linux dsp 播放音频文件

#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <stdlib.h>
#include <stdio.h>
#include <linux/soundcard.h>
/* 下面的三个参数是跟具体文件相关
* cmd： file 音频文件
* [file pass.wav] =>> pass.wav: RIFF (little-endian) data, WAVE audio, Microsoft PCM, 16 bit, mono 44100 Hz
*　　1. 16位
*　　2. mono为当声道=1, Stereo为立体声=2
*　　3. 44100HZ为频率这个大家都知道，及一秒钟采集或者播放音频的bit数量。
*/
#define RATE 44100
#define SIZE 16
#define CHANNELS 1 // 1表示单声道，2为立体/* 缓冲区 */
unsigned char buff[RATE * SIZE * CHANNELS / 8]; //buff里面正好放一秒钟的音频

int main()
{
int fd;
int wavfd; /* wav文件的描述符 */
int arg; /* ioctl参数 */
int ret; /* 返回值 */
/* 打开dsp音频设备 */
fd = open("/dev/dsp", O_WRONLY);
if (fd < 0) {
printf("open of /dev/dsp failed");
exit(1);
}
wavfd = open("pass.wav",O_RDONLY);
if (wavfd < 0) {
printf("open of wav failed");
close(fd);
exit(1);
}

/* 设置bit */
arg = SIZE;
ret = ioctl(fd, SOUND_PCM_WRITE_BITS, &arg);
if (ret == -1)
perror("SOUND_PCM_WRITE_BITS ioctl failed");
if (arg != SIZE)
perror("unable to set sample size");

/* 设置channels */
arg = CHANNELS;
ret = ioctl(fd, SOUND_PCM_WRITE_CHANNELS, &arg);
if (ret == -1)
perror("SOUND_PCM_WRITE_CHANNELS ioctl failed");
if (arg != CHANNELS)
perror("unable to set number of channels");

/* 设置rate */
arg = RATE;
ret = ioctl(fd, SOUND_PCM_WRITE_RATE, &arg);
if (ret == -1)
perror("SOUND_PCM_WRITE_WRITE ioctl failed");

/* 从wav文件中读buff大小的内容，然后写入/dev/dsp中，直到文件结束 */
　　/* Q：这里我试验时播放了两次，不知道啥情况，如果大家也遇到了请指教。*/
while ((ret = read(wavfd, buff, sizeof(buff))) > 0) {
//printf("read size = %d\n", ret);
write(fd, buff, sizeof(buff));
/* 下面的代码用于在更改播放文件的参数时，播放掉缓冲区内的内容 */
ret = ioctl(fd, SOUND_PCM_SYNC, 0);
if (ret == -1)
perror("SOUND_PCM_SYNC ioctl failed");
}

close(fd);
close(wavfd);
}

下面是封装的接口可以直接拿过来使用：

void play_audio(int rate, int bits, int channels, char *filename)
{
int fd;
int wavfd; /* wav文件的描述符 */
int arg; /* ioctl arg */
int ret; /* return value */

unsigned char buff[rate * bits * channels / 8]; //buff里面正好放一秒钟的音频
/* open device */
fd = open("/dev/dsp", O_WRONLY);
if (fd < 0) {
printf("open of /dev/dsp failed");
exit(1);
}
wavfd = open(filename, O_RDONLY);
if (wavfd < 0) {
printf("open of wav failed");
close(fd);
exit(1);
}

/* set bits */
arg = bits;
ret = ioctl(fd, SOUND_PCM_WRITE_BITS, &arg);
if (ret == -1)
perror("SOUND_PCM_WRITE_BITS ioctl failed");
if (arg != SIZE)
perror("unable to set sample size");

/* set channels */
arg = channels;
ret = ioctl(fd, SOUND_PCM_WRITE_CHANNELS, &arg);
if (ret == -1)
perror("SOUND_PCM_WRITE_CHANNELS ioctl failed");
if (arg != CHANNELS)
perror("unable to set number of channels");

/* set rate */
arg = rate;
ret = ioctl(fd, SOUND_PCM_WRITE_RATE, &arg);
if (ret == -1)
perror("SOUND_PCM_WRITE_WRITE ioctl failed");

/* 从wav文件中读buff大小的内容，然后写入/dev/dsp中，直到文件结束 */
while ((ret = read(wavfd, buff, sizeof(buff))) > 0) {
printf("read size = %d\n", ret);
write(fd, buff, sizeof(buff));
/* 下面的代码用于在更改播放文件的参数时，播放掉缓冲区内的内容 */
ret = ioctl(fd, SOUND_PCM_SYNC, 0);
if (ret == -1)
perror("SOUND_PCM_SYNC ioctl failed");
}

close(fd);
close(wavfd);
}