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initial forking of open-al to create multiple listeners
author Robert McIntyre <rlm@mit.edu>
date Tue, 25 Oct 2011 13:02:31 -0700
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-1:000000000000 0:f9476ff7637e
1 /**
2 * OpenAL cross platform audio library
3 * Copyright (C) 2009 by Chris Robinson.
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Library General Public
6 * License as published by the Free Software Foundation; either
7 * version 2 of the License, or (at your option) any later version.
8 *
9 * This library is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * Library General Public License for more details.
13 *
14 * You should have received a copy of the GNU Library General Public
15 * License along with this library; if not, write to the
16 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
17 * Boston, MA 02111-1307, USA.
18 * Or go to http://www.gnu.org/copyleft/lgpl.html
19 */
20
21 #include "config.h"
22
23 #include <math.h>
24 #include <stdlib.h>
25
26 #include "alMain.h"
27 #include "alFilter.h"
28 #include "alAuxEffectSlot.h"
29 #include "alError.h"
30 #include "alu.h"
31
32
33 typedef struct ALechoState {
34 // Must be first in all effects!
35 ALeffectState state;
36
37 ALfloat *SampleBuffer;
38 ALuint BufferLength;
39
40 // The echo is two tap. The delay is the number of samples from before the
41 // current offset
42 struct {
43 ALuint delay;
44 } Tap[2];
45 ALuint Offset;
46 // The LR gains for the first tap. The second tap uses the reverse
47 ALfloat GainL;
48 ALfloat GainR;
49
50 ALfloat FeedGain;
51
52 ALfloat Gain[MAXCHANNELS];
53
54 FILTER iirFilter;
55 ALfloat history[2];
56 } ALechoState;
57
58 static ALvoid EchoDestroy(ALeffectState *effect)
59 {
60 ALechoState *state = (ALechoState*)effect;
61 if(state)
62 {
63 free(state->SampleBuffer);
64 state->SampleBuffer = NULL;
65 free(state);
66 }
67 }
68
69 static ALboolean EchoDeviceUpdate(ALeffectState *effect, ALCdevice *Device)
70 {
71 ALechoState *state = (ALechoState*)effect;
72 ALuint maxlen, i;
73
74 // Use the next power of 2 for the buffer length, so the tap offsets can be
75 // wrapped using a mask instead of a modulo
76 maxlen = (ALuint)(AL_ECHO_MAX_DELAY * Device->Frequency) + 1;
77 maxlen += (ALuint)(AL_ECHO_MAX_LRDELAY * Device->Frequency) + 1;
78 maxlen = NextPowerOf2(maxlen);
79
80 if(maxlen != state->BufferLength)
81 {
82 void *temp;
83
84 temp = realloc(state->SampleBuffer, maxlen * sizeof(ALfloat));
85 if(!temp)
86 return AL_FALSE;
87 state->SampleBuffer = temp;
88 state->BufferLength = maxlen;
89 }
90 for(i = 0;i < state->BufferLength;i++)
91 state->SampleBuffer[i] = 0.0f;
92
93 return AL_TRUE;
94 }
95
96 static ALvoid EchoUpdate(ALeffectState *effect, ALCcontext *Context, const ALeffectslot *Slot)
97 {
98 ALechoState *state = (ALechoState*)effect;
99 ALCdevice *Device = Context->Device;
100 ALuint frequency = Device->Frequency;
101 ALfloat lrpan, cw, g, gain;
102 ALuint i;
103
104 state->Tap[0].delay = (ALuint)(Slot->effect.Params.Echo.Delay * frequency) + 1;
105 state->Tap[1].delay = (ALuint)(Slot->effect.Params.Echo.LRDelay * frequency);
106 state->Tap[1].delay += state->Tap[0].delay;
107
108 lrpan = Slot->effect.Params.Echo.Spread*0.5f + 0.5f;
109 state->GainL = aluSqrt( lrpan);
110 state->GainR = aluSqrt(1.0f-lrpan);
111
112 state->FeedGain = Slot->effect.Params.Echo.Feedback;
113
114 cw = cos(2.0*M_PI * LOWPASSFREQCUTOFF / frequency);
115 g = 1.0f - Slot->effect.Params.Echo.Damping;
116 state->iirFilter.coeff = lpCoeffCalc(g, cw);
117
118 gain = Slot->Gain;
119 for(i = 0;i < MAXCHANNELS;i++)
120 state->Gain[i] = 0.0f;
121 for(i = 0;i < Device->NumChan;i++)
122 {
123 enum Channel chan = Device->Speaker2Chan[i];
124 state->Gain[chan] = gain;
125 }
126 }
127
128 static ALvoid EchoProcess(ALeffectState *effect, const ALeffectslot *Slot, ALuint SamplesToDo, const ALfloat *SamplesIn, ALfloat (*SamplesOut)[MAXCHANNELS])
129 {
130 ALechoState *state = (ALechoState*)effect;
131 const ALuint mask = state->BufferLength-1;
132 const ALuint tap1 = state->Tap[0].delay;
133 const ALuint tap2 = state->Tap[1].delay;
134 ALuint offset = state->Offset;
135 ALfloat samp[2], smp;
136 ALuint i;
137 (void)Slot;
138
139 for(i = 0;i < SamplesToDo;i++,offset++)
140 {
141 // Sample first tap
142 smp = state->SampleBuffer[(offset-tap1) & mask];
143 samp[0] = smp * state->GainL;
144 samp[1] = smp * state->GainR;
145 // Sample second tap. Reverse LR panning
146 smp = state->SampleBuffer[(offset-tap2) & mask];
147 samp[0] += smp * state->GainR;
148 samp[1] += smp * state->GainL;
149
150 // Apply damping and feedback gain to the second tap, and mix in the
151 // new sample
152 smp = lpFilter2P(&state->iirFilter, 0, smp+SamplesIn[i]);
153 state->SampleBuffer[offset&mask] = smp * state->FeedGain;
154
155 SamplesOut[i][FRONT_LEFT] += state->Gain[FRONT_LEFT] * samp[0];
156 SamplesOut[i][FRONT_RIGHT] += state->Gain[FRONT_RIGHT] * samp[1];
157 SamplesOut[i][SIDE_LEFT] += state->Gain[SIDE_LEFT] * samp[0];
158 SamplesOut[i][SIDE_RIGHT] += state->Gain[SIDE_RIGHT] * samp[1];
159 SamplesOut[i][BACK_LEFT] += state->Gain[BACK_LEFT] * samp[0];
160 SamplesOut[i][BACK_RIGHT] += state->Gain[BACK_RIGHT] * samp[1];
161 }
162 state->Offset = offset;
163 }
164
165 ALeffectState *EchoCreate(void)
166 {
167 ALechoState *state;
168
169 state = malloc(sizeof(*state));
170 if(!state)
171 return NULL;
172
173 state->state.Destroy = EchoDestroy;
174 state->state.DeviceUpdate = EchoDeviceUpdate;
175 state->state.Update = EchoUpdate;
176 state->state.Process = EchoProcess;
177
178 state->BufferLength = 0;
179 state->SampleBuffer = NULL;
180
181 state->Tap[0].delay = 0;
182 state->Tap[1].delay = 0;
183 state->Offset = 0;
184 state->GainL = 0.0f;
185 state->GainR = 0.0f;
186
187 state->iirFilter.coeff = 0.0f;
188 state->iirFilter.history[0] = 0.0f;
189 state->iirFilter.history[1] = 0.0f;
190
191 return &state->state;
192 }