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/*
* 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.
*/
/************************************************************************/
/* */
/* Project:: */
/* $Author: beq07716 $*/
/* $Revision: 1000 $*/
/* $Date: 2010-06-28 13:08:20 +0200 (Mon, 28 Jun 2010) $*/
/* */
/************************************************************************/
#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
}
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