发一份能过 V4L2 接口 读到摄像头图片信息 并将其保存下来

旋风炫云

#include <fcntl.h>
#include <stdio.h>
#include <sys/ioctl.h>
#include <stdlib.h>
#include <linux/types.h>
#include <linux/videodev2.h>
#include <malloc.h>
#include <math.h>
#include <string.h>
#include <sys/mman.h>
#include <errno.h>
#include <assert.h>

#define FILE_VIDEO  "/dev/video0"
#define JPG "./image%d.jpg"

typedef struct{
    void *start;
    int length;
}BUFTYPE;
BUFTYPE *usr_buf;
static unsigned int n_buffer = 0;

//set video capture ways(mmap)
int init_mmap(int fd)
{
    //to request frame cache, contain requested counts
    struct v4l2_requestbuffers reqbufs;
    //request V4L2 driver allocation video cache
    //this cache is locate in kernel and need mmap mapping
    memset(&reqbufs, 0, sizeof(reqbufs));
    reqbufs.count = 4;
    reqbufs.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    reqbufs.memory = V4L2_MEMORY_MMAP;

    if(-1 == ioctl(fd,VIDIOC_REQBUFS,&reqbufs)){
        perror("Fail to ioctl 'VIDIOC_REQBUFS'");
        exit(EXIT_FAILURE);
    }

    n_buffer = reqbufs.count;
    printf("n_buffer = %d\n", n_buffer);
    usr_buf = calloc(reqbufs.count, sizeof(BUFTYPE));
    if(usr_buf == NULL){
        printf("Out of memory\n");
        exit(-1);
    }

    //map kernel cache to user process
    for(n_buffer = 0; n_buffer < reqbufs.count; ++n_buffer){
        //stand for a frame
        struct v4l2_buffer buf;
        memset(&buf, 0, sizeof(buf));
        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        buf.memory = V4L2_MEMORY_MMAP;
        buf.index = n_buffer;
         
        //check the information of the kernel cache requested
        if(-1 == ioctl(fd,VIDIOC_QUERYBUF,&buf))
        {
            perror("Fail to ioctl : VIDIOC_QUERYBUF");
            exit(EXIT_FAILURE);
        }


    printf(" buf.length =%d\n", buf.length);


        usr_buf[n_buffer].length = buf.length;
        usr_buf[n_buffer].start =
            mmap(
                    NULL,
                    buf.length,
                    PROT_READ | PROT_WRITE,
                    MAP_SHARED,
                    fd,
                    buf.m.offset
                ); //mmap(0, fbSize, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);


     if(MAP_FAILED == usr_buf[n_buffer].start)
        {
            perror("Fail to mmap");
            exit(EXIT_FAILURE);
        }

    printf(" usr_buf[%d].start=0x%x length=0x%x \n" , n_buffer, usr_buf[n_buffer].start ,buf.length);


        
    }
    return 0;
}

//initial camera device
int init_camera_device(int fd)
{
    //decive fuction, such as video input
    struct v4l2_capability cap;
    //video standard,such as PAL,NTSC
    struct v4l2_standard std;
    //frame format
    struct v4l2_format tv_fmt;
    //check control
    struct v4l2_queryctrl query;
    //detail control value
    struct v4l2_fmtdesc fmt;
    int ret;
    //get the format of video supply
    memset(&fmt, 0, sizeof(fmt));
    fmt.index = 0;
    //supply to image capture
    fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    // show all format of supply
    printf("Support format:\n");
    while(ioctl(fd, VIDIOC_ENUM_FMT, &fmt) == 0){
        fmt.index++;
        printf("pixelformat = ''%c%c%c%c''\ndescription = ''%s''\n",fmt.pixelformat & 0xFF, (fmt.pixelformat >> 8) & 0xFF,(fmt.pixelformat >> 16) & 0xFF, (fmt.pixelformat >> 24) & 0xFF,fmt.description);
    }
    //check video decive driver capability
    ret = ioctl(fd, VIDIOC_QUERYCAP, &cap);
    if(ret < 0){
        perror("Fail to ioctl VIDEO_QUERYCAP");
        exit(EXIT_FAILURE);
    }

    //judge wherher or not to be a video-get device
    if(!(cap.capabilities & V4L2_BUF_TYPE_VIDEO_CAPTURE))
    {
        printf("The Current device is not a video capture device\n");
        exit(-1);
    }

    //judge whether or not to supply the form of video stream
    if(!(cap.capabilities & V4L2_CAP_STREAMING))
    {
        printf("The Current device does not support streaming i/o\n");
        exit(EXIT_FAILURE);
    }

    //set the form of camera capture data



    tv_fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;


#if 0
    tv_fmt.fmt.pix.width = 640;
    tv_fmt.fmt.pix.height = 360;
#else

    tv_fmt.fmt.pix.width = 1280;
    tv_fmt.fmt.pix.height = 960;


#endif


   
    tv_fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_MJPEG;
    //V4L2_PIX_FMT_YUYV
    tv_fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
    if (ioctl(fd, VIDIOC_S_FMT, &tv_fmt)< 0) {
        printf("VIDIOC_S_FMT\n");
        exit(-1);
        close(fd);
    }
    //initial video capture way(mmap)
    init_mmap(fd);
    return 0;
}

int open_camera_device()
{
    int fd;
    //open video device with block
    fd = open(FILE_VIDEO, O_RDWR /* required */ | O_NONBLOCK, 0);//打开设备
    if(fd < 0){
        perror(FILE_VIDEO);
        exit(EXIT_FAILURE);
    }
    return fd;
}

int start_capture(int fd)
{
    unsigned int i;
    enum v4l2_buf_type type;
    //place the kernel cache to a queue
    for(i = 0; i < n_buffer; i++){
        struct v4l2_buffer buf;
        memset(&buf, 0, sizeof(buf));
        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        buf.memory = V4L2_MEMORY_MMAP;
        buf.index = i;

        if(-1 == ioctl(fd, VIDIOC_QBUF, &buf)){
            perror("Fail to ioctl 'VIDIOC_QBUF'");
            exit(EXIT_FAILURE);
        }
    }

    //start capture data
    type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    if(-1 == ioctl(fd, VIDIOC_STREAMON, &type)){
        printf("i=%d.\n", i);
        perror("VIDIOC_STREAMON");
        close(fd);
        exit(EXIT_FAILURE);
    }
    return 0;
}


int process_image(void *addr, int length)
{
    int fd;
    static int num = 0;
    char image_name[20];

    printf("%s addr = 0x%x  length= %d \n" , __func__,addr,length);

    sprintf(image_name, JPG, num++);

    if((fd= open(image_name,O_CREAT|O_WRONLY)) == NULL){

        
        printf("Fail to fopen");
        exit(EXIT_FAILURE);
        
    }
   
    write(fd,addr, length);
    sync( );
    close(fd);
   
       return 0;
   
   
  }












int read_frame(int fd)
{
    struct v4l2_buffer buf;
    unsigned int i;
    memset(&buf, 0, sizeof(buf));

   printf("%s run   place 1 \n",__func__);

   
    buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    buf.memory = V4L2_MEMORY_MMAP;
    //put cache from queue
    if(-1 == ioctl(fd, VIDIOC_DQBUF,&buf)){
        perror("Fail to ioctl 'VIDIOC_DQBUF'");
        exit(EXIT_FAILURE);
    }

    assert(buf.index < n_buffer);
    //read process space's data to a file
    printf("buf.index=%d\n",buf.index);

    process_image(usr_buf[buf.index].start, buf.bytesused);


    printf("%s run   place 2 \n",__func__);

    if(-1 == ioctl(fd, VIDIOC_QBUF,&buf)){
        perror("Fail to ioctl 'VIDIOC_QBUF'");
        exit(EXIT_FAILURE);
    }


    printf("%s run   place 3 \n",__func__);
   
    return 1;
}

int mainloop(int fd)
{
    int count =20;

    while(count-- > 0)
    {
        for(;;)
        {
            fd_set fds;
            struct timeval tv;
            int r;

            printf("count = %d \n", count);
        
            FD_ZERO(&fds);
            FD_SET(fd,&fds);

            /*Timeout*/
            tv.tv_sec = 200;
            tv.tv_usec = 0;
            r = select(fd + 1,&fds,NULL,NULL,&tv);

            if(-1 == r)
            {
                if(EINTR == errno)
                    continue;
                perror("Fail to select");
                exit(EXIT_FAILURE);
            }

            if(0 == r)
            {
                fprintf(stderr,"select Timeout\n");
                exit(-1);
            }

            if(read_frame(fd))
                break;
        }
    }
    return 0;
}

void stop_capture(int fd)
{
    enum v4l2_buf_type type;
    type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    if(-1 == ioctl(fd,VIDIOC_STREAMOFF,&type))
    {
        perror("Fail to ioctl 'VIDIOC_STREAMOFF'");
        exit(EXIT_FAILURE);
    }
    return;
}

void close_camera_device(int fd)
{
    unsigned int i;
    for(i = 0;i < n_buffer; i++)
    {
        if(-1 == munmap(usr_buf.start,usr_buf.length)){
            exit(-1);
        }
    }
    free(usr_buf);

    if(-1 == close(fd))
    {
        perror("Fail to close fd");
        exit(EXIT_FAILURE);
    }
    return;
}

int main()
{


    int fd;
    fd = open_camera_device();
    init_camera_device(fd);
    start_capture(fd);
    mainloop(fd);
    stop_capture(fd);
    close_camera_device(fd);

  
    return 0;
}

thanky0u58

郑先生

  

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playflash

谢谢分享。楼主做出实物了吗