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      1 /*
      2  ** Copyright 2003-2010, VisualOn, Inc.
      3  **
      4  ** Licensed under the Apache License, Version 2.0 (the "License");
      5  ** you may not use this file except in compliance with the License.
      6  ** You may obtain a copy of the License at
      7  **
      8  **     http://www.apache.org/licenses/LICENSE-2.0
      9  **
     10  ** Unless required by applicable law or agreed to in writing, software
     11  ** distributed under the License is distributed on an "AS IS" BASIS,
     12  ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  ** See the License for the specific language governing permissions and
     14  ** limitations under the License.
     15  */
     16 
     17 /**************************************************************************
     18 *      File: gpclip.c                                                     *
     19 *                                                                         *
     20 *      Description:To avoid unstable synthesis on frame erasure, the gain *
     21 *      need to be limited(gain pitch < 1.0) when the following            *
     22 *      case occurs                                                        *
     23 *      a resonance on LPC filter(lp_disp < 60Hz)                          *
     24 *      a good pitch prediction (lp_gp > 0.95)                             *
     25 *                                                                         *
     26 ***************************************************************************/
     27 #include "typedef.h"
     28 #include "basic_op.h"
     29 
     30 #define DIST_ISF_MAX    307                /* 120 Hz (6400Hz=16384) */
     31 #define DIST_ISF_THRES  154                /* 60     (6400Hz=16384) */
     32 #define GAIN_PIT_THRES  14746              /* 0.9 in Q14 */
     33 #define GAIN_PIT_MIN    9830               /* 0.6 in Q14 */
     34 #define M               16
     35 
     36 
     37 void Init_gp_clip(
     38 		Word16 mem[]                          /* (o) : memory of gain of pitch clipping algorithm */
     39 		)
     40 {
     41 	mem[0] = DIST_ISF_MAX;
     42 	mem[1] = GAIN_PIT_MIN;
     43 }
     44 
     45 
     46 Word16 Gp_clip(
     47 		Word16 mem[]                          /* (i/o) : memory of gain of pitch clipping algorithm */
     48 	      )
     49 {
     50 	Word16 clip = 0;
     51 	if ((mem[0] < DIST_ISF_THRES) && (mem[1] > GAIN_PIT_THRES))
     52 		clip = 1;
     53 
     54 	return (clip);
     55 }
     56 
     57 
     58 void Gp_clip_test_isf(
     59 		Word16 isf[],                         /* (i)   : isf values (in frequency domain)           */
     60 		Word16 mem[]                          /* (i/o) : memory of gain of pitch clipping algorithm */
     61 		)
     62 {
     63 	Word16 dist, dist_min;
     64 	Word32 i;
     65 
     66 	dist_min = vo_sub(isf[1], isf[0]);
     67 
     68 	for (i = 2; i < M - 1; i++)
     69 	{
     70 		dist = vo_sub(isf[i], isf[i - 1]);
     71 		if(dist < dist_min)
     72 		{
     73 			dist_min = dist;
     74 		}
     75 	}
     76 
     77 	dist = extract_h(L_mac(vo_L_mult(26214, mem[0]), 6554, dist_min));
     78 
     79 	if (dist > DIST_ISF_MAX)
     80 	{
     81 		dist = DIST_ISF_MAX;
     82 	}
     83 	mem[0] = dist;
     84 
     85 	return;
     86 }
     87 
     88 
     89 void Gp_clip_test_gain_pit(
     90 		Word16 gain_pit,                      /* (i) Q14 : gain of quantized pitch                    */
     91 		Word16 mem[]                          /* (i/o)   : memory of gain of pitch clipping algorithm */
     92 		)
     93 {
     94 	Word16 gain;
     95 	Word32 L_tmp;
     96 	L_tmp = (29491 * mem[1])<<1;
     97 	L_tmp += (3277 * gain_pit)<<1;
     98 
     99 	gain = extract_h(L_tmp);
    100 
    101 	if(gain < GAIN_PIT_MIN)
    102 	{
    103 		gain = GAIN_PIT_MIN;
    104 	}
    105 	mem[1] = gain;
    106 	return;
    107 }
    108 
    109 
    110 
    111