linux下ALSA播放声音的源程序

//linux下ALSA播放声音的源程序
//@note 编译的时候，使用到了asound 的lib 所以要添加-lasoud库
#include <stdio.h>
/* Use the newer ALSA API */
#define ALSA_PCM_NEW_HW_PARAMS_API

#include <alsa/asoundlib.h>

int main() 
{
    long loops;
    int rc;
    int size;
    snd_pcm_t *handle;
    snd_pcm_hw_params_t *params;
    unsigned int val;
    int dir;
    snd_pcm_uframes_t frames;
    snd_pcm_uframes_t periodsize;
    char *buffer;
    FILE *fp = fopen("play.wav", "rb");
    if(fp == NULL)
    return 0;
    fseek(fp, 100, SEEK_SET);
    /* Open PCM device for playback. */
    rc = snd_pcm_open(&handle, "default",
                    SND_PCM_STREAM_PLAYBACK, 0);//SND_PCM_NONBLOCK);
    if (rc < 0) {
    fprintf(stderr,
            "unable to open pcm device: %s\n",
            snd_strerror(rc));
    exit(1);
    }

    /* Allocate a hardware parameters object. */
    snd_pcm_hw_params_alloca(¶ms);

    /* Fill it in with default values. */
    snd_pcm_hw_params_any(handle, params);

    /* Set the desired hardware parameters. */

    /* Interleaved mode */
    snd_pcm_hw_params_set_access(handle, params,
                      SND_PCM_ACCESS_RW_INTERLEAVED);

    /* Signed 16-bit little-endian format */
    snd_pcm_hw_params_set_format(handle, params,
                              SND_PCM_FORMAT_S16_LE);

    /* Two channels (stereo) */
    snd_pcm_hw_params_set_channels(handle, params, 1);

    /* 44100 bits/second sampling rate (CD quality) */
    val = 8000;
    snd_pcm_hw_params_set_rate_near(handle, params,
                                  &val, &dir);

    /* Set period size to 32 frames. */
    frames = 32;
    periodsize = frames * 2;
    rc = snd_pcm_hw_params_set_buffer_size_near(handle, params, &periodsize);
    if (rc < 0) 
    {
         printf("Unable to set buffer size %li : %s\n", frames * 2, snd_strerror(rc));
         
    }
          periodsize /= 2;
    rc = snd_pcm_hw_params_set_period_size_near(handle, params, &periodsize, 0);
    if (rc < 0) 
    {
        printf("Unable to set period size %li : %s\n", periodsize,  snd_strerror(rc));
    }
    
    /* Write the parameters to the driver */
    rc = snd_pcm_hw_params(handle, params);
    if (rc < 0) {
    fprintf(stderr,
            "unable to set hw parameters: %s\n",
            snd_strerror(rc));
    }

    /* Use a buffer large enough to hold one period */
    snd_pcm_hw_params_get_period_size(params, &frames, &dir);
                                
    size = frames * 2; /* 2 bytes/sample, 2 channels */
    buffer = (char *) malloc(size);
    fprintf(stderr,
            "size = %d\n",
            size);
    /* We want to loop for 5 seconds */
    //snd_pcm_hw_params_get_period_time(params,
    //                                &val, &dir);
    //snd_pcm_start(handle);
    while (1) 
    {
        rc = fread(buffer, 1, size, fp);
        if(rc == 0) 
        {
              fprintf(stderr, "end of file on input\n");
              break;
        } 
        else if (rc != size) 
        {
        }

        while(rc = snd_pcm_writei(handle, buffer, frames)<0)
        {
            usleep(2000);
            if (rc == -EPIPE)
            {
                  /* EPIPE means underrun */
                  fprintf(stderr, "underrun occurred\n");
                  snd_pcm_prepare(handle);
            } 
            else if (rc < 0) 
            {
                  fprintf(stderr,
                      "error from writei: %s\n",
                      snd_strerror(rc));
            }  
        }
        //snd_pcm_drain(handle);
        //usleep(7000);
        //printf("#\n");
    }
    snd_pcm_drain(handle);
    snd_pcm_close(handle);
    free(buffer);
    fclose(fp);
    return 0;
}