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authorChris Robinson <[email protected]>2017-06-25 08:00:55 -0700
committerChris Robinson <[email protected]>2017-06-25 08:00:55 -0700
commit4b7cbb50ab0bff14f697afb2e76b9aa3c15892d2 (patch)
tree856d58a0248ff978899c271064e45d36b8193cdc
parentbe552a35e69eed01cbc658a31c7bf8d7c40d430c (diff)
Add a whitenoise generator to altonegen
-rw-r--r--examples/altonegen.c69
1 files changed, 50 insertions, 19 deletions
diff --git a/examples/altonegen.c b/examples/altonegen.c
index 422e6d66..628e695d 100644
--- a/examples/altonegen.c
+++ b/examples/altonegen.c
@@ -35,6 +35,7 @@
#include <stdlib.h>
#include <string.h>
#include <assert.h>
+#include <limits.h>
#include <math.h>
#include "AL/al.h"
@@ -53,6 +54,7 @@ enum WaveType {
WT_Sawtooth,
WT_Triangle,
WT_Impulse,
+ WT_WhiteNoise,
};
static const char *GetWaveTypeName(enum WaveType type)
@@ -64,10 +66,17 @@ static const char *GetWaveTypeName(enum WaveType type)
case WT_Sawtooth: return "sawtooth";
case WT_Triangle: return "triangle";
case WT_Impulse: return "impulse";
+ case WT_WhiteNoise: return "noise";
}
return "(unknown)";
}
+static inline ALuint dither_rng(ALuint *seed)
+{
+ *seed = (*seed * 96314165) + 907633515;
+ return *seed;
+}
+
static void ApplySin(ALfloat *data, ALdouble g, ALuint srate, ALuint freq)
{
ALdouble smps_per_cycle = (ALdouble)srate / freq;
@@ -81,6 +90,7 @@ static void ApplySin(ALfloat *data, ALdouble g, ALuint srate, ALuint freq)
*/
static ALuint CreateWave(enum WaveType type, ALuint freq, ALuint srate)
{
+ ALuint seed = 22222;
ALint data_size;
ALfloat *data;
ALuint buffer;
@@ -89,25 +99,44 @@ static ALuint CreateWave(enum WaveType type, ALuint freq, ALuint srate)
data_size = srate * sizeof(ALfloat);
data = calloc(1, data_size);
- if(type == WT_Sine)
- ApplySin(data, 1.0, srate, freq);
- else if(type == WT_Square)
- for(i = 1;freq*i < srate/2;i+=2)
- ApplySin(data, 4.0/M_PI * 1.0/i, srate, freq*i);
- else if(type == WT_Sawtooth)
- for(i = 1;freq*i < srate/2;i++)
- ApplySin(data, 2.0/M_PI * ((i&1)*2 - 1.0) / i, srate, freq*i);
- else if(type == WT_Triangle)
- for(i = 1;freq*i < srate/2;i+=2)
- ApplySin(data, 8.0/(M_PI*M_PI) * (1.0 - (i&2)) / (i*i), srate, freq*i);
- else if(type == WT_Impulse)
+ switch(type)
{
- /* NOTE: Impulse isn't really a waveform, but it can still be useful to
- * test (other than resampling, the ALSOFT_DEFAULT_REVERB environment
- * variable can prove useful here to test the reverb response).
- */
- for(i = 0;i < srate;i++)
- data[i] = (i%(srate/freq)) ? 0.0f : 1.0f;
+ case WT_Sine:
+ ApplySin(data, 1.0, srate, freq);
+ break;
+ case WT_Square:
+ for(i = 1;freq*i < srate/2;i+=2)
+ ApplySin(data, 4.0/M_PI * 1.0/i, srate, freq*i);
+ break;
+ case WT_Sawtooth:
+ for(i = 1;freq*i < srate/2;i++)
+ ApplySin(data, 2.0/M_PI * ((i&1)*2 - 1.0) / i, srate, freq*i);
+ break;
+ case WT_Triangle:
+ for(i = 1;freq*i < srate/2;i+=2)
+ ApplySin(data, 8.0/(M_PI*M_PI) * (1.0 - (i&2)) / (i*i), srate, freq*i);
+ break;
+ case WT_Impulse:
+ /* NOTE: Impulse isn't handled using additive synthesis, and is
+ * instead just a non-0 sample at a given rate. This can still be
+ * useful to test (other than resampling, the ALSOFT_DEFAULT_REVERB
+ * environment variable can prove useful here to test the reverb
+ * response).
+ */
+ for(i = 0;i < srate;i++)
+ data[i] = (i%(srate/freq)) ? 0.0f : 1.0f;
+ break;
+ case WT_WhiteNoise:
+ /* NOTE: WhiteNoise is just uniform set of uncorrelated values, and
+ * is not influenced by the waveform frequency.
+ */
+ for(i = 0;i < srate;i++)
+ {
+ ALuint rng0 = dither_rng(&seed);
+ ALuint rng1 = dither_rng(&seed);
+ data[i] = (ALfloat)(rng0*(1.0/UINT_MAX) - rng1*(1.0/UINT_MAX));
+ }
+ break;
}
/* Buffer the audio data into a new buffer object. */
@@ -166,7 +195,7 @@ int main(int argc, char *argv[])
" --help/-h This help text\n"
" -t <seconds> Time to play a tone (default 5 seconds)\n"
" --waveform/-w <type> Waveform type: sine (default), square, sawtooth,\n"
-" triangle, impulse\n"
+" triangle, impulse, noise\n"
" --freq/-f <hz> Tone frequency (default 1000 hz)\n"
" --srate/-s <sample rate> Sampling rate (default output rate)\n",
appname
@@ -192,6 +221,8 @@ int main(int argc, char *argv[])
wavetype = WT_Triangle;
else if(strcmp(argv[i], "impulse") == 0)
wavetype = WT_Impulse;
+ else if(strcmp(argv[i], "noise") == 0)
+ wavetype = WT_WhiteNoise;
else
fprintf(stderr, "Unhandled waveform: %s\n", argv[i]);
}