Linux平台音频测试程序

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一个音频测试程序，录音并播放。代码如下：

#include <unistd.h>#include <fcntl.h>#include <sys/types.h>#include <sys/ioctl.h>#include <stdlib.h>#include <stdio.h>#include <signal.h>#include <linux/soundcard.h>#define LENGTH 3    /* 存储秒数 */#define RATE 8000   /* 采样频率 */#define SIZE 8      /* 量化位数 */#define CHANNELS 1  /* 声道数目 *//* 用于保存数字音频数据的内存缓冲区 */unsigned char buf[LENGTH*RATE*SIZE*CHANNELS/8];int fd = -1;/* 声音设备的文件描述符 */static void sig_int(int signum){    printf("\ncatch a SIGINT signal, you may be press Ctrl+C.\n");    printf("ready to quit\n");    if (fd > 0)    {        close(fd);        fd = -1;    }    exit(0);}int main(int argc, char* argv[]){    int arg;/* 用于ioctl调用的参数 */    int status;   /* 系统调用的返回值 */        signal(SIGINT, sig_int);        /* 打开声音设备 */    fd = open("/dev/dsp", O_RDWR);    if (fd < 0)    {        perror("open of /dev/dsp failed");        exit(1);    }        /* 设置采样时的量化位数 */    arg = SIZE;    status = ioctl(fd, SOUND_PCM_WRITE_BITS, &arg);    if (status == -1)    {        perror("SOUND_PCM_WRITE_BITS ioctl failed");        exit(1);    }    if (arg != SIZE)    {        perror("unable to set sample size");        exit(1);    }    /* 设置采样时的声道数目 */    arg = CHANNELS;     status = ioctl(fd, SOUND_PCM_WRITE_CHANNELS, &arg);    if (status == -1)    {        perror("SOUND_PCM_WRITE_CHANNELS ioctl failed");        exit(1);    }    if (arg != CHANNELS)    {        perror("unable to set number of channels");        exit(1);    }    /* 设置采样时的采样频率 */    arg = RATE;    status = ioctl(fd, SOUND_PCM_WRITE_RATE, &arg);    if (status == -1)    {        perror("SOUND_PCM_WRITE_WRITE ioctl failed");        exit(1);    }    /* 循环，直到按下Control-C */    while (1)    {        printf("Say something:\n");        status = read(fd, buf, sizeof(buf)); /* 录音 */        if (status != sizeof(buf))            perror("read wrong number of bytes");        printf("You said:\n");        status = write(fd, buf, sizeof(buf)); /* 回放 */        if (status != sizeof(buf))            perror("wrote wrong number of bytes");        /* 在继续录音前等待回放结束 */        status = ioctl(fd, SOUND_PCM_SYNC, 0);         if (status == -1)            perror("SOUND_PCM_SYNC ioctl failed");    }}

如果不想编写代码，可以在终端输入以下命令进行测试：

cat /dev/dsp > /dev/dsp

PS：设备需要有麦克风和音频接口。实测中发现一直在“沙沙”的声音。待研究。

李迟 2017.5.31 周三

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