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Add a whitenoise generator to altonegen

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This commit is contained in:
Chris Robinson
2017-06-25 08:00:55 -07:00
parent be552a35e6
commit 4b7cbb50ab
1 changed files with 50 additions and 19 deletions
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examples/altonegen.c
+50 -19
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@@ -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]);
}