a-comp: Fix noise floor - asymptotics

diff --git a/libs/plugins/a-comp.lv2/a-comp.c b/libs/plugins/a-comp.lv2/a-comp.c
index e14f4ee004d9333e353a970761cacf03ad8af69b..06d4a6181ca78ada986044b7c149745a0ea59fc9 100644 (file)
--- a/libs/plugins/a-comp.lv2/a-comp.c
+++ b/libs/plugins/a-comp.lv2/a-comp.c
@@ -83,7 +83,6 @@ typedef struct {
        float old_yg;
 
        float makeup_gain;
-       float tau;
 
 #ifdef LV2_EXTENDED
        LV2_Inline_Display_Image_Surface surf;
@@ -126,7 +125,7 @@ instantiate(const LV2_Descriptor* descriptor,
 
        acomp->srate = rate;
        acomp->old_yl=acomp->old_y1=acomp->old_yg=0.f;
-       acomp->tau = (1.0 - exp (-2.f * M_PI * 25.f / acomp->srate));
+       acomp->makeup_gain = 1.f;
 #ifdef LV2_EXTENDED
        acomp->need_expose = true;
        acomp->v_lvl_out = -70.f;
@@ -291,7 +290,7 @@ run_mono(LV2_Handle instance, uint32_t n_samples)
        float makeup_target = from_dB(makeup);
        float makeup_gain = acomp->makeup_gain;
 
-       const float tau = acomp->tau;
+       const float tau = (1.0 - exp (-2.f * M_PI * n_samples * 25.f / acomp->srate));
 
        if (*acomp->enable <= 0) {
                ratio = 1.f;
@@ -363,7 +362,6 @@ run_mono(LV2_Handle instance, uint32_t n_samples)
 
                lgaininp = in0 * Lgain;
 
-               makeup_gain += tau * (makeup_target - makeup_gain) + 1e-12;
                output[i] = lgaininp * makeup_gain;
 
                max = (fabsf(output[i]) > max) ? fabsf(output[i]) : sanitize_denormal(max);
@@ -375,6 +373,12 @@ run_mono(LV2_Handle instance, uint32_t n_samples)
                acomp->old_yg = Lyg;
        }
 
+       if ( fabsf(makeup_target - makeup_gain) < 1e-6 ) {
+               makeup_gain = 1.0;
+       } else {
+               makeup_gain += tau * (makeup_target - makeup_gain) + 1e-12;
+       }
+
        *(acomp->outlevel) = (max < 0.0056f) ? -45.f : to_dB(max);
        acomp->makeup_gain = makeup_gain;
 
@@ -441,7 +445,7 @@ run_stereo(LV2_Handle instance, uint32_t n_samples)
        float makeup_target = from_dB(makeup);
        float makeup_gain = acomp->makeup_gain;
 
-       const float tau = acomp->tau;
+       const float tau = (1.0 - exp (-2.f * M_PI * n_samples * 25.f / acomp->srate));
 
        if (*acomp->enable <= 0) {
                ratio = 1.f;
@@ -516,8 +520,6 @@ run_stereo(LV2_Handle instance, uint32_t n_samples)
                lgaininp = in0 * Lgain;
                rgaininp = in1 * Lgain;
 
-               makeup_gain += tau * (makeup_target - makeup_gain) + 1e-12;
-
                output0[i] = lgaininp * makeup_gain;
                output1[i] = rgaininp * makeup_gain;
 
@@ -530,6 +532,12 @@ run_stereo(LV2_Handle instance, uint32_t n_samples)
                acomp->old_yg = Lyg;
        }
 
+       if ( fabsf(makeup_target - makeup_gain) < 1e-6 ) {
+               makeup_gain = 1.0;
+       } else {
+               makeup_gain += tau * (makeup_target - makeup_gain) + 1e-12;
+       }
+
        *(acomp->outlevel) = (max < 0.0056f) ? -45.f : to_dB(max);
        acomp->makeup_gain = makeup_gain;