diff options
Diffstat (limited to 'Alc/effects')
| -rw-r--r-- | Alc/effects/compressor.c | 122 |
1 files changed, 58 insertions, 64 deletions
diff --git a/Alc/effects/compressor.c b/Alc/effects/compressor.c index 4ec28f9a..a5f1953b 100644 --- a/Alc/effects/compressor.c +++ b/Alc/effects/compressor.c @@ -27,6 +27,13 @@ #include "alu.h" +#define AMP_ENVELOPE_MIN 0.5f +#define AMP_ENVELOPE_MAX 2.0f + +#define ATTACK_TIME 0.1f /* 100ms to rise from min to max */ +#define RELEASE_TIME 0.2f /* 200ms to drop from max to min */ + + typedef struct ALcompressorState { DERIVE_FROM_TYPE(ALeffectState); @@ -35,9 +42,9 @@ typedef struct ALcompressorState { /* Effect parameters */ ALboolean Enabled; - ALfloat AttackRate; - ALfloat ReleaseRate; - ALfloat GainCtrl; + ALfloat AttackMult; + ALfloat ReleaseMult; + ALfloat EnvFollower; } ALcompressorState; static ALvoid ALcompressorState_Destruct(ALcompressorState *state); @@ -55,9 +62,9 @@ static void ALcompressorState_Construct(ALcompressorState *state) SET_VTABLE2(ALcompressorState, ALeffectState, state); state->Enabled = AL_TRUE; - state->AttackRate = 0.0f; - state->ReleaseRate = 0.0f; - state->GainCtrl = 1.0f; + state->AttackMult = 1.0f; + state->ReleaseMult = 1.0f; + state->EnvFollower = 1.0f; } static ALvoid ALcompressorState_Destruct(ALcompressorState *state) @@ -67,11 +74,17 @@ static ALvoid ALcompressorState_Destruct(ALcompressorState *state) static ALboolean ALcompressorState_deviceUpdate(ALcompressorState *state, ALCdevice *device) { - const ALfloat attackTime = device->Frequency * 0.2f; /* 200ms Attack */ - const ALfloat releaseTime = device->Frequency * 0.4f; /* 400ms Release */ - - state->AttackRate = 1.0f / attackTime; - state->ReleaseRate = 1.0f / releaseTime; + /* Number of samples to do a full attack and release (non-integer sample + * counts are okay). + */ + const ALfloat attackCount = (ALfloat)device->Frequency * ATTACK_TIME; + const ALfloat releaseCount = (ALfloat)device->Frequency * RELEASE_TIME; + + /* Calculate per-sample multipliers to attack and release at the desired + * rates. + */ + state->AttackMult = powf(AMP_ENVELOPE_MAX/AMP_ENVELOPE_MIN, 1.0f/attackCount); + state->ReleaseMult = powf(AMP_ENVELOPE_MIN/AMP_ENVELOPE_MAX, 1.0f/releaseCount); return AL_TRUE; } @@ -97,71 +110,52 @@ static ALvoid ALcompressorState_process(ALcompressorState *state, ALsizei Sample for(base = 0;base < SamplesToDo;) { - ALfloat temps[64][4]; - ALsizei td = mini(64, SamplesToDo-base); - - /* Load samples into the temp buffer first. */ - for(j = 0;j < 4;j++) - { - for(i = 0;i < td;i++) - temps[i][j] = SamplesIn[j][i+base]; - } + ALfloat gains[256]; + ALsizei td = mini(256, SamplesToDo-base); + ALfloat env = state->EnvFollower; + /* Generate the per-sample gains from the signal envelope. */ if(state->Enabled) { - ALfloat gain = state->GainCtrl; - ALfloat output, amplitude; - - for(i = 0;i < td;i++) + for(i = 0;i < td;++i) { - /* Roughly calculate the maximum amplitude from the 4-channel - * signal, and attack or release the gain control to reach it. + /* Clamp the absolute amplitude to the defined envelope limits, + * then attack or release the envelope to reach it. + */ + ALfloat amplitude = clampf(fabsf(SamplesIn[0][base+i]), + AMP_ENVELOPE_MIN, AMP_ENVELOPE_MAX); + if(amplitude > env) + env = minf(env*state->AttackMult, amplitude); + else if(amplitude < env) + env = maxf(env*state->ReleaseMult, amplitude); + + /* Apply the reciprocal of the envelope to normalize the volume + * (compress the dynamic range). */ - amplitude = fabsf(temps[i][0]); - amplitude = maxf(amplitude + fabsf(temps[i][1]), - maxf(amplitude + fabsf(temps[i][2]), - amplitude + fabsf(temps[i][3]))); - if(amplitude > gain) - gain = minf(gain+state->AttackRate, amplitude); - else if(amplitude < gain) - gain = maxf(gain-state->ReleaseRate, amplitude); - - /* Apply the inverse of the gain control to normalize/compress - * the volume. */ - output = 1.0f / clampf(gain, 0.5f, 2.0f); - for(j = 0;j < 4;j++) - temps[i][j] *= output; + gains[i] = 1.0f / env; } - - state->GainCtrl = gain; } else { - ALfloat gain = state->GainCtrl; - ALfloat output, amplitude; - - for(i = 0;i < td;i++) + /* Same as above, except the amplitude is forced to 1. This helps + * ensure smooth gain changes when the compressor is turned on and + * off. + */ + for(i = 0;i < td;++i) { - /* Same as above, except the amplitude is forced to 1. This - * helps ensure smooth gain changes when the compressor is - * turned on and off. - */ - amplitude = 1.0f; - if(amplitude > gain) - gain = minf(gain+state->AttackRate, amplitude); - else if(amplitude < gain) - gain = maxf(gain-state->ReleaseRate, amplitude); - - output = 1.0f / clampf(gain, 0.5f, 2.0f); - for(j = 0;j < 4;j++) - temps[i][j] *= output; - } + ALfloat amplitude = 1.0f; + if(amplitude > env) + env = minf(env*state->AttackMult, amplitude); + else if(amplitude < env) + env = maxf(env*state->ReleaseMult, amplitude); - state->GainCtrl = gain; + gains[i] = 1.0f / env; + } } + state->EnvFollower = env; - /* Now mix to the output. */ - for(j = 0;j < 4;j++) + /* Now compress the signal amplitude to output. */ + for(j = 0;j < MAX_EFFECT_CHANNELS;j++) { for(k = 0;k < NumChannels;k++) { @@ -170,7 +164,7 @@ static ALvoid ALcompressorState_process(ALcompressorState *state, ALsizei Sample continue; for(i = 0;i < td;i++) - SamplesOut[k][base+i] += gain * temps[i][j]; + SamplesOut[k][base+i] += SamplesIn[k][base+i] * gains[i] * gain; } } |