The result is in the accumulator, store in the destination buffer. */
00343       *pDst++ = (q15_t) (__SSAT((sum0 >> 15), 16));
00344 
00345       j++;
00346 
00347       /* Decrement the loop counter */
00348       i--;
00349     }
00350 
00351     /* Advance the state pointer by 1        
00352      * to process the next group of interpolation factor number samples */
00353     pState = pState + 1;
00354 
00355     /* Decrement the loop counter */
00356     blkCnt--;
00357   }
00358 
00359 
00360   /* Processing is complete.    
00361    ** Now copy the last phaseLen - 1 samples to the satrt of the state buffer.    
00362    ** This prepares the state buffer for the next function call. */
00363 
00364   /* Points to the start of the state buffer */
00365   pStateCurnt = S->pState;
00366 
00367   i = ((uint32_t) phaseLen - 1u) >> 2u;
00368 
00369   /* copy data */
00370   while(i > 0u)
00371   {
00372 #ifndef UNALIGNED_SUPPORT_DISABLE
00373 
00374     *__SIMD32(pStateCurnt)++ = *__SIMD32(pState)++;
00375     *__SIMD32(pStateCurnt)++ = *__SIMD32(pState)++;
00376 
00377 #else
00378 
00379     *pStateCurnt++ = *pState++;
00380     *pStateCurnt++ = *pState++;
00381     *pStateCurnt++ = *pState++;
00382     *pStateCurnt++ = *pState++;
00383     
00384 #endif  /*  #ifndef UNALIGNED_SUPPORT_DISABLE   */
00385     
00386     /* Decrement the loop counter */
00387     i--;
00388   }
00389 
00390   i = ((uint32_t) phaseLen - 1u) % 0x04u;
00391 
00392   while(i > 0u)
00393   {
00394     *pStateCurnt++ = *pState++;
00395 
00396     /* Decrement the loop counter */
00397     i--;
00398   }
00399 }
00400 
00401 #else
00402 
00403   /* Run the below code for Cortex-M0 */
00404 
00405 void arm_fir_interpolate_q15(
00406   const arm_fir_interpolate_instance_q15 * S,
00407   q15_t * pSrc,
00408   q15_t * pDst,
00409   uint32_t blockSize)
00410 {
00411   q15_t *pState = S->pState;                     /* State pointer                                            */
00412   q15_t *pCoeffs = S->pCoeffs;                   /* Coefficient pointer                                      */
00413   q15_t *pStateCurnt;                            /* Points to the current sample of the state                */
00414   q15_t *ptr1, *ptr2;                            /* Temporary pointers for state and coefficient buffers     */
00415   q63_t sum;                                     /* Accumulator */
00416   q15_t x0, c0;                                  /* Temporary variables to hold state and coefficient values */
00417   uint32_t i, blkCnt, tapCnt;                    /* Loop counters                                            */
00418   uint16_t phaseLen = S->phaseLength;            /* Length of each polyphase filter component */
00419 
00420 
00421   /* S->pState buffer contains previous frame (phaseLen - 1) samples */
00422   /* pStateCurnt points to the location where the new input data should be written */
00423   pStateCurnt = S->pState + (phaseLen - 1u);
00424 
00425   /* Total number of intput samples */
00426   blkCnt = blockSize;
00427 
00428   /* Loop over the blockSize. */
00429   while(blkCnt > 0u)
00430   {
00431     /* Copy new input sample into the state buffer */
00432     *pStateCurnt++ = *pSrc++;
00433 
00434     /* Loop over the Interpolation factor. */
00435     i = S->L;
00436 
00437     while(i > 0u)
00438     {
00439       /* Set accumulator to zero */
00440       sum = 0;
00441 
00442       /* Initialize state pointer */
00443       ptr1 = pState;
00444 
00445       /* Initialize coefficient pointer */
00446       ptr2 = pCoeffs + (i - 1u);
00447 
00448       /* Loop over the polyPhase length */
00449       tapCnt = (uint32_t) phaseLen;
00450 
00451       while(tapCnt > 0u)
00452       {
00453         /* Read the coefficient */
00454         c0 = *ptr2;
00455 
00456         /* Increment the coefficient pointer by interpolation factor times. */
00457         ptr2 += S->L;
00458 
00459         /* Read the input sample */
00460         x0 = *ptr1++;
00461 
00462         /* Perform the multiply-accumulate */
00463         sum += ((q31_t) x0 * c0);
00464 
00465         /* Decrement the loop counter */
00466         tapCnt--;
00467       }
00468 
00469       /* Store the result after converting to 1.15 format in the destination buffer */
00470       *pDst++ = (q15_t) (__SSAT((sum >> 15), 16));
00471 
00472       /* Decrement the loop counter */
00473       i--;
00474     }
00475 
00476     /* Advance the state pointer by 1           
00477      * to process the next group of interpolation factor number samples */
00478     pState = pState + 1;
00479 
00480     /* Decrement the loop counter */
00481     blkCnt--;
00482   }
00483 
00484   /* Processing is complete.         
00485    ** Now copy the last phaseLen - 1 samples to the start of the state buffer.       
00486    ** This prepares the state buffer for the next function call. */
00487 
00488   /* Points to the start of the state buffer */
00489   pStateCurnt = S->pState;
00490 
00491   i = (uint32_t) phaseLen - 1u;
00492 
00493   while(i > 0u)
00494   {
00495     *pStateCurnt++ = *pState++;
00496 
00497     /* Decrement the loop counter */
00498     i--;
00499   }
00500 
00501 }
00502 
00503 #endif /*   #ifndef ARM_MATH_CM0_FAMILY */
00504 
00505 
00506  /**    
00507   * @} end of FIR_Interpolate group    
00508   */