Implement ff_scale_vector_to_given_sum_of_squares()

to aid generic gain control routines. Changes
for qcelp are included. Patch Collin McQuillan.

Originally committed as revision 20450 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/acelp_vectors.c

@@ -22,6 +22,7 @@
 
 #include <inttypes.h>
 #include "avcodec.h"
+#include "celp_math.h"
 #include "acelp_vectors.h"
 #include "celp_math.h"
 
@@ -177,3 +178,14 @@ void ff_adaptative_gain_control(float *buf_out, float speech_energ,
 
     *gain_mem = mem;
 }
+
+void ff_scale_vector_to_given_sum_of_squares(float *out, const float *in,
+                                             float sum_of_squares, const int n)
+{
+    int i;
+    float scalefactor = ff_dot_productf(in, in, n);
+    if (scalefactor)
+        scalefactor = sqrt(sum_of_squares / scalefactor);
+    for (i = 0; i < n; i++)
+        out[i] = in[i] * scalefactor;
+}

libavcodec/acelp_vectors.h

@@ -176,4 +176,22 @@ void ff_weighted_vector_sumf(float *out, const float *in_a, const float *in_b,
 void ff_adaptative_gain_control(float *buf_out, float speech_energ,
                                 int size, float alpha, float *gain_mem);
 
+/**
+ * Set the sum of squares of a signal by scaling
+ *
+ * @param out output samples
+ * @param in input samples
+ * @param sum_of_squares new sum of squares
+ * @param n number of samples
+ *
+ * @note If the input is zero (or its energy underflows), the output is zero.
+ *       This is the behavior of AGC in the AMR reference decoder. The QCELP
+ *       reference decoder seems to have undefined behavior.
+ *
+ * TIA/EIA/IS-733 2.4.8.3-2/3/4/5, 2.4.8.6
+ * 3GPP TS 26.090 6.1 (6)
+ */
+void ff_scale_vector_to_given_sum_of_squares(float *out, const float *in,
+                                             float sum_of_squares, const int n);
+
 #endif /* AVCODEC_ACELP_VECTORS_H */

libavcodec/qcelpdec.c

@@ -405,31 +405,6 @@ static void compute_svector(QCELPContext *q, const float *gain,
     }
 }
 
-/**
- * Compute the gain control
- *
- * @param v_in gain-controlled vector
- * @param v_ref vector to control gain of
- *
- * @return gain control
- *
- * FIXME: If v_ref is a zero vector, it energy is zero
- *        and the behavior of the gain control is
- *        undefined in the specs.
- *
- * TIA/EIA/IS-733 2.4.8.3-2/3/4/5, 2.4.8.6
- */
-static float compute_gain_ctrl(const float *v_ref, const float *v_in, const int len)
-{
-    float scalefactor = ff_dot_productf(v_in, v_in, len);
-
-    if(scalefactor)
-        scalefactor = sqrt(ff_dot_productf(v_ref, v_ref, len) / scalefactor);
-    else
-        av_log_missing_feature(NULL, "Zero energy for gain control", 1);
-    return scalefactor;
-}
-
 /**
  * Apply generic gain control.
  *
@@ -442,15 +417,13 @@ static float compute_gain_ctrl(const float *v_ref, const float *v_in, const int
 static void apply_gain_ctrl(float *v_out, const float *v_ref,
                             const float *v_in)
 {
-    int   i, j, len;
-    float scalefactor;
+    int i;
 
-    for(i=0, j=0; i<4; i++)
-    {
-        scalefactor = compute_gain_ctrl(v_ref + j, v_in + j, 40);
-        for(len=j+40; j<len; j++)
-            v_out[j] = scalefactor * v_in[j];
-    }
+    for (i = 0; i < 160; i += 40)
+        ff_scale_vector_to_given_sum_of_squares(v_out + i, v_in + i,
+                                                ff_dot_productf(v_ref + i,
+                                                                v_ref + i, 40),
+                                                40);
 }
 
 /**