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-rw-r--r--Alc/effects/autowah.c142
1 files changed, 71 insertions, 71 deletions
diff --git a/Alc/effects/autowah.c b/Alc/effects/autowah.c
index 29ec02af..785fdb28 100644
--- a/Alc/effects/autowah.c
+++ b/Alc/effects/autowah.c
@@ -28,16 +28,11 @@
#include "alAuxEffectSlot.h"
-/* You can tweak the octave of this dynamic filter just changing next macro
- * guitar - (default) 2.0f
- * bass - 4.0f
- */
-#define OCTAVE 2.0f
-
-
-/* We use a lfo with a custom low-pass filter to generate autowah
- * effect and a high-pass filter to avoid distortion and aliasing.
- * By adding the two filters up, we obtain a dynamic bandpass filter.
+/* Auto-wah is simply a low-pass filter with a cutoff frequency that shifts up
+ * or down depending on the input signal, and a resonant peak at the cutoff.
+ *
+ * Currently, we assume a cutoff frequency range of 500hz (no amplitude) to
+ * 3khz (peak gain). Peak gain is assumed to be in normalized scale.
*/
typedef struct ALautowahState {
@@ -47,49 +42,42 @@ typedef struct ALautowahState {
ALfloat Gain[MaxChannels];
/* Effect parameters */
- ALfloat AttackTime;
- ALfloat ReleaseTime;
+ ALfloat AttackRate;
+ ALfloat ReleaseRate;
ALfloat Resonance;
ALfloat PeakGain;
- ALuint Frequency;
+ ALfloat GainCtrl;
+ ALfloat Frequency;
/* Samples processing */
- ALuint lfo;
- ALfilterState low_pass;
- ALfilterState high_pass;
+ ALfilterState LowPass;
} ALautowahState;
static ALvoid ALautowahState_Destruct(ALautowahState *UNUSED(state))
{
}
-static ALboolean ALautowahState_deviceUpdate(ALautowahState *UNUSED(state), ALCdevice *UNUSED(device))
+static ALboolean ALautowahState_deviceUpdate(ALautowahState *state, ALCdevice *device)
{
+ state->Frequency = device->Frequency;
return AL_TRUE;
}
-static ALvoid ALautowahState_update(ALautowahState *state, ALCdevice *Device, const ALeffectslot *Slot)
+static ALvoid ALautowahState_update(ALautowahState *state, ALCdevice *device, const ALeffectslot *slot)
{
- const ALfloat cutoff = LOWPASSFREQREF / (Device->Frequency * 4.0f);
- const ALfloat bandwidth = (cutoff / 2.0f) / (cutoff * 0.67f);
+ ALfloat attackTime, releaseTime;
ALfloat gain;
- /* computing high-pass filter coefficients */
- ALfilterState_setParams(&state->high_pass, ALfilterType_HighPass, 1.0f,
- cutoff, bandwidth);
+ attackTime = slot->EffectProps.Autowah.AttackTime * state->Frequency;
+ releaseTime = slot->EffectProps.Autowah.ReleaseTime * state->Frequency;
- state->AttackTime = Slot->EffectProps.Autowah.AttackTime;
- state->ReleaseTime = Slot->EffectProps.Autowah.ReleaseTime;
- state->Frequency = Device->Frequency;
- state->PeakGain = Slot->EffectProps.Autowah.PeakGain;
- state->Resonance = Slot->EffectProps.Autowah.Resonance;
+ state->AttackRate = 1.0f / attackTime;
+ state->ReleaseRate = 1.0f / releaseTime;
+ state->PeakGain = slot->EffectProps.Autowah.PeakGain;
+ state->Resonance = slot->EffectProps.Autowah.Resonance;
- state->lfo = 0;
-
- ALfilterState_clear(&state->low_pass);
-
- gain = sqrtf(1.0f / Device->NumChan) * Slot->Gain;
- SetGains(Device, gain, state->Gain);
+ gain = sqrtf(1.0f / device->NumChan) * slot->Gain;
+ SetGains(device, gain, state->Gain);
}
static ALvoid ALautowahState_process(ALautowahState *state, ALuint SamplesToDo, const ALfloat *SamplesIn, ALfloat (*SamplesOut)[BUFFERSIZE])
@@ -101,46 +89,53 @@ static ALvoid ALautowahState_process(ALautowahState *state, ALuint SamplesToDo,
{
ALfloat temps[64];
ALuint td = minu(SamplesToDo-base, 64);
+ ALfloat gain = state->GainCtrl;
for(it = 0;it < td;it++)
{
ALfloat smp = SamplesIn[it+base];
- ALfloat frequency, omega, alpha, peak;
-
- /* lfo for low-pass shaking */
- if((state->lfo++) % 30 == 0)
- {
- /* Using custom low-pass filter coefficients, to handle the resonance and peak-gain properties. */
- frequency = (1.0f + cosf(state->lfo * (1.0f / lerp(1.0f, 4.0f, state->AttackTime * state->ReleaseTime)) * F_2PI / state->Frequency)) / OCTAVE;
- frequency = expf((frequency - 1.0f) * 6.0f);
-
- /* computing cutoff frequency and peak gain */
- omega = F_PI * frequency;
- alpha = sinf(omega) / (16.0f * (state->Resonance / AL_AUTOWAH_MAX_RESONANCE));
- peak = lerp(1.0f, 10.0f, state->PeakGain / AL_AUTOWAH_MAX_PEAK_GAIN);
-
- /* computing low-pass filter coefficients */
- state->low_pass.b[0] = (1.0f - cosf(omega)) / 2.0f;
- state->low_pass.b[1] = 1.0f - cosf(omega);
- state->low_pass.b[2] = (1.0f - cosf(omega)) / 2.0f;
- state->low_pass.a[0] = 1.0f + alpha / peak;
- state->low_pass.a[1] = -2.0f * cosf(omega);
- state->low_pass.a[2] = 1.0f - alpha / peak;
-
- state->low_pass.b[2] /= state->low_pass.a[0];
- state->low_pass.b[1] /= state->low_pass.a[0];
- state->low_pass.b[0] /= state->low_pass.a[0];
- state->low_pass.a[2] /= state->low_pass.a[0];
- state->low_pass.a[1] /= state->low_pass.a[0];
- state->low_pass.a[0] /= state->low_pass.a[0];
- }
-
- /* do high-pass filter */
- smp = ALfilterState_processSingle(&state->high_pass, smp);
-
- /* do low-pass filter */
- temps[it] = ALfilterState_processSingle(&state->low_pass, smp);
+ ALfloat alpha, w0;
+ ALfloat amplitude;
+ ALfloat cutoff;
+
+ /* Similar to compressor, we get the current amplitude of the
+ * incoming signal, and attack or release to reach it. */
+ amplitude = fabs(smp);
+ if(amplitude > gain)
+ gain = minf(gain+state->AttackRate, amplitude);
+ else if(amplitude < gain)
+ gain = maxf(gain-state->ReleaseRate, amplitude);
+ gain = maxf(gain, GAIN_SILENCE_THRESHOLD);
+
+ /* FIXME: What range does the filter cover? */
+ cutoff = lerp(500.0f, 3000.0f, minf(gain / state->PeakGain, 1.0f));
+
+ /* The code below is like calling ALfilterState_setParams with
+ * ALfilterType_LowPass. However, instead of passing a bandwidth,
+ * we use the resonance property for Q. This also inlines the call.
+ */
+ w0 = F_2PI * cutoff / state->Frequency;
+
+ /* FIXME: Resonance controls the resonant peak, or Q. How? Not sure
+ * that Q = resonance*0.1. */
+ alpha = sinf(w0) / (2.0f * state->Resonance*0.1f);
+ state->LowPass.b[0] = (1.0f - cosf(w0)) / 2.0f;
+ state->LowPass.b[1] = 1.0f - cosf(w0);
+ state->LowPass.b[2] = (1.0f - cosf(w0)) / 2.0f;
+ state->LowPass.a[0] = 1.0f + alpha;
+ state->LowPass.a[1] = -2.0f * cosf(w0);
+ state->LowPass.a[2] = 1.0f - alpha;
+
+ state->LowPass.b[2] /= state->LowPass.a[0];
+ state->LowPass.b[1] /= state->LowPass.a[0];
+ state->LowPass.b[0] /= state->LowPass.a[0];
+ state->LowPass.a[2] /= state->LowPass.a[0];
+ state->LowPass.a[1] /= state->LowPass.a[0];
+ state->LowPass.a[0] /= state->LowPass.a[0];
+
+ temps[it] = ALfilterState_processSingle(&state->LowPass, smp);
}
+ state->GainCtrl = gain;
for(kt = 0;kt < MaxChannels;kt++)
{
@@ -176,8 +171,13 @@ static ALeffectState *ALautowahStateFactory_create(ALautowahStateFactory *UNUSED
if(!state) return NULL;
SET_VTABLE2(ALautowahState, ALeffectState, state);
- ALfilterState_clear(&state->low_pass);
- ALfilterState_clear(&state->high_pass);
+ state->AttackRate = 0.0f;
+ state->ReleaseRate = 0.0f;
+ state->Resonance = 0.0f;
+ state->PeakGain = 1.0f;
+ state->GainCtrl = 1.0f;
+
+ ALfilterState_clear(&state->LowPass);
return STATIC_CAST(ALeffectState, state);
}
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-13 19:03:25 +0000