oss.c

《linux驱动程序设计从入门到精通》一书中所有的程序代码含驱动和相应的应用程序

void main()
{
	int audio_fd;
	//打开音频设备
	if ((audio_fd = open("/dev/dsp",omode,0)) == -1) {
		perror("/dev/dsp");
		exit(1);
	}
    //设置音频格式、声道数、采样频率
	int format;
	format = AFMT_S16_NE;
	if (ioctl(audio_fd,SNDCTL_DSP_SETFMT, &format) == -1) {
		perror("SNDCTL_DSP_SETFMT");
		exit(1);
	}
	int channels = 2;
	if (ioctl(audio_fd, SNDCTL_DSP_CHANNELS, & channels) == -1) {
		perror("SNDCTL_DSP_CHANNELS");
		exit(1);
	}
	int speed = 44100;  //44.1 KHz
	if (ioctl(audio_fd, SNDCTL_DSP_SPEED, &speed) == -1) {
		perror("SNDCTL_DSP_SPEED");
		exit(1);
	}
	int music_fd;	
    signed short applicbuf[2048];         
	int count;
	if (mode == PLAY) {//播放模式
		if ((music_fd = open(filename, O_RDONLY, 0)) == -1) {
			perror(filename);
			exit(1);
		}
        //从文件中读音频数据，直接发送到音频设备
		while ((count = read(music_fd, applicbuf, 2048)) > 0) {
			write(audio_fd, applicbuf, count);
		}
	} 
	else //录音模式
	{
		if ((music_fd = open(filename, O_WRONLY | O_CREAT, 0)) == -1) {
            perror(filename);
            exit(1);
        }
		int mixer_fd;
        if ((mixer_fd = open("/dev/mixer", O_WRONLY)) == -1) {
			perror("open /dev/mixer error");
            exit(1);
        }
        //设置录音源
        int testchan = SOUND_MIXER_CD;  		
		int recsrc = (1 << testchan);  
   	    if (ioctl(mixer_fd, SOUND_MIXER_WRITE_RECSRC,&recsrc) == -1) {
			perror("CD");
			exit(1);
		}
		int totalbyte= speed * channels * 2 * 60 * 3;
		int totalword = totalbyte/2;
		int total = 0；
			while (total != totalword) {
				if (totalword - total >= 2048) 
					count = 2048;
				else 
					count = totalword - total;
				read(audio_fd, applicbuf, count);//录音
				write(music_fd, applicbuf, count);//写入文件
				total += count;   		
			}
			close(mixer_fd);
	}
	close(audio_fd);
	close(music_fd);
	return 0;
}