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 /************************************************************************/ 24 /* FUNCTION: */ 25 /* LVMixer3_VarSlope_SetTimeConstant */ 26 /* */ 27 /* DESCRIPTION: */ 28 /* This function calculates the step change for fractional gain for a */ 29 /* given time constant, sample rate and num channels */ 30 /* Delta=(2147483647*4*1000)/(NumChannels*SampleRate*Tc_millisec) */ 31 /* in Q 0.31 format */ 32 /* */ 33 /* PARAMETERS: */ 34 /* pStream - ptr to Instance Parameter Structure LVMixer3_st for an*/ 35 /* Audio Stream */ 36 /* Tc_millisec - TimeConstant i.e time required in milli second to */ 37 /* go from linear fractional gain of 0 to 0.99999999 */ 38 /* Fs - LVM_Fs_en enumerator for Sampling Frequency */ 39 /* NumChannels - Number of channels in Audio Stream 1=Mono, 2=Stereo */ 40 /* */ 41 /* UPDATES: */ 42 /* Delta - the step change for fractional gain per 4 samples */ 43 /* in Q0.31 format for a given Time Constant, */ 44 /* Sample Rate and NumChannels */ 45 /* RETURNS: */ 46 /* void */ 47 /************************************************************************/ 48 49 void LVC_Mixer_VarSlope_SetTimeConstant( LVMixer3_st *pStream, 50 LVM_INT32 Tc_millisec, 51 LVM_Fs_en Fs, 52 LVM_INT16 NumChannels) 53 { 54 LVM_INT32 DeltaTable[9]={1073741824, 55 779132389, 56 715827882, 57 536870912, 58 389566194, 59 357913941, 60 268435456, 61 194783097, 62 178956971}; 63 Mix_Private_st *pInstance=(Mix_Private_st *)pStream->PrivateParams; 64 LVM_INT32 Delta=DeltaTable[Fs]; 65 66 LVM_INT32 Current; 67 LVM_INT32 Target; 68 69 Delta=Delta>>(NumChannels-1); 70 71 /* Get gain values */ 72 Current = LVC_Mixer_GetCurrent( pStream ); 73 Target = LVC_Mixer_GetTarget( pStream ); 74 75 if (Current != Target) 76 { 77 Tc_millisec = Tc_millisec * 32767 / (Current - Target); 78 if (Tc_millisec<0) Tc_millisec = -Tc_millisec; 79 80 if(Tc_millisec==0) 81 Delta=0x7FFFFFFF; 82 else 83 Delta=Delta/Tc_millisec; 84 85 if(Delta==0) 86 Delta=1; // If Time Constant is so large that Delta is 0, assign minimum value to Delta 87 } 88 else 89 { 90 Delta =1; // Minimum value for proper call-backs (setting it to zero has some problems, to be corrected) 91 } 92 93 94 pInstance->Delta=Delta; // Delta=(2147483647*4*1000)/(NumChannels*SampleRate*Tc_millisec) in Q 0.31 format 95 } 96
