linux+音频应用编程

#include <stdio.h>
#include <stdlib.h>
#include <portaudio.h>

#define SAMPLE_RATE (44100)
#define FRAMES_PER_BUFFER (64)

typedef struct {
    float frequency;
    float amplitude;
    int sampleIndex;
    float phase;
} SineWave;

static int paCallback(const void *inputBuffer, void *outputBuffer,
                      unsigned long framesPerBuffer,
                      const PaStreamCallbackTimeInfo* timeInfo,
                      PaStreamCallbackFlags statusFlags,
                      void *userData) {
    SineWave *data = (SineWave*)userData;
    float *out = (float*)outputBuffer;
    unsigned int i;
    (void)inputBuffer; // Prevent unused variable warning

    for (i = 0; i < framesPerBuffer; i++) {
        *out++ = data->amplitude * sin(data->phase);
        data->phase += 2.0f * M_PI * data->frequency / SAMPLE_RATE;
        if (data->phase > 2.0f * M_PI) {
            data->phase -= 2.0f * M_PI;
        }
    }
    return paContinue;
}

int main(void) {
    PaStream *stream;
    PaError err;
    SineWave data;

    data.frequency = 440.0f; // 440 Hz
    data.amplitude = 0.5f;
    data.sampleIndex = 0;
    data.phase = 0.0f;

    err = Pa_Initialize();
    if (err != paNoError) goto error;

    err = Pa_OpenDefaultStream(&stream,
                               0, // no input channels
                               1, // 1 output channel
                               paFloat32, // 32 bit floating point output
                               SAMPLE_RATE,
                               FRAMES_PER_BUFFER,
                               paCallback,
                               &data);
    if (err != paNoError) goto error;

    err = Pa_StartStream(stream);
    if (err != paNoError) goto error;

    printf("Playing for 5 seconds.\n");
    Pa_Sleep(5000);

    err = Pa_StopStream(stream);
    if (err != paNoError) goto error;

    err = Pa_CloseStream(stream);
    if (err != paNoError) goto error;

    Pa_Terminate();
    printf("Done.\n");

    return 0;

error:
    Pa_Terminate();
    fprintf(stderr, "An error occurred while using the portaudio stream\n");
    fprintf(stderr, "Error number: %d\n", err);
    fprintf(stderr, "Error message: %s\n", Pa_GetErrorText(err));
    return -1;
}

gcc -o sine_wave sine_wave.c -lportaudio -lm
./sine_wave