C语言高级应用---操作linux下V4L2摄像头应用程序【转】

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目录(?)[-]

    采集方式
    V4L2操作流程点击这个网址说得很详细了这里不多说
    httpbaikebaiducomview5494174htm

我们都知道，想要驱动Linux下的摄像头，其实很简单，照着V4L2的手册一步步来写，很快就可以写出来，但是在写之前我们要注意改变系统的一些配置，使系统支持framebuffer，在dev下产生fb0这样的节点，这样我们才能在linux系统上操作Camera摄像头,framebuffer在之前的博文已经有说过了，这里就不再提了。

有需要了解framebuffer的那么请点击:http://baike.baidu.com/view/3351639.htm

       最重要的，我们需要改一个脚本，在/dev/grub.conf，我们来看看怎么改:

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    # grub.conf generated by anaconda  
    #  
    # Note that you do not have to rerun grub after making changes to this file  
    # NOTICE:  You have a /boot partition.  This means that  
    #          all kernel and initrd paths are relative to /boot/, eg.  
    #          root (hd0,0)  
    #          kernel /vmlinuz-version ro root=/dev/sdb2  
    #          initrd /initrd-[generic-]version.img  
    #boot=/dev/sdb  
    default=0  
    timeout=5  
    splashimage=(hd0,0)/grub/splash.xpm.gz  
    hiddenmenu  
    title CentOS (2.6.32-431.el6.i686)  
        root (hd0,0)  
        kernel /vmlinuz-2.6.32-431.el6.i686 ro root=UUID=2bc12537-d6c1-4e67-b4e5-e9c466205554 nomodeset rd_NO_LUKS  KEYBOARDTYPE=pc KEYTABLE=us rd_NO_MD crashkernel=auto LANG=zh_CN.UTF-8 rd_NO_LVM rd_NO_DM rhgb quiet vga=0x318  
        initrd /initramfs-2.6.32-431.el6.i686.img  


通常情况下，要让framebuffer生效，要加一句vga=???(这里是参数)，简单介绍一下:

我写vga=0x318就是默认就设置为1024x768x24bpp模式。当然还有其它的模式:如下图，根据自己的系统来配置。
色彩     640x400     640x480     800x600     1024x768     1280x1024     1600x1200
4bits     ?     ?     0x302     ?     ?     ?
8bits     0x300     0x301     0x303     0x305     0x307     0x31C
15bits     ?     0x310     0x313     0x316     0x319     0x31D
16bits     ?     0x311     0x314     0x317     0x31A     0x31E
24bits     ?     0x312     0x315     0x318     0x31B     0x31F
32bits     ?     ?     ?     ?     ?     ?
配置完成以后，我们先来了解一下V4L2的主要功能。
V4L2就使程序有发现设备和操作设备的能力.它主要是用一系列的回调函数来实现这些功能。像设置摄像头的频率、帧频、视频压缩格式和图像参数等等。当然也可以用于其他多媒体的开发，如音频等。
但是此框架只能运行在Linux操作系统之上。v4L2是针对uvc免驱usb设备的编程框架 ，主要用于采集usb摄像头等，编程模式如下：

采集方式
打开视频设备后，可以设置该视频设备的属性，例如裁剪、缩放等。这一步是可选的。在Linux编程中，一般使用ioctl函数来对设备的I/O通道进行管理：
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    extern int ioctl (int __fd, unsigned long int __request, …) __THROW;  
    __fd：设备的ID，例如刚才用open函数打开视频通道后返回的cameraFd；  
    __request：具体的命令标志符。  
    在进行V4L2开发中，一般会用到以下的命令标志符：  
    VIDIOC_REQBUFS：分配内存  
    VIDIOC_QUERYBUF：把VIDIOC_REQBUFS中分配的数据缓存转换成物理地址  
    VIDIOC_QUERYCAP：查询驱动功能  
    VIDIOC_ENUM_FMT：获取当前驱动支持的视频格式  
    VIDIOC_S_FMT：设置当前驱动的频捕获格式  
    VIDIOC_G_FMT：读取当前驱动的频捕获格式  
    VIDIOC_TRY_FMT：验证当前驱动的显示格式  
    VIDIOC_CROPCAP：查询驱动的修剪能力  
    VIDIOC_S_CROP：设置视频信号的边框  
    VIDIOC_G_CROP：读取视频信号的边框  
    VIDIOC_QBUF：把数据放回缓存队列  
    VIDIOC_DQBUF：把数据从缓存中读取出来  
    VIDIOC_STREAMON：开始视频显示函数  
    VIDIOC_STREAMOFF：结束视频显示函数  
    VIDIOC_QUERYSTD：检查当前视频设备支持的标准，例如PAL或NTSC。  
    这些IO调用，有些是必须的，有些是可选择的。  


V4L2操作流程:点击这个网址，说得很详细了，这里不多说。
http://baike.baidu.com/view/5494174.htm
接下来我们来看看实战部分,下面是我自己写的程序接口,可以实现视频采集:生气
1、project.c
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    #include <stdio.h>  
    #include <unistd.h>  
    #include <fcntl.h>  
    #include "j-yuv.h"  
    #include "CameralOpt.h"  
    #include "FrameBufferOpt.h"  
      
    #define    WIDTH   640  
    #define    HIGHT   480  
      
    int main(void)  
    {  
        char yuyv[WIDTH*HIGHT*2];  
        char bmp[WIDTH*HIGHT*3];  
      
    //  set_bmp_header((struct bmp_header_t *)bmp, WIDTH, HIGHT);  
        //初始化摄像头  
        Init_Cameral(WIDTH , HIGHT );  
        //初始化framebuffer  
        Init_FrameBuffer(WIDTH , HIGHT );   
      
        //开启摄像头  
        Start_Cameral();  
        //采集一张图片  
        int count = 0 ;   
        while(1)  
        {  
            Get_Picture(yuyv);  
            yuyv2rgb24(yuyv, bmp, WIDTH, HIGHT);  
            Write_FrameBuffer(bmp);  
    //      printf("count:%d \n" , count++);  
        }  
        //关闭摄像头  
        Stop_Cameral();  
        //关闭Framebuffer  
        Exit_Framebuffer();  
        //退出  
        Exit_Cameral();  
          
        return 0;  
    }  

2、juv.h
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    #ifndef __JYUV_H  
    #define __JYUV_H  
      
    typedef unsigned char  u8;  
    typedef unsigned short u16;  
    typedef unsigned int   u32;  
      
    #pragma pack(1)  
    //定义bmp头  
    struct bmp_header_t{  
        u16        magic;  
        u32       file_size;  
        u32       RESERVED1;  
        u32       offset;         //54 bytes 表示54个偏移量  
      
        u32       head_num;    //40  
        u32       width;  
        u32       height;  
        u16       color_planes; //1  
        u16       bit_count;  
        u32       bit_compression; //0  
        u32       image_size; //except the size of header  
        u32       h_resolution;  
        u32       v_resolution;  
        u32       color_num;  
        u32       important_colors;  
    };  
      
    #pragma pack()  
      
    void set_bmp_header(struct bmp_header_t * header, u32 width, u32 height);  
    int yuyv2rgb24(u8 *yuyv, u8 *rgb, u32 width, u32 height);  
      
    #endif /* __JYUV_H */   

3、juv.c
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    #include "j-yuv.h"  
      
    #define BIT_COUNT   24  
      
    void set_bmp_header(struct bmp_header_t *header, u32 width, u32 height)  
    {  
        header->magic = 0x4d42;  
        header->image_size = width * height * BIT_COUNT/8;  
        header->file_size = header->image_size + 54;  
        header->RESERVED1 = 0;  
        header->offset = 54;  
      
        header->head_num = 40;  
        header->width = width;  
        header->height = height;  
        header->color_planes = 1;  
        header->bit_count = BIT_COUNT;  
        header->bit_compression = 0;  
        header->h_resolution = 0;  
        header->v_resolution = 0;  
        header->color_num = 0;  
        header->important_colors = 0;  
    }  
    //yuyv转rgb24的算法实现  
    int yuyv2rgb24(u8 *yuyv, u8 *rgb, u32 width, u32 height)  
    {  
        u32 i, in, rgb_index = 0;  
        u8 y0, u0, y1, v1;  
        int r, g, b;  
        u32 out = 0, x, y;  
       
        for(in = 0; in < width * height * 2; in += 4)  
        {  
        y0 = yuyv[in+0];  
        u0 = yuyv[in+1];  
        y1 = yuyv[in+2];  
        v1 = yuyv[in+3];  
      
        for (i = 0; i < 2; i++)  
        {  
            if (i)  
                y = y1;  
            else  
                y = y0;   
            r = y + (140 * (v1-128))/100;  //r  
            g = y - (34 * (u0-128))/100 - (71 * (v1-128))/100; //g  
            b = y + (177 * (u0-128))/100; //b  
            if(r > 255)   r = 255;  
                if(g > 255)   g = 255;  
                if(b > 255)   b = 255;  
                if(r < 0)     r = 0;  
                if(g < 0)     g = 0;  
                if(b < 0)     b = 0;  
      
            y = height - rgb_index/width -1;  
            x = rgb_index%width;  
            rgb[(y*width+x)*3+0] = b;  
            rgb[(y*width+x)*3+1] = g;  
            rgb[(y*width+x)*3+2] = r;  
            rgb_index++;  
        }  
        }  
        return 0;  
    }  

4、FrameBufferOpt.c
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    #include "FrameBufferOpt.h"  
      
    static int Frame_fd ;   
    static int *FrameBuffer = NULL ;   
    static int W , H ;  
      
    //初始化framebuffer  
    int Init_FrameBuffer(int Width , int Higth)  
    {  
        W = Width ;   
        H = Higth ;   
        Frame_fd = open("/dev/fb" , O_RDWR);  
        if(-1 == Frame_fd)  
        {  
            perror("open frame buffer fail");  
            return -1 ;   
        }  
      
    //根本就不用CPU搬运   用DMA做为搬运工  
    FrameBuffer = mmap(0, 1280*1024*4 , PROT_READ | PROT_WRITE , MAP_SHARED , Frame_fd ,0 );  
        if(FrameBuffer == (void *)-1)  
        {  
            perror("memory map fail");  
            return -2 ;  
        }  
        return 0 ;   
    }  
      
    //写入framebuffer  
    int Write_FrameBuffer(const char *buffer)  
    {  
        int row  , col ;   
        char *p = NULL ;   
        for(row = 0 ; row <1024 ; row++)  
        {  
            for(col = 0 ; col < 1280 ;  col++)  
            {  
                if((row < H)  && (col < W))  
                {  
                    p = (char *)(buffer + (row * W+ col ) * 3);   
                    FrameBuffer[row*1280+col] = RGB((unsigned char)(*(p+2)),(unsigned char)(*(p+1)),(unsigned char )(*p));  
                }  
            }  
        }  
        return 0 ;   
    }  
      
    //退出framebuffer  
    int Exit_Framebuffer(void)  
    {  
        munmap(FrameBuffer ,  W*H*4);  
        close(Frame_fd);  
        return 0 ;   
    }  

5、FrameBufferOpt.h
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    #ifndef  _FRAMEBUFFEROPT_H  
    #define  _FRAMEBUFFEROPT_H  
      
    #include <stdio.h>  
    #include <fcntl.h>  
    #include <unistd.h>  
    #include <sys/mman.h>  
      
      
    #define    RGB(r,g,b)       ((r<<16)|(g<<8)|b)  
      
    //初始化ramebuffer  
    int Init_FrameBuffer(int Width , int Higth);  
      
    //写数据到framebuffer  
    int Write_FrameBuffer(const char *buffer);  
      
    //退出framebuffer  
    int Exit_Framebuffer(void);  
      
      
      
    #endif //_FRAMEBUFFEROPT_H  

6、CameralOpt.h
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    #ifndef  _CAMERALOPT_H  
    #define  _CAMERALOPT_H  
      
    #include <stdio.h>  
    #include <linux/videodev2.h>  
    #include <fcntl.h>  
    #include <unistd.h>  
    #include <string.h>  
    #include <stdlib.h>  
    #include <errno.h>  
    #include <sys/mman.h>  
      
    #define   COUNT  3  
    //初始化摄像头  
    int Init_Cameral(int Width , int Hight);  
    int Exit_Cameral(void); //退出摄像头  
    //摄像头开始采集  
    int Start_Cameral(void);  
    int Stop_Cameral(void);//停止摄像头  
    //获取摄像头的数据  
    int Get_Picture(char *buffer);  
      
    #endif  //_CAMERALOPT_H  

7、CameralOpt.c
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    #include "CameralOpt.h"  
    int video_fd ;   
    int length ;   
    char *yuv[COUNT] ;   
    struct v4l2_buffer  enqueue  , dequeue ;  //定义出入队的操作结构体成员  
      
    int Init_Cameral(int Width , int Hight)  
    {  
        //参数检查  
        char *videodevname = NULL ;   
        videodevname = "/dev/video0" ;   
          
        //打开设备  
        video_fd = open(videodevname , O_RDWR);  
        if(-1 == video_fd )  
        {  
            perror("open video device fail");  
            return -1 ;   
        }  
      
        int i ;   
        int ret ;   
        struct v4l2_format  format ;   
        format.type = V4L2_BUF_TYPE_VIDEO_CAPTURE ;   
        format.fmt.pix.width  = Width;   
        format.fmt.pix.height = Hight;   
        format.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV ;  //我支持的格式是这个  
      
        ret = ioctl(video_fd , VIDIOC_S_FMT , &format);  
        if(ret != 0)  
        {  
            perror("set video format fail");  
            return -2 ;   
        }  
      
      
        //申请buffer,切割成几个部分  
        //3  
        struct v4l2_requestbuffers  requestbuffer ;   
        requestbuffer.count = COUNT ;   
        requestbuffer.type = V4L2_BUF_TYPE_VIDEO_CAPTURE ;   
        requestbuffer.memory = V4L2_MEMORY_MMAP ;   
      
        ret = ioctl(video_fd , VIDIOC_REQBUFS , &requestbuffer);  
        if(ret != 0)  
        {  
            perror("request buffer fail ");  
            return -3  ;  
        }  
          
          
        //querybuffer  
        struct v4l2_buffer querybuffer ;   
        querybuffer.type =  V4L2_BUF_TYPE_VIDEO_CAPTURE ;   
        querybuffer.memory = V4L2_MEMORY_MMAP ;   
      
        for(i = 0 ; i < COUNT ; i++)  
        {  
            querybuffer.index = i ;       
      
            ret = ioctl(video_fd , VIDIOC_QUERYBUF , &querybuffer);  
            if(ret != 0)  
            {  
                perror("query buffer fail");  
                return -4 ;   
            }  
          
    //      printf("index:%d length:%d  offset:%d \n" ,   
    //      querybuffer.index , querybuffer.length , querybuffer.m.offset);  
            length = querybuffer.length ;   
      
            //将摄像头内存印射到进程的内存地址  
            yuv[i] = mmap(0,querybuffer.length , PROT_READ | PROT_WRITE , MAP_SHARED , video_fd , querybuffer.m.offset );  
      
      
            //列队  
              
            struct v4l2_buffer  queuebuffer ;   
            queuebuffer.type = V4L2_BUF_TYPE_VIDEO_CAPTURE ;   
            queuebuffer.memory =  V4L2_MEMORY_MMAP ;   
            queuebuffer.index = i ;       
      
            ret = ioctl(video_fd , VIDIOC_QBUF , &queuebuffer);  
            if(ret != 0)  
            {  
                perror("queuebuffer fail");  
                return -5 ;   
            }  
        }  
        //初始化入队出队  
        enqueue.type = V4L2_BUF_TYPE_VIDEO_CAPTURE ;   
        dequeue.type = V4L2_BUF_TYPE_VIDEO_CAPTURE ;   
        enqueue.memory = V4L2_MEMORY_MMAP ;   
        dequeue.memory = V4L2_MEMORY_MMAP ;   
      
        return 0 ;   
    }  
      
    int Exit_Cameral(void)  
    {  
        int i ;   
        for(i = 0 ; i < COUNT ; i++)  
            munmap(yuv+i , length);  
        close(video_fd);  
        return 0 ;   
    }  
      
    int Start_Cameral(void)  
    {  
        //开启摄像头  
        int ret ;   
        int on = 1 ;   
        ret = ioctl(video_fd , VIDIOC_STREAMON , &on);  
        if(ret != 0)  
        {  
            perror("start Cameral fail");  
            return -1 ;   
        }  
        return 0 ;   
    }  
    int Stop_Cameral(void)  
    {  
        //停止摄像头  
        int ret ;   
        int off= 1 ;   
        ret = ioctl(video_fd , VIDIOC_STREAMOFF, &off);  
        if(ret != 0)  
        {  
            perror("stop Cameral fail");  
            return -1 ;   
        }  
        return 0 ;  
    }  
      
    int Get_Picture(char *buffer)  
    {  
        int ret ;   
        //出队  
        ret = ioctl(video_fd , VIDIOC_DQBUF , &dequeue);  
        if(ret != 0)  
        {  
            perror("dequeue fail");  
            return -1 ;   
        }  
      
        //获取图片数据 YUV   yuv[dequeue.index]  
        memcpy(buffer , yuv[dequeue.index] , dequeue.length);  
    //  write(yuyv_fd , yuv[dequeue.index] , dequeue.length);  
      
        enqueue.index = dequeue.index ;   
        ret = ioctl(video_fd , VIDIOC_QBUF , &enqueue);  
        if(ret != 0)  
        {  
            perror("enqueue fail");  
            return -2 ;   
        }  
        return 0 ;   
    }