Exynos4412 OV5640摄像头（三）—— 应用程序

落日映苍穹つ 2022-01-21 06:21 503阅读 0赞

内核配置完并且烧录镜像后，就可以编写应用程序了。这里使用迅为提供的测试程序，该程序的功能是通过OV5640录制一段50帧（大小可设置）的视频，并生成out.yuv视频文件，可以通过yuv播放器或二进制编辑器进行验证。

该程序调用了V4L2，那什么是V4L2呢？ V4L2为linux下视频设备程序提供了一套接口规范。包括一套数据结构和底层V4L2驱动接口。只能在linux下使用。它使程序有发现设备和操作设备的能力。它主要是用一系列的回调函数来实现这些功能。像设置摄像头的频率、帧频、视频压缩格式和图像参数等等。当然也可以用于其他多媒体的开发，如音频等。

可以参考这篇文章学习V4L2——[v4l2的学习建议和流程解析][v4l2]

应用程序，YUV播放器及二进制编辑器下载：[https://download.csdn.net/download/q1449516487/11231366][https_download.csdn.net_download_q1449516487_11231366]

下面是应用程序的代码及注释：包含4个文件（build.sh、camera.h、camera.c、main.c）

build.sh：运行build.sh进行编译

#build.sh
    arm-none-linux-gnueabi-g++ -o camera camera.cpp main.cpp -static

camera.h：摄像头的h文件

#ifndef CAMERA_H
    #define CAMERA_H
    
    #include <sys/types.h>
    
    #define CLEAR(x) memset (&(x), 0, sizeof (x))
    
    //视频IO模式
    typedef enum {
        IO_METHOD_READ, IO_METHOD_MMAP, IO_METHOD_USERPTR,
    } io_method;
    
    //本地缓存区
    struct buffer {
        void * start;
        size_t length;//buffer's length is different from cap_image_size
    };
    
    class Camera
    {
    public:
        Camera(char *DEV_NAME,int w,int h, int camer_type);
        ~Camera();
        bool OpenDevice();//打开设备
        void CloseDevice();
        bool GetBuffer(unsigned char *image);//获取数据流
        unsigned int getImageSize();
    
    private:
        char dev_name[50];//设备名称
        io_method io;//IO
        int fd;//描述符	
        int width;//宽
        int height;//高
        struct buffer * buffers ;//共享内存
        unsigned int n_buffers ;//index
        unsigned int cap_image_size ;//to keep the real image size!!		//图像大小
    
        bool init_device(void);//初始化设备
        //void init_read(unsigned int buffer_size);
        bool init_mmap(void);//创建共享内存
        //void init_userp(unsigned int buffer_size);
        void uninit_device(void);//卸载设备
        bool start_capturing(void);//开始捕获
        void stop_capturing(void);//停止捕获
        void mainloop(unsigned char *image);//
        int read_frame(unsigned char *image);//读帧
        void close_device(void);//关闭设备
        bool open_device(void);//打开设备
        bool process_image(unsigned char *image,const void * p);//处理图像
    
        void errno_exit(const char * s);//错误退出
        int xioctl(int fd, int request, void * arg);//ioctl
    };
    
    #endif // CAMERA_H

camera.c：摄像头的c文件

#include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <assert.h>
    #include <getopt.h>             /* getopt_long() */
    #include <fcntl.h>              /* low-level i/o */
    #include <unistd.h>
    #include <errno.h>
    #include <malloc.h>
    #include <sys/stat.h>
    #include <sys/time.h>
    #include <sys/mman.h>
    #include <sys/ioctl.h>
    #include <asm/types.h>          /* for videodev2.h */
    #include <linux/videodev2.h>
    #include "camera.h"
    
    int c_camera_type = 0;
    
    Camera::Camera(char *DEV_NAME, int w, int h, int camera_type)
    {
        memcpy(dev_name,DEV_NAME,strlen(DEV_NAME));
    
    	//设置IO模式
        io = IO_METHOD_MMAP;//IO_METHOD_READ;//IO_METHOD_MMAP;
        cap_image_size=0;//图像大小
        width=w;//宽
        height=h;//高
    
    	if(1 == camera_type)
    	{
    		c_camera_type = 1;//摄像头类型（1:UVC,0:ITU）
    	}
    }
    
    Camera::~Camera(){
    
    }
    
    //返回图像大小
    unsigned int Camera::getImageSize(){
        return cap_image_size;
    }
    
    void Camera::CloseDevice() {
        stop_capturing();
        uninit_device();
        close_device();
    }
    
    void Camera::errno_exit(const char * s) {
        fprintf(stderr, "%s error %d, %s\n", s, errno, strerror(errno));
        exit(EXIT_FAILURE);
    }
    int Camera::xioctl(int fd, int request, void * arg) {
        int r;
        do
            r = ioctl(fd, request, arg);
        while (-1 == r && EINTR == errno);
        return r;
    }
    
    //读取图像帧
    int Camera::read_frame(unsigned char *image) {
        struct v4l2_buffer buf;
    
        CLEAR (buf);
        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        buf.memory = V4L2_MEMORY_MMAP;
    
    	//VIDIOC_DQBUF 命令向驱动获取已经存放有视频数据的缓存，\
    	v4l2_buffer 的各个域几乎都会被更新，但主要的参数也是 index，\
    	应用程序会根据 index 确定可用数据的起始地址和范围。
        if (-1 == xioctl(fd, VIDIOC_DQBUF, &buf)) {
            switch (errno) {
            case EAGAIN:
    		printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
                return 0;
            case EIO:
    		printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
                /* Could ignore EIO, see spec. */
                /* fall through */
            default:
    		printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
                errno_exit("VIDIOC_DQBUF");
            }
        }
    	printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
        assert(buf.index < n_buffers);
    	printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
        memcpy(image,buffers[0].start,cap_image_size);
    
    	//VIDIOC_QBUF 命令向驱动传递应用程序已经处理完的缓存，\
    	即将缓存加入空闲可捕获视频的队列，传递的主要参数为 index
        if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
            errno_exit("VIDIOC_QBUF");
    
        return 1;
    }
    
    void Camera::stop_capturing(void) {
        enum v4l2_buf_type type;
        switch (io) {
        case IO_METHOD_READ:
            /* Nothing to do. */
            break;
        case IO_METHOD_MMAP:
        case IO_METHOD_USERPTR:
            type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
            if (-1 == xioctl(fd, VIDIOC_STREAMOFF, &type))
                errno_exit("VIDIOC_STREAMOFF");
            break;
        }
    }
    bool Camera::start_capturing(void) {
        unsigned int i;
        enum v4l2_buf_type type;
    	printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
        for (i = 0; i < n_buffers; ++i) {
            struct v4l2_buffer buf;
            CLEAR (buf);
            buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
            buf.memory = V4L2_MEMORY_MMAP;
            buf.index = i;
            if (-1 == xioctl(fd, VIDIOC_QBUF, &buf))
    	{
    		printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
                return false;
    	}
        }
        type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        if (-1 == xioctl(fd, VIDIOC_STREAMON, &type))
        {
    	printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
            return false;
         }
    	printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
        return true;
    }
    
    
    void Camera::uninit_device(void) {
        unsigned int i;
        switch (io) {
        case IO_METHOD_READ:
            free(buffers[0].start);
            break;
        case IO_METHOD_MMAP:
            for (i = 0; i < n_buffers; ++i)
                if (-1 == munmap(buffers[i].start, buffers[i].length))
                    errno_exit("munmap");
            break;
        case IO_METHOD_USERPTR:
            for (i = 0; i < n_buffers; ++i)
                free(buffers[i].start);
            break;
        }
        free(buffers);
    }
    
    //申请一片连续的内存用于缓存视频信息
    bool Camera::init_mmap(void) {
        struct v4l2_requestbuffers req;
        CLEAR (req);
    
        req.count = 4;//count 指定根据图像占用空间大小申请的缓存区个数
        req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;//type 为视频捕获模式
        req.memory = V4L2_MEMORY_MMAP;//memory 为内存区的使用方式
    
    	//VIDIOC_REQBUFS 命令通过结构 v4l2_requestbuffers 请求驱动申请一片连续的内存用于缓存视频信息
        if (-1 == xioctl(fd, VIDIOC_REQBUFS, &req)) {
            if (EINVAL == errno) {
                fprintf(stderr, "%s does not support "
                        "memory mapping\n", dev_name);
                return false;
            } else {
                return false;
            }
        }
    	
        if (req.count < 2) {
    		//缓冲区内存不足
            fprintf(stderr, "Insufficient buffer memory on %s\n", dev_name);
            return false;
        }
    
    	//本地视频缓冲区
        buffers = (buffer*)calloc(req.count, sizeof(*buffers));
        if (!buffers) {
            fprintf(stderr, "Out of memory\n");
            return false;
        }
    
    	//req.count表示缓存区个数
        for (n_buffers = 0; n_buffers < req.count; ++n_buffers) {
            struct v4l2_buffer buf;
            CLEAR (buf);
    		//bytesused 为缓存已使用空间大小
    		//flags 为缓存当前状态（常见值有 V4L2_BUF_FLAG_MAPPED | V4L2_BUF_FLAG_QUEUED | V4L2_BUF_FLAG_DONE，分别代表当前缓存已经映射、缓存可以采集数据、缓存可以提取数据）
    		//timestamp 为时间戳
    		//sequence为缓存序号
    		//offset 为当前缓存与内存区起始地址的偏移
    		//length 为缓存大小
    		//reserved 一般用于传递物理地址值
    		//
            buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;//type 为视频捕获模式
            buf.memory = V4L2_MEMORY_MMAP;//memory 为缓存使用方式
            buf.index = n_buffers;//index 为缓存编号
    
    		//VIDIOC_QUERYBUF 命令通过结构 v4l2_buffer 查询驱动申请的内存区信息
            if (-1 == xioctl(fd, VIDIOC_QUERYBUF, &buf))
                errno_exit("VIDIOC_QUERYBUF");
    
            buffers[n_buffers].length = buf.length;//buf.length 为缓存大小
            buffers[n_buffers].start = mmap(NULL /* start anywhere */, buf.length,
                                            PROT_READ | PROT_WRITE /* required */,
                                            MAP_SHARED /* recommended */, fd, buf.m.offset);
            if (MAP_FAILED == buffers[n_buffers].start)
                return false;
        }
        return true;
    }
    
    //初始化摄像头
    bool Camera::init_device(void) {
        struct v4l2_capability cap;//设备操作模式
    
        struct v4l2_cropcap cropcap;
        struct v4l2_crop crop;
    
        struct v4l2_format fmt;//视频格式
        unsigned int min;
    
    	//VIDIOC_QUERYCAP 命令通过结构 v4l2_capability 获取设备支持的操作模式
        if (-1 == xioctl(fd, VIDIOC_QUERYCAP, &cap)) {
    	printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
            if (EINVAL == errno) {
                fprintf(stderr, "%s is no V4L2 device\n", dev_name);
                return false;
            } else {
                return false;
            }
        }
    
    	//cap.capabilities属性代表设备支持的操作模式，常见的值有 V4L2_CAP_VIDEO_CAPTURE | V4L2_CAP_STREAMING 表示是一个视频捕捉设备并且具有数据流控制模式
    	//V4L2_CAP_VIDEO_CAPTURE表示是一个视频捕捉设备
        if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
    	printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
            fprintf(stderr, "%s is no video capture device\n", dev_name);
            return false;
        }
    
    	printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
    	//设备IO模式
        switch (io){
    		case IO_METHOD_READ:
    			//V4L2_CAP_READWRITE表示设备支持读写模式
    			if (!(cap.capabilities & V4L2_CAP_READWRITE)) {
    			printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
    				fprintf(stderr, "%s does not support read i/o\n", dev_name);
    				return false;
    			}
    			break;
    
    		case IO_METHOD_MMAP:
    		case IO_METHOD_USERPTR:
    			printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
    			//V4L2_CAP_STREAMING表示设备支持数据流控模式
    			if (!(cap.capabilities & V4L2_CAP_STREAMING)) {
    			printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
    				fprintf(stderr, "%s does not support streaming i/o\n", dev_name);
    				return false;
    			}
    			break;
        }
    
        v4l2_input input;//视频输入
    
        memset(&input, 0, sizeof(struct v4l2_input));
        input.index = 0;
    
    	//VIDIOC_S_INPUT表示设备选择输入源input
        int rtn = ioctl(fd, VIDIOC_S_INPUT, &input);
        if (rtn < 0) {
            printf("VIDIOC_S_INPUT:rtn(%d)\n", rtn);
            return false;
        }
    	printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
        printf("-#-#-#-#-#-#-#-#-#-#-#-#-#-\n");
        printf("\n");
        crop finished!
    
    
        //set the format
        CLEAR (fmt);
    
    	//V4L2_BUF_TYPE_VIDEO_CAPTURE表示设置视频捕获模式为视频捕捉模式
    	//在此模式下 fmt 联合体采用域 v4l2_pix_format：
    	//width 为视频的宽
    	//height 为视频的高
    	//pixelformat 为视频数据格式（常见的值有 V4L2_PIX_FMT_YUV422P | V4L2_PIX_FMT_RGB565）
    	//bytesperline 为一行图像占用的字节数
    	//sizeimage 则为图像占用的总字节数
    	//colorspace 指定设备的颜色空间
        fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    
        fmt.fmt.pix.width = width;
        fmt.fmt.pix.height = height;
        //V4L2_PIX_FMT_YVU420, V4L2_PIX_FMT_YUV420 — 具有1/2水平和垂直色度分辨率的平面格式，也称为YUV 4:2:0
        //V4L2_PIX_FMT_YUYV — 压缩格式与1/2水平色度分辨率，也称为YUV 4:2:2
        fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUV420;//V4L2_PIX_FMT_YUYV;//V4L2_PIX_FMT_YUV420;//V4L2_PIX_FMT_YUYV;
    	//fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
        //fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
        {
            printf("-#-#-#-#-#-#-#-#-#-#-#-#-#-\n");
            printf("=====will set fmt to (%d, %d)--", fmt.fmt.pix.width,
                   fmt.fmt.pix.height);
            if (fmt.fmt.pix.pixelformat == V4L2_PIX_FMT_YUYV) {
                printf("V4L2_PIX_FMT_YUYV\n");
            } else if (fmt.fmt.pix.pixelformat == V4L2_PIX_FMT_YUV420) {
                printf("V4L2_PIX_FMT_YUV420\n");
            } else if (fmt.fmt.pix.pixelformat == V4L2_PIX_FMT_NV12) {
                printf("V4L2_PIX_FMT_NV12\n");
            }
        }
    	printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
    
    	printf("************** %s, line = %d(camera_type = %d)\n", __FUNCTION__, __LINE__, c_camera_type);
    
        if(c_camera_type == 0)//ITU
        {
    		//VIDIOC_S_FMT选择视频格式
        	if (-1 == xioctl(fd, VIDIOC_S_FMT, &fmt))
        	{
    			printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
            	return false;
         	}
         }
    
    #if 1
        if(c_camera_type == 0)
        {
        	fmt.type = V4L2_BUF_TYPE_PRIVATE;
    		//VIDIOC_S_FMT选择视频格式
        	if (-1 == xioctl(fd, VIDIOC_S_FMT, &fmt))
        	{
            	printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
            	return false;
         	}
        }
    	fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    #endif
    	// CLEAR (fmt);
    #if 1
    	//VIDIOC_G_FMT表示查询视频格式
        if (-1 == xioctl(fd, VIDIOC_G_FMT, &fmt))
        {
    	printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
            return false;
         }
    #endif
    	printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
        printf("=====after set fmt\n");
        printf("    fmt.fmt.pix.width = %d\n", fmt.fmt.pix.width);
        printf("    fmt.fmt.pix.height = %d\n", fmt.fmt.pix.height);
        printf("    fmt.fmt.pix.sizeimage = %d\n", fmt.fmt.pix.sizeimage);
    	//sizeimage表示图像占用的总字节数
        cap_image_size = fmt.fmt.pix.sizeimage;
    	//bytesperline为一行图像占用的字节数
        printf("    fmt.fmt.pix.bytesperline = %d\n", fmt.fmt.pix.bytesperline);
        printf("-#-#-#-#-#-#-#-#-#-#-#-#-#-\n");
        printf("\n");
    
    
        /* Note VIDIOC_S_FMT may change width and height. */
        printf("-#-#-#-#-#-#-#-#-#-#-#-#-#-\n");
        /* Buggy driver paranoia. */
        min = fmt.fmt.pix.width * 2;
    	//bytesperline为一行图像占用的字节数
        if (fmt.fmt.pix.bytesperline < min)
            fmt.fmt.pix.bytesperline = min;
    
        min = (unsigned int)width*height*3/2;
        printf("min:%d\n",min);
    
    	//sizeimage表示图像占用的总字节数
        if (fmt.fmt.pix.sizeimage < min)
            fmt.fmt.pix.sizeimage = min;
        cap_image_size = fmt.fmt.pix.sizeimage;
        printf("After Buggy driver paranoia\n");
        printf("    >>fmt.fmt.pix.sizeimage = %d\n", fmt.fmt.pix.sizeimage);
        printf("    >>fmt.fmt.pix.bytesperline = %d\n", fmt.fmt.pix.bytesperline);
        printf("-#-#-#-#-#-#-#-#-#-#-#-#-#-\n");
        printf("\n");
    
    	//申请一片连续的内存用于缓存视频信息
        init_mmap();
    
        return true;
    }
    
    //关闭设备
    void Camera::close_device(void) {
        if (-1 == close(fd))
            errno_exit("close");
        fd = -1;
    }
    
    //打开设备
    bool Camera::open_device(void) {
        struct stat st;//struct stat描述一个linux系统文件系统中的文件属性的结构
        if (-1 == stat(dev_name, &st)) {
            fprintf(stderr, "Cannot identify '%s': %d, %s\n", dev_name, errno,
                    strerror(errno));
            return false;
        }
        if (!S_ISCHR(st.st_mode)) {//判断是否字符设备
            fprintf(stderr, "%s is no device\n", dev_name);
            return false;
        }
        fd = open(dev_name, O_RDWR /* required */| O_NONBLOCK, 0);//O_RDWR读写  O_NONBLOCK非阻塞，读不到数据返回-1
        if (-1 == fd) {
            fprintf(stderr, "Cannot open '%s': %d, %s\n", dev_name, errno,
                    strerror(errno));
            return false;
        }
        return true;
    }
    
    //打开设备
    bool Camera::OpenDevice(){
        if (open_device()) {//打开摄像头
            printf("open success\n");
            if (init_device()) {//初始化摄像头
    			printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
    			if (start_capturing())
    			printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
                return true;
            }
    		else
    		{
    			printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
    		}
        } else
            printf("open failed\n");
    
    	printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
        return false;
    }
    
    //
    bool Camera::GetBuffer(unsigned char *image){
        fd_set fds;
        struct timeval tv;
        int r;
        FD_ZERO(&fds);
        FD_SET(fd, &fds);
        /* Timeout. */
        tv.tv_sec = 2;
        tv.tv_usec = 0;
        r = select(fd + 1, &fds, NULL, NULL, &tv);
        if (-1 == r) {
            errno_exit("select");
        }
        if (0 == r) {
    	printf("************** %s, line = %d\n", __FUNCTION__, __LINE__);
            fprintf(stderr, "select timeout\n");
            exit(EXIT_FAILURE);
        }
        read_frame(image);//读取图像帧
    }

main.c：应用程序

#include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <malloc.h>
    #include <time.h>
    #include "camera.h"
    
    #define DEV_NAME_LENGTH		50
    #define NUM_FRAM		50
    
    int main(int argc, char ** argv) {
        //char *dev_name = "/dev/video0";	//ITU
        //char *dev_name = "/dev/video1";	//UVC
        char *dev_name = NULL;
        FILE * outf = 0;
        unsigned int image_size;//图像大小
    
    	//dev/video0为ITU, dev/video1为UVC
        int camera_type = 0;//0:ITU, 1:UVC	
        int width=640;
        int height=480;
    
        if(argc != 3)
        {
    		printf("usage: ./camera /dev/video0 640x480\n");
    		return 0;
        }
    
    	dev_name = (char *)malloc(sizeof(char) * DEV_NAME_LENGTH);
    	if(!dev_name)
    	{
    		printf("malloc mem error\n");
    		return -1;
    	}
    
        memset(dev_name, 0, sizeof(char) * DEV_NAME_LENGTH);//为新申请的内存做初始化工作
    	strcpy(dev_name, argv[1]);
    
    	if(!strcmp(dev_name, "/dev/video1"))
    	{
    		camera_type = 1;//dev/video1为UVC
    	}
    	else
    	{
    		camera_type = 0;//dev/video0为ITU
    	}
    
    	if(!strcmp(argv[2], "640x480"))
    	{
    		width = 640;
        	height = 480;
    	}
    	else if(!strcmp(argv[2], "800x600"))
    	{
    		width = 800;
            height = 600;
    	}
    	else
    	{
    		width = 640;
            height = 480;
    	}
    
        outf = fopen("out.yuv", "wb");//打开一个文件，用于保存视频
        Camera *camera;
        unsigned char image[width*height*2];
    
        clock_t starttime, endtime;
        double totaltime;
    
    	//创建摄像头对象
        camera=new Camera(dev_name,width,height, camera_type);
    
    	//打开摄像头
        if(!camera->OpenDevice()){
    	printf("fun:%s, line = %d\n", __FUNCTION__, __LINE__);
            return -1;
        }
    
    	printf("fun:%s, line = %d\n", __FUNCTION__, __LINE__);
        image_size=camera->getImageSize();
    
    	printf("fun:%s, line = %d\n", __FUNCTION__, __LINE__);
        starttime = clock();
        //int frames=50;
        unsigned int writesize=0;
    	printf("fun:%s, line = %d\n", __FUNCTION__, __LINE__);
    
    	//写NUM_FRAM 帧图像到out.yuv文件中
        for(int i=0;i<NUM_FRAM;i++){
            if(!camera->GetBuffer(image)){
    		printf("fun:%s, line = %d\n", __FUNCTION__, __LINE__);
                break;
            }
    		printf("fun:%s, line = %d\n", __FUNCTION__, __LINE__);
            writesize=fwrite(image,1,image_size,outf);//向文件写数据
            //fflush(outf);
            printf("frame:%d,writesize:%d\n",i,writesize);
        }
    
    	printf("fun:%s, line = %d\n", __FUNCTION__, __LINE__);
        endtime = clock();
        totaltime = (double)( (endtime - starttime)/(double)CLOCKS_PER_SEC );//总时间
        printf("time :%f, rate :%f\n",totaltime,NUM_FRAM/totaltime);
        camera->CloseDevice();
        fclose(outf);
        return 0;
    }

[v4l2]: https://www.cnblogs.com/silence-hust/p/4464291.html
[https_download.csdn.net_download_q1449516487_11231366]: https://download.csdn.net/download/q1449516487/11231366