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;
}