| /* |
| * Copyright (C) 2004-2010 NXP Software |
| * Copyright (C) 2010 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #include "LVM_Types.h" |
| #include "LVM_Macros.h" |
| #include "LVC_Mixer_Private.h" |
| |
| |
| /************************************************************************/ |
| /* FUNCTION: */ |
| /* LVMixer3_VarSlope_SetTimeConstant */ |
| /* */ |
| /* DESCRIPTION: */ |
| /* This function calculates the step change for fractional gain for a */ |
| /* given time constant, sample rate and num channels */ |
| /* Delta=(2147483647*4*1000)/(NumChannels*SampleRate*Tc_millisec) */ |
| /* in Q 0.31 format */ |
| /* */ |
| /* PARAMETERS: */ |
| /* pStream - ptr to Instance Parameter Structure LVMixer3_st for an*/ |
| /* Audio Stream */ |
| /* Tc_millisec - TimeConstant i.e time required in milli second to */ |
| /* go from linear fractional gain of 0 to 0.99999999 */ |
| /* Fs - LVM_Fs_en enumerator for Sampling Frequency */ |
| /* NumChannels - Number of channels in Audio Stream 1=Mono, 2=Stereo */ |
| /* */ |
| /* UPDATES: */ |
| /* Delta - the step change for fractional gain per 4 samples */ |
| /* in Q0.31 format for a given Time Constant, */ |
| /* Sample Rate and NumChannels */ |
| /* RETURNS: */ |
| /* void */ |
| /************************************************************************/ |
| |
| void LVC_Mixer_VarSlope_SetTimeConstant( LVMixer3_st *pStream, |
| LVM_INT32 Tc_millisec, |
| LVM_Fs_en Fs, |
| LVM_INT16 NumChannels) |
| { |
| LVM_INT32 DeltaTable[9]={1073741824, |
| 779132389, |
| 715827882, |
| 536870912, |
| 389566194, |
| 357913941, |
| 268435456, |
| 194783097, |
| 178956971}; |
| Mix_Private_st *pInstance=(Mix_Private_st *)pStream->PrivateParams; |
| LVM_INT32 Delta=DeltaTable[Fs]; |
| |
| LVM_INT32 Current; |
| LVM_INT32 Target; |
| |
| Delta=Delta>>(NumChannels-1); |
| |
| /* Get gain values */ |
| Current = LVC_Mixer_GetCurrent( pStream ); |
| Target = LVC_Mixer_GetTarget( pStream ); |
| |
| if (Current != Target) |
| { |
| Tc_millisec = Tc_millisec * 32767 / (Current - Target); |
| if (Tc_millisec<0) Tc_millisec = -Tc_millisec; |
| |
| if(Tc_millisec==0) |
| Delta=0x7FFFFFFF; |
| else |
| Delta=Delta/Tc_millisec; |
| |
| if(Delta==0) |
| Delta=1; // If Time Constant is so large that Delta is 0, assign minimum value to Delta |
| } |
| else |
| { |
| Delta =1; // Minimum value for proper call-backs (setting it to zero has some problems, to be corrected) |
| } |
| |
| |
| pInstance->Delta=Delta; // Delta=(2147483647*4*1000)/(NumChannels*SampleRate*Tc_millisec) in Q 0.31 format |
| } |