add generic synthesizer clip option and biquad lpf

[vg.git] / vg_audio_dsp.h

diff --git a/vg_audio_dsp.h b/vg_audio_dsp.h
index 0eaeb544ae6855da0687b106ad10eb8e0d4f3b15..48926e282628eb476e5bd2b78eda908eb0b2450a 100644 (file)
--- a/vg_audio_dsp.h
+++ b/vg_audio_dsp.h
@@ -4,8 +4,7 @@
 #define VG_GAME
 #include "vg/vg.h"
 
-static struct vg_dsp
-{
+static struct vg_dsp{
    float            *buffer;
    u32               allocations;
 
@@ -16,6 +15,8 @@ static struct vg_dsp
                      echo_tunings[8],
                      reverb_wet_mix,
                      reverb_dry_mix;
+
+   vg_rand           rand;
 }
 vg_dsp;
 
@@ -56,12 +57,35 @@ struct dsp_schroeder
    float gain;
 };
 
-static inline void dsp_read_delay( struct dsp_delay *delay, float *s )
-{
-   u32 index = delay->cur+1;
+struct dsp_biquad {
+   f32 a0, a1, a2, b1, b2, c0, d0,
+       xnz1, xnz2, ynz1, ynz2, offset;
+};
+
+static f32 dsp_biquad_process( struct dsp_biquad *bq, f32 xn ){
+   f32 yn = + bq->a0*xn + bq->a1*bq->xnz1 + bq->a2*bq->xnz2 
+            - bq->b1*bq->ynz1 - bq->b2*bq->ynz2;
+   bq->xnz2 = bq->xnz1;
+   bq->xnz1 = xn;
+   bq->ynz2 = bq->ynz1;
+   bq->ynz1 = yn;
+   return yn + bq->offset;
+}
+
+static void dsp_init_biquad_butterworth_lpf( struct dsp_biquad *bq, f32 fc ){
+   f32 c = 1.0f/tanf(VG_PIf*fc / 44100.0f);
+   bq->a0 = 1.0f / (1.0f + sqrtf(2.0f)*c + powf(c, 2.0f) );
+   bq->a1 = 2.0f * bq->a0;
+   bq->a2 = bq->a0;
+   bq->b1 = 2.0f * bq->a0*(1.0f - powf(c, 2.0f));
+   bq->b2 = bq->a0 * (1.0f - sqrtf(2.0f)*c + powf(c, 2.0f) );
+}
+
+static inline void dsp_read_delay( struct dsp_delay *delay, float *s, u32 t ){
+   u32 index = delay->cur+t;
 
    if( index >= delay->length )
-      index = 0;
+      index -= delay->length;
 
    *s = delay->buffer[ index ];
 }
@@ -123,7 +147,7 @@ static inline void dsp_process_schroeder( struct dsp_schroeder *sch,
    float dry = *input;
 
    float delay_output;
-   dsp_read_delay( &sch->M, &delay_output );
+   dsp_read_delay( &sch->M, &delay_output, 1 );
 
    float feedback_attenuated = delay_output * sch->gain,
          input_feedback_sum  = dry + feedback_attenuated;
@@ -149,8 +173,8 @@ static void async_vg_dsp_alloc_texture( void *payload, u32 size )
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );
 }
 
-static void vg_dsp_init( void )
-{
+static void vg_dsp_init( void ){
+   vg_rand_seed( &vg_dsp.rand, 461 );
    vg_dsp.buffer = vg_linear_alloc( vg_mem.rtmemory, 1024*1024*1 );
    vg_dsp.view_texture_buffer = vg_linear_alloc( vg_mem.rtmemory, 512*512 );
 
@@ -162,12 +186,12 @@ static void vg_dsp_init( void )
    float sizes[] = 
          { 2.0f, 4.0f, 8.0f, 16.0f,   32.0f, 64.0f, 128.0f, 256.0f };
 
-   float reflection_variance = 0.1f;
+   float variance = 0.1f;
 
    for( int i=0; i<8; i++ ){
       float reflection_time = ((sizes[i])/343.0f) * 1000.0f;
 
-      float var   = 1.0f + (vg_randf64()*2.0f - 1.0f) * reflection_variance,
+      float var   = 1.0f + (vg_randf64(&vg_dsp.rand)*2.0f - 1.0f) * variance,
             total = reflection_time * var;
 
       dsp_init_delay( &__echos[i], total / 1000.0f );
@@ -191,7 +215,7 @@ static void vg_dsp_process( float *stereo_in, float *stereo_out )
 
    for( int i=0; i<8; i++ ){
       float echo;
-      dsp_read_delay(  __echos+i, &echo );
+      dsp_read_delay(  __echos+i, &echo, 1 );
       dsp_write_lpf( __echos_lpf+i, &echo );
       dsp_read_lpf(  __echos_lpf+i, &echo );