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/**
* OpenAL cross platform audio library
* Copyright (C) 2009 by Chris Robinson.
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
* Or go to http://www.gnu.org/copyleft/lgpl.html
*/
#include "config.h"
#include <math.h>
#include <stdlib.h>
#include "alMain.h"
#include "alFilter.h"
#include "alAuxEffectSlot.h"
#include "alError.h"
#include "alu.h"
typedef struct ALechoState {
// Must be first in all effects!
ALeffectState state;
ALfloat *SampleBuffer;
ALuint BufferLength;
// The echo is two tap. The delay is the number of samples from before the
// current offset
struct {
ALuint delay;
} Tap[2];
ALuint Offset;
// The LR gains for the first tap. The second tap uses the reverse
ALfloat GainL;
ALfloat GainR;
ALfloat FeedGain;
FILTER iirFilter;
ALfloat history[2];
} ALechoState;
ALvoid EchoDestroy(ALeffectState *effect)
{
ALechoState *state = (ALechoState*)effect;
if(state)
{
free(state->SampleBuffer);
state->SampleBuffer = NULL;
free(state);
}
}
ALboolean EchoDeviceUpdate(ALeffectState *effect, ALCdevice *Device)
{
ALechoState *state = (ALechoState*)effect;
ALuint maxlen, i;
// Use the next power of 2 for the buffer length, so the tap offsets can be
// wrapped using a mask instead of a modulo
maxlen = (ALuint)(AL_ECHO_MAX_DELAY * Device->Frequency) + 1;
maxlen += (ALuint)(AL_ECHO_MAX_LRDELAY * Device->Frequency) + 1;
maxlen = NextPowerOf2(maxlen);
if(maxlen != state->BufferLength)
{
void *temp;
temp = realloc(state->SampleBuffer, maxlen * sizeof(ALfloat));
if(!temp)
{
alSetError(AL_OUT_OF_MEMORY);
return AL_FALSE;
}
state->SampleBuffer = temp;
state->BufferLength = maxlen;
}
for(i = 0;i < state->BufferLength;i++)
state->SampleBuffer[i] = 0.0f;
return AL_TRUE;
}
ALvoid EchoUpdate(ALeffectState *effect, ALCcontext *Context, const ALeffect *Effect)
{
ALechoState *state = (ALechoState*)effect;
ALuint frequency = Context->Device->Frequency;
ALfloat lrpan, cw, a, g;
state->Tap[0].delay = (ALuint)(Effect->Echo.Delay * frequency) + 1;
state->Tap[1].delay = (ALuint)(Effect->Echo.LRDelay * frequency);
state->Tap[1].delay += state->Tap[0].delay;
lrpan = Effect->Echo.Spread*0.5f + 0.5f;
state->GainL = aluSqrt( lrpan);
state->GainR = aluSqrt(1.0f-lrpan);
state->FeedGain = Effect->Echo.Feedback;
cw = cos(2.0*M_PI * LOWPASSFREQCUTOFF / frequency);
g = 1.0f - Effect->Echo.Damping;
a = 0.0f;
if(g < 0.9999f) // 1-epsilon
a = (1 - g*cw - aluSqrt(2*g*(1-cw) - g*g*(1 - cw*cw))) / (1 - g);
state->iirFilter.coeff = a;
}
ALvoid EchoProcess(ALeffectState *effect, const ALeffectslot *Slot, ALuint SamplesToDo, const ALfloat *SamplesIn, ALfloat (*SamplesOut)[OUTPUTCHANNELS])
{
ALechoState *state = (ALechoState*)effect;
const ALuint mask = state->BufferLength-1;
const ALuint tap1 = state->Tap[0].delay;
const ALuint tap2 = state->Tap[1].delay;
ALuint offset = state->Offset;
const ALfloat gain = Slot->Gain;
ALfloat samp[2], smp;
ALuint i;
for(i = 0;i < SamplesToDo;i++,offset++)
{
// Sample first tap
smp = state->SampleBuffer[(offset-tap1) & mask];
samp[0] = smp * state->GainL;
samp[1] = smp * state->GainR;
// Sample second tap. Reverse LR panning
smp = state->SampleBuffer[(offset-tap2) & mask];
samp[0] += smp * state->GainR;
samp[1] += smp * state->GainL;
// Apply damping and feedback gain to the second tap, and mix in the
// new sample
smp = lpFilter2P(&state->iirFilter, 0, smp+SamplesIn[i]);
state->SampleBuffer[offset&mask] = smp * state->FeedGain;
// Apply slot gain
samp[0] *= gain;
samp[1] *= gain;
SamplesOut[i][FRONT_LEFT] += samp[0];
SamplesOut[i][FRONT_RIGHT] += samp[1];
SamplesOut[i][SIDE_LEFT] += samp[0];
SamplesOut[i][SIDE_RIGHT] += samp[1];
SamplesOut[i][BACK_LEFT] += samp[0];
SamplesOut[i][BACK_RIGHT] += samp[1];
}
state->Offset = offset;
}
ALeffectState *EchoCreate(void)
{
ALechoState *state;
state = malloc(sizeof(*state));
if(!state)
{
alSetError(AL_OUT_OF_MEMORY);
return NULL;
}
state->state.Destroy = EchoDestroy;
state->state.DeviceUpdate = EchoDeviceUpdate;
state->state.Update = EchoUpdate;
state->state.Process = EchoProcess;
state->BufferLength = 0;
state->SampleBuffer = NULL;
state->Tap[0].delay = 0;
state->Tap[1].delay = 0;
state->Offset = 0;
state->GainL = 0.0f;
state->GainR = 0.0f;
state->iirFilter.coeff = 0.0f;
state->iirFilter.history[0] = 0.0f;
state->iirFilter.history[1] = 0.0f;
return &state->state;
}
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