偶看新闻l1l2l3是什么颜色:Linux音频编程2 音频录放框架
来源：百度文库 编辑：偶看新闻 时间：2024/05/02 08:41:59
音频录放框架下面给出一个利用声卡上的DSP设备进行声音录制和回放的基本框架，它的功能是先录制几秒种音频数据，将其存放在内存缓冲区中，然后再进行回放，其所有的功能都是通过读写/dev/dsp设备文件来完成的：
/* * sound.c */#include #include #include #include #include #include #include #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 main(){int fd; /*声音设备的文件描述符*/
int arg; /*用于ioctl调用的参数*/
int status; /*系统调用的返回值*/
/*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"); if (arg != SIZE) perror("unable to set sample size"); /*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"); if (arg != CHANNELS) perror("unable to set number of channels"); /*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"); /*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"); }} /* * mixer.c */#include #include #include #include #include #include /*用来存储所有可用混音设备的名称*/
const char *sound_device_names[] = SOUND_DEVICE_NAMES; int fd; /*混音设备所对应的文件描述符*/
int devmask, stereodevs; /*混音器信息对应的位图掩码*/
char *name; /*显示命令的使用方法及所有可用的混音设备*/
void usage(){ int i; fprintf(stderr, "usage: %s \n" " %s \n\n" "Where is one of:\n", name, name); for (i = 0 ; i < SOUND_MIXER_NRDEVICES ; i++)if ((1 << i) & devmask) /*只显示有效的混音设备*/
fprintf(stderr, "%s ", sound_device_names[i]); fprintf(stderr, "\n"); exit(1);} int main(int argc, char *argv[]){int left, right, level; /*增益设置*/
int status; /*系统调用的返回值*/
int device; /*选用的混音设备*/
char *dev; /*混音设备的名称*/
int i; name = argv[0]; /*以只读方式打开混音设备*/
fd = open("/dev/mixer", O_RDONLY); if (fd == -1) { perror("unable to open /dev/mixer"); exit(1); } /*获得所需要的信息*/
status = ioctl(fd, SOUND_MIXER_READ_DEVMASK, &devmask); if (status == -1) perror("SOUND_MIXER_READ_DEVMASK ioctl failed"); status = ioctl(fd, SOUND_MIXER_READ_STEREODEVS, &stereodevs); if (status == -1) perror("SOUND_MIXER_READ_STEREODEVS ioctl failed"); /*检查用户输入*/
if (argc != 3 && argc != 4) usage(); /*保存用户输入的混音器名称*/
dev = argv[1]; /*确定即将用到的混音设备*/
for (i = 0 ; i < SOUND_MIXER_NRDEVICES ; i++) if (((1 << i) & devmask) && !strcmp(dev, sound_device_names[i])) break;if (i == SOUND_MIXER_NRDEVICES) { /*没有找到匹配项*/
fprintf(stderr, "%s is not a valid mixer device\n", dev); usage(); } /*查找到有效的混音设备*/
device = i; /*获取增益值*/
if (argc == 4) {/*左、右声道均给定*/
left = atoi(argv[2]); right = atoi(argv[3]); } else {/*左、右声道设为相等*/
left = atoi(argv[2]); right = atoi(argv[2]); } /*对非立体声设备给出警告信息*/
if ((left != right) && !((1 << i) & stereodevs)) { fprintf(stderr, "warning: %s is not a stereo device\n", dev); } /*将两个声道的值合到同一变量中*/
level = (right << 8) + left; /*设置增益*/
status = ioctl(fd, MIXER_WRITE(device), &level); if (status == -1) { perror("MIXER_WRITE ioctl failed"); exit(1); } /*获得从驱动返回的左右声道的增益*/
left = level & 0xff; right = (level & 0xff00) >> 8; /*显示实际设置的增益*/
fprintf(stderr, "%s gain set to %d%% / %d%%\n", dev, left, right); /*关闭混音设备*/
close(fd); return 0;} [xiaowp@linuxgam sound]$ ./mixerusage: ./mixer ./mixer Where is one of: vol pcm speaker line mic cd igain line1 phin video [xiaowp@linuxgam sound]$ ./mixer cd 80 90cd gain set to 80% / 90%