rlm@0: /**
rlm@0:  * OpenAL cross platform audio library
rlm@0:  * Copyright (C) 2009 by Chris Robinson.
rlm@0:  * This library is free software; you can redistribute it and/or
rlm@0:  *  modify it under the terms of the GNU Library General Public
rlm@0:  *  License as published by the Free Software Foundation; either
rlm@0:  *  version 2 of the License, or (at your option) any later version.
rlm@0:  *
rlm@0:  * This library is distributed in the hope that it will be useful,
rlm@0:  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
rlm@0:  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
rlm@0:  *  Library General Public License for more details.
rlm@0:  *
rlm@0:  * You should have received a copy of the GNU Library General Public
rlm@0:  *  License along with this library; if not, write to the
rlm@0:  *  Free Software Foundation, Inc., 59 Temple Place - Suite 330,
rlm@0:  *  Boston, MA  02111-1307, USA.
rlm@0:  * Or go to http://www.gnu.org/copyleft/lgpl.html
rlm@0:  */
rlm@0: 
rlm@0: #include "config.h"
rlm@0: 
rlm@0: #include <math.h>
rlm@0: #include <stdlib.h>
rlm@0: 
rlm@0: #include "alMain.h"
rlm@0: #include "alFilter.h"
rlm@0: #include "alAuxEffectSlot.h"
rlm@0: #include "alError.h"
rlm@0: #include "alu.h"
rlm@0: 
rlm@0: 
rlm@0: typedef struct ALechoState {
rlm@0:     // Must be first in all effects!
rlm@0:     ALeffectState state;
rlm@0: 
rlm@0:     ALfloat *SampleBuffer;
rlm@0:     ALuint BufferLength;
rlm@0: 
rlm@0:     // The echo is two tap. The delay is the number of samples from before the
rlm@0:     // current offset
rlm@0:     struct {
rlm@0:         ALuint delay;
rlm@0:     } Tap[2];
rlm@0:     ALuint Offset;
rlm@0:     // The LR gains for the first tap. The second tap uses the reverse
rlm@0:     ALfloat GainL;
rlm@0:     ALfloat GainR;
rlm@0: 
rlm@0:     ALfloat FeedGain;
rlm@0: 
rlm@0:     ALfloat Gain[MAXCHANNELS];
rlm@0: 
rlm@0:     FILTER iirFilter;
rlm@0:     ALfloat history[2];
rlm@0: } ALechoState;
rlm@0: 
rlm@0: static ALvoid EchoDestroy(ALeffectState *effect)
rlm@0: {
rlm@0:     ALechoState *state = (ALechoState*)effect;
rlm@0:     if(state)
rlm@0:     {
rlm@0:         free(state->SampleBuffer);
rlm@0:         state->SampleBuffer = NULL;
rlm@0:         free(state);
rlm@0:     }
rlm@0: }
rlm@0: 
rlm@0: static ALboolean EchoDeviceUpdate(ALeffectState *effect, ALCdevice *Device)
rlm@0: {
rlm@0:     ALechoState *state = (ALechoState*)effect;
rlm@0:     ALuint maxlen, i;
rlm@0: 
rlm@0:     // Use the next power of 2 for the buffer length, so the tap offsets can be
rlm@0:     // wrapped using a mask instead of a modulo
rlm@0:     maxlen  = (ALuint)(AL_ECHO_MAX_DELAY * Device->Frequency) + 1;
rlm@0:     maxlen += (ALuint)(AL_ECHO_MAX_LRDELAY * Device->Frequency) + 1;
rlm@0:     maxlen  = NextPowerOf2(maxlen);
rlm@0: 
rlm@0:     if(maxlen != state->BufferLength)
rlm@0:     {
rlm@0:         void *temp;
rlm@0: 
rlm@0:         temp = realloc(state->SampleBuffer, maxlen * sizeof(ALfloat));
rlm@0:         if(!temp)
rlm@0:             return AL_FALSE;
rlm@0:         state->SampleBuffer = temp;
rlm@0:         state->BufferLength = maxlen;
rlm@0:     }
rlm@0:     for(i = 0;i < state->BufferLength;i++)
rlm@0:         state->SampleBuffer[i] = 0.0f;
rlm@0: 
rlm@0:     return AL_TRUE;
rlm@0: }
rlm@0: 
rlm@0: static ALvoid EchoUpdate(ALeffectState *effect, ALCcontext *Context, const ALeffectslot *Slot)
rlm@0: {
rlm@0:     ALechoState *state = (ALechoState*)effect;
rlm@0:     ALCdevice *Device = Context->Device;
rlm@0:     ALuint frequency = Device->Frequency;
rlm@0:     ALfloat lrpan, cw, g, gain;
rlm@0:     ALuint i;
rlm@0: 
rlm@0:     state->Tap[0].delay = (ALuint)(Slot->effect.Params.Echo.Delay * frequency) + 1;
rlm@0:     state->Tap[1].delay = (ALuint)(Slot->effect.Params.Echo.LRDelay * frequency);
rlm@0:     state->Tap[1].delay += state->Tap[0].delay;
rlm@0: 
rlm@0:     lrpan = Slot->effect.Params.Echo.Spread*0.5f + 0.5f;
rlm@0:     state->GainL = aluSqrt(     lrpan);
rlm@0:     state->GainR = aluSqrt(1.0f-lrpan);
rlm@0: 
rlm@0:     state->FeedGain = Slot->effect.Params.Echo.Feedback;
rlm@0: 
rlm@0:     cw = cos(2.0*M_PI * LOWPASSFREQCUTOFF / frequency);
rlm@0:     g = 1.0f - Slot->effect.Params.Echo.Damping;
rlm@0:     state->iirFilter.coeff = lpCoeffCalc(g, cw);
rlm@0: 
rlm@0:     gain = Slot->Gain;
rlm@0:     for(i = 0;i < MAXCHANNELS;i++)
rlm@0:         state->Gain[i] = 0.0f;
rlm@0:     for(i = 0;i < Device->NumChan;i++)
rlm@0:     {
rlm@0:         enum Channel chan = Device->Speaker2Chan[i];
rlm@0:         state->Gain[chan] = gain;
rlm@0:     }
rlm@0: }
rlm@0: 
rlm@0: static ALvoid EchoProcess(ALeffectState *effect, const ALeffectslot *Slot, ALuint SamplesToDo, const ALfloat *SamplesIn, ALfloat (*SamplesOut)[MAXCHANNELS])
rlm@0: {
rlm@0:     ALechoState *state = (ALechoState*)effect;
rlm@0:     const ALuint mask = state->BufferLength-1;
rlm@0:     const ALuint tap1 = state->Tap[0].delay;
rlm@0:     const ALuint tap2 = state->Tap[1].delay;
rlm@0:     ALuint offset = state->Offset;
rlm@0:     ALfloat samp[2], smp;
rlm@0:     ALuint i;
rlm@0:     (void)Slot;
rlm@0: 
rlm@0:     for(i = 0;i < SamplesToDo;i++,offset++)
rlm@0:     {
rlm@0:         // Sample first tap
rlm@0:         smp = state->SampleBuffer[(offset-tap1) & mask];
rlm@0:         samp[0] = smp * state->GainL;
rlm@0:         samp[1] = smp * state->GainR;
rlm@0:         // Sample second tap. Reverse LR panning
rlm@0:         smp = state->SampleBuffer[(offset-tap2) & mask];
rlm@0:         samp[0] += smp * state->GainR;
rlm@0:         samp[1] += smp * state->GainL;
rlm@0: 
rlm@0:         // Apply damping and feedback gain to the second tap, and mix in the
rlm@0:         // new sample
rlm@0:         smp = lpFilter2P(&state->iirFilter, 0, smp+SamplesIn[i]);
rlm@0:         state->SampleBuffer[offset&mask] = smp * state->FeedGain;
rlm@0: 
rlm@0:         SamplesOut[i][FRONT_LEFT]  += state->Gain[FRONT_LEFT]  * samp[0];
rlm@0:         SamplesOut[i][FRONT_RIGHT] += state->Gain[FRONT_RIGHT] * samp[1];
rlm@0:         SamplesOut[i][SIDE_LEFT]   += state->Gain[SIDE_LEFT]   * samp[0];
rlm@0:         SamplesOut[i][SIDE_RIGHT]  += state->Gain[SIDE_RIGHT]  * samp[1];
rlm@0:         SamplesOut[i][BACK_LEFT]   += state->Gain[BACK_LEFT]   * samp[0];
rlm@0:         SamplesOut[i][BACK_RIGHT]  += state->Gain[BACK_RIGHT]  * samp[1];
rlm@0:     }
rlm@0:     state->Offset = offset;
rlm@0: }
rlm@0: 
rlm@0: ALeffectState *EchoCreate(void)
rlm@0: {
rlm@0:     ALechoState *state;
rlm@0: 
rlm@0:     state = malloc(sizeof(*state));
rlm@0:     if(!state)
rlm@0:         return NULL;
rlm@0: 
rlm@0:     state->state.Destroy = EchoDestroy;
rlm@0:     state->state.DeviceUpdate = EchoDeviceUpdate;
rlm@0:     state->state.Update = EchoUpdate;
rlm@0:     state->state.Process = EchoProcess;
rlm@0: 
rlm@0:     state->BufferLength = 0;
rlm@0:     state->SampleBuffer = NULL;
rlm@0: 
rlm@0:     state->Tap[0].delay = 0;
rlm@0:     state->Tap[1].delay = 0;
rlm@0:     state->Offset = 0;
rlm@0:     state->GainL = 0.0f;
rlm@0:     state->GainR = 0.0f;
rlm@0: 
rlm@0:     state->iirFilter.coeff = 0.0f;
rlm@0:     state->iirFilter.history[0] = 0.0f;
rlm@0:     state->iirFilter.history[1] = 0.0f;
rlm@0: 
rlm@0:     return &state->state;
rlm@0: }