Alc/alcEcho.c

   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 panning gains for the two taps */
  47     ALfloat Gain[2][MaxChannels];
  48
  49     ALfloat FeedGain;
  50
  51     FILTER iirFilter;
  52     ALfloat history[2];
  53 } ALechoState;
  54
  55 static ALvoid EchoDestroy(ALeffectState *effect)
  56 {
  57     ALechoState *state = (ALechoState*)effect;
  58     if(state)
  59     {
  60         free(state->SampleBuffer);
  61         state->SampleBuffer = NULL;
  62         free(state);
  63     }
  64 }
  65
  66 static ALboolean EchoDeviceUpdate(ALeffectState *effect, ALCdevice *Device)
  67 {
  68     ALechoState *state = (ALechoState*)effect;
  69     ALuint maxlen, i;
  70
  71     // Use the next power of 2 for the buffer length, so the tap offsets can be
  72     // wrapped using a mask instead of a modulo
  73     maxlen  = fastf2u(AL_ECHO_MAX_DELAY * Device->Frequency) + 1;
  74     maxlen += fastf2u(AL_ECHO_MAX_LRDELAY * Device->Frequency) + 1;
  75     maxlen  = NextPowerOf2(maxlen);
  76
  77     if(maxlen != state->BufferLength)
  78     {
  79         void *temp;
  80
  81         temp = realloc(state->SampleBuffer, maxlen * sizeof(ALfloat));
  82         if(!temp)
  83             return AL_FALSE;
  84         state->SampleBuffer = temp;
  85         state->BufferLength = maxlen;
  86     }
  87     for(i = 0;i < state->BufferLength;i++)
  88         state->SampleBuffer[i] = 0.0f;
  89
  90     return AL_TRUE;
  91 }
  92
  93 static ALvoid EchoUpdate(ALeffectState *effect, ALCdevice *Device, const ALeffectslot *Slot)
  94 {
  95     ALechoState *state = (ALechoState*)effect;
  96     ALuint frequency = Device->Frequency;
  97     ALfloat lrpan, cw, g, gain;
  98     ALfloat dirGain;
  99     ALuint i;
 100
 101     state->Tap[0].delay = fastf2u(Slot->effect.Echo.Delay * frequency) + 1;
 102     state->Tap[1].delay = fastf2u(Slot->effect.Echo.LRDelay * frequency);
 103     state->Tap[1].delay += state->Tap[0].delay;
 104
 105     lrpan = Slot->effect.Echo.Spread;
 106
 107     state->FeedGain = Slot->effect.Echo.Feedback;
 108
 109     cw = cosf(F_PI*2.0f * LOWPASSFREQREF / frequency);
 110     g = 1.0f - Slot->effect.Echo.Damping;
 111     state->iirFilter.coeff = lpCoeffCalc(g, cw);
 112
 113     gain = Slot->Gain;
 114     for(i = 0;i < MaxChannels;i++)
 115     {
 116         state->Gain[0][i] = 0.0f;
 117         state->Gain[1][i] = 0.0f;
 118     }
 119
 120     dirGain = fabsf(lrpan);
 121
 122     /* First tap panning */
 123     ComputeAngleGains(Device, atan2f(-lrpan, 0.0f), (1.0f-dirGain)*F_PI, gain, state->Gain[0]);
 124
 125     /* Second tap panning */
 126     ComputeAngleGains(Device, atan2f(+lrpan, 0.0f), (1.0f-dirGain)*F_PI, gain, state->Gain[1]);
 127 }
 128
 129 static ALvoid EchoProcess(ALeffectState *effect, ALuint SamplesToDo, const ALfloat *SamplesIn, ALfloat (*SamplesOut)[MaxChannels])
 130 {
 131     ALechoState *state = (ALechoState*)effect;
 132     const ALuint mask = state->BufferLength-1;
 133     const ALuint tap1 = state->Tap[0].delay;
 134     const ALuint tap2 = state->Tap[1].delay;
 135     ALuint offset = state->Offset;
 136     ALfloat smp;
 137     ALuint i, k;
 138
 139     for(i = 0;i < SamplesToDo;i++,offset++)
 140     {
 141         /* First tap */
 142         smp = state->SampleBuffer[(offset-tap1) & mask];
 143         for(k = 0;k < MaxChannels;k++)
 144             SamplesOut[i][k] += smp * state->Gain[0][k];
 145
 146         /* Second tap */
 147         smp = state->SampleBuffer[(offset-tap2) & mask];
 148         for(k = 0;k < MaxChannels;k++)
 149             SamplesOut[i][k] += smp * state->Gain[1][k];
 150
 151         // Apply damping and feedback gain to the second tap, and mix in the
 152         // new sample
 153         smp = lpFilter2P(&state->iirFilter, 0, smp+SamplesIn[i]);
 154         state->SampleBuffer[offset&mask] = smp * state->FeedGain;
 155     }
 156     state->Offset = offset;
 157 }
 158
 159 ALeffectState *EchoCreate(void)
 160 {
 161     ALechoState *state;
 162
 163     state = malloc(sizeof(*state));
 164     if(!state)
 165         return NULL;
 166
 167     state->state.Destroy = EchoDestroy;
 168     state->state.DeviceUpdate = EchoDeviceUpdate;
 169     state->state.Update = EchoUpdate;
 170     state->state.Process = EchoProcess;
 171
 172     state->BufferLength = 0;
 173     state->SampleBuffer = NULL;
 174
 175     state->Tap[0].delay = 0;
 176     state->Tap[1].delay = 0;
 177     state->Offset = 0;
 178
 179     state->iirFilter.coeff = 0.0f;
 180     state->iirFilter.history[0] = 0.0f;
 181     state->iirFilter.history[1] = 0.0f;
 182
 183     return &state->state;
 184 }