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      1 /*
      2  *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
      3  *
      4  *  Use of this source code is governed by a BSD-style license
      5  *  that can be found in the LICENSE file in the root of the source
      6  *  tree. An additional intellectual property rights grant can be found
      7  *  in the file PATENTS.  All contributing project authors may
      8  *  be found in the AUTHORS file in the root of the source tree.
      9  */
     10 
     11 /******************************************************************
     12 
     13  iLBC Speech Coder ANSI-C Source Code
     14 
     15  WebRtcIlbcfix_GainDequant.c
     16 
     17 ******************************************************************/
     18 
     19 #include "defines.h"
     20 #include "constants.h"
     21 
     22 /*----------------------------------------------------------------*
     23  *  decoder for quantized gains in the gain-shape coding of
     24  *  residual
     25  *---------------------------------------------------------------*/
     26 
     27 int16_t WebRtcIlbcfix_GainDequant(
     28     /* (o) quantized gain value (Q14) */
     29     int16_t index, /* (i) quantization index */
     30     int16_t maxIn, /* (i) maximum of unquantized gain (Q14) */
     31     int16_t stage /* (i) The stage of the search */
     32                                                 ){
     33   int16_t scale;
     34   const int16_t *gain;
     35 
     36   /* obtain correct scale factor */
     37 
     38   scale=WEBRTC_SPL_ABS_W16(maxIn);
     39   scale = WEBRTC_SPL_MAX(1638, scale);  /* if lower than 0.1, set it to 0.1 */
     40 
     41   /* select the quantization table and return the decoded value */
     42   gain = WebRtcIlbcfix_kGain[stage];
     43 
     44   return (int16_t)((scale * gain[index] + 8192) >> 14);
     45 }
     46