p6.7.c

linux下的音频设备（声卡、扬声器）文件编程

//p6.7.c
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <linux/soundcard.h>

#define Audio_Device "/dev/dsp"
/*
  不同的声音文件有着不同的播放参数，这些参数可以使用file命令获得
*/
#define Sample_Size 16  
#define Sample_Rate 8000 /* 取样率 */

int play_sound(char *filename){
  struct stat stat_buf;
  unsigned char *buf = NULL;
  int handler,fd;
  int result;
  int arg,status;

/*
打开声音文件，将文件读入内存
*/
  fd = open(filename, O_RDONLY);
  if (fd<0)
      return -1;

  if (fstat(fd, &stat_buf)) {
     close(fd);
     return -1;
 }
  if (!stat_buf.st_size) {
	close(fd);
	return -1;
  }

  buf = malloc(stat_buf.st_size);
  if (!buf) {
	close(fd);
	return -1;
  }

  if (read(fd, buf, stat_buf.st_size) < 0) {
	free(buf);
	close(fd);
	return -1;
  }

 /*
打开声卡设备，并设置声卡播放参数，这些参数必须与声音文件参数一致
 */
  handler = open(Audio_Device, O_WRONLY);
  if (handler == -1) {
	perror("open Audio_Device fail");
	return -1;
 }
 
  arg=Sample_Rate;
  status=ioctl(handler,SOUND_PCM_WRITE_RATE,&arg);
  if(status==-1){
        perror("error from SOUND_PCM_WRITE_RATE ioctl");
        return -1;
}

  arg=Sample_Size;
  status=ioctl(handler,SOUND_PCM_WRITE_BITS,&arg);
  if(status==-1){
	  perror("error from SOUND_PCM_WRITE_BITS ioctl");
	  return -1;
  }

  result=write(handler,buf,stat_buf.st_size);
  if(result==-1){
       perror("Fail to play the sound!");
       return -1;
  }


  free(buf);
  close(fd);
  close(handler);
  return result;
}


void main(void)
{
  play_sound("/root/Online.wav");
}