Linux下V4L2拍照



一、源码test.c

#include <fcntl.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <linux/videodev2.h>

int main(){
//////
int fd = open( "/dev/video0",O_RDWR);
printf( "TK------->>>fd is %d\n",fd);
//////
struct v4l2_capability cap;
ioctl(fd,VIDIOC_QUERYCAP,&cap);
printf( "TK---------->>>>>Driver Name:%s\nCard Name:%s\nBus info:%s\n",cap.driver,cap.card,cap.bus_info);
//////
struct v4l2_fmtdesc fmtdesc;
fmtdesc.index = 0; fmtdesc.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
while(ioctl(fd,VIDIOC_ENUM_FMT,&fmtdesc) != -1){
printf( "TK-------->>>>>fmtdesc.description is %s\n",fmtdesc.description);
fmtdesc.index ++;
}
//////
struct v4l2_format fmt;
fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
ioctl(fd,VIDIOC_G_FMT,&fmt);
printf( "TK----------->>>>>fmt.fmt.width is %d\nfmt.fmt.pix.height is %d\nfmt.fmt.pix.colorspace is %d\n",fmt.fmt.pix.width,fmt.fmt.pix.height,fmt.fmt.pix.colorspace);
//////
struct v4l2_requestbuffers req;
req.count = 4;
req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
req.memory = V4L2_MEMORY_MMAP;
ioctl(fd,VIDIOC_REQBUFS,&req);
struct buffer{
void *start;
unsigned int length;
}*buffers;
buffers = (struct buffer*) calloc (req.count, sizeof(*buffers));
unsigned int n_buffers = 0;
for(n_buffers = 0; n_buffers < req.count; ++n_buffers){
struct v4l2_buffer buf;
memset(&buf, 0, sizeof(buf));
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = n_buffers;
if(ioctl(fd,VIDIOC_QUERYBUF,&buf) == -1){
printf( "TK---------_>>>>>>error\n");
close(fd);
exit( -1);
}
buffers[n_buffers].length = buf.length;
buffers[n_buffers].start = mmap( NULL,buf.length,PROT_READ|PROT_WRITE,MAP_SHARED,fd,buf.m.offset);
if(MAP_FAILED == buffers[n_buffers].start){
printf( "TK--------__>>>>>error 2\n");
close(fd);
exit( -1);
}
}
////
unsigned int i;
enum v4l2_buf_type type;
for(i = 0; i < 4; i++){
struct v4l2_buffer buf;
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = i;
ioctl(fd,VIDIOC_QBUF,&buf);
}
type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
ioctl(fd,VIDIOC_STREAMON,&type);
////
struct v4l2_buffer buf;
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
ioctl(fd,VIDIOC_DQBUF,&buf);
char path[ 20];
snprintf(path, sizeof(path), "./yuyv%d",buf.index);
int fdyuyv = open(path,O_WRONLY|O_CREAT, 00700);
printf( "TK--------->>>>fdyuyv is %d\n",fdyuyv);
int resultyuyv = write(fdyuyv,buffers[buf.index].start, 1280* 720* 2);
printf( "TK--------->>>resultyuyv is %d\n",resultyuyv);
close(fdyuyv);
////
close(fd);
return 0;
}

二、编译运行

gcc test.c -o rest

./test

三、结果

在本目录下生成yuyv0这样一个文件，是jpeg编码后的文件。

四、极力推荐一款window下的图像查看工具YUVviewerPlus

  该工具可以将原始yuyv（如yuv422选择yuy2，需要后缀改为.yuv），rgb（rgb24选择gbmp24，需要后缀改为.bmp）等数据文件显示出来。

  另外说明：yuyv和jpeg数据大小为width*height*2；rgb为width*height*3；单位为Bytes。