采用V4L2接口通过中断将内核状态读取到的数据映射到用户空间：

 以下代码是将内核空间与用户空间进行映射

for(int i = 0; i <4;i++) {mapbuffer.index = i;ret = ioctl(fd,VIDIOC_QUERYBUF,&mapbuffer); //从内核空间中查询一个空间作映射if (ret < 0){perror("查询内核空间失败");}//映射到用户空间mptr[i] = (unsigned char *)mmap(NULL,mapbuffer.length,PROT_READ|PROT_WRITE,MAP_SHARED,fd,mapbuffer.m.offset);size[i] = mapbuffer.length; //保存映射长度用于后期释放//查询后通知内核已经放回ret = ioctl(fd,VIDIOC_QBUF,&mapbuffer);if (ret < 0){perror("放回失败");}}

以下代码是通过中断获取内核态的数据，并在用户态对数据进行内存拷贝，即将数据拷贝到数组，方便其他线程进行数据处理和数据展示

struct v4l2_buffer readbuffer;readbuffer.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; //每个结构体都需要设置type为这个参赛要记住ret = ioctl(fd,VIDIOC_DQBUF,&readbuffer);int read_len = mapbuffer.length;int send_len = 1024;//printf("%d \n",read_len);if (ret < 0){perror("读取数据失败");}if(1){void *ptr = mptr[readbuffer.index];memcpy(jpg_buff, ptr, readbuffer.length); 
}

问题描述2

在网页前端播放视频，首先视频是一帧帧图像组成的，这里我们每间隔一个短时间就发送一帧，同时http 客户端和服务端采用keep-live长连接形式。为了加快速度，这里我采用了两个线程，现成1读取视频，并将图像帧放在一个公共数组中，线程2将公共数组中的数据通过tcp传输发送给客户端。

同时，线程1和线程之间采用的是条件变量进行同步

解决方案2：

多线程共享全局变量加快视频读取速度和图像发送速度：

​

线程1

 pthread_mutex_lock(&lock);void *ptr = mptr[readbuffer.index];memcpy(jpg_buff, ptr, readbuffer.length);//将读取到的图像拷贝到字符数组       pthread_mutex_unlock(&lock);pthread_cond_signal(&hasNode);

线程2

pthread_cond_wait(&hasNode,&lock);
void *ppptr = jpg_buff;
pthread_mutex_unlock(&lock);

这里的jpg_buff是共享全局数组 

问题描述3

网页长连接设置问题：

服务器端在返回报文头时，加上

"Content-Type:multipart/x-mixed-replace;

即表示当前连接是基于长连接

解决方案：

提示：这里填写该问题的具体解决方案：

下面是报文头的内容 

/*
HTTP长连接处理客户端请求
"HTTP/1.0 200 OK\r\n"
"Server: wbyq\r\n"
"Content-Type:multipart/x-mixed-replace;boundary=boundarydonotcross\r\n"
"\r\n"
"--boundarydonotcross\r\n"
*/

这是程序运行时的效果图：

需要在与开发板同一个局域网的终端上网址中键入：192.168.0.105:8080

其中192.168.0.105是开发板的ip地址 

最后附上总代码

#include <stdio.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <assert.h>
#include <fcntl.h>
#include <jpeglib.h>
#include <linux/fb.h>
#include <linux/videodev2.h>
#include <netinet/in.h>
#include <netinet/ip.h> /* superset of previous */
#include <pthread.h>
#include "sd_usb_pic.h"
#include <string.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/types.h>          /* See NOTES */
#include <unistd.h>
#include <sys/time.h>#define HTTP_PORT 8080   //HTTP服务器端口号
pthread_mutex_t mutex;
pthread_cond_t hasNode = PTHREAD_COND_INITIALIZER;
pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
char jpg_buff[614400]; //保存从USB摄像头读取的图像矩阵
int send_html_cnt = 0 ;
/*
服务端响应客户端请求"HTTP/1.1 200 OK\r\n"
"Content-type:image/jpeg\r\n"
"Content-Length:1234\r\n"
"\r\n"形参：c_fd  --客户端套接字type  --文件类型file  --要发送的文件
返回值：0成功，其它失败
*/
void *ppp_tr = NULL;
int fd_fb;                                                    
static struct fb_var_screeninfo var; /* LCD可变参数 */
static unsigned int *fb_base = NULL; /* Framebuffer映射基地址 */                    
int lcd_w = 800 ,lcd_h= 480; //定义显示器分辨率/*
形参：c_fd  --客户端套接字type  --文件类型file  --要发送的文件
返回值：0成功，其它失败
*/
int Http_SendData(int c_fd,const char *type,const char *file)
{int fd=open(file,O_RDONLY);//打开文件if(fd<0)return -1;//打开文件失败struct stat statbuf;fstat(fd,&statbuf);if(statbuf.st_size<=0){close(fd);return -2;}char buff[1024]={0};snprintf(buff,sizeof(buff),"HTTP/1.1 200 OK\r\n""Content-type:%s\r\n""Content-Length:%ld\r\n""\r\n",type,statbuf.st_size);if(write(c_fd,buff,strlen(buff))!=strlen(buff)){close(fd);return -3;//发送数据头失败}/*发送文件内容*/int size;while(1){size=read(fd,buff,sizeof(buff));if(write(c_fd,buff,size)!=size)break;//发送失败if(size!=sizeof(buff))break;//发送完成}close(fd);return 0;
}int Http_SendPic(int c_fd,const char *type,const char *file)
{char buff[1024]={0};snprintf(buff,sizeof(buff),"HTTP/1.1 200 OK\r\n""Content-type:%s\r\n""Content-Length:%ld\r\n""\r\n",type,614400);if(write(c_fd,buff,strlen(buff))!=strlen(buff)){return -3;//发送数据头失败}/*发送文件内容*/int size;int cnt = 0 ; pthread_mutex_lock(&mutex);void *ppptr = jpg_buff;while(1){int size= 1024;int wt_len = write(c_fd,ppptr,size);//发送失败cnt += wt_len ; ppptr += wt_len ; if(cnt >= 614400  ) {break;}//发送完成}pthread_mutex_unlock(&mutex);return 0;
}int Http_SendPic1(int c_fd,const char *type,const char *file)
{char buff[1024]={0};snprintf(buff,sizeof(buff),"HTTP/1.1 200 OK\r\n""Server:LiMeng \r\n""Content-type:image/jpeg\r\n""Content-Length:%ld\r\n""\r\n",614400);if(write(c_fd,buff,strlen(buff))!=strlen(buff)){return -3;//发送数据头失败}/*发送文件内容*/int size;int cnt = 0 ; pthread_mutex_lock(&mutex);void *ppptr = jpg_buff;while(1){int size= 1024;int wt_len = write(c_fd,ppptr,size);//发送失败cnt += wt_len ; ppptr += wt_len ; if(cnt >= 614400  ) {break;}//发送完成}pthread_mutex_unlock(&mutex);return 0;
}/*
HTTP长连接处理客户端请求
"HTTP/1.0 200 OK\r\n"
"Server: wbyq\r\n"
"Content-Type:multipart/x-mixed-replace;boundary=boundarydonotcross\r\n"
"\r\n"
"--boundarydonotcross\r\n"
*/int Http_Content(int c_fd)
{char buff[1024]={0};/*建立长连接*/snprintf(buff,sizeof(buff),"HTTP/1.0 200 OK\r\n""Server: wbyq\r\n""Content-Type:multipart/x-mixed-replace;boundary=boundarydonotcross\r\n""\r\n""--boundarydonotcross\r\n");if(write(c_fd,buff,strlen(buff))!=strlen(buff))return -1;//发送报文头失败int jpe_image_size = 614400;//保存jpeg图像大小//int send_html_cnt = 0 ;clock_t t1;t1 = clock();char save_name[10];int save_idx = 0 ;struct timeval start_time, end_time;while(1){//auto beg = clock();t1 = clock();pthread_cond_wait(&hasNode,&lock);//printf("wait time is %d us \n",  (clock() - t1)   ); auto beg = clock();gettimeofday(&start_time, NULL);/*(1)响应报文头"Content-type:image/jpeg\r\n""Content-Length:666\r\n""\r\n"*/snprintf(buff,sizeof(buff),	"Content-type:image/jpeg\r\n""Content-Length:%d\r\n""\r\n",jpe_image_size);if(write(c_fd,buff,strlen(buff))!=strlen(buff)){return -2;//响应报文头失败}/*发送jpg图像数据*///pthread_mutex_lock(&mutex);//互斥锁上锁//pthread_cond_wait(&hasNode,&lock);void *ppptr = jpg_buff;//void *ppptr = ppp_tr;//sprintf(save_name,"my_%d.jpg",save_idx++);//FILE *file=fopen(save_name, "w");//fwrite(ppptr , 614400, 1,file);//close(file);int cnt = 0 ; while(1){int size= 1024 * 600;//int size= 1024 ;int wt_len = write(c_fd,ppptr,size);//发送失败cnt += wt_len ; ppptr += wt_len ; if(cnt >= 614400  ) {break;}//发送完成}  //pthread_mutex_unlock(&mutex);//互斥锁上锁//pthread_mutex_unlock(&lock);//sleep(20);/*(3)发送间隔字符串"\r\n""--boundarydonotcross\r\n"*/strcpy(buff,"\r\n--boundarydonotcross\r\n");if(write(c_fd,buff,strlen(buff))!=strlen(buff)){break;//发送间隔符失败}auto end = clock();gettimeofday(&end_time, NULL);double timeuse = (end_time.tv_sec - start_time.tv_sec) + (double)(end_time.tv_usec - start_time.tv_usec) / 1000000.0;//printf("sendtime is %d us \n",  (end - beg)   ); //printf("send cnt is %d us \n",  send_html_cnt   ); send_html_cnt++;//pthread_mutex_unlock(&lock);//usleep(40000);//auto beg = clock();//printf("sendtime is %d ms \n",  (end - beg)   ); printf("sendtime is %d ms \n",  timeuse   ); pthread_mutex_unlock(&lock);usleep(1);}return -4;//发送图像数据失败
}/*线程工作函数*/
void *pth_work(void *arg)
{int c_fd=*(int *)arg;free(arg);char buff[1024]={0};int size;size=read(c_fd,buff,sizeof(buff)-1);if(size<=0){close(c_fd);pthread_exit(NULL);}buff[size]='\0';printf("buff=%s\n",buff);if(strstr(buff,"GET / HTTP/1.1"))//请求网页文件{Http_SendData(c_fd,"text/html","./html/image.html");}else if(strstr(buff,"GET /1.bmp HTTP/1.1")){Http_SendData(c_fd,"application/x-bmp","./html/1.bmp");}else if(strstr(buff,"GET /my.jpg HTTP/1.1")){//Http_SendData(c_fd,"application/x-jpg","./html/my.jpg");//Http_SendPic(c_fd,"application/x-jpg","./html/my.jpg");Http_Content(c_fd);}else if(strstr(buff,"GET /my_32.jpg HTTP/1.1")){Http_SendData(c_fd,"application/x-bmp","./html/my_32.jpg");}else if(strstr(buff,"GET /100.bmp HTTP/1.1")){Http_SendData(c_fd,"application/x-bmp","./html/100.bmp");}else if(strstr(buff,"GET /favicon.ico HTTP/1.1")){Http_SendData(c_fd,"image/x-icon","./html/wmp.ico");}else{Http_SendData(c_fd,"application/x-jpg","./html/limeng.jpg");//Http_SendData(c_fd,"application/x-bmp","./html/my.jpg");}close(c_fd);//printf("22222222222222222222222   \n");pthread_exit(NULL);
}int generate_pic() 
{int fd = open("/dev/video0",O_RDWR); //打开摄像头设备if (fd < 0){perror("打开设备失败");return -1;}struct v4l2_format vfmt;vfmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; //摄像头采集vfmt.fmt.pix.width = 640; //设置摄像头采集参数，不可以任意设置vfmt.fmt.pix.height = 480;vfmt.fmt.pix.pixelformat = V4L2_PIX_FMT_MJPEG; //设置视频采集格式为mjpg格式int ret = ioctl(fd,VIDIOC_S_FMT,&vfmt);if (ret < 0){perror("设置格式失败1");}//申请内核空间struct v4l2_requestbuffers reqbuffer;reqbuffer.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;reqbuffer.count = 4; //申请4个缓冲区reqbuffer.memory = V4L2_MEMORY_MMAP;  //映射方式ret = ioctl(fd,VIDIOC_REQBUFS,&reqbuffer);if (ret < 0){perror("申请空间失败");}//映射unsigned char *mptr[4];//保存映射后用户空间的首地址unsigned int size[4];struct v4l2_buffer mapbuffer;//初始化type和indexmapbuffer.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;for(int i = 0; i <4;i++) {mapbuffer.index = i;ret = ioctl(fd,VIDIOC_QUERYBUF,&mapbuffer); //从内核空间中查询一个空间作映射if (ret < 0){perror("查询内核空间失败");}//映射到用户空间mptr[i] = (unsigned char *)mmap(NULL,mapbuffer.length,PROT_READ|PROT_WRITE,MAP_SHARED,fd,mapbuffer.m.offset);size[i] = mapbuffer.length; //保存映射长度用于后期释放//查询后通知内核已经放回ret = ioctl(fd,VIDIOC_QBUF,&mapbuffer); if (ret < 0){perror("放回失败");}}//开始采集int type = V4L2_BUF_TYPE_VIDEO_CAPTURE;ret = ioctl(fd,VIDIOC_STREAMON,&type); if (ret < 0){ perror("开启失败");}//定义一个空间存储解码后的rgbint sum = 0;//这里是用来控制读取的帧的数量 实际场景下 可以不要这个限制int read_cnt = 0 ;//记录读取图像线程char save_name[10];int save_idx = 0 ;struct timeval start_time, end_time;while(1){struct v4l2_buffer readbuffer;readbuffer.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; //每个结构体都需要设置type为这个参赛要记住ret = ioctl(fd,VIDIOC_DQBUF,&readbuffer); int read_len = mapbuffer.length;int send_len = 1024;//printf("%d \n",read_len);if (ret < 0){perror("读取数据失败");}if(1){//void *ptr = mptr[readbuffer.index];//pthread_mutex_lock(&mutex);//gettimeofday(&start_time, NULL);pthread_mutex_lock(&lock);void *ptr = mptr[readbuffer.index];///ppp_tr = mptr[readbuffer.index];//auto beg = clock();//printf("read frame %d \n",beg);//printf("read frame %d  %d  %d \n",read_cnt++,send_html_cnt,beg);//pthread_mutex_lock(&mutex);memcpy(jpg_buff, ptr, readbuffer.length);//将读取到的图像拷贝到字符数组//ppp_tr = ptr ; //auto end  = clock();//gettimeofday(&end_time, NULL);//double timeuse = (end_time.tv_sec - start_time.tv_sec) + (double)(end_time.tv_usec - start_time.tv_usec) / 1000000.0;sprintf(save_name,"my_%d.jpg",save_idx++);//int fd = open(save_name,  O_CREAT |O_WRONLY|O_TRUNC,0666);//char buf[1024*600]={0};//FILE *file=fopen(save_name, "w");//fwrite(mptr[readbuffer.index] , readbuffer.length, 1,file);//fwrite(ptr , readbuffer.length, 1,file);//close(file);//write(fd,buf,1024 * 600);//close(fd);pthread_mutex_unlock(&lock);pthread_cond_signal(&hasNode);//gettimeofday(&end_time, NULL);//pthread_mutex_unlock(&mutex);auto end  = clock();//printf("runtime is %f \n",  (end - beg) / CLOCKS_PER_SEC  ); //printf("runtime is %f \n",  (end - beg)   ); printf("runtime is %d ms \n",  timeuse   ); //sleep(20);usleep(1);}//通知内核使用完毕ret = ioctl(fd, VIDIOC_QBUF, &readbuffer);if(ret < 0){perror("放回队列失败");}}//停止采集ret = ioctl(fd,VIDIOC_STREAMOFF,&type);//释放映射for(int i=0; i<4; i)munmap(mptr[i], size[i]);close(fd); //关闭文件return 0;err1:close(fd_fb);return -1;
}void shuijiao()
{struct timeval start_time, end_time;while(1){gettimeofday(&start_time, NULL);pthread_cond_wait(&hasNode,&lock);usleep(10000);pthread_mutex_unlock(&lock);gettimeofday(&end_time, NULL);double timeuse = (end_time.tv_sec - start_time.tv_sec) + (double)(end_time.tv_usec - start_time.tv_usec) / 1000000.0;//printf("shuijiao   time is %f  ms \n",  timeuse * 1000   );}
}int main()
{int sockfd=socket(AF_INET,SOCK_STREAM,0);if(sockfd==-1){printf("创建网络套接字失败\n");return 0;}/*允许绑定已使用的端口号*/int on = 1;setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));/*绑定端口号*/struct sockaddr_in s_addr={.sin_family=AF_INET,//IPV4.sin_port=htons(HTTP_PORT),.sin_addr.s_addr=INADDR_ANY};if(bind(sockfd,(const struct sockaddr *)&s_addr,sizeof(s_addr))){printf("绑定端口号失败\n");return 0;}/*设置监听数量*/listen(sockfd,100);/*等待客户端连接*/struct sockaddr_in c_addr;socklen_t len=sizeof(c_addr);int c_fd;pthread_t pthid;int *p=NULL;pthread_t pthid1;pthread_create(&pthid1,NULL,generate_pic,NULL);pthread_detach(pthid1);//设置为分离属性//shuijiao();//while(1){shuijiao();}while(1){c_fd=accept(sockfd,(struct sockaddr *)&c_addr,&len);if(c_fd==-1){printf("客户端连接失败\n");continue;}printf("套接字 : %d  连接成功,%s:%d\n",c_fd,inet_ntoa(c_addr.sin_addr),ntohs(c_addr.sin_port));p=malloc(4);*p=c_fd;pthread_create(&pthid,NULL,pth_work,p);pthread_detach(pthid);//设置为分离属性}
}

代码的编译命令是

gcc serv.c -o serv -ljpeg