- work on evs decoder

src/libs/libevs/lib_com/gs_preech.cpp

@@ -0,0 +1,94 @@
+/*====================================================================================
+    EVS Codec 3GPP TS26.443 Nov 13, 2018. Version 12.11.0 / 13.7.0 / 14.3.0 / 15.1.0
+  ====================================================================================*/
+
+#include <math.h>
+#include "options.h"
+#include "cnst.h"
+#include "rom_com.h"
+#include "prot.h"
+
+
+/*-------------------------------------------------------------------*
+ * Local constants
+ *-------------------------------------------------------------------*/
+
+#define ATT_LENGHT            64
+#define ATT_SEG_LEN           (L_FRAME/ATT_LENGHT)
+#define INV_ATT_SEG_LEN       (1.0f/ATT_SEG_LEN)
+#define INV_L_FRAME           (1.0f/L_FRAME)
+
+
+/*-------------------------------------------------------------------*
+ * pre_echo_att()
+ *
+ * Attenuation of the pre-echo when encoder specifies an attack
+ *-------------------------------------------------------------------*/
+
+void pre_echo_att(
+    float *Last_frame_ener,     /* i/o: Energy of the last frame         */
+    float *exc,                 /* i/o: Excitation of the current frame  */
+    const short attack_flag,          /* i  : flag signalling attack encoded by AC mode (GSC) */
+    const short last_coder_type       /* i  : Last coder type                  */
+)
+{
+    float etmp;
+    float etmp1;
+    float finc[ATT_LENGHT], ratio;
+    short attack_pos, i;
+
+    if ( attack_flag == 1 && last_coder_type == AUDIO)
+    {
+        /*-------------------------------------------------------------------------*
+         * Find where the onset (attack) occurs by computing the energy per section
+         * The inverse weighting aims to favor the first maxima in case of
+         * gradual onset
+         *-------------------------------------------------------------------------*/
+
+        for(i = 0; i < ATT_LENGHT; i++)
+        {
+            finc[i] = sum2_f( exc + i*ATT_SEG_LEN, ATT_SEG_LEN )*((float)(ATT_LENGHT-i)/(ATT_LENGHT));
+        }
+
+        etmp = -1;
+        attack_pos = maximum(finc, ATT_LENGHT, &etmp);
+
+        /* Scaled the maximum energy and allowed 6 dB increase*/
+        etmp *= INV_ATT_SEG_LEN;
+        etmp1 = etmp;
+        *Last_frame_ener *= 4.0f;
+
+        /* If the maximum normalized energy > last frame energy + 6dB */
+        if( etmp > *Last_frame_ener && attack_pos > 0 )
+        {
+            /* Find the average energy before the attack */
+            etmp = sum_f( finc, attack_pos ) +  0.01f;
+            etmp /= (attack_pos*ATT_SEG_LEN);
+
+            /* Find the correction factor and apply it before the attack */
+            ratio = (float)sqrt(*Last_frame_ener/etmp);
+
+
+            /* Pre-echo atttenuation should never increase the energy */
+            ratio = min(ratio, 1.0f);
+            for(i = 0; i < attack_pos*ATT_SEG_LEN; i++)
+            {
+                exc[i] *= ratio;
+            }
+        }
+        *Last_frame_ener = etmp1;
+    }
+    else
+    {
+        /*-------------------------------------------------------*
+         * In normal cases, just compute the energy of the frame
+         *-------------------------------------------------------*/
+
+        etmp = sum2_f( exc, L_FRAME ) + 0.01f;
+
+        etmp *= INV_L_FRAME;
+        *Last_frame_ener = etmp;
+    }
+
+    return;
+}