解决mini2440声卡全双工问题，实现同时录音及播放

#include <unistd.h> #include <fcntl.h> #include <sys/types.h> #include <sys/ioctl.h> #include <stdlib.h> #include <stdio.h> #include <linux/soundcard.h> #include <pthread.h> #define LENGTH 3 #define RATE 8000 #define SIZE 8 #define CHANNELS 1 unsigned char buf[LENGTH * RATE * SIZE * CHANNELS /8]; int main() { int fd_r,fd_w; int arg; int status; pid_t pid; int recing = 1,playing = 0; pid = fork(); if(pid < 0){ perror("error in fork/n"); } if(pid == 0){ fd_r = open("/dev/dsp",O_RDONLY); if(fd_r < 0){ perror("open read of /dev/dsp failed"); exit(1); } arg = SIZE; status = ioctl(fd_r,SOUND_PCM_WRITE_BITS,&arg); if(status == -1) perror("SOUND_PCM_WRITE_BITS ioctl failed"); if(arg != SIZE) perror("unable to set sample size"); arg = CHANNELS; status = ioctl(fd_r,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"); arg = RATE; status = ioctl(fd_r,SOUND_PCM_WRITE_RATE,&arg); if(status == -1) perror("SOUND_PCM_WRITE_WRITE ioctl failed"); while(1) { if(playing== 0){ recing = 1; printf("Say something:"); status = read(fd_r,buf,sizeof(buf)); /* recording*/ if(status != sizeof(buf)) perror("read wrong number of bytes"); recing = 0; } } } else { fd_w = open("/dev/dsp",O_WRONLY); if(fd_w < 0) { perror("open write of /dev/dsp failed"); exit(1); } arg = SIZE; status = ioctl(fd_w,SOUND_PCM_WRITE_BITS,&arg); if(status == -1) perror("SOUND_PCM_WRITE_BITS ioctl failed"); if(arg != SIZE) perror("unable to set sample size"); arg = CHANNELS; status = ioctl(fd_w,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"); arg = RATE; status = ioctl(fd_w,SOUND_PCM_WRITE_RATE,&arg); if(status == -1) perror("SOUND_PCM_WRITE_WRITE ioctl failed"); while(1) { if(recing == 0){ playing = 1; status = write(fd_w,buf,sizeof(buf)); /* playback */ if(status != sizeof(buf)) perror("wrote wrong number of bytes"); status = ioctl(fd_w,SOUND_PCM_SYNC,0); if(status == -1) perror("SOUND_PCM_SYNC ioctl failed"); playing = 0; } } } }