V4L(Video for Linux)使用摄像头实验笔记(一)

前言

正文

1，先是驱动，我在想USB摄像头的话USB总线协议部分Linux应该已经有了，我只要基于这个USB总线协议上增加一层摄像头的通信协议就可以了。于是我就想把我的摄像头拆了看看里面用的是什么芯片，结果没有舍得拆，于是我干脆先到淘宝网物品信息部分看看有没有我的M2200所用芯片信息，结果查出了芯片供应商是中星微但具体芯片型号没有，我舍不得拆，怎么办。我突然想起来我的摄像头是免驱的，既然windows都自带它的驱动，就说明芯片那边使用的协议一定也是符合某个标准的。上于是在网上捣鼓了一下，我靠，有好多论文和论坛都在讲关于USB摄像头驱动，居然有这么多人在玩摄像头，看来我落伍了。看着看着我渐渐的明白了，原来有个V4L（video for Linux）协议，果不其然。既然Linux都已经自带了摄像头驱动，那我就不写了。但是我要看看我的CentOS6.3有没有集成摄像头驱动，我把摄像头插上，windows给我自动安装程序，安装完了，好像又安装了一个vmware usb device什么东东。不管它（后来才知道windows关机后再启动虚拟机就不会安装vmware usb device了，要设置下：虚拟机->可移动设备->usb设备上钩一下），然后再lsmod | grep video下就能看到uvcvideo、videodev之类的模块如图1，用ll /dev命令也就能看到video0这个设备文件了如图2。

图1

图2

v4l.h头文件

#ifndef _V4L_H_
#define _V4L_H_

#include
#include //stdio.h and stdlib.h are needed by perror function
#include
#include
#include //O_RDWR
#include
#include //unistd.h and sys/mman.h are needed by mmap function
#include //false and true
#include
#include //v4l API

typedef struct _v4l_struct
{
int fd;
struct video_capability capability;
struct video_picture picture;
struct video_mmap mmap;
struct video_mbuf mbuf;
unsigned char *map;
int frame_current;
int frame_using[VIDEO_MAX_FRAME];
}v4l_device;

extern int v4l_open(char*,v4l_device*);
extern int v4l_close(v4l_device*);
extern int v4l_get_capability(v4l_device*);
extern int v4l_get_picture(v4l_device*);
extern int v4l_get_mbuf(v4l_device*);
extern int v4l_set_picture(v4l_device*,int,int,int,int,int);
extern int v4l_grab_picture(v4l_device*,unsigned int);
extern int v4l_mmap_init(v4l_device*);
extern int v4l_grab_init(v4l_device*,int,int);
extern int v4l_grab_frame(v4l_device*,int);
extern int v4l_grab_sync(v4l_device*);

#define DEFAULT_DEVICE "/dev/video0"

int v4l_open(char *dev,v4l_device *vd)
{
if(!dev)
dev=DEFAULT_DEVICE;
if((vd->fd=open(dev,O_RDWR))<0)
{
perror("v4l_open fail");
return -1;

}
if(v4l_get_capability(vd))
return -1;
printf("video capture device name:%s\n",vd->capability.name);
if(v4l_get_picture(vd))
return -1;
printf("frames number is %d\n",vd->mbuf.frames);
return 0;
}

int v4l_close(v4l_device *vd)
{
munmap(vd->map,vd->mbuf.size);
close(vd->fd);
return 0;
}

int v4l_get_capability(v4l_device *vd)
{
if(ioctl(vd->fd,VIDIOCGCAP,&vd->capability)<0)
{
perror("v4l_get_capability fail");
return -1;
}
return 0;
}

int v4l_get_picture(v4l_device *vd)
{
if(ioctl(vd->fd,VIDIOCGPICT,&vd->picture)<0)
{
perror("v4l_get_picture fail");
return -1;
}
return 0;
}

int v4l_get_mbuf(v4l_device *vd)
{
if(ioctl(vd->fd,VIDIOCGMBUF,&vd->mbuf)<0)
{
perror("v4l_get_mbuf fail");
return -1;
}
return 0;
}

int v4l_set_picture(v4l_device *vd,int br,int hue,int col,int cont,int white)
{
if(br)
vd->picture.brightness=br;
if(hue)
vd->picture.hue=hue;
if(col)
vd->picture.colour=col;
if(cont)
vd->picture.contrast=cont;
if(white)
vd->picture.whiteness=white;
if(ioctl(vd->fd,VIDIOCSPICT,&vd->picture)<0)
{
perror("v4l_set_picture fail");
return -1;
}
return 0;
}

int v4l_grab_picture(v4l_device *vd,unsigned int size)
{
if(read(vd->fd,vd->map,size)==0)
return -1;
return 0;
}

int v4l_mmap_init(v4l_device *vd)
{
if(v4l_get_mbuf(vd)<0)
return -1;
if((vd->map=(unsigned char*)mmap(0,vd->mbuf.size,PROT_READ|PROT_WRITE,MAP_SHARED,vd->fd,0))<0)
{
perror("v4l_mmap_init fail");
return -1;
}
return 0;
}

int v4l_grab_