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#include <SDL/SDL.h>
#include <SDL/SDL_audio.h>
#include <queue>
#include <cmath>
const int AMPLITUDE = 28000;
const int FREQUENCY = 44100;
struct BeepObject
{
double freq;
int samplesLeft;
};
class Beeper
{
private:
double v;
std::queue<BeepObject> beeps;
public:
Beeper();
~Beeper();
void beep(double freq, int duration);
void generateSamples(Sint16 *stream, int length);
void wait();
};
void audio_callback(void*, Uint8*, int);
Beeper::Beeper()
{
SDL_AudioSpec desiredSpec;
desiredSpec.freq = FREQUENCY;
desiredSpec.format = AUDIO_S16SYS;
desiredSpec.channels = 1;
desiredSpec.samples = 2048;
desiredSpec.callback = audio_callback;
desiredSpec.userdata = this;
SDL_AudioSpec obtainedSpec;
// you might want to look for errors here
SDL_OpenAudio(&desiredSpec, &obtainedSpec);
// start play audio
SDL_PauseAudio(0);
}
Beeper::~Beeper()
{
SDL_CloseAudio();
}
void Beeper::generateSamples(Sint16 *stream, int length)
{
int i = 0;
while (i < length) {
if (beeps.empty()) {
while (i < length) {
stream[i] = 0;
i++;
}
return;
}
BeepObject& bo = beeps.front();
int samplesToDo = std::min(i + bo.samplesLeft, length);
bo.samplesLeft -= samplesToDo - i;
while (i < samplesToDo) {
stream[i] = AMPLITUDE * std::sin(v * 2 * M_PI / FREQUENCY);
i++;
v += bo.freq;
}
if (bo.samplesLeft == 0) {
beeps.pop();
}
}
}
void Beeper::beep(double freq, int duration)
{
BeepObject bo;
bo.freq = freq;
bo.samplesLeft = duration * FREQUENCY / 1000;
SDL_LockAudio();
beeps.push(bo);
SDL_UnlockAudio();
}
void Beeper::wait()
{
int size;
do {
SDL_Delay(20);
SDL_LockAudio();
size = beeps.size();
SDL_UnlockAudio();
} while (size > 0);
}
void audio_callback(void *_beeper, Uint8 *_stream, int _length)
{
Sint16 *stream = (Sint16*) _stream;
int length = _length / 2;
Beeper* beeper = (Beeper*) _beeper;
beeper->generateSamples(stream, length);
}
int main(int argc, char* argv[])
{
SDL_Init(SDL_INIT_AUDIO);
int duration = 1000;
double Hz = 440;
Beeper b;
b.beep(Hz, duration);
b.wait();
return 0;
}
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