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_SetTimeConstant */ 25 /* */ 26 /* DESCRIPTION: */ 27 /* This function calculates the step change for fractional gain for a */ 28 /* given time constant, sample rate and num channels */ 29 /* Delta=(2147483647*4*1000)/(NumChannels*SampleRate*Tc_millisec) */ 30 /* in Q 0.31 format */ 31 /* */ 32 /* PARAMETERS: */ 33 /* pStream - ptr to Instance Parameter Structure LVMixer3_st for an*/ 34 /* Audio Stream */ 35 /* Tc_millisec - TimeConstant i.e time required in milli second to */ 36 /* go from linear fractional gain of 0 to 0.99999999 */ 37 /* Fs - LVM_Fs_en enumerator for Sampling Frequency */ 38 /* NumChannels - Number of channels in Audio Stream 1=Mono, 2=Stereo */ 39 /* */ 40 /* UPDATES: */ 41 /* Delta - the step change for fractional gain per 4 samples */ 42 /* in Q0.31 format for a given Time Constant, */ 43 /* Sample Rate and NumChannels */ 44 /* RETURNS: */ 45 /* void */ 46 /************************************************************************/ 47 #ifdef BUILD_FLOAT 48 void LVC_Mixer_SetTimeConstant(LVMixer3_FLOAT_st *pStream, 49 LVM_INT32 Tc_millisec, 50 LVM_Fs_en Fs, 51 LVM_INT16 NumChannels) 52 { 53 #ifdef HIGHER_FS 54 LVM_FLOAT DeltaTable[11] = {0.500000f,/*8000*/ 55 0.362812f,/*11025*/ 56 0.333333f,/*12000*/ 57 0.250000f,/*16000*/ 58 0.181406f,/*22050*/ 59 0.166666f,/*24000*/ 60 0.125000f,/*32000*/ 61 0.090703f,/*44100*/ 62 0.083333f,/*48000*/ 63 0.041667f,/*96000*/ 64 0.020833f};/*192000*/ 65 #else 66 LVM_FLOAT DeltaTable[9] = {0.500000f,/*8000*/ 67 0.362812f,/*11025*/ 68 0.333333f,/*12000*/ 69 0.250000f,/*16000*/ 70 0.181406f,/*22050*/ 71 0.166666f,/*24000*/ 72 0.125000f,/*32000*/ 73 0.090703f,/*44100*/ 74 0.083333f};/*48000*/ 75 #endif 76 77 Mix_Private_FLOAT_st *pInstance = (Mix_Private_FLOAT_st *)pStream->PrivateParams; 78 LVM_FLOAT Delta = DeltaTable[Fs]; 79 Delta = Delta / (NumChannels); 80 81 if(Tc_millisec == 0) 82 Delta = 1.000000f; 83 else 84 Delta = Delta / Tc_millisec; 85 86 if(Delta == 0) 87 Delta = 0.0000000005f; /* If Time Constant is so large that Delta is 0, \ 88 assign minimum value to Delta */ 89 pInstance->Delta = Delta; // Delta=(2147483647*4*1000)/(NumChannels*SampleRate*Tc_millisec) 90 } 91 #else 92 void LVC_Mixer_SetTimeConstant(LVMixer3_st *pStream, 93 LVM_INT32 Tc_millisec, 94 LVM_Fs_en Fs, 95 LVM_INT16 NumChannels) 96 { 97 LVM_INT32 DeltaTable[9]={1073741824, 98 779132389, 99 715827882, 100 536870912, 101 389566194, 102 357913941, 103 268435456, 104 194783097, 105 178956971}; 106 Mix_Private_st *pInstance=(Mix_Private_st *)pStream->PrivateParams; 107 LVM_INT32 Delta=DeltaTable[Fs]; 108 Delta=Delta>>(NumChannels-1); 109 110 if(Tc_millisec==0) 111 Delta=0x7FFFFFFF; 112 else 113 Delta=Delta/Tc_millisec; 114 115 if(Delta==0) 116 Delta=1; // If Time Constant is so large that Delta is 0, assign minimum value to Delta 117 118 pInstance->Delta=Delta; // Delta=(2147483647*4*1000)/(NumChannels*SampleRate*Tc_millisec) in Q 0.31 format 119 } 120 #endif 121