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
LVC_Mixer_VarSlope_SetTimeConstant(LVMixer3_st * pStream,LVM_INT32 Tc_millisec,LVM_Fs_en Fs,LVM_INT16 NumChannels)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