[正点原子i.MX6UL] v4l2+framebuffer预览USB摄像头(三)：实时预览

Jmhh247 · 2020-03-21 17:23:57

关键字：正点原子，i.MX6UL，linux, framebuffer

- 主机环境：ubuntu16.04-64bit
- 硬件版本：正点原子i.MX6UL emmc

固件帖在本站：[[正点原子i.MX6UL开发板] 编译uboot、linux、buildroot-rootfs](https://whycan.cn/t_3550.html)

---

#### 一、本篇目标

接上篇- [[正点原子i.MX6UL]v4l2+framebuffer预览USB摄像头(二)：显示照片](https://whycan.cn/t_3888.html)

如题，本篇主要实现在LCD(framebuffer)上实时预览USB摄像头画面。

有了前面两篇的代码实现，本篇的功能已经呼之欲出了，下面直接上代码。

#### 二、代码实现

本代码把采集到的USB摄像头数据，先由YUYV转成RGB888，然后由RGB888再转换成LCD需要的RGB565，最终把数据复制到显存完成显示。

重复这个过程即可实现简单的USB摄像头实时预览。

v4l2grap-uvc-bmponfb-run-x.c：

/*
 * @FilePath: /0321/v4l2grap-uvc-bmponfb-run-x.c
 * @Version: 1.0.0
 * @Author: zys
 * @LastAuthor: zys
 * @CreationDate: 2020-02-04 11:33:25
 * @LastEditTime: 2020-03-21 16:47:10
 * @Description :  在LCD上实时预览USB摄像头画面。
 */


/*----------------------------------------------------------------------------*/
/* change log ----------------------------------------------------------------*/
/*
    
0321
yz imx6ul test ok.


-build:
    $ARMGCC v4l2grap-uvc-bmponfb-run-x.c -o v4l2grap-uvc-bmponfb-run-x

-tftp get:    
    cp v4l2grap-uvc-bmponfb-run-x /tftpboot/
    tftp -g -r v4l2grap-uvc-bmponfb-run-x 192.168.1.133       
        
*/



/*----------------------------------------------------------------------------*/
/* Includes ------------------------------------------------------------------*/
#include <fcntl.h>
#include <linux/videodev2.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <linux/fb.h>


/* Private define ------------------------------------------------------------*/
#define _UVC_CAM_HEIGHT (480)
#define _UVC_CAM_WIDTH  (640)
#define IMAGEHEIGHT     _UVC_CAM_HEIGHT
#define IMAGEWIDTH      _UVC_CAM_WIDTH

#define NB_BUFFER 4

/* Private macro -------------------------------------------------------------*/
/* Private typedef -----------------------------------------------------------*/
struct vdIn {
    int   fd;
    char* videodevice;

    // v4l2
    struct v4l2_capability     cap;
    struct v4l2_format         fmt;
    struct v4l2_fmtdesc        fmtdesc;
    struct v4l2_streamparm     setfps;
    struct v4l2_requestbuffers rb;

    void* mem[NB_BUFFER];
    int   memlength[NB_BUFFER];

    unsigned char* framebuffer;
    int            framesizeIn;

    int width;
    int height;
    int fps;


    FILE* fp_bmp;
};

/*_attribute__((packed))的作用是告诉编译器取消结构在编译过程中的优化对齐  */

//14byte文件头
typedef struct
{
    unsigned char cfType[2];  //文件类型，"BM"(0x4D42)
    unsigned int  cfSize;     //文件大小（字节）
    unsigned int  cfReserved; //保留，值为0
    unsigned int  cfoffBits;  //数据区相对于文件头的偏移量（字节）
} __attribute__((packed)) BITMAPFILEHEADER;


//40byte信息头
typedef struct
{
    unsigned int       ciSize;            //BITMAPFILEHEADER所占的字节数
    unsigned int       ciWidth;           //宽度
    unsigned int       ciHeight;          //高度
    unsigned short int ciPlanes;          //目标设备的位平面数，值为1
    unsigned short int ciBitCount;        //每个像素的位数
    char               ciCompress[4];     //压缩说明
    unsigned int       ciSizeImage;       //用字节表示的图像大小，该数据必须是4的倍数
    unsigned int       ciXPelsPerMeter;   //目标设备的水平像素数/米
    unsigned int       ciYPelsPerMeter;   //目标设备的垂直像素数/米
    unsigned int       ciClrUsed;         //位图使用调色板的颜色数
    unsigned           intciClrImportant; //指定重要的颜色数，当该域的值等于颜色数时（或者等于0时），表示所有颜色都一样重要
} __attribute__((packed)) BITMAPINFOHEADER;

typedef struct
{
    unsigned char blue;
    unsigned char green;
    unsigned char red;
} __attribute__((packed)) PIXEL; //颜色模式RGB



/* Private function prototypes -----------------------------------------------*/
/* Private variables ---------------------------------------------------------*/
static struct vdIn   uvc_cam;
static unsigned char rgb888_buffer[IMAGEWIDTH * IMAGEHEIGHT * 3];

static int   xres           = 0;
static int   yres           = 0;
static int   bits_per_pixel = 0;
static char* fb_addr        = NULL;
static char* fb_buf1        = NULL;

/* Global  variables ---------------------------------------------------------*/
/* Private functions ---------------------------------------------------------*/


void yuyv_to_rgb888(void)
{
    int            i, j;
    unsigned char  y1, y2, u, v;
    int            r1, g1, b1, r2, g2, b2;
    unsigned char* pointer;
    double         rbase = 0;
    double         gbase = 0;
    double         bbase = 0;


    pointer = uvc_cam.framebuffer;


    for (i = 0; i < IMAGEHEIGHT; i++) {
        for (j = 0; j < (IMAGEWIDTH / 2); j++) {
            y1 = *(pointer + ((i * (IMAGEWIDTH / 2) + j) << 2));
            u  = *(pointer + ((i * (IMAGEWIDTH / 2) + j) << 2) + 1);
            y2 = *(pointer + ((i * (IMAGEWIDTH / 2) + j) << 2) + 2);
            v  = *(pointer + ((i * (IMAGEWIDTH / 2) + j) << 2) + 3);


            rbase = 1.042 * (v - 128);
            gbase = 0.34414 * (u - 128) + 0.71414 * (v - 128);
            bbase = 1.772 * (u - 128);

            r1 = y1 + rbase;
            g1 = y1 - gbase;
            b1 = y1 + bbase;

            r2 = y2 + rbase;
            g2 = y2 - gbase;
            b2 = y2 + bbase;


            if (r1 > 255)
                r1 = 255;
            else if (r1 < 0)
                r1 = 0;

            if (b1 > 255)
                b1 = 255;
            else if (b1 < 0)
                b1 = 0;

            if (g1 > 255)
                g1 = 255;
            else if (g1 < 0)
                g1 = 0;

            if (r2 > 255)
                r2 = 255;
            else if (r2 < 0)
                r2 = 0;

            if (b2 > 255)
                b2 = 255;
            else if (b2 < 0)
                b2 = 0;

            if (g2 > 255)
                g2 = 255;
            else if (g2 < 0)
                g2 = 0;


            *(rgb888_buffer + ((IMAGEHEIGHT - 1 - i) * (IMAGEWIDTH / 2) + j) * 6)     = (unsigned char)b1;
            *(rgb888_buffer + ((IMAGEHEIGHT - 1 - i) * (IMAGEWIDTH / 2) + j) * 6 + 1) = (unsigned char)g1;
            *(rgb888_buffer + ((IMAGEHEIGHT - 1 - i) * (IMAGEWIDTH / 2) + j) * 6 + 2) = (unsigned char)r1;
            *(rgb888_buffer + ((IMAGEHEIGHT - 1 - i) * (IMAGEWIDTH / 2) + j) * 6 + 3) = (unsigned char)b2;
            *(rgb888_buffer + ((IMAGEHEIGHT - 1 - i) * (IMAGEWIDTH / 2) + j) * 6 + 4) = (unsigned char)g2;
            *(rgb888_buffer + ((IMAGEHEIGHT - 1 - i) * (IMAGEWIDTH / 2) + j) * 6 + 5) = (unsigned char)r2;
        }
    }

    // printf("yuyv to rgb888 done\n");
}




int v4l2_init(void)
{
    int                i = 0;
    int                ret;
    struct v4l2_buffer buf;


    // 1. open cam
    if ((uvc_cam.fd = open(uvc_cam.videodevice, O_RDWR)) == -1) {
        printf("ERROR opening V4L interface\n");
        return -1;
    }

    // 2. querycap
    memset(&uvc_cam.cap, 0, sizeof(struct v4l2_capability));
    ret = ioctl(uvc_cam.fd, VIDIOC_QUERYCAP, &uvc_cam.cap);

    if (ret < 0) {
        printf("Error opening device %s: unable to query device.\n", uvc_cam.videodevice);
        return -1;
    }
    else {
        printf("driver:\t\t%s\n", uvc_cam.cap.driver);
        printf("card:\t\t%s\n", uvc_cam.cap.card);
        printf("bus_info:\t%s\n", uvc_cam.cap.bus_info);
        printf("version:\t%d\n", uvc_cam.cap.version);
        printf("capabilities:\t%x\n", uvc_cam.cap.capabilities);

        if ((uvc_cam.cap.capabilities & V4L2_CAP_VIDEO_CAPTURE) == V4L2_CAP_VIDEO_CAPTURE) {
            printf("%s: \tsupports capture.\n", uvc_cam.videodevice);
        }

        if ((uvc_cam.cap.capabilities & V4L2_CAP_STREAMING) == V4L2_CAP_STREAMING) {
            printf("%s: \tsupports streaming.\n", uvc_cam.videodevice);
        }
    }

    // 3. set format in

    // 3.1 enum fmt
    printf("\nSupport format:\n");

    memset(&uvc_cam.fmtdesc, 0, sizeof(struct v4l2_fmtdesc));
    uvc_cam.fmtdesc.index = 0;
    uvc_cam.fmtdesc.type  = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    while (ioctl(uvc_cam.fd, VIDIOC_ENUM_FMT, &uvc_cam.fmtdesc) != -1) {
        printf("\t%d.%s\n", uvc_cam.fmtdesc.index + 1, uvc_cam.fmtdesc.description);
        uvc_cam.fmtdesc.index++;
    }

    // 3.2 set fmt
    memset(&uvc_cam.fmt, 0, sizeof(struct v4l2_format));
    uvc_cam.fmt.type                = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    uvc_cam.fmt.fmt.pix.width       = uvc_cam.width;
    uvc_cam.fmt.fmt.pix.height      = uvc_cam.height;
    uvc_cam.fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
    uvc_cam.fmt.fmt.pix.field       = V4L2_FIELD_ANY;

    ret = ioctl(uvc_cam.fd, VIDIOC_S_FMT, &uvc_cam.fmt);
    if (ret < 0) {
        printf("Unable to set format\n");
        return -1;
    }

    // 3.3 get fmt
    ret = ioctl(uvc_cam.fd, VIDIOC_G_FMT, &uvc_cam.fmt);
    if (ret < 0) {
        printf("Unable to get format\n");
        return -1;
    }
    else {
        printf("\nfmt.type:\t\t%d\n", uvc_cam.fmt.type);
        printf("pix.pixelformat:\t%c%c%c%c\n", uvc_cam.fmt.fmt.pix.pixelformat & 0xFF, (uvc_cam.fmt.fmt.pix.pixelformat >> 8) & 0xFF, (uvc_cam.fmt.fmt.pix.pixelformat >> 16) & 0xFF, (uvc_cam.fmt.fmt.pix.pixelformat >> 24) & 0xFF);
        printf("pix.height:\t\t%d\n", uvc_cam.fmt.fmt.pix.height);
        printf("pix.width:\t\t%d\n", uvc_cam.fmt.fmt.pix.width);
        printf("pix.field:\t\t%d\n", uvc_cam.fmt.fmt.pix.field);
    }


    // 4. set fps
    memset(&uvc_cam.setfps, 0, sizeof(struct v4l2_streamparm));
    uvc_cam.setfps.type                                  = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    uvc_cam.setfps.parm.capture.timeperframe.numerator   = 1;
    uvc_cam.setfps.parm.capture.timeperframe.denominator = 25;

    ret = ioctl(uvc_cam.fd, VIDIOC_S_PARM, &uvc_cam.setfps);

    if (ret < 0) {
        printf("Unable to set frame rate\n");
        return -1;
    }
    else {
        printf("set fps OK!\n");
    }

    ret = ioctl(uvc_cam.fd, VIDIOC_G_PARM, &uvc_cam.setfps);

    if (ret < 0) {
        printf("Unable to get frame rate\n");
        return -1;
    }
    else {
        printf("get fps OK:\n");
        printf("timeperframe.numerator  : %d\n", uvc_cam.setfps.parm.capture.timeperframe.numerator);
        printf("timeperframe.denominator: %d\n", uvc_cam.setfps.parm.capture.timeperframe.denominator);
        printf("set fps : %d\n", 1 * uvc_cam.setfps.parm.capture.timeperframe.denominator / uvc_cam.setfps.parm.capture.timeperframe.numerator);
    }

    // 5. enum framesizes

    while (1) {
        struct v4l2_fmtdesc fmtdesc;
        memset(&fmtdesc, 0, sizeof(struct v4l2_fmtdesc));
        fmtdesc.index = i++;
        fmtdesc.type  = V4L2_BUF_TYPE_VIDEO_CAPTURE;

        if (ioctl(uvc_cam.fd, VIDIOC_ENUM_FMT, &fmtdesc) < 0) {
            break;
        }

        printf("Supported format: %s\n", fmtdesc.description);
        struct v4l2_frmsizeenum fsenum;
        memset(&fsenum, 0, sizeof(struct v4l2_frmsizeenum));
        fsenum.pixel_format = uvc_cam.fmtdesc.pixelformat;

        int j = 0;

        while (1) {
            fsenum.index = j;
            j++;

            if (ioctl(uvc_cam.fd, VIDIOC_ENUM_FRAMESIZES, &fsenum) == 0) {
                if (uvc_cam.fmt.fmt.pix.pixelformat == fmtdesc.pixelformat) {
                    printf("\tSupported size with the current format: %dx%d\n", fsenum.discrete.width, fsenum.discrete.height);
                }
                else {
                    printf("\tSupported size: %dx%d\n", fsenum.discrete.width, fsenum.discrete.height);
                }
            }
            else {
                break;
            }
        }
    }

    // 6. request buffers
    memset(&uvc_cam.rb, 0, sizeof(struct v4l2_requestbuffers));
    uvc_cam.rb.count  = NB_BUFFER;
    uvc_cam.rb.type   = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    uvc_cam.rb.memory = V4L2_MEMORY_MMAP;

    ret = ioctl(uvc_cam.fd, VIDIOC_REQBUFS, &uvc_cam.rb);

    if (ret < 0) {
        printf("Unable to allocate buffers\n");
        return -1;
    }

    // 6.1 map the buffers

    for (i = 0; i < NB_BUFFER; i++) {
        memset(&buf, 0, sizeof(struct v4l2_buffer));
        buf.index  = i;
        buf.type   = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        buf.memory = V4L2_MEMORY_MMAP;

        ret = ioctl(uvc_cam.fd, VIDIOC_QUERYBUF, &buf);
        if (ret < 0) {
            printf("Unable to query buffer\n");
            return -1;
        }

        uvc_cam.mem[i] = mmap(NULL, buf.length, PROT_READ | PROT_WRITE, MAP_SHARED, uvc_cam.fd, buf.m.offset);
        if (uvc_cam.mem[i] == MAP_FAILED) {
            printf("Unable to map buffer\n");
            return -1;
        }
        uvc_cam.memlength[i] = buf.length;
    }


    // 6.2 queue the buffers.
    for (i = 0; i < NB_BUFFER; i++) {
        memset(&buf, 0, sizeof(struct v4l2_buffer));
        buf.index  = i;
        buf.type   = V4L2_BUF_TYPE_VIDEO_CAPTURE;
        buf.memory = V4L2_MEMORY_MMAP;
        ret        = ioctl(uvc_cam.fd, VIDIOC_QBUF, &buf);
        if (ret < 0) {
            printf("Unable to queue buffer\n");
            return -1;
        }
    }

    // 7. malloc yuyv buf
    uvc_cam.framesizeIn = uvc_cam.width * uvc_cam.height << 1; // w * h * 2
    uvc_cam.framebuffer = (unsigned char*)calloc(1, (size_t)uvc_cam.framesizeIn);

    if (uvc_cam.framebuffer == NULL) {
        printf("err calloc memory\n");
        return -1;
    }

    printf("init %s \t[OK]\n", uvc_cam.videodevice);

    return 0;
}

void v4l2_exit(void)
{
    free(uvc_cam.framebuffer);
    close(uvc_cam.fd);
}

int v4l2_enable(void)
{
    int type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    int ret;

    ret = ioctl(uvc_cam.fd, VIDIOC_STREAMON, &type);
    if (ret < 0) {
        printf("Unable to start capture\n");
        return ret;
    }

    printf("start capture\n");

    return 0;
}

int v4l2_disable(void)
{
    int type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    int ret;

    ret = ioctl(uvc_cam.fd, VIDIOC_STREAMOFF, &type);
    if (ret < 0) {
        printf("Unable to stop capture\n");
        return ret;
    }

    printf("stop capture\n");

    return 0;
}

int v4l2_uvc_grap(void)
{
    int                ret;
    struct v4l2_buffer buf;


    memset(&buf, 0, sizeof(struct v4l2_buffer));
    buf.type   = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    buf.memory = V4L2_MEMORY_MMAP;

    ret = ioctl(uvc_cam.fd, VIDIOC_DQBUF, &buf);
    if (ret < 0) {
        printf("Unable to dequeue buffer\n");
        exit(1);
    }

    memcpy(uvc_cam.framebuffer, uvc_cam.mem[buf.index], uvc_cam.framesizeIn);

    ioctl(uvc_cam.fd, VIDIOC_QBUF, &buf);

    // printf("buf index: %d\n", buf.index);

    return 0;
}




int save_bmp(char* bmp_name)
{
    FILE*            fp;
    BITMAPFILEHEADER bf;
    BITMAPINFOHEADER bi;

    printf("save bmp  function\n");

    fp = fopen(bmp_name, "wb");
    if (fp == NULL) {
        printf("open errror\n");
        return (-1);
    }

    //Set BITMAPINFOHEADER
    memset(&bi, 0, sizeof(BITMAPINFOHEADER));
    bi.ciSize      = 40;
    bi.ciWidth     = IMAGEWIDTH;
    bi.ciHeight    = IMAGEHEIGHT;
    bi.ciPlanes    = 1;
    bi.ciBitCount  = 24;
    bi.ciSizeImage = IMAGEWIDTH * IMAGEHEIGHT * 3;


    //Set BITMAPFILEHEADER
    memset(&bf, 0, sizeof(BITMAPFILEHEADER));
    bf.cfType[0]  = 'B';
    bf.cfType[1]  = 'M';
    bf.cfSize     = 54 + bi.ciSizeImage;
    bf.cfReserved = 0;
    bf.cfoffBits  = 54;


    fwrite(&bf, 14, 1, fp);
    fwrite(&bi, 40, 1, fp);
    fwrite(rgb888_buffer, bi.ciSizeImage, 1, fp);

    printf("save %s done\n", bmp_name);

    fclose(fp);

    return 0;
}

int fb_init(void)
{
    int                      fbfd, fb_size;
    struct fb_var_screeninfo vinfo;
    struct fb_fix_screeninfo finfo;

    fbfd = open("/dev/fb0", O_RDWR | O_CREAT, S_IRWXU);
    if (fbfd < 0) {
        printf("open error\n");
        exit(1);
    }

    if (ioctl(fbfd, FBIOGET_VSCREENINFO, &vinfo)) {
        printf("Error reading variable information.\n");
        exit(1);
    }


    if (ioctl(fbfd, FBIOGET_FSCREENINFO, &finfo)) {
        printf("Error reading variable information.\n");
        exit(1);
    }
    
    printf("R:%d,G:%d,B:%d \n", vinfo.red, vinfo.green, vinfo.blue);
    printf("%dx%d, %dbpp\n", vinfo.xres, vinfo.yres, vinfo.bits_per_pixel);

    xres           = vinfo.xres;
    yres           = vinfo.yres;
    bits_per_pixel = vinfo.bits_per_pixel;
    fb_size        = xres * yres * ((bits_per_pixel + 7) / 8);

    printf("fbsize: %d \n", fb_size);

    if ((fb_addr = (char*)mmap(0, fb_size, PROT_READ | PROT_WRITE, MAP_SHARED, fbfd, 0)) < 0) {
        printf("fb mmap error\n");
        exit(1);
    }

    fb_buf1 = (char*)calloc(1, fb_size);

    if (fb_buf1 == NULL) {
        printf("fb buf1 calloc err!\n");
    }    

    printf("fb init ok!\n");

    return fb_size;
}



void bmp_data_to_fbbuf(char* pbuf, int fb_size)
{
    int                   line_x, line_y;
    long int              location = 0;
    static unsigned short b, g, r;
    static unsigned short rgb; /*2个字节*/
    PIXEL                 pix;
    int                   pixcnt = 0;
    char*                 psrc   = pbuf;

    pixcnt = 0;


    // --每次处理一个像素
    for (line_y = 0; line_y < IMAGEHEIGHT; line_y++) {
        for (line_x = 0; line_x < IMAGEWIDTH; line_x++) {

            //-- ok
            pix.blue  = psrc[pixcnt++];
            pix.green = psrc[pixcnt++];
            pix.red   = psrc[pixcnt++];


            r   = ((pix.red >> 3) << 11) & 0xf800;
            g   = ((pix.green >> 2) << 5) & 0x07e0;
            b   = (pix.blue >> 3) & 0x001f;
            rgb = r | g | b;

            location = line_x*2+(IMAGEHEIGHT - 1 - line_y)*xres*2;

            //--先放到缓存里面
            *((unsigned short*)(fb_buf1 + location)) = rgb;
        }
    }
}

void fb_update(int fb_size)
{
    // --更新整屏
    memcpy(fb_addr, fb_buf1, fb_size);
}



int main(int argc, char const* argv[])
{
    char vdname[15];
    int fb_size;

    printf("\n----- v4l2 run on fb app start ----- \n");

    if (argc < 2) {

        printf("need:/dev/videox\n");
        printf("like:%s /dev/video1\n", argv[0]);

        printf("app exit.\n\n");
        exit(1);
    }

    snprintf(vdname, 12, argv[1]);

    memset(&uvc_cam, 0, sizeof(struct vdIn));
    uvc_cam.videodevice = vdname;
    printf("using: \t\t%s\n", uvc_cam.videodevice);


    uvc_cam.width  = _UVC_CAM_WIDTH;
    uvc_cam.height = _UVC_CAM_HEIGHT;

    // 1. init cam
    if (v4l2_init() < 0) {
        goto app_exit;
    }

    fb_size = fb_init();


    v4l2_enable();
    usleep(5 * 1000);

    while (1) {
        // 2. grap uvc
        v4l2_uvc_grap();
        yuyv_to_rgb888();

        // 3. show on fb
        bmp_data_to_fbbuf(rgb888_buffer, fb_size);
        fb_update(fb_size);
    }

app_exit:
    printf("app exit.\n\n");
    v4l2_exit();

    return 0;
}





/*************************** (C) COPYRIGHT 2020 ZYS ************END OF FILE****/

#### 三、测试程序

- 编译程序

# $ARMGCC是我给工具链设置的环境变量
$ARMGCC v4l2grap-uvc-bmponfb-run-x.c -o v4l2grap-uvc-bmponfb-run-x

- 确认开发板的USB相机设备号

重要：记得插上USB相机！

# ls /dev/video*
/dev/video0  /dev/video1  /dev/video2
# cat /sys/class/video4linux/video1/name
Aoni HD Camera
#

- 运行程序

先把程序复制到开发板，推荐用NFS或TFTP。

运行程序：

# ./v4l2grap-uvc-bmponfb-run-x /dev/video1

----- v4l2 run on fb app start -----
using:          /dev/video1
driver:         uvcvideo
card:           Aoni HD Camera
bus_info:       usb-ci_hdrc.1-1.4
version:        262415
capabilities:   84200001
/dev/video1:    supports capture.
/dev/video1:    supports streaming.

Support format:
        1.MJPEG
        2.YUV 4:2:2 (YUYV)

fmt.type:               1
pix.pixelformat:        YUYV
pix.height:             480
pix.width:              640
pix.field:              1
set fps OK!
get fps OK:
timeperframe.numerator  : 1
timeperframe.denominator: 25
set fps : 25
Supported format: MJPEG
        Supported size: 640x480
        Supported size: 1280x720
        Supported size: 1184x656
        Supported size: 1024x576
        Supported size: 960x720
        Supported size: 960x540
        Supported size: 864x486
        Supported size: 800x600
        Supported size: 752x423
        Supported size: 640x360
        Supported size: 320x240
Supported format: YUV 4:2:2 (YUYV)
        Supported size with the current format: 640x480
        Supported size with the current format: 1280x720
        Supported size with the current format: 1184x656
        Supported size with the current format: 1024x576
        Supported size with the current format: 960x720
        Supported size with the current format: 960x540
        Supported size with the current format: 864x486
        Supported size with the current format: 800x600
        Supported size with the current format: 752x423
        Supported size with the current format: 640x360
        Supported size with the current format: 320x240
init /dev/video1        [OK]
R:11,G:5,B:0
1024x600, 16bpp
fbsize: 1228800
fb init ok!
start capture
^C
#

- 预览效果

由于用的yuyv格式，需要转成rgb，转换过程比较花时间，导致帧率较低。(如果用mjpg格式帧率还是不错的。)

画面快速晃动时，有明显的撕裂现象。

尽管有些瑕疵，但是这三篇不忘初心(没有太监)，最终完成了原计划的功能，本篇完。

最近编辑记录 Jmhh247 (2020-03-21 17:24:22)

WhyCan Forum(哇酷开发者社区)

楼主 #1 2020-03-21 17:23:57 分享评论

[正点原子i.MX6UL] v4l2+framebuffer预览USB摄像头(三)：实时预览

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