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
", 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
", 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);
}