Add a new compressor/limiter

This is just for the output limiter right now, but in the future can be used
for the compressor EFX effect. The parameters are also hardcoded, but can be
made configurable after 1.18.

1 files changed, 2 insertions, 93 deletions

diff --git a/Alc/ALu.c b/Alc/ALu.c
index fec31b34..103d7962 100644
--- a/Alc/ALu.c
+++ b/Alc/ALu.c
@@ -100,17 +100,6 @@ const aluMatrixf IdentityMatrixf = {{
 }};
 
 
-struct OutputLimiter *alloc_limiter(void)
-{
-    struct OutputLimiter *limiter = al_calloc(16, sizeof(*limiter));
-    /* Limiter attack drops -80dB in 50ms. */
-    limiter->AttackRate = 0.05f;
-    /* Limiter release raises +80dB in 1s. */
-    limiter->ReleaseRate = 1.0f;
-    limiter->Gain = 1.0f;
-    return limiter;
-}
-
 void DeinitVoice(ALvoice *voice)
 {
     struct ALvoiceProps *props;
@@ -1538,78 +1527,6 @@ static void ApplyDistanceComp(ALfloatBUFFERSIZE *restrict Samples, DistanceComp
 }
 
 
-static_assert(LIMITER_VALUE_MAX < (UINT_MAX/LIMITER_WINDOW_SIZE), "LIMITER_VALUE_MAX is too big");
-
-static void ApplyLimiter(struct OutputLimiter *Limiter,
-                         ALfloat (*restrict OutBuffer)[BUFFERSIZE], const ALsizei NumChans,
-                         const ALfloat AttackRate, const ALfloat ReleaseRate,
-                         ALfloat *restrict Values, const ALsizei SamplesToDo)
-{
-    bool do_limit = false;
-    ALsizei c, i;
-
-    OutBuffer = ASSUME_ALIGNED(OutBuffer, 16);
-    Values = ASSUME_ALIGNED(Values, 16);
-
-    for(i = 0;i < SamplesToDo;i++)
-        Values[i] = 0.0f;
-
-    /* First, find the maximum amplitude (squared) for each sample position in each channel. */
-    for(c = 0;c < NumChans;c++)
-    {
-        for(i = 0;i < SamplesToDo;i++)
-        {
-            ALfloat amp = OutBuffer[c][i];
-            Values[i] = maxf(Values[i], amp*amp);
-        }
-    }
-
-    /* Next, calculate the gains needed to limit the output. */
-    {
-        ALfloat lastgain = Limiter->Gain;
-        ALsizei wpos = Limiter->Pos;
-        ALuint sum = Limiter->SquaredSum;
-        ALfloat gain, rms;
-
-        for(i = 0;i < SamplesToDo;i++)
-        {
-            sum -= Limiter->Window[wpos];
-            Limiter->Window[wpos] = fastf2u(minf(Values[i]*65536.0f, LIMITER_VALUE_MAX));
-            sum += Limiter->Window[wpos];
-
-            rms = sqrtf((ALfloat)sum / ((ALfloat)LIMITER_WINDOW_SIZE*65536.0f));
-
-            /* Clamp the minimum RMS to 0dB. The uint used for the squared sum
-             * inherently limits the maximum RMS to about 21dB, thus the gain
-             * ranges from 0dB to -21dB.
-             */
-            gain = 1.0f / maxf(rms, 1.0f);
-            if(lastgain >= gain)
-                lastgain = maxf(lastgain*AttackRate, gain);
-            else
-                lastgain = minf(lastgain/ReleaseRate, gain);
-            do_limit |= (lastgain < 1.0f);
-            Values[i] = lastgain;
-
-            wpos = (wpos+1)&LIMITER_WINDOW_MASK;
-        }
-
-        Limiter->Gain = lastgain;
-        Limiter->Pos = wpos;
-        Limiter->SquaredSum = sum;
-    }
-    if(do_limit)
-    {
-        /* Finally, apply the gains to each channel. */
-        for(c = 0;c < NumChans;c++)
-        {
-            for(i = 0;i < SamplesToDo;i++)
-                OutBuffer[c][i] *= Values[i];
-        }
-    }
-}
-
-
 /* NOTE: Non-dithered conversions have unused extra parameters. */
 static inline ALfloat aluF2F(ALfloat val, ...)
 { return val; }
@@ -1857,7 +1774,7 @@ void aluMixData(ALCdevice *device, ALvoid *buffer, ALsizei size)
         {
             ALfloat (*OutBuffer)[BUFFERSIZE] = device->RealOut.Buffer;
             ALsizei OutChannels = device->RealOut.NumChannels;
-            struct OutputLimiter *Limiter = device->Limiter;
+            struct Compressor *Limiter = device->Limiter;
             ALfloat *DitherValues;
 
             /* Use NFCtrlData for temp value storage. */
@@ -1865,15 +1782,7 @@ void aluMixData(ALCdevice *device, ALvoid *buffer, ALsizei size)
                               SamplesToDo, OutChannels);
 
             if(Limiter)
-            {
-                const ALfloat AttackRate = powf(0.0001f, 1.0f/(device->Frequency*Limiter->AttackRate));
-                const ALfloat ReleaseRate = powf(0.0001f, 1.0f/(device->Frequency*Limiter->ReleaseRate));
-
-                /* Use NFCtrlData for temp value storage. */
-                ApplyLimiter(Limiter, OutBuffer, OutChannels,
-                    AttackRate, ReleaseRate, device->NFCtrlData, SamplesToDo
-                );
-            }
+                ApplyCompression(Limiter, OutChannels, SamplesToDo, OutBuffer);
 
             /* Dithering. Step 1, generate whitenoise (uniform distribution of
              * random values between -1 and +1). Use NFCtrlData for random