diff options
| -rw-r--r-- | examples/altonegen.c | 69 |
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]); } |