Linux下V4L2框架基于SDL库本地USB摄像头监控

1.摄像头框架编程步骤

(1)打开摄像头设备(/dev/video0 、/dev/video1 )；

(2)设置图像格式：VIDIOC_S_FMT(视频捕获格式、图像颜色数据格式、图像宽和高)；

(3)申请缓冲区：VIDIOC_REQBUFS(缓冲区数量、缓冲映射方式、视频捕获格式)；

(4)将缓冲区映射到进程空间：VIDIOC_QUERYBUF(要映射的缓冲区下标、缓冲映射方式、视频捕获格式)；

(5)将缓冲区添加到队列中：VIDIOC_QBUF(映射的缓冲区下标、缓冲映射方式、视频捕获格式)；

(6)开启摄像头采集：VIDIOC_STREAMON (视频捕获格式) (7)从采集队列中取出图像数据，通过SDL图像渲染；

2.摄像头v4L2框架应用编程示例

#include 
#include 
#include 
#include 
#include 
struct video
{
	int width;//摄像头采集图像宽
	int height;//摄像头采集图像高
	char *mmapbuf[4];//保存映射的地址
	int mmap_size;/*映射缓冲区大小*/
};
/*摄像头应用编程框架*/
int Video_Init(u8 *dev,int video_fd,struct video *video_info)
{
    /*1.打开摄像设备文件*/
	video_fd=open(dev,O_RDWR);
	if(video_fd<0)return -1;
    /*2.图像数据格式*/
	struct v4l2_format video_format;
	memset(&video_format,0,sizeof(struct v4l2_format));
	video_format.type=V4L2_BUF_TYPE_VIDEO_CAPTURE;//捕获格式
	video_format.fmt.pix.width=1920;
	video_format.fmt.pix.height=1080;
	video_format.fmt.pix.pixelformat=V4L2_PIX_FMT_YUYV;
	if(ioctl(video_fd,VIDIOC_S_FMT,&video_format))return -2;
	video_info->width=video_format.fmt.pix.width;
	video_info->height=video_format.fmt.pix.height;
    printf("图像尺寸:%d * %dn",video_info->width,video_info->height);
    /*3.申请空间*/
	struct v4l2_requestbuffers video_requestbuffers;
	memset(&video_requestbuffers,0,sizeof(struct v4l2_requestbuffers));
	video_requestbuffers.count=4;//缓冲区个数
	video_requestbuffers.type=V4L2_BUF_TYPE_VIDEO_CAPTURE;//V4L2捕获框架格式
	video_requestbuffers.memory=V4L2_MEMORY_MMAP;//内存映射
	if(ioctl(video_fd,VIDIOC_REQBUFS,&video_requestbuffers))return -3;
	printf("缓冲区个数:%dn",video_requestbuffers.count);
	/*4.将缓冲映射到进程空间*/
	int i=0;
	struct v4l2_buffer video_buffer;
	for(i=0;immap_size=video_buffer.length;/*映射大小*/
        video_info->mmapbuf[i]=mmap(NULL,video_buffer.length,PROT_READ|PROT_WRITE,MAP_SHARED,video_fd,video_buffer.m.offset);
	}
	/*5.将缓冲区添加到采集队列*/
	for(i=0;i

3.摄像头采集图像处理线程

/*线程清理函数*/
void pth_routine(void *arg)
{
    /*关闭摄像头*/
	free(arg);
	pthread_mutex_lock(&fastmutex);//互斥锁上锁
	pthread_cond_broadcast(&cond);//广播唤醒所有线程
    pthread_mutex_unlock(&fastmutex);//互斥锁解锁
	video_flag=0;
	printf("资源清理完成n");
}
/*摄像头处理线程*/
void *Video_CollectImage(void *arg)
{
	u8 *rgb=malloc(video_info.height*video_info.width*3);//申请图像数据缓冲区
	if(rgb==NULL)
	{
		pthread_exit(NULL);/*结束线程*/
	}
	pthread_cleanup_push(pth_routine,rgb);
	struct pollfd fds;
	fds.fd=video_fd;//监听摄像头描述符
	fds.events=POLLIN;//读事件
	fds.revents=0;
	struct v4l2_buffer video_buff;
	while(video_flag)
	{
		poll(&fds,1,-1);
		/*1.从队列中取数据*/
		memset(&video_buff,0,sizeof(struct v4l2_buffer));
		video_buff.memory=V4L2_MEMORY_MMAP;//内存映射
		video_buff.type=V4L2_BUF_TYPE_VIDEO_CAPTURE;//V4L2视频捕获
		if(ioctl(video_fd,VIDIOC_DQBUF,&video_buff))break;
		/*yuv转RGB*/
		yuv_to_rgb(video_info.mmapbuf[video_buff.index],rgb,video_info.width,video_info.height);//颜色数据转换
        pthread_mutex_lock(&fastmutex);//互斥锁上锁
        memcpy(rgb_buff,rgb,video_info.height*video_info.width*3);
        pthread_cond_broadcast(&cond);//广播唤醒所有线程
        pthread_mutex_unlock(&fastmutex);//互斥锁解锁
		/*3.将缓冲区添加到队列*/
		if(ioctl(video_fd,VIDIOC_QBUF,&video_buff))break;
	}
	pthread_cleanup_pop(1);/*注销清理函数*/
}

4.YUYV(YUV422)转RGB888

/*YUYV转RGB888*/
void yuv_to_rgb(unsigned char *yuv_buffer,unsigned char *rgb_buffer,int iWidth,int iHeight)
{
	int x;
	int z=0;
	unsigned char *ptr = rgb_buffer;
	unsigned char *yuyv= yuv_buffer;
	for (x = 0; x < iWidth*iHeight; x++)
	{
		int r, g, b;
		int y, u, v;
		if (!z)
		y = yuyv[0] << 8;
		else
		y = yuyv[2] << 8;
		u = yuyv[1] - 128;
		v = yuyv[3] - 128;
		b = (y + (359 * v)) >> 8;
		g = (y - (88 * u) - (183 * v)) >> 8;
		r = (y + (454 * u)) >> 8;
		*(ptr++) = (b > 255) ? 255 : ((b < 0) ? 0 : b);
		*(ptr++) = (g > 255) ? 255 : ((g < 0) ? 0 : g);
		*(ptr++) = (r > 255) ? 255 : ((r < 0) ? 0 : r);
		if(z++)
		{
			z = 0;
			yuyv += 4;
		}
	}
}

5.主函数main.c

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include "video.h"

#define CAMERA_DEV "/dev/video0" //摄像头设备节点
int video_fd;/*摄像头描述符*/
struct video video_info;/*摄像头结构体信息*/
void *Video_CollectImage(void *arg);/*摄像头图像采集*/
u8 *rgb_buff=NULL;
u8 video_flag=1;
pthread_mutex_t fastmutex = PTHREAD_MUTEX_INITIALIZER;//互斥锁
pthread_cond_t cond = PTHREAD_COND_INITIALIZER;//条件变量
typedef enum
{
	false=0,
	true,
}bool;
int main()
{
    /*初始化摄像头*/
    video_fd=Video_Init(CAMERA_DEV,video_fd,&video_info);
    if(video_fd<=0)
    {
        printf("摄像头初始化失败,res=%dn",video_fd);
        return 0;
    }    
    /*创建窗口 */
	SDL_Window *window=SDL_CreateWindow("SDL_VIDEO", SDL_WINDOWPOS_CENTERED,SDL_WINDOWPOS_CENTERED,800,480,SDL_WINDOW_ALLOW_HIGHDPI|SDL_WINDOW_RESIZABLE);
    /*创建渲染器*/
	SDL_Renderer *render=SDL_CreateRenderer(window,-1,SDL_RENDERER_ACCELERATED);
	/*清空渲染器*/
	SDL_RenderClear(render);
    printf("图像尺寸:%d * %dn",video_info.width,video_info.height);
    /*创建纹理*/
	SDL_Texture*sdltext=SDL_CreateTexture(render,SDL_PIXELFORMAT_RGB24,SDL_TEXTUREACCESS_STREAMING,video_info.width,video_info.height);
    /*创建摄像头采集线程*/
    u8 *rgb_data=malloc(video_info.height*video_info.width*3);
    rgb_buff=malloc(video_info.height*video_info.width*3);//保存RGB颜色数据
   //printf("size=%dn",video_info.mmap_size);
    video_flag=1;/*摄像头采集标志*/
    pthread_t pthid;
    pthread_create(&pthid,NULL,Video_CollectImage, NULL);
    bool quit=true;
	SDL_Event event;
	SDL_Rect rect;
	while(quit)
	{
		while(SDL_PollEvent(&event))/*事件监测*/
		{
			if(event.type==SDL_QUIT)/*退出事件*/
			{
				quit=false;
				video_flag=0;
				pthread_cancel(pthid);/*杀死指定线程*/
				continue;
			}
		}
		if(!video_flag)
		{
			quit=false;
			continue;
		}
		pthread_mutex_lock(&fastmutex);//互斥锁上锁
		pthread_cond_wait(&cond,&fastmutex);
		memcpy(rgb_data,rgb_buff,video_info.height*video_info.width*3);
		pthread_mutex_unlock(&fastmutex);//互斥锁解锁
		SDL_UpdateTexture(sdltext,NULL,rgb_data, video_info.width*3);
		//SDL_RenderCopy(render, sdltext, NULL,NULL); // 拷贝纹理到渲染器
		SDL_RenderCopyEx(render, sdltext,NULL,NULL,0,NULL,SDL_FLIP_NONE);
		SDL_RenderPresent(render); // 渲染
	}
    SDL_DestroyTexture(sdltext);/*销毁纹理*/
    SDL_DestroyRenderer(render);/*销毁渲染器*/
    SDL_DestroyWindow(window);/*销毁窗口 */
    SDL_Quit();/*关闭SDL*/
    pthread_mutex_destroy(&fastmutex);/*销毁互斥锁*/
    pthread_cond_destroy(&cond);/*销毁条件变量*/
	free(rgb_buff);
	free(rgb_data);
}

6.运行效果

审核编辑：刘清