frameworks/base/media/libeffects/lvm/lib/Common/src/LVC_Mixer_SetTarget.c

   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_SetTarget                                                 */
  25 /*                                                                      */
  26 /* DESCRIPTION:                                                         */
  27 /*  This function updates the private instance parameters: Shift,Target,*/
  28 /*  Current for a given Audio Stream based on new value of TargetGain   */
  29 /*                                                                      */
  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   */
  39 /*                    for an Audio Stream                               */
  40 /*  TargetGain      - TargetGain value in Q 16.15 format                */
  41 /*                                                                      */
  42 /* RETURNS:                                                             */
  43 /*  void                                                                */
  44 /*                                                                      */
  45 /************************************************************************/
  46
  47 void LVC_Mixer_SetTarget(LVMixer3_st *pStream,
  48                         LVM_INT32           TargetGain)
  49 {
  50     LVM_INT32       Shift=0;
  51     LVM_INT32       CurrentGain;
  52     LVM_INT32       MaxGain=TargetGain;                     // MaxGain is in Q16.15 format
  53     Mix_Private_st  *pInstance=(Mix_Private_st *)pStream->PrivateParams;
  54     CurrentGain=pInstance->Current>>(16-pInstance->Shift);  // CurrentGain in Q16.15 format
  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 }