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
48void LVC_Mixer_SetTimeConstant(LVMixer3_st *pStream,
49                            LVM_INT32           Tc_millisec,
50                            LVM_Fs_en           Fs,
51                            LVM_INT16           NumChannels)
52{
53    LVM_INT32   DeltaTable[9]={1073741824,
54                               779132389,
55                               715827882,
56                               536870912,
57                               389566194,
58                               357913941,
59                               268435456,
60                               194783097,
61                               178956971};
62    Mix_Private_st  *pInstance=(Mix_Private_st *)pStream->PrivateParams;
63    LVM_INT32   Delta=DeltaTable[Fs];
64    Delta=Delta>>(NumChannels-1);
65
66    if(Tc_millisec==0)
67        Delta=0x7FFFFFFF;
68    else
69        Delta=Delta/Tc_millisec;
70
71    if(Delta==0)
72        Delta=1;                // If Time Constant is so large that Delta is 0, assign minimum value to Delta
73
74    pInstance->Delta=Delta;     // Delta=(2147483647*4*1000)/(NumChannels*SampleRate*Tc_millisec) in Q 0.31 format
75}
76