一、USB摄像头驱动

之前的文章已经介绍了orangepi-zero2的LCD显示屏的使用，本文集中于usb摄像头数据的采集以及数据的处理。usb摄像头采集出来的数据是YUV格式的，因此不能直接用于LCD的显示，由之前的文章（orangepi-zero2实时显示USB摄像头图像）可知LCD的驱动框架输入数据是rgb565。理论的知识不讲太多了：

word is cheap show me the code

二、上代码

本文程序做了一定的改进，一共使用了三种方案：

使用opencv的库函数进行yuv转rgb和缩放。
使用opencv库函数进行图像的缩放，自编程序将yuv转rgb。
自编程序进行图像缩放和yuv转rgb。
在程序的开头有三个宏定义，三个宏定义分别对应三个不同的场景。

/*
*以下宏定义主要用来选择不同的方案：
*   YUV2RGB_OPENCV_ALL：yuv转rgb和尺寸的缩放全部采用opencv。
*   YUV2RGB_OPENCV_RESIZE：图片的缩放采用opencv。
*   YUV2RGB：不采用opencv。可以不依赖于opencv的库。
*/
//只能使用以下的宏定义一个
//#define YUV2RGB_OPENCV_ALL 1
//#define YUV2RGB_OPENCV_RESIZE 1
#define YUV2RGB_C 1

在使用的时候按照实际情况使用其中一个宏定义就可以了。such as：
如果没有opencv库函数，就可以只使用以下宏定义：

#define YUV2RGB_C 1

如果有opencv库，可以使用另外另两个宏定义。

/*** 简单的USB摄像头采集，显示程序* The simplest USB camera acquisition and display program.** 赵先森 Mr.Z* https://blog.csdn.net/qq_37280428** 本程序实现采集usb摄像头的yuv数据，并实时显示到SPI-LCD屏上* This program achieves the acquisition of USB camera * YUV data, and real-time display to SPI-LCD screen*/#include <stdio.h>
#include <stdlib.h>#include <linux/videodev2.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <unistd.h>
#include <linux/videodev2.h>
#include <linux/version.h>
#include <sys/utsname.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <errno.h>
#include <time.h>
#include "stdint.h"
#include <linux/fb.h>typedef unsigned char u8;/*
*以下宏定义主要用来选择不同的方案：
*   YUV2RGB_OPENCV_ALL：yuv转rgb和尺寸的缩放全部采用opencv。
*
*   YUV2RGB_OPENCV_RESIZE：图片的缩放采用opencv。
*
*   YUV2RGB：不采用opencv。可以不依赖于opencv的库。
*///只能使用以下的宏定义一个
//#define YUV2RGB_OPENCV_ALL 1
//#define YUV2RGB_OPENCV_RESIZE 1
#define YUV2RGB_C 1//使用opencv就必须包含头文件
#if defined(YUV2RGB_OPENCV_ALL) || defined(YUV2RGB_OPENCV_RESIZE)#include <opencv2/opencv.hpp>
using namespace cv;#endif // DEBUG#define RGB2RGB565(R, G, B) ((((R) >> 3) << 11) | (((G) >> 2) << 5) | ((B) >> 3)) & 0XFFFF#define WIDHT 640
#define HEIGHT 480
#define FPS 25//摄像头获取的初始化代码
#define V4L_BUFFERS_DEFAULT 4 //4个缓存帧
#define V4L_BUFFERS_MAX 8     //最大是八个unsigned int nbufs = V4L_BUFFERS_DEFAULT;void *mem0[V4L_BUFFERS_MAX];
struct v4l2_buffer buf0;
//用到的变量：double what_time_is_it_now()
{struct timeval time;if (gettimeofday(&time, NULL)){return 0;}return (double)time.tv_sec + (double)time.tv_usec * .000001;
}//正常返回dev  错误返回 -1
int usb_video_init()
{//打开视频设备初始化：struct v4l2_capability cap;int ret, dev;dev = open("/dev/video0", O_RDWR);if (dev < 0){printf("dev open fail ...\n");return -1;}memset(&cap, 0, sizeof(cap));ret = ioctl(dev, VIDIOC_QUERYCAP, &cap);if (ret < 0){printf("Unable to query buffer cap1...\n");close(dev);return -1;}else{printf("driver:\t\t%s\n", cap.driver);printf("card:\t\t%s\n", cap.card);printf("bus_info:\t%s\n", cap.bus_info);printf("version:\t%d\n", cap.version);printf("capabilities:\t%x\n", cap.capabilities);}//设置视频格式：struct v4l2_format fmt;memset(&fmt, 0, sizeof(fmt));fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;fmt.fmt.pix.width = WIDHT;fmt.fmt.pix.height = HEIGHT;fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;ret = ioctl(dev, VIDIOC_S_FMT, &fmt);if (ret < 0){printf("Unable to query buffer cap2...\n");close(dev);return -1;}else{printf("fmt.type:\t\t%d\n", fmt.type);printf("pix.pixelformat:\t%c%c%c%c\n", fmt.fmt.pix.pixelformat & 0xFF, (fmt.fmt.pix.pixelformat >> 8) & 0xFF, (fmt.fmt.pix.pixelformat >> 16) & 0xFF, (fmt.fmt.pix.pixelformat >> 24) & 0xFF);printf("pix.height:\t\t%d\n", fmt.fmt.pix.height);printf("pix.width:\t\t%d\n", fmt.fmt.pix.width);printf("pix.field:\t\t%d\n", fmt.fmt.pix.field);}//设置帧率：struct v4l2_streamparm parm;memset(&parm, 0, sizeof(parm));parm.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;ret = ioctl(dev, VIDIOC_G_PARM, &parm);if (ret < 0){printf("Unable to query buffer parm1...\n");close(dev);return -1;}parm.parm.capture.timeperframe.numerator = 1;parm.parm.capture.timeperframe.denominator = FPS;ret = ioctl(dev, VIDIOC_S_PARM, &parm);if (ret < 0){printf("Unable to query buffer parm2...\n");close(dev);return -1;}printf("Fps:\t\t%d\n", parm.parm.capture.timeperframe.denominator);//申请视频缓存：struct v4l2_requestbuffers rb;memset(&rb, 0, sizeof(rb));rb.count = nbufs;rb.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;rb.memory = V4L2_MEMORY_MMAP;ret = ioctl(dev, VIDIOC_REQBUFS, &rb);if (ret < 0){printf("Unable to query buffer rb...\n");close(dev);return -1;}nbufs = rb.count;//映射缓存：for (int i = 0; i < nbufs; ++i){memset(&buf0, 0, sizeof(buf0));buf0.index = i;buf0.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;buf0.memory = V4L2_MEMORY_MMAP;ret = ioctl(dev, VIDIOC_QUERYBUF, &buf0);if (ret < 0){printf("Unable to query buffer buf01 %d...\n", i);close(dev);return -1;}printf("leng: %d  \n", buf0.length);mem0[i] = mmap(0, buf0.length, PROT_READ | PROT_WRITE, MAP_SHARED, dev, buf0.m.offset);if ((unsigned char *)-1 == mem0[i]){printf("mem[%d] err...\n", i);close(dev);return -1;}}//将缓存插入队列：for (int i = 0; i < nbufs; ++i){memset(&buf0, 0, sizeof(buf0));buf0.index = i;buf0.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;buf0.memory = V4L2_MEMORY_MMAP;ret = ioctl(dev, VIDIOC_QBUF, &buf0);if (ret < 0){printf("Unable to query buffer buf02 %d...\n", i);close(dev);return -1;}}//开启视频流：int type = V4L2_BUF_TYPE_VIDEO_CAPTURE;ret = ioctl(dev, VIDIOC_STREAMON, &type);if (ret < 0){printf("Unable to query buffer type...\n");close(dev);return -1;}return dev;
}
#ifdef YUV2RGB_OPENCV_ALLstatic void display_pic_opencv(void *base, unsigned int width, unsigned int height, unsigned int stride, uint8_t *frame)
{unsigned int xcoi, ycoi;unsigned short rgb565_color = 0;unsigned int data_888 = 0;unsigned short R, G, B;unsigned int iPixelAddr = 0;Mat pic_resize;unsigned short *screen_base = (unsigned short *)base;//建立两个空的buf,rgb的和yuv的Mat buf_rgb(480, 640, CV_8UC3);//yuv为16位，两个字节，将数据转转化到mat的yuv数组Mat buf_yuv(480, 640, CV_8UC2, (uint8_t *)frame);//转化到将yuv数据转化到RGB88cvtColor(buf_yuv, buf_rgb, COLOR_YUV2RGB_YUYV); //函数第三个参数需要视YUV图像格式而定//将480 * 640  转化成128 * 160resize(buf_rgb, pic_resize, Size(160, 128), INTER_LANCZOS4); 调整大小unsigned int num = 0;for (ycoi = 0; ycoi < height; ycoi++){for (xcoi = 0; xcoi < width; xcoi += 1){int i = xcoi + ycoi * width;R = pic_resize.data[3 * i];G = pic_resize.data[3 * i + 1];B = pic_resize.data[3 * i + 2];rgb565_color = RGB2RGB565(R, G, B);screen_base[i] = rgb565_color;}iPixelAddr += width * 2;}
}
#endif#ifdef YUV2RGB_Cstatic void display_pic(void *base, unsigned int width, unsigned int height, unsigned int stride, uint8_t *frame)
{unsigned int xcoi, ycoi;unsigned short rgb565_color = 0;unsigned int data_888 = 0;unsigned short R, G, B;unsigned int iPixelAddr = 0;unsigned short *screen_base = (unsigned short *)base;unsigned int num = 0;for (ycoi = 0; ycoi < height; ycoi++){for (xcoi = 0; xcoi < width; xcoi += 1){int i = xcoi + ycoi * width;R = frame[3 * i];G = frame[3 * i + 1];B = frame[3 * i + 2];rgb565_color = RGB2RGB565(R, G, B);screen_base[i] = rgb565_color;}iPixelAddr += width * 2;}
}#endif#ifdef YUV2RGB_OPENCV_RESIZEstatic void display_pic_open_re(void *base, unsigned int width, unsigned int height, unsigned int stride, uint8_t *frame)
{unsigned int xcoi, ycoi;unsigned short rgb565_color = 0;unsigned int data_888 = 0;unsigned short R, G, B;unsigned int iPixelAddr = 0;Mat pic_resize;unsigned short *screen_base = (unsigned short *)base;//rgbMat buf_rgb(480, 640, CV_8UC3, (uint8_t *)frame);resize(buf_rgb, pic_resize, Size(160, 128), INTER_LANCZOS4); 调整大小unsigned int num = 0;for (ycoi = 0; ycoi < height; ycoi++){for (xcoi = 0; xcoi < width; xcoi += 1){int i = xcoi + ycoi * width;R = pic_resize.data[3 * i];G = pic_resize.data[3 * i + 1];B = pic_resize.data[3 * i + 2];rgb565_color = RGB2RGB565(R, G, B);screen_base[i] = rgb565_color;}iPixelAddr += width * 2;}
}
#endifvoid Yuv422_toRGB(uint8_t *yuv, uint8_t *rgb, int source_width, int source_height, int target_width, int target_height)
{float scale_x;float scale_y;if (target_width >= source_width) //不能放大，只能缩小{scale_x = 1;}else{scale_x = (float)source_width / target_width;}if (target_height >= source_height) //不能放大，只能缩小{scale_y = 1;}else{scale_y = (float)source_height / target_height;}float y_t = 0, x_t = 0; //目标行列是否取样判断int y_t_count = 0; //目标行int x_t_count = 0; //目标列int r, g, b;int y0, y1, u, v;int p, p_t;   //指针int p0, p_t0; //每一行开始的指针scale_x = scale_x * 4; //一次处理2个点，4个数据for (int h = 0; h < source_height; h++){if (h >= y_t) //取样条件满足{y_t += scale_y; //更新取样条件p0 = h * source_width * 2;           //输入图片指针起点 YUV422是两个数据一个点p_t0 = y_t_count * target_width * 3; //输出图像指针起点 RGB是3个数据一个点x_t = 0;x_t_count = 0; //开始新的一行，重置for (int w = 0; w < source_width * 2; w += 4) //一次取4个数值（两个点）{if (w >= x_t) //满足取样条件{x_t += scale_x; //更新取样条件p = p0 + w;                 //输入指针p_t = p_t0 + x_t_count * 3; //输出指针y0 = (int)yuv[p]; //YUYVp++;u = (int)yuv[p];p++;y1 = (int)yuv[p];p++;v = (int)yuv[p];r = y0 + (int)(1.370705 * (v - 128));g = y0 - (int)(0.698001 * (v - 128)) - (int)(0.337633 * (u - 128));b = y0 + (int)(1.732446 * (u - 128));rgb[p_t] = r > 255 ? 0xFF : (r < 0 ? 0x00 : (unsigned char)r); //R值大于255 或小于0 越界处理p_t++;rgb[p_t] = g > 255 ? 0xFF : (g < 0 ? 0x00 : (unsigned char)g); //G值大于255 或小于0 越界处理p_t++;rgb[p_t] = b > 255 ? 0xFF : (b < 0 ? 0x00 : (unsigned char)b); //B值大于255 或小于0 越界处理x_t_count++; //处理完一个点if (x_t_count >= target_width)break; //超过停止//处理第二个点r = y1 + (int)(1.370705 * (v - 128));g = y1 - (int)(0.698001 * (v - 128)) - (int)(0.337633 * (u - 128));b = y1 + (int)(1.732446 * (u - 128));p_t++;rgb[p_t] = r > 255 ? 0xFF : (r < 0 ? 0x00 : (unsigned char)r); //R值大于255 或小于0 越界处理p_t++;rgb[p_t] = g > 255 ? 0xFF : (g < 0 ? 0x00 : (unsigned char)g); //G值大于255 或小于0 越界处理p_t++;rgb[p_t] = b > 255 ? 0xFF : (b < 0 ? 0x00 : (unsigned char)b); //B值大于255 或小于0 越界处理x_t_count++;if (x_t_count >= target_width)break; //超过停止}}y_t_count++;if (y_t_count >= target_height)break; //超过停止}}
}int main(int argc, char **argv)
{int dev;//初始化h264摄像头dev = usb_video_init();while (dev < 0){printf("h264 cam init err...111\n");sleep(5);dev = usb_video_init();}printf("h264 cam init ok..............111\n");struct fb_var_screeninfo fb_var = {0};struct fb_fix_screeninfo fb_fix = {0};unsigned int screensize;int fd;static void *base = NULL;// 打开LCDfd = open("/dev/fb1", O_RDWR);if (fd < 0){printf("Error: Failed to open /dev/fb0 device.\n");return fd;}// 获取framebuffer设备的参数信息ioctl(fd, FBIOGET_VSCREENINFO, &fb_var);ioctl(fd, FBIOGET_FSCREENINFO, &fb_fix);// mmap映射screensize = fb_var.yres * fb_fix.line_length;//printf("lie: %d   hang:  %d   %d   %d\n", fb_var.yres, fb_var.xres, fb_fix.line_length, fb_var.bits_per_pixel);base = mmap(NULL, screensize, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);if (MAP_FAILED == base){close(fd);perror("mmap error");return -1;}memset(base, 0x00, screensize); // 显存清零uint8_t *frame_yuv, *frame_rgb;int frame_length = 0;int frame_size = 640 * 480 * 3;frame_yuv = (uint8_t *)malloc(frame_size);if (NULL == frame_yuv){perror("malloc err...:");}//rgb888frame_rgb = (uint8_t *)malloc(frame_size);if (NULL == frame_rgb){perror("malloc err...:");}//循环显示for (;;){double start, end;start = what_time_is_it_now();/*接受摄像头传输的图像数据start*/memset(&buf0, 0, sizeof(buf0));buf0.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;buf0.memory = V4L2_MEMORY_MMAP;ioctl(dev, VIDIOC_DQBUF, &buf0);//拷贝当前摄像头数据到发送数组memcpy(frame_yuv, (u8 *)mem0[buf0.index], buf0.bytesused);frame_length = buf0.bytesused;ioctl(dev, VIDIOC_QBUF, &buf0);/*接受摄像头传输的图像数据end*/#ifdef YUV2RGB_OPENCV_ALL//图形的转换和缩放都是利用OPENCVdisplay_pic_opencv(base, fb_var.xres, fb_var.yres, fb_fix.line_length, frame_yuv);#elif YUV2RGB_OPENCV_RESIZE//使用openc,进行图片的缩放。效果稍微好一些Yuv422_toRGB(frame_yuv, frame_rgb, WIDHT, HEIGHT,640,480);display_pic_open_re(base, fb_var.xres, fb_var.yres, fb_fix.line_length, frame_rgb);#elif YUV2RGB_C//未使用opencv，全部采用C语言进行数据的处理和转化，但是效果比较差，(主要是差在图形缩放那个地方)Yuv422_toRGB(frame_yuv, frame_rgb, WIDHT, HEIGHT,160,128);display_pic(base, fb_var.xres, fb_var.yres, fb_fix.line_length, frame_rgb);#endif // DEBUGprintf("time:%f\n",(what_time_is_it_now()-start)*1000);}free(frame_yuv);free(frame_rgb);return 0;
}

鸣谢
该函数是参考的某一个博主的文章，但是我现在找不到了，所以这里特别感谢一下。

void Yuv422_toRGB(uint8_t *yuv, uint8_t *rgb, int source_width, int source_height, int target_width, int target_height)

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orangepi-zero2使用tft-lcd实时显示USB摄像头图像-2

目录

一、USB摄像头驱动

二、上代码

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