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
