typedef struct _v4ldevice

{int fd;//设备号

struct video_capability capability;

struct video_channel channel[10];

struct video_picture picture;

struct video_clip clip;

struct video_window window;

struct video_capture capture;

struct video_buffer buffer;

struct video_mmap mmap;

struct video_mbuf mbuf;

struct video_unit unit;

unsigned char *map;//mmap方式获取数据时，数据的首地址

pthread_mutex_t mutex;

int frame;

int framestat[2];

int overlay;

}v4ldevice;

* struct video_capability

name[32] Canonical name for this interface 

type Type of interface 

channels Number of radio/tv channels if appropriate 

audios Number of audio devices if appropriate 

maxwidth Maximum capture width in pixels 

maxheight Maximum capture height in pixels 

minwidth Minimum capture width in pixels 

minheight Minimum capture height in pixels

int v4lgetcapability(v4ldevice *vd)

{

if(ioctl(vd->fd, VIDIOCGCAP, &(vd->capability)) < 0) {

v4lperror("v4lopen:VIDIOCGCAP");

return -1;

}

return 0;

}

* struct video_picture 

brightness Picture brightness 

hue Picture hue (colour only) 

colour Picture colour (colour only) 

contrast Picture contrast 

whiteness The whiteness (greyscale only) 

depth The capture depth (may need to match the frame buffer depth) 

palette Reports the palette that should be used for this image

* struct video_mbuf 

size The number of bytes to map 

frames The number of frames 

offsets The offset of each frame