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_VarSlope_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 /************************************************************************/
LVC_Mixer_VarSlope_SetTimeConstant(LVMixer3_FLOAT_st * pStream,LVM_INT32 Tc_millisec,LVM_Fs_en Fs,LVM_INT16 NumChannels)47 void LVC_Mixer_VarSlope_SetTimeConstant(LVMixer3_FLOAT_st* pStream, LVM_INT32 Tc_millisec,
48 LVM_Fs_en Fs, LVM_INT16 NumChannels) {
49 LVM_FLOAT DeltaTable[13] = {0.500000f, /*8000*/
50 0.362812f, /*11025*/
51 0.333333f, /*12000*/
52 0.250000f, /*16000*/
53 0.181406f, /*22050*/
54 0.166666f, /*24000*/
55 0.125000f, /*32000*/
56 0.090703f, /*44100*/
57 0.083333f, /*48000*/
58 0.045352f, /*88200*/
59 0.041666f, /*96000*/
60 0.022676f, /*176400*/
61 0.020833f}; /*192000*/
62 LVM_FLOAT Tc_millisec_float;
63 Mix_Private_FLOAT_st* pInstance = (Mix_Private_FLOAT_st*)pStream->PrivateParams;
64 LVM_FLOAT Delta = DeltaTable[Fs];
65
66 LVM_FLOAT Current;
67 LVM_FLOAT Target;
68
69 Delta = Delta / (NumChannels);
70
71 /* Get gain values */
72 Current = pInstance->Current;
73 Target = pInstance->Target;
74
75 if (Current != Target) {
76 Tc_millisec_float = (LVM_FLOAT)(Tc_millisec) / (Current - Target);
77 if (Tc_millisec_float < 0) Tc_millisec_float = -Tc_millisec_float;
78
79 if (Tc_millisec == 0)
80 Delta = 1.000000f;
81 else
82 Delta = Delta / Tc_millisec_float;
83
84 if (Delta == 0)
85 Delta = 0.0000000005f; /* If Time Constant is so large that Delta is 0, \
86 assign minimum value to Delta */
87 } else {
88 Delta = 0.0000000005f; /* Minimum value for proper call-backs \
89 (setting it to zero has some problems, to be corrected) */
90 }
91
92 pInstance->Delta = Delta; // Delta=(2147483647*4*1000)/(NumChannels*SampleRate*Tc_millisec)
93 }
94