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      1 /*
      2  * Copyright (C) 2004-2010 NXP Software
      3  * Copyright (C) 2010 The Android Open Source Project
      4  *
      5  * Licensed under the Apache License, Version 2.0 (the "License");
      6  * you may not use this file except in compliance with the License.
      7  * You may obtain a copy of the License at
      8  *
      9  *      http://www.apache.org/licenses/LICENSE-2.0
     10  *
     11  * Unless required by applicable law or agreed to in writing, software
     12  * distributed under the License is distributed on an "AS IS" BASIS,
     13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     14  * See the License for the specific language governing permissions and
     15  * limitations under the License.
     16  */
     17 
     18 #include "LVM_Types.h"
     19 #include "LVM_Macros.h"
     20 #include "LVC_Mixer_Private.h"
     21 
     22 /************************************************************************/
     23 /* FUNCTION:                                                            */
     24 /*   LVMixer3_Init                                                      */
     25 /*                                                                      */
     26 /* DESCRIPTION:                                                         */
     27 /*  This intialization function intializes the private instance         */
     28 /*  paramters for a given Audio Stream based on TargetGain and          */
     29 /*  CurrentGain                                                         */
     30 /*  This function caclulates the "Shift" required to provide the        */
     31 /*  integer part of TargetGain and fractional gain values "Target" and  */
     32 /*  "Current" based on maximum(TargetGain,CurrentGain)                  */
     33 /*  E.g. CurrentGain=1.9 and TargetGain=2.5 then based on               */
     34 /*  MaxGain of 2.5, Shift = 2, Current=1.9/4=0.475, Target=2.5/4=0.625  */
     35 /*  Therefore integer gain of 4 is provided by Left Shift of 2 and      */
     36 /*  fraction gain is provided through Current=0.475 and Target=0.625    */
     37 /* PARAMETERS:                                                          */
     38 /*  pStream     - ptr to Instance Parameter Structure LVMixer3_st for an*/
     39 /*                Audio Stream                                          */
     40 /*  TargetGain  - TargetGain value in Q 16.15 format                    */
     41 /*  CurrentGain - CurrentGain value in Q 16.15 format                   */
     42 /*                                                                      */
     43 /* RETURNS:                                                             */
     44 /*  void                                                                */
     45 /*                                                                      */
     46 /************************************************************************/
     47 
     48 void LVC_Mixer_Init( LVMixer3_st *pStream,
     49                     LVM_INT32           TargetGain,
     50                     LVM_INT32           CurrentGain)
     51 {
     52     LVM_INT16       Shift=0;
     53     LVM_INT32       MaxGain=TargetGain;         // MaxGain is in Q16.15 format
     54     Mix_Private_st  *pInstance=(Mix_Private_st *)pStream->PrivateParams;
     55     if(CurrentGain>MaxGain)
     56         MaxGain=CurrentGain;                    // MaxGain=max(CurrentGain,TargetGain)
     57 
     58     MaxGain=MaxGain>>15;                        // MaxGain in Q31.0 format i.e Integer part only
     59     while(MaxGain>0){                           // Update Shift required to provide integer gain
     60         Shift++;
     61         MaxGain=MaxGain>>1;
     62     }
     63     pInstance->Target=TargetGain<<(16-Shift);   // Update fractional gain Target
     64     pInstance->Current=CurrentGain<<(16-Shift); // Update fractional gain Current
     65     pInstance->Shift=Shift;                     // Update Shift
     66 }
     67 
     68