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相机硬件模组大致在智能硬件上数据流
cmos----mipi----isp----v4l2---hal---------.jni ----app
下面介绍v4l2如何获取一张图像yuv图像
gcc -o jhf jhf.c
./jhf
#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;
}