simple-tone: sin() lookup tables

src/simple-tone-generator.c

@@ -1,7 +1,7 @@
 /*
  * simple-tone-generator.c
  *
- * Copyright (C) 2011 Kamal Mostafa <kamal@whence.com>
+ * Copyright (C) 2011-2012 Kamal Mostafa <kamal@whence.com>
  *
  *  This program is free software: you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -26,6 +26,67 @@
 #include "simpleaudio.h"
 
 
+
+static unsigned int sin_table_len;
+static short *sin_table_short;
+static float *sin_table_float;
+
+void
+simpleaudio_tone_init( unsigned int new_sin_table_len )
+{
+    sin_table_len = new_sin_table_len;
+
+    if ( sin_table_len != 0 ) {
+	sin_table_short = realloc(sin_table_short, sin_table_len * sizeof(short));
+	sin_table_float = realloc(sin_table_float, sin_table_len * sizeof(float));
+	if ( !sin_table_short || !sin_table_float ) {
+	    perror("malloc");
+	    assert(0);
+	}
+
+	unsigned int i;
+	for ( i=0; i<sin_table_len; i++ )
+	    sin_table_short[i] = 32767 * sin(M_PI*2.0*(float)i/sin_table_len);
+	for ( i=0; i<sin_table_len; i++ )
+	    sin_table_float[i] = sinf(M_PI*2.0*(float)i/sin_table_len);
+
+    } else {
+	if ( sin_table_short ) {
+	    free(sin_table_short);
+	    sin_table_short = NULL;
+	}
+	if ( sin_table_float ) {
+	    free(sin_table_float);
+	    sin_table_float = NULL;
+	}
+    }
+}
+
+/*
+ * in: turns (0.0 to 1.0)    out: (-32767 to +32767)
+ */
+static inline short
+sin_lu_short( float turns )
+{
+    turns = fmodf(turns, 1.0);
+    int t = (float)sin_table_len * turns;
+    // assert ( t >= 0 && t < sin_table_len );
+    return sin_table_short[t];
+}
+
+/*
+ * in: turns (0.0 to 1.0)    out: -1.0 to +1.0
+ */
+static inline float
+sin_lu_float( float turns )
+{
+    turns = fmodf(turns, 1.0);
+    int t = (float)sin_table_len * turns;
+    // assert ( t >= 0 && t < sin_table_len );
+    return sin_table_float[t];
+}
+
+
 /* "current" phase state of the tone generator */
 static float sa_tone_cphase = 0.0;
 
@@ -48,25 +109,38 @@ simpleaudio_tone(simpleaudio *sa_out, float tone_freq, size_t nsamples_dur)
 	float wave_nsamples = simpleaudio_get_rate(sa_out) / tone_freq;
 	size_t i;
 
-#define SINE_PHASE_ANGLE  ( M_PI*2.0*(i/wave_nsamples + sa_tone_cphase) )
+#define TURNS_TO_RADIANS(t)	( M_PI*2.0 * (t) )
+
+#define SINE_PHASE_TURNS	( (float)i/wave_nsamples + sa_tone_cphase )
+#define SINE_PHASE_RADIANS	TURNS_TO_RADIANS(SINE_PHASE_TURNS)
 
 	switch ( simpleaudio_get_format(sa_out) ) {
 
 	    case SA_SAMPLE_FORMAT_FLOAT:
 		{
 		    float *float_buf = buf;
-		    for ( i=0; i<nsamples_dur; i++ )
+		    if ( sin_table_float ) {
-			float_buf[i] = sinf(SINE_PHASE_ANGLE);
+			for ( i=0; i<nsamples_dur; i++ )
+			    float_buf[i] = sin_lu_float(SINE_PHASE_TURNS);
+		    } else {
+			for ( i=0; i<nsamples_dur; i++ )
+			    float_buf[i] = sinf(SINE_PHASE_RADIANS);
+		    }
 		}
 		break;
 
 	    case SA_SAMPLE_FORMAT_S16:
 		{
-		    short *float_buf = buf;
+		    short *short_buf = buf;
-		    for ( i=0; i<nsamples_dur; i++ )
+		    if ( sin_table_short ) {
-			float_buf[i] = 32767 * sinf(SINE_PHASE_ANGLE);
+			for ( i=0; i<nsamples_dur; i++ )
+			    short_buf[i] = sin_lu_short(SINE_PHASE_TURNS);
+		    } else {
+			for ( i=0; i<nsamples_dur; i++ )
+			    short_buf[i] = 32767 * sinf(SINE_PHASE_RADIANS);
+		    }
+		    break;
 		}
-		break;
 
 	    default:
 		assert(0);

src/simpleaudio.h

@@ -1,7 +1,7 @@
 /*
  * simpleaudio.h
  *
- * Copyright (C) 2011 Kamal Mostafa <kamal@whence.com>
+ * Copyright (C) 2011-2012 Kamal Mostafa <kamal@whence.com>
  *
  *  This program is free software: you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -95,5 +95,7 @@ simpleaudio_tone_reset();
 void
 simpleaudio_tone(simpleaudio *sa_out, float tone_freq, size_t nsamples_dur);
 
+void
+simpleaudio_tone_init( unsigned int new_sin_table_len );
 
 #endif