shithub: sox

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interpolate for accurate pitch

--- a/scripts/synth.sh

+++ b/scripts/synth.sh

@@ -24,20 +24,20 @@

 A1="pl %-17 pl %-12 pl %-9 pl %-5 pl %0 pl %4"

 B1="pl %-15 pl %-10 pl %-7 pl %-3 pl %2 pl %6"

-e="delay 0 .02 .04 .06 .08 .1 remix - overdrive 40 gain -10 fade 0"

+e="delay 0 .02 .04 .06 .08 .1 remix - overdrive 40 gain -11 fade 0"

 s="$sox -q -n -p synth 0 0 0 80 87"

-$play -m \

+$play -m -v .8 \

 "|$sox \

 \"|$sox -n -p synth noise fade 0 .5 .48 trim 0 .15\" \

 \"|$sox -n -p synth noise fade h 0 .26 .11 gain -35 lowpass -1 12k\" \

--p splice .15,.06,0 gain -14 lowpass -1 12k highpass -1 9k \

+-p splice .15,.06,0 gain -15 lowpass -1 12k highpass -1 9k \

 equalizer 14k 1.3 13 \

 equalizer 9500 10 8 \

 equalizer 7000 10 8 \

 equalizer 5200 10 8 \

 equalizer 3800 10 8 \

-equalizer 1500 10 8 pad 0 .21 remix 1 1 repeat 72" \

+equalizer 1500 10 8 pad 0 .21 remix 1 1 reverb 20 repeat 72" \

 "|$sox \

 \"|$sox -n -p trim 0 1.4\" \

 \"|$s $A0 $e 4 .1 bend .4,+200,.3\" \

--- a/src/synth.c

+++ b/src/synth.c

@@ -159,8 +159,9 @@

   double cycle_start_time_s;

   double last_out;

   PinkNoise pink_noise;

-  float *buffer;

-  size_t buffer_len;

+

+  double * buffer;

+  size_t buffer_len, pos, dx, dy, acc;

 } channel_t;

@@ -394,10 +395,13 @@

     set_default_parameters(chan, i);

     if (chan->type == synth_pluck) {

       int32_t r = 0;

-      float colour = pow(2., 4 * (chan->p2 - 1));

-      float dc = 0, a = 6.9 / (chan->p2 < .25? chan->p2  / .25 * 11 + 7 :

+      double colour = pow(2., 4 * (chan->p2 - 1));

+      double dc = 0, a = 6.9 / (chan->p2 < .25? chan->p2  / .25 * 11 + 7 :

                      chan->p2 <= .55? 18 :  (1-chan->p2) / .45 * 3 + 15);

       chan->buffer_len = effp->in_signal.rate / chan->freq + .5;

+      chan->dx = chan->freq * 1000 + .5;

+      chan->dy = effp->in_signal.rate / chan->buffer_len * 1000 + .5;

+      chan->pos = chan->acc = 0;

       chan->buffer = malloc(chan->buffer_len * sizeof(*chan->buffer));

       chan->buffer[0] = 0;

       for (j = 1; j < chan->buffer_len; dc += chan->buffer[j++])

@@ -584,10 +588,16 @@

           break;

         case synth_pluck: {

-          size_t j = synth->samples_done % chan->buffer_len;

-          synth_out = chan->buffer[j];

-          chan->buffer[j] = chan->p3 * (synth_out + chan->last_out); 

-          chan->last_out = synth_out;

+          size_t pos1 = chan->pos + 1 == chan->buffer_len? 0 : chan->pos + 1;

+          double t = (double)chan->acc / chan->dy;

+          synth_out = chan->buffer[chan->pos] * (1-t) + chan->buffer[pos1] * t;

+          for (chan->acc+=chan->dx; chan->acc>=chan->dy; chan->acc-=chan->dy) {

+            t = chan->buffer[chan->pos];

+            chan->buffer[chan->pos] =

+              chan->p3 * (chan->buffer[chan->pos] + chan->last_out);

+            chan->last_out = t;

+            chan->pos = chan->pos + 1 == chan->buffer_len? 0 : chan->pos + 1;

+          }

           break;

         }