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 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.Echo.Delay * frequency) + 1;
 105     state->Tap[1].delay = (ALuint)(Slot->effect.Echo.LRDelay * frequency);
 106     state->Tap[1].delay += state->Tap[0].delay;
 107
 108     lrpan = Slot->effect.Echo.Spread*0.5f + 0.5f;
 109     state->GainL = aluSqrt(     lrpan);
 110     state->GainR = aluSqrt(1.0f-lrpan);
 111
 112     state->FeedGain = Slot->effect.Echo.Feedback;
 113
 114     cw = aluCos(F_PI*2.0f * LOWPASSFREQCUTOFF / frequency);
 115     g = 1.0f - Slot->effect.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, 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
 138     for(i = 0;i < SamplesToDo;i++,offset++)
 139     {
 140         // Sample first tap
 141         smp = state->SampleBuffer[(offset-tap1) & mask];
 142         samp[0] = smp * state->GainL;
 143         samp[1] = smp * state->GainR;
 144         // Sample second tap. Reverse LR panning
 145         smp = state->SampleBuffer[(offset-tap2) & mask];
 146         samp[0] += smp * state->GainR;
 147         samp[1] += smp * state->GainL;
 148
 149         // Apply damping and feedback gain to the second tap, and mix in the
 150         // new sample
 151         smp = lpFilter2P(&state->iirFilter, 0, smp+SamplesIn[i]);
 152         state->SampleBuffer[offset&mask] = smp * state->FeedGain;
 153
 154         SamplesOut[i][FRONT_LEFT]  += state->Gain[FRONT_LEFT]  * samp[0];
 155         SamplesOut[i][FRONT_RIGHT] += state->Gain[FRONT_RIGHT] * samp[1];
 156         SamplesOut[i][SIDE_LEFT]   += state->Gain[SIDE_LEFT]   * samp[0];
 157         SamplesOut[i][SIDE_RIGHT]  += state->Gain[SIDE_RIGHT]  * samp[1];
 158         SamplesOut[i][BACK_LEFT]   += state->Gain[BACK_LEFT]   * samp[0];
 159         SamplesOut[i][BACK_RIGHT]  += state->Gain[BACK_RIGHT]  * samp[1];
 160     }
 161     state->Offset = offset;
 162 }
 163
 164 ALeffectState *EchoCreate(void)
 165 {
 166     ALechoState *state;
 167
 168     state = malloc(sizeof(*state));
 169     if(!state)
 170         return NULL;
 171
 172     state->state.Destroy = EchoDestroy;
 173     state->state.DeviceUpdate = EchoDeviceUpdate;
 174     state->state.Update = EchoUpdate;
 175     state->state.Process = EchoProcess;
 176
 177     state->BufferLength = 0;
 178     state->SampleBuffer = NULL;
 179
 180     state->Tap[0].delay = 0;
 181     state->Tap[1].delay = 0;
 182     state->Offset = 0;
 183     state->GainL = 0.0f;
 184     state->GainR = 0.0f;
 185
 186     state->iirFilter.coeff = 0.0f;
 187     state->iirFilter.history[0] = 0.0f;
 188     state->iirFilter.history[1] = 0.0f;
 189
 190     return &state->state;
 191 }