Diff: src/Cortex-M4-M3/FilteringFunctions/arm_fir_interpolate_q31.c

Revision:

0:1014af42efd9

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/Cortex-M4-M3/FilteringFunctions/arm_fir_interpolate_q31.c	Thu Mar 10 15:07:50 2011 +0000
@@ -0,0 +1,239 @@
+/*-----------------------------------------------------------------------------  
+* Copyright (C) 2010 ARM Limited. All rights reserved.  
+*  
+* $Date:        29. November 2010  
+* $Revision: 	V1.0.3  
+*  
+* Project: 	    CMSIS DSP Library  
+* Title:		arm_fir_interpolate_q31.c  
+*  
+* Description:	Q31 FIR interpolation.  
+*  
+* Target Processor: Cortex-M4/Cortex-M3
+*  
+* Version 1.0.3 2010/11/29 
+*    Re-organized the CMSIS folders and updated documentation.  
+*   
+* Version 1.0.2 2010/11/11  
+*    Documentation updated.   
+*  
+* Version 1.0.1 2010/10/05   
+*    Production release and review comments incorporated.  
+*  
+* Version 1.0.0 2010/09/20   
+*    Production release and review comments incorporated  
+*  
+* Version 0.0.7  2010/06/10   
+*    Misra-C changes done  
+* ---------------------------------------------------------------------------*/ 
+ 
+#include "arm_math.h" 
+ 
+/**  
+ * @ingroup groupFilters  
+ */ 
+ 
+/**  
+ * @addtogroup FIR_Interpolate  
+ * @{  
+ */ 
+ 
+/**  
+ * @brief Processing function for the Q31 FIR interpolator.  
+ * @param[in] *S        points to an instance of the Q31 FIR interpolator 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  
+ * The function is implemented using an internal 64-bit accumulator.  
+ * The accumulator has a 2.62 format and maintains full precision of the intermediate multiplication results but provides only a single guard bit.  
+ * Thus, if the accumulator result overflows it wraps around rather than clip.  
+ * In order to avoid overflows completely the input signal must be scaled down by <code>1/(numTaps/L)</code>.  
+ * since <code>numTaps/L</code> additions occur per output sample.  
+ * After all multiply-accumulates are performed, the 2.62 accumulator is truncated to 1.32 format and then saturated to 1.31 format.  
+ */ 
+ 
+ 
+void arm_fir_interpolate_q31( 
+  const arm_fir_interpolate_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 *ptr1, *ptr2;                            /* Temporary pointers for state and coefficient buffers */ 
+  q63_t sum0;                                    /* Accumulators */ 
+  q31_t x0, c0;                                  /* Temporary variables to hold state and coefficient values */ 
+  uint32_t i, blkCnt, j;                         /* Loop counters */ 
+  uint16_t phaseLen = S->phaseLength, tapCnt;    /* Length of each polyphase filter component */ 
+ 
+ 
+  /* S->pState buffer contains previous frame (phaseLen - 1) samples */ 
+  /* pStateCurnt points to the location where the new input data should be written */ 
+  pStateCurnt = S->pState + ((q31_t) phaseLen - 1); 
+ 
+  /* Total number of intput samples */ 
+  blkCnt = blockSize; 
+ 
+  /* Loop over the blockSize. */ 
+  while(blkCnt > 0u) 
+  { 
+    /* Copy new input sample into the state buffer */ 
+    *pStateCurnt++ = *pSrc++; 
+ 
+    /* Address modifier index of coefficient buffer */ 
+    j = 1u; 
+ 
+    /* Loop over the Interpolation factor. */ 
+    i = S->L; 
+    while(i > 0u) 
+    { 
+      /* Set accumulator to zero */ 
+      sum0 = 0; 
+ 
+      /* Initialize state pointer */ 
+      ptr1 = pState; 
+ 
+      /* Initialize coefficient pointer */ 
+      ptr2 = pCoeffs + (S->L - j); 
+ 
+      /* Loop over the polyPhase length. Unroll by a factor of 4.  
+       ** Repeat until we've computed numTaps-(4*S->L) coefficients. */ 
+      tapCnt = phaseLen >> 2; 
+      while(tapCnt > 0u) 
+      { 
+ 
+        /* Read the coefficient */ 
+        c0 = *(ptr2); 
+ 
+        /* Upsampling is done by stuffing L-1 zeros between each sample.  
+         * So instead of multiplying zeros with coefficients,  
+         * Increment the coefficient pointer by interpolation factor times. */ 
+        ptr2 += S->L; 
+ 
+        /* Read the input sample */ 
+        x0 = *(ptr1++); 
+ 
+        /* Perform the multiply-accumulate */ 
+        sum0 += (q63_t) x0 *c0; 
+ 
+        /* Read the coefficient */ 
+        c0 = *(ptr2); 
+ 
+        /* Increment the coefficient pointer by interpolation factor times. */ 
+        ptr2 += S->L; 
+ 
+        /* Read the input sample */ 
+        x0 = *(ptr1++); 
+ 
+        /* Perform the multiply-accumulate */ 
+        sum0 += (q63_t) x0 *c0; 
+ 
+        /* Read the coefficient */ 
+        c0 = *(ptr2); 
+ 
+        /* Increment the coefficient pointer by interpolation factor times. */ 
+        ptr2 += S->L; 
+ 
+        /* Read the input sample */ 
+        x0 = *(ptr1++); 
+ 
+        /* Perform the multiply-accumulate */ 
+        sum0 += (q63_t) x0 *c0; 
+ 
+        /* Read the coefficient */ 
+        c0 = *(ptr2); 
+ 
+        /* Increment the coefficient pointer by interpolation factor times. */ 
+        ptr2 += S->L; 
+ 
+        /* Read the input sample */ 
+        x0 = *(ptr1++); 
+ 
+        /* Perform the multiply-accumulate */ 
+        sum0 += (q63_t) x0 *c0; 
+ 
+        /* Decrement the loop counter */ 
+        tapCnt--; 
+      } 
+ 
+      /* If the polyPhase length is not a multiple of 4, compute the remaining filter taps */ 
+      tapCnt = phaseLen & 0x3u; 
+ 
+      while(tapCnt > 0u) 
+      { 
+        /* Read the coefficient */ 
+        c0 = *(ptr2); 
+ 
+        /* Increment the coefficient pointer by interpolation factor times. */ 
+        ptr2 += S->L; 
+ 
+        /* Read the input sample */ 
+        x0 = *(ptr1++); 
+ 
+        /* Perform the multiply-accumulate */ 
+        sum0 += (q63_t) x0 *c0; 
+ 
+        /* Decrement the loop counter */ 
+        tapCnt--; 
+      } 
+ 
+      /* The result is in the accumulator, store in the destination buffer. */ 
+      *pDst++ = (q31_t) (sum0 >> 31); 
+ 
+      /* Increment the address modifier index of coefficient buffer */ 
+      j++; 
+ 
+      /* Decrement the loop counter */ 
+      i--; 
+    } 
+ 
+    /* Advance the state pointer by 1  
+     * to process the next group of interpolation factor number samples */ 
+    pState = pState + 1; 
+ 
+    /* Decrement the loop counter */ 
+    blkCnt--; 
+  } 
+ 
+  /* Processing is complete.  
+   ** Now copy the last phaseLen - 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; 
+ 
+  tapCnt = (phaseLen - 1u) >> 2u; 
+ 
+  /* copy data */ 
+  while(tapCnt > 0u) 
+  { 
+    *pStateCurnt++ = *pState++; 
+    *pStateCurnt++ = *pState++; 
+    *pStateCurnt++ = *pState++; 
+    *pStateCurnt++ = *pState++; 
+ 
+    /* Decrement the loop counter */ 
+    tapCnt--; 
+  } 
+ 
+  tapCnt = (phaseLen - 1u) % 0x04u; 
+ 
+  /* copy data */ 
+  while(tapCnt > 0u) 
+  { 
+    *pStateCurnt++ = *pState++; 
+ 
+    /* Decrement the loop counter */ 
+    tapCnt--; 
+  } 
+} 
+ 
+ /**  
+  * @} end of FIR_Interpolate group  
+  */