2021年12月29日 | 4412 使用usb摄像头拍照YUYV格式

一、内核设置

Linux内核中已经带有很完善的USB摄像头驱动，支持几乎所有的USB摄像头，我们只需要配置内核，选择上相应的Sensor型号即可。

配置内核，支持USB摄像头：

    Device Drivers --->

        <*> Multimedia support --->

            <*> Video For Linux

            [*] Enable Video For Linux API 1 (DEPRECATED)

            [*] Video capture adapters --->

                [*] V4L USB devices --->

                    <*> USB Video Class (UVC)

                    [*] UVC input events device support

                    [*] GSPCA based webcams --->

到这里，我们就可以选择所需要的USB摄像头驱动，当然也可以选择所有的USB摄像头驱动支持（这样编译出的内核会比较大）

GSPCA是一个万能摄像头驱动程序，进入GSPCA based webcams进行选择。

插入USB摄像头（我使用的UVC摄像头），会提示：

usb 1-1.1: new full speed USB device using s3c2410-ohci and address 3

usb 1-1.1: New USB device found, idVendor=0ac8, idProduct=3450

usb 1-1.1: New USB device strings: Mfr=1, Product=2, SerialNumber=0

usb 1-1.1: Product: Deasy USB2.0 Camera

usb 1-1.1: Manufacturer: Vimicro Corp.

uvcvideo: Found UVC 1.00 device Deasy USB2.0 Camera (0ac8:3450)

input: Deasy USB2.0 Camera as 

/devices/platform/s3c2410-ohci/usb1/1-1/1-1.1/1-1.1:1.0/input/input3

它的设备名称是：/dev/video0

USB摄像头一般都是基于V4L2架构的，需要编写V4L2架构的程序来操作摄像头

二、编写V4L2的应用程序

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#define CAMERA_DEVICE "/dev/video0"

#define CAPTURE_FILE "frame.jpg?imageView2/2/w/550"

#define VIDEO_WIDTH  640

#define VIDEO_HEIGHT 480

#define VIDEO_FORMAT V4L2_PIX_FMT_YUYV

#define BUFFER_COUNT 4

typedef struct VideoBuffer {

    void *start;

    size_t length;

}VideoBuffer;

int fd;             //摄像头文件描述符

void open_camera(char *path);

void get_camera_info();

void get_vedio_info();

//打开设备

void open_camera(char *path)

{

    fd = open(CAMERA_DEVICE, O_RDWR, 0);

    if(fd < 0) {

        printf("Open %s failedn", CAMERA_DEVICE);

        exit(EXIT_FAILURE);

    }

}

//获取驱动信息

void get_camera_info()

{

    struct v4l2_capability cap;

    ret = ioctl(fd, VIDIOC_QUERYCAP, &cap);

    if(ret < 0) {

        printf("VIDIOC_QUERYCAP failed (%d)n", ret);

        return ret;

    }

    // Print capability informations

    printf("Capbility Informations:n");

    printf("*tdriver: %sn", cap.driver);

    printf("*tcard: %sn", cap.card);

    printf("*tbus_info: %sn", cap.bus_info);

    printf("*tversion: %08Xn", cap.version);

    printf("*tcapabilities: %08Xn", cap.capabilities);

}

//获取视频格式

void get_vedio_info()

{

    struct v4l2_format fmt;

    memset(&fmt, 0, sizeof(fmt));

    fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

    ret = ioctl(fd, VIDIOC_G_FMT, &fmt);

    if(ret < 0) {

        printf("VIDIOC_G_FMT failed (%d)n", ret);

        return ret;

    }

    // Print Stream Format

    printf("Stream Format Informations:n");

    printf("*ttype: %dn", fmt.type);

    printf("*twidth: %dn", fmt.fmt.pix.width);

    printf("*theight: %dn", fmt.fmt.pix.height);

    char fmtstr[8];

    memset(fmtstr, 0, 8);

    memcpy(fmtstr, &fmt.fmt.pix.pixelformat, 4);

    printf("*tpixelformat: %sn", fmtstr);

    printf("*tfield: %dn", fmt.fmt.pix.field);

    printf("*tbytesperline: %dn", fmt.fmt.pix.bytesperline);

    printf("*tsizeimage: %dn", fmt.fmt.pix.sizeimage);

    printf("*tcolorspace: %dn", fmt.fmt.pix.colorspace);

    printf("*tpriv: %dn", fmt.fmt.pix.priv);

    //    printf("*traw_data: %sn", fmt.fmt.raw_data);

    /* 显示所有支持的格式 */

    struct v4l2_fmtdesc fmtdesc;

    fmtdesc.index = 0;

    fmtdesc.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

    printf("Support format:n");

    while(ioctl(fd, VIDIOC_ENUM_FMT, &fmtdesc) != -1) {

        printf("t%d.%sn", fmtdesc.index+1, fmtdesc.description);

        fmtdesc.index++;

    }

}

int main()

{

    int i, ret;

    open_camera(CAMERA_DEVICE);

    get_camera_info();

    get_vedio_info();

    //请求分配内存

    struct v4l2_requestbuffers reqbuf;

    reqbuf.count = BUFFER_COUNT;

    reqbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

    reqbuf.memory = V4L2_MEMORY_MMAP;

    ret = ioctl(fd, VIDIOC_REQBUFS, &reqbuf);

    if(ret < 0) {

        printf("VIDIOC_REQBUFS failed (%d)n", ret);

        return ret;

    }

    //获取空间

    VideoBuffer *buffers = calloc(reqbuf.count, sizeof(*buffers));

    if(!buffers) {

        //映射

        fprintf(stderr, "Out of memoryn");

        exit(EXIT_FAILURE);

    }    

    for(i=0;i        struct v4l2_buffer buf;

        memset(&buf, 0, sizeof(buf));

        buf.index = i;

        buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

        buf.memory = V4L2_MEMORY_MMAP;

        ret = ioctl(fd, VIDIOC_QUERYBUF, &buf);

        if(ret < 0) {

            printf("VIDIOC_QUERYBUF (%d) failed (%d)n", i, ret);

            return ret;

        }

        // mmap buffer

        buffers[i].length = buf.length;

        buffers[i].start = (char *)mmap(0, buf.length, PROT_READ|PROT_WRITE, MAP_SHARED, 

            fd, buf.m.offset);

        if(buffers[i].start == MAP_FAILED) {

            printf("mmap (%d) failed: %sn", i, strerror(errno));

            return -1;

        }

        // Queen buffer

        ret = ioctl(fd, VIDIOC_QBUF, &buf);

        if(ret < 0) {

            printf("VIDIOC_QBUF (%d) failed (%d)n", i, ret);

            return -1;

        }

        printf("Frame buffer: %d: address=0x%x, length=%dn", i,

            (unsigned int)buffers[i].start, buffers[i].length);

    }

    // 开始录制

    struct v4l2_buffer buf;

    enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

    buf.index = 0;

    buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

    buf.memory = V4L2_MEMORY_MMAP;

    ret = ioctl(fd, VIDIOC_STREAMON, &type);

    if (ret < 0) {

        printf("VIDIOC_STREAMON failed (%d)n", ret);

        return ret;

    }

    // Get frame

    ret = ioctl(fd, VIDIOC_DQBUF, &buf);

    if (ret < 0) {

        printf("VIDIOC_DQBUF failed (%d)n", ret);

        return ret;

    }

    // Process the frame

    FILE *fp = fopen(CAPTURE_FILE, "wb");

    if (fp < 0) {

        printf("open frame data file failedn");

        return -1;

    }

    fwrite(buffers[buf.index].start, 1, buf.length, fp);

    fclose(fp);

    printf("Capture one frame saved in %sn", CAPTURE_FILE);

    // Re-queen buffer

    ret = ioctl(fd, VIDIOC_QBUF, &buf);

    if (ret < 0) {

        printf("VIDIOC_QBUF failed (%d)n", ret);

        return ret;

    }

    // Release the resource

    for(i=0;i<4;i++) {

        munmap(buffers[i].start, buffers[i].length);

    }

    close(fd);

    printf("Camera test Done.n");

    return 0;

}

三、使用软件打开

不过要选择对应的格式：