Normalize reverb time to sample rate

For consistent decay across different sample rates
Closes #563

src/effect_platervbstereo.cpp

@@ -85,6 +85,7 @@ const int16_t AudioWaveformSine[257] = {
 
 AudioEffectPlateReverb::AudioEffectPlateReverb(float32_t samplerate)
 {
+    m_samplerate = samplerate;
     input_attn = 0.5f;
     in_allp_k = INP_ALLP_COEFF;
 
@@ -200,7 +201,8 @@ void AudioEffectPlateReverb::doReverb(const float32_t* inblockL, const float32_t
     }
     cleanup_done = false;
 
-    rv_time = rv_time_k;
+    rv_time = rv_time_k * (m_samplerate / 44100.0f);
+    float32_t rv_time_scaler_scaled = rv_time_scaler * (m_samplerate / 44100.0f);
 
     for (uint16_t i=0; i < len; i++) 
     {
@@ -300,7 +302,7 @@ void AudioEffectPlateReverb::doReverb(const float32_t* inblockL, const float32_t
         temp1 = lpf1 - hpf1;
         hpf1 += temp1 * lp_hipass_f;
         acc = lpf1 + temp2*lp_hidamp_k + hpf1*lp_lodamp_k;
-        acc = acc * rv_time * rv_time_scaler;                                                                // scale by the reveb time
+        acc = acc * rv_time * rv_time_scaler_scaled;                                                                // scale by the reveb time
         
         input = acc + in_allp_out_L;
 
@@ -319,7 +321,7 @@ void AudioEffectPlateReverb::doReverb(const float32_t* inblockL, const float32_t
         temp1 = lpf2 - hpf2;
         hpf2 += temp1 * lp_hipass_f;
         acc = lpf2 + temp2*lp_hidamp_k + hpf2*lp_lodamp_k;
-        acc = acc * rv_time * rv_time_scaler;             
+        acc = acc * rv_time * rv_time_scaler_scaled;             
 
         input = acc + in_allp_out_R;
 
@@ -338,7 +340,7 @@ void AudioEffectPlateReverb::doReverb(const float32_t* inblockL, const float32_t
         temp1 = lpf3 - hpf3;
         hpf3 += temp1 * lp_hipass_f;
         acc = lpf3 + temp2*lp_hidamp_k + hpf3*lp_lodamp_k;
-        acc = acc * rv_time * rv_time_scaler;              
+        acc = acc * rv_time * rv_time_scaler_scaled;              
 
         input = acc + in_allp_out_L;       
 
@@ -357,7 +359,7 @@ void AudioEffectPlateReverb::doReverb(const float32_t* inblockL, const float32_t
         temp1 = lpf4 - hpf4;
         hpf4 += temp1 * lp_hipass_f;
         acc = lpf4 + temp2*lp_hidamp_k + hpf4*lp_lodamp_k;
-        acc = acc * rv_time * rv_time_scaler;              
+        acc = acc * rv_time * rv_time_scaler_scaled;              
 
         lp_allp_out = acc;
 

src/effect_platervbstereo.h

@@ -113,6 +113,7 @@ private:
     bool bypass = false;
     float32_t reverb_level;
     float32_t input_attn;
+    float32_t m_samplerate; // store the sample rate
 
     float32_t in_allp_k;            // input allpass coeff 
     float32_t in_allp1_bufL[224];   // input allpass buffers