Move envelope gain to IIR filter

FluidSynth · Feb 22, 2025 · b17700c · b17700c
1 parent 5cc6db7
commit b17700c
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Showing 4 changed files with 38 additions and 54 deletions.
diff --git a/src/rvoice/fluid_iir_filter.cpp b/src/rvoice/fluid_iir_filter.cpp
@@ -156,9 +156,9 @@ fluid_iir_filter_apply_local(fluid_iir_filter_t *iir_filter, fluid_real_t *dsp_b
 
         int fres_incr_count = iir_filter->fres_incr_count;
         int q_incr_count = iir_filter->q_incr_count;
-
-        fluid_real_t dsp_centernode;
-        int dsp_i;
+        
+        fluid_real_t dsp_amp = iir_filter->amp;
+        fluid_real_t dsp_amp_incr = iir_filter->amp_incr;
 
         /* filter (implement the voice filter according to SoundFont standard) */
 
@@ -173,21 +173,30 @@ fluid_iir_filter_apply_local(fluid_iir_filter_t *iir_filter, fluid_real_t *dsp_b
          * doesn't change.
          */
 
-        for (dsp_i = 0; dsp_i < count; dsp_i++)
+        for (int dsp_i = 0; dsp_i < count; dsp_i++)
         {
             /* The filter is implemented in Direct-II form. */
-            dsp_centernode = dsp_buf[dsp_i] - dsp_a1 * dsp_hist1 - dsp_a2 * dsp_hist2;
+            fluid_real_t dsp_centernode = dsp_buf[dsp_i] - dsp_a1 * dsp_hist1 - dsp_a2 * dsp_hist2;
             fluid_real_t sample = dsp_b02 * (dsp_centernode + dsp_hist2) + dsp_b1 * dsp_hist1;
             dsp_hist2 = dsp_hist1;
             dsp_hist1 = dsp_centernode;
 
-            dsp_buf[dsp_i] = AMPLIFY ? dsp_amp * sample : sample;
             /* Alternatively, it could be implemented in Transposed Direct Form II */
             // fluid_real_t dsp_input = dsp_buf[dsp_i];
             // dsp_buf[dsp_i] = dsp_b02 * dsp_input + dsp_hist1;
             // dsp_hist1 = dsp_b1 * dsp_input - dsp_a1 * dsp_buf[dsp_i] + dsp_hist2;
             // dsp_hist2 = dsp_b02 * dsp_input - dsp_a2 * dsp_buf[dsp_i];
 
+            if(AMPLIFY)
+            {
+                dsp_buf[dsp_i] = dsp_amp * sample;
+                dsp_amp += dsp_amp_incr;
+            }
+            else
+            {
+                dsp_buf[dsp_i] = sample;
+            }
+
             if (fres_incr_count > 0 || q_incr_count > 0)
             {
                 if (fres_incr_count > 0)
@@ -221,6 +230,7 @@ fluid_iir_filter_apply_local(fluid_iir_filter_t *iir_filter, fluid_real_t *dsp_b
 
         iir_filter->fres_incr_count = fres_incr_count;
         iir_filter->q_incr_count = q_incr_count;
+        iir_filter->amp = dsp_amp;
 
         fluid_check_fpe("voice_filter");
     }
@@ -232,10 +242,8 @@ extern "C" void fluid_iir_filter_apply(fluid_iir_filter_t *resonant_filter,
                                        int count,
                                        fluid_real_t output_rate)
 {
-    if (resonant_custom_filter->type != FLUID_IIR_DISABLED)
-    {
-        fluid_iir_filter_apply_local<false>(resonant_custom_filter, dsp_buf, count, output_rate);
-    }
+    fluid_iir_filter_apply_local<false>(resonant_custom_filter, dsp_buf, count, output_rate);
+    // This is the last filter in the chain, the default SF2 filter that always runs. This one must apply the final envelope gain.
     fluid_iir_filter_apply_local<true>(resonant_filter, dsp_buf, count, output_rate);
 }
 

diff --git a/src/rvoice/fluid_iir_filter.h b/src/rvoice/fluid_iir_filter.h
@@ -60,14 +60,19 @@ struct _fluid_iir_filter_t
     fluid_real_t last_fres;         /* The filter's current (smoothed out) resonance frequency in Hz, which will converge towards its target fres once fres_incr_count has become zero */
     fluid_real_t fres_incr;         /* The linear increment of fres each sample */
     int fres_incr_count;            /* The number of samples left for the smoothed last_fres adjustment to complete */
-    
+
     fluid_real_t last_q;            /* The filter's current (smoothed) Q-factor (or "bandwidth", or "resonance-friendlyness") on a linear scale. Just like fres, this will converge towards its target Q once q_incr_count has become zero. */
     fluid_real_t q_incr;            /* The linear increment of q each sample */
     int q_incr_count;               /* The number of samples left for the smoothed Q adjustment to complete */
 #ifdef DBG_FILTER
     fluid_real_t target_fres;       /* The filter's target fres, that last_fres should converge towards - for debugging only */
     fluid_real_t target_q;          /* The filter's target Q - for debugging only */
 #endif
+
+    // the final gain amplifier to be applied by the last filter in the chain, zero for all other filters
+    fluid_real_t amp;                /* current linear amplitude */
+    fluid_real_t amp_incr;           /* amplitude increment value for the next FLUID_BUFSIZE samples */
+
 };
 
 typedef struct _fluid_iir_filter_t fluid_iir_filter_t;

diff --git a/src/rvoice/fluid_rvoice.h b/src/rvoice/fluid_rvoice.h
@@ -127,9 +127,6 @@ struct _fluid_rvoice_dsp_t
 
     /* Dynamic input to the interpolator below */
 
-    fluid_real_t amp;                /* current linear amplitude */
-    fluid_real_t amp_incr;		/* amplitude increment value for the next FLUID_BUFSIZE samples */
-
     fluid_phase_t phase;             /* the phase (current sample offset) of the sample wave */
     fluid_real_t phase_incr;	/* the phase increment for the next FLUID_BUFSIZE samples */
 };

diff --git a/src/rvoice/fluid_rvoice_dsp.cpp b/src/rvoice/fluid_rvoice_dsp.cpp
@@ -134,8 +134,6 @@ fluid_rvoice_dsp_interpolate_none_local(fluid_rvoice_t *rvoice, fluid_real_t *FL
     fluid_phase_t dsp_phase_incr;
     const short int *FLUID_RESTRICT dsp_data = voice->sample->data;
     const char *FLUID_RESTRICT dsp_data24 = voice->sample->data24;
-    fluid_real_t dsp_amp = voice->amp;
-    fluid_real_t dsp_amp_incr = voice->amp_incr;
     unsigned short dsp_i = 0;
     unsigned int dsp_phase_index;
     unsigned int end_index;
@@ -154,12 +152,11 @@ fluid_rvoice_dsp_interpolate_none_local(fluid_rvoice_t *rvoice, fluid_real_t *FL
         {
             fluid_real_t sample = fluid_rvoice_get_float_sample<IS_24BIT>(dsp_data, dsp_data24, dsp_phase_index);
 
-            dsp_buf[dsp_i] = dsp_amp * sample;
+            dsp_buf[dsp_i] = sample;
 
             /* increment phase and amplitude */
             fluid_phase_incr(dsp_phase, dsp_phase_incr);
             dsp_phase_index = fluid_phase_index_round(dsp_phase);	/* round to nearest point */
-            dsp_amp += dsp_amp_incr;
         }
 
         /* break out if not looping (buffer may not be full) */
@@ -183,7 +180,6 @@ fluid_rvoice_dsp_interpolate_none_local(fluid_rvoice_t *rvoice, fluid_real_t *FL
     }
 
     voice->phase = dsp_phase;
-    voice->amp = dsp_amp;
 
     return (dsp_i);
 }
@@ -201,8 +197,6 @@ fluid_rvoice_dsp_interpolate_linear_local(fluid_rvoice_t *rvoice, fluid_real_t *
     fluid_phase_t dsp_phase_incr;
     const short int *FLUID_RESTRICT dsp_data = voice->sample->data;
     const char *FLUID_RESTRICT dsp_data24 = voice->sample->data24;
-    fluid_real_t dsp_amp = voice->amp;
-    fluid_real_t dsp_amp_incr = voice->amp_incr;
     unsigned short dsp_i = 0;
     unsigned int dsp_phase_index;
     unsigned int end_index;
@@ -238,12 +232,11 @@ fluid_rvoice_dsp_interpolate_linear_local(fluid_rvoice_t *rvoice, fluid_real_t *
             sample =  (coeffs[0] * fluid_rvoice_get_float_sample<IS_24BIT>(dsp_data, dsp_data24, dsp_phase_index)
                      + coeffs[1] * fluid_rvoice_get_float_sample<IS_24BIT>(dsp_data, dsp_data24, dsp_phase_index + 1));
 
-            dsp_buf[dsp_i] = dsp_amp * sample;
+            dsp_buf[dsp_i] = sample;
 
             /* increment phase and amplitude */
             fluid_phase_incr(dsp_phase, dsp_phase_incr);
             dsp_phase_index = fluid_phase_index(dsp_phase);
-            dsp_amp += dsp_amp_incr;
         }
 
         /* break out if buffer filled */
@@ -263,12 +256,11 @@ fluid_rvoice_dsp_interpolate_linear_local(fluid_rvoice_t *rvoice, fluid_real_t *
             sample =  (coeffs[0] * fluid_rvoice_get_float_sample<IS_24BIT>(dsp_data, dsp_data24, dsp_phase_index)
                      + coeffs[1] * point);
 
-            dsp_buf[dsp_i] = dsp_amp * sample;
+            dsp_buf[dsp_i] = sample;
 
             /* increment phase and amplitude */
             fluid_phase_incr(dsp_phase, dsp_phase_incr);
             dsp_phase_index = fluid_phase_index(dsp_phase);
-            dsp_amp += dsp_amp_incr;	/* increment amplitude */
         }
 
         if(!LOOPING)
@@ -293,7 +285,6 @@ fluid_rvoice_dsp_interpolate_linear_local(fluid_rvoice_t *rvoice, fluid_real_t *
     }
 
     voice->phase = dsp_phase;
-    voice->amp = dsp_amp;
 
     return (dsp_i);
 }
@@ -311,8 +302,6 @@ fluid_rvoice_dsp_interpolate_4th_order_local(fluid_rvoice_t *rvoice, fluid_real_
     fluid_phase_t dsp_phase_incr;
     const short int *FLUID_RESTRICT dsp_data = voice->sample->data;
     const char *FLUID_RESTRICT dsp_data24 = voice->sample->data24;
-    fluid_real_t dsp_amp = voice->amp;
-    fluid_real_t dsp_amp_incr = voice->amp_incr;
     unsigned short dsp_i = 0;
     unsigned int dsp_phase_index;
     unsigned int start_index, end_index;
@@ -363,12 +352,11 @@ fluid_rvoice_dsp_interpolate_4th_order_local(fluid_rvoice_t *rvoice, fluid_real_
                      + coeffs[2] * fluid_rvoice_get_float_sample<IS_24BIT>(dsp_data, dsp_data24, dsp_phase_index + 1)
                      + coeffs[3] * fluid_rvoice_get_float_sample<IS_24BIT>(dsp_data, dsp_data24, dsp_phase_index + 2));
 
-            dsp_buf[dsp_i] = dsp_amp * sample;
+            dsp_buf[dsp_i] = sample;
 
             /* increment phase and amplitude */
             fluid_phase_incr(dsp_phase, dsp_phase_incr);
             dsp_phase_index = fluid_phase_index(dsp_phase);
-            dsp_amp += dsp_amp_incr;
         }
 
         /* interpolate the sequence of sample points */
@@ -382,12 +370,11 @@ fluid_rvoice_dsp_interpolate_4th_order_local(fluid_rvoice_t *rvoice, fluid_real_
                      + coeffs[2] * fluid_rvoice_get_float_sample<IS_24BIT>(dsp_data, dsp_data24, dsp_phase_index + 1)
                      + coeffs[3] * fluid_rvoice_get_float_sample<IS_24BIT>(dsp_data, dsp_data24, dsp_phase_index + 2));
 
-            dsp_buf[dsp_i] = dsp_amp * sample;
+            dsp_buf[dsp_i] = sample;
 
             /* increment phase and amplitude */
             fluid_phase_incr(dsp_phase, dsp_phase_incr);
             dsp_phase_index = fluid_phase_index(dsp_phase);
-            dsp_amp += dsp_amp_incr;
         }
 
         /* break out if buffer filled */
@@ -409,12 +396,11 @@ fluid_rvoice_dsp_interpolate_4th_order_local(fluid_rvoice_t *rvoice, fluid_real_
                      + coeffs[2] * fluid_rvoice_get_float_sample<IS_24BIT>(dsp_data, dsp_data24, dsp_phase_index + 1)
                      + coeffs[3] * end_point1);
 
-            dsp_buf[dsp_i] = dsp_amp * sample;
+            dsp_buf[dsp_i] = sample;
 
             /* increment phase and amplitude */
             fluid_phase_incr(dsp_phase, dsp_phase_incr);
             dsp_phase_index = fluid_phase_index(dsp_phase);
-            dsp_amp += dsp_amp_incr;
         }
 
         end_index++;	/* we're now interpolating the last point */
@@ -431,12 +417,11 @@ fluid_rvoice_dsp_interpolate_4th_order_local(fluid_rvoice_t *rvoice, fluid_real_
                      + coeffs[2] * end_point1
                      + coeffs[3] * end_point2);
 
-            dsp_buf[dsp_i] = dsp_amp * sample;
+            dsp_buf[dsp_i] = sample;
 
             /* increment phase and amplitude */
             fluid_phase_incr(dsp_phase, dsp_phase_incr);
             dsp_phase_index = fluid_phase_index(dsp_phase);
-            dsp_amp += dsp_amp_incr;
         }
 
         if(!LOOPING)
@@ -467,7 +452,6 @@ fluid_rvoice_dsp_interpolate_4th_order_local(fluid_rvoice_t *rvoice, fluid_real_
     }
 
     voice->phase = dsp_phase;
-    voice->amp = dsp_amp;
 
     return (dsp_i);
 }
@@ -485,8 +469,6 @@ fluid_rvoice_dsp_interpolate_7th_order_local(fluid_rvoice_t *rvoice, fluid_real_
     fluid_phase_t dsp_phase_incr;
     const short int *FLUID_RESTRICT dsp_data = voice->sample->data;
     const char *FLUID_RESTRICT dsp_data24 = voice->sample->data24;
-    fluid_real_t dsp_amp = voice->amp;
-    fluid_real_t dsp_amp_incr = voice->amp_incr;
     unsigned short dsp_i = 0;
     unsigned int dsp_phase_index;
     unsigned int start_index, end_index;
@@ -550,12 +532,11 @@ fluid_rvoice_dsp_interpolate_7th_order_local(fluid_rvoice_t *rvoice, fluid_real_
                      + coeffs[5] * fluid_rvoice_get_float_sample<IS_24BIT>(dsp_data, dsp_data24, dsp_phase_index + 2)
                      + coeffs[6] * fluid_rvoice_get_float_sample<IS_24BIT>(dsp_data, dsp_data24, dsp_phase_index + 3));
 
-            dsp_buf[dsp_i] = dsp_amp * sample;
+            dsp_buf[dsp_i] = sample;
 
             /* increment phase and amplitude */
             fluid_phase_incr(dsp_phase, dsp_phase_incr);
             dsp_phase_index = fluid_phase_index(dsp_phase);
-            dsp_amp += dsp_amp_incr;
         }
 
         start_index++;
@@ -574,12 +555,11 @@ fluid_rvoice_dsp_interpolate_7th_order_local(fluid_rvoice_t *rvoice, fluid_real_
                      + coeffs[5] * fluid_rvoice_get_float_sample<IS_24BIT>(dsp_data, dsp_data24, dsp_phase_index + 2)
                      + coeffs[6] * fluid_rvoice_get_float_sample<IS_24BIT>(dsp_data, dsp_data24, dsp_phase_index + 3));
 
-            dsp_buf[dsp_i] = dsp_amp * sample;
+            dsp_buf[dsp_i] = sample;
 
             /* increment phase and amplitude */
             fluid_phase_incr(dsp_phase, dsp_phase_incr);
             dsp_phase_index = fluid_phase_index(dsp_phase);
-            dsp_amp += dsp_amp_incr;
         }
 
         start_index++;
@@ -598,12 +578,11 @@ fluid_rvoice_dsp_interpolate_7th_order_local(fluid_rvoice_t *rvoice, fluid_real_
                      + coeffs[5] * fluid_rvoice_get_float_sample<IS_24BIT>(dsp_data, dsp_data24, dsp_phase_index + 2)
                      + coeffs[6] * fluid_rvoice_get_float_sample<IS_24BIT>(dsp_data, dsp_data24, dsp_phase_index + 3));
 
-            dsp_buf[dsp_i] = dsp_amp * sample;
+            dsp_buf[dsp_i] = sample;
 
             /* increment phase and amplitude */
             fluid_phase_incr(dsp_phase, dsp_phase_incr);
             dsp_phase_index = fluid_phase_index(dsp_phase);
-            dsp_amp += dsp_amp_incr;
         }
 
         start_index -= 2;	/* set back to original start index */
@@ -623,12 +602,11 @@ fluid_rvoice_dsp_interpolate_7th_order_local(fluid_rvoice_t *rvoice, fluid_real_
                      + coeffs[5] * fluid_rvoice_get_float_sample<IS_24BIT>(dsp_data, dsp_data24, dsp_phase_index + 2)
                      + coeffs[6] * fluid_rvoice_get_float_sample<IS_24BIT>(dsp_data, dsp_data24, dsp_phase_index + 3));
 
-            dsp_buf[dsp_i] = dsp_amp * sample;
+            dsp_buf[dsp_i] = sample;
 
             /* increment phase and amplitude */
             fluid_phase_incr(dsp_phase, dsp_phase_incr);
             dsp_phase_index = fluid_phase_index(dsp_phase);
-            dsp_amp += dsp_amp_incr;
         }
 
         /* break out if buffer filled */
@@ -653,12 +631,11 @@ fluid_rvoice_dsp_interpolate_7th_order_local(fluid_rvoice_t *rvoice, fluid_real_
                      + coeffs[5] * fluid_rvoice_get_float_sample<IS_24BIT>(dsp_data, dsp_data24, dsp_phase_index + 2)
                      + coeffs[6] * end_points[0]);
 
-            dsp_buf[dsp_i] = dsp_amp * sample;
+            dsp_buf[dsp_i] = sample;
 
             /* increment phase and amplitude */
             fluid_phase_incr(dsp_phase, dsp_phase_incr);
             dsp_phase_index = fluid_phase_index(dsp_phase);
-            dsp_amp += dsp_amp_incr;
         }
 
         end_index++;	/* we're now interpolating the 2nd to last point */
@@ -677,12 +654,11 @@ fluid_rvoice_dsp_interpolate_7th_order_local(fluid_rvoice_t *rvoice, fluid_real_
                      + coeffs[5] * end_points[0]
                      + coeffs[6] * end_points[1]);
 
-            dsp_buf[dsp_i] = dsp_amp * sample;
+            dsp_buf[dsp_i] = sample;
 
             /* increment phase and amplitude */
             fluid_phase_incr(dsp_phase, dsp_phase_incr);
             dsp_phase_index = fluid_phase_index(dsp_phase);
-            dsp_amp += dsp_amp_incr;
         }
 
         end_index++;	/* we're now interpolating the last point */
@@ -701,12 +677,11 @@ fluid_rvoice_dsp_interpolate_7th_order_local(fluid_rvoice_t *rvoice, fluid_real_
                      + coeffs[5] * end_points[1]
                      + coeffs[6] * end_points[2]);
 
-            dsp_buf[dsp_i] = dsp_amp * sample;
+            dsp_buf[dsp_i] = sample;
 
             /* increment phase and amplitude */
             fluid_phase_incr(dsp_phase, dsp_phase_incr);
             dsp_phase_index = fluid_phase_index(dsp_phase);
-            dsp_amp += dsp_amp_incr;
         }
 
         if(!LOOPING)
@@ -743,7 +718,6 @@ fluid_rvoice_dsp_interpolate_7th_order_local(fluid_rvoice_t *rvoice, fluid_real_
     fluid_phase_decr(dsp_phase, (fluid_phase_t)0x80000000);
 
     voice->phase = dsp_phase;
-    voice->amp = dsp_amp;
 
     return (dsp_i);
 }