celp_math: cleanup ff_dot_product()

based on code & idea by vitor
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/celp_math.c

@@ -197,14 +197,14 @@ int ff_log2(uint32_t value)
     return (power_int << 15) + value;
 }
 
-int ff_dot_product(const int16_t *a, const int16_t *b, int length, int shift)
+int ff_dot_product(const int16_t *a, const int16_t *b, int length)
 {
-    int i, sum = 0;
+    int i;
+    int64_t sum = 0;
+
+    for (i = 0; i < length; i++)
+        sum += MUL16(a[i], b[i]);
 
-    for (i = 0; i < length; i++) {
-        int64_t prod = av_clipl_int32(MUL64(a[i], b[i]) << shift);
-        sum = av_clipl_int32(sum + prod);
-    }
     return sum;
 }
 

libavcodec/celp_math.h

@@ -68,11 +68,10 @@ static inline int bidir_sal(int value, int offset)
  * @param a input data array
  * @param b input data array
  * @param length number of elements
- * @param shift the result is scaled by 2^shift
  *
  * @return dot product = sum of elementwise products
  */
-int ff_dot_product(const int16_t *a, const int16_t *b, int length, int shift);
+int ff_dot_product(const int16_t *a, const int16_t *b, int length);
 
 /**
  * returns the dot product.

libavcodec/g723_1.c

@@ -553,7 +553,7 @@ static void gen_acb_excitation(int16_t *vector, int16_t *prev_excitation,
     /* Calculate adaptive vector */
     cb_ptr += subfrm.ad_cb_gain * 20;
     for (i = 0; i < SUBFRAME_LEN; i++) {
-        sum = ff_dot_product(residual + i, cb_ptr, PITCH_ORDER, 1);
+        sum = ff_dot_product(residual + i, cb_ptr, PITCH_ORDER)<<1;
         vector[i] = av_clipl_int32((sum << 1) + (1 << 15)) >> 16;
     }
 }
@@ -579,7 +579,7 @@ static int autocorr_max(G723_1_Context *p, int offset, int *ccr_max,
     limit     = FFMIN(FRAME_LEN + PITCH_MAX - offset - length, pitch_lag + 3);
 
     for (i = pitch_lag - 3; i <= limit; i++) {
-        ccr = ff_dot_product(buf, buf + dir * i, length, 1);
+        ccr = ff_dot_product(buf, buf + dir * i, length)<<1;
 
         if (ccr > *ccr_max) {
             *ccr_max = ccr;
@@ -678,17 +678,17 @@ static void comp_ppf_coeff(G723_1_Context *p, int offset, int pitch_lag,
         return;
 
     /* Compute target energy */
-    energy[0] = ff_dot_product(buf, buf, SUBFRAME_LEN, 1);
+    energy[0] = ff_dot_product(buf, buf, SUBFRAME_LEN)<<1;
 
     /* Compute forward residual energy */
     if (fwd_lag)
         energy[2] = ff_dot_product(buf + fwd_lag, buf + fwd_lag,
-                                   SUBFRAME_LEN, 1);
+                                   SUBFRAME_LEN)<<1;
 
     /* Compute backward residual energy */
     if (back_lag)
         energy[4] = ff_dot_product(buf - back_lag, buf - back_lag,
-                                   SUBFRAME_LEN, 1);
+                                   SUBFRAME_LEN)<<1;
 
     /* Normalize and shorten */
     temp1 = 0;
@@ -749,7 +749,7 @@ static int comp_interp_index(G723_1_Context *p, int pitch_lag,
     ccr   = av_clipl_int32((int64_t)ccr + (1 << 15)) >> 16;
 
     /* Compute target energy */
-    tgt_eng  = ff_dot_product(buf, buf, SUBFRAME_LEN * 2, 1);
+    tgt_eng  = ff_dot_product(buf, buf, SUBFRAME_LEN * 2)<<1;
     *exc_eng = av_clipl_int32(tgt_eng + (1 << 15)) >> 16;
 
     if (ccr <= 0)
@@ -757,7 +757,7 @@ static int comp_interp_index(G723_1_Context *p, int pitch_lag,
 
     /* Compute best energy */
     best_eng = ff_dot_product(buf - index, buf - index,
-                              SUBFRAME_LEN * 2, 1);
+                              SUBFRAME_LEN * 2)<<1;
     best_eng = av_clipl_int32((int64_t)best_eng + (1 << 15)) >> 16;
 
     temp = best_eng * *exc_eng >> 3;
@@ -911,9 +911,9 @@ static void formant_postfilter(G723_1_Context *p, int16_t *lpc, int16_t *buf)
 
         /* Compute auto correlation coefficients */
         auto_corr[0] = ff_dot_product(temp_vector, temp_vector + 1,
-                                      SUBFRAME_LEN - 1, 1);
+                                      SUBFRAME_LEN - 1)<<1;
         auto_corr[1] = ff_dot_product(temp_vector, temp_vector,
-                                      SUBFRAME_LEN, 1);
+                                      SUBFRAME_LEN)<<1;
 
         /* Compute reflection coefficient */
         temp = auto_corr[1] >> 16;