/** * 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; }