V4L2编程

最新推荐文章于 2025-06-27 16:07:46 发布

ding6078051

最新推荐文章于 2025-06-27 16:07:46 发布

阅读量1.5k

点赞数

CC 4.0 BY-SA版权

分类专栏： V4L2 文章标签：编程 struct standards input buffer query

本文链接：https://blog.youkuaiyun.com/ding6078051/article/details/7472141

V4L2 专栏收录该内容

1 篇文章

订阅专栏

常用的结构体(参见/usr/include/linux/videodev2.h)：

struct v4l2_requestbuffers reqbufs;        //向驱动申请帧缓冲的请求，里面包含申请的个数
struct v4l2_capability cap;                      //这个设备的功能，比如是否是视频输入设备
struct v4l2_input input;                           //视频输入
struct v4l2_standard std;                        //视频的制式，比如PAL，NTSC
struct v4l2_format fmt;                            //帧的格式，比如宽度，高度等

struct v4l2_buffer buf;                            //代表驱动中的一帧
v4l2_std_id stdid;                                   //视频制式，例如：V4L2_STD_PAL_B
struct v4l2_queryctrl query;                   //查询的控制
struct v4l2_control control;                    //具体控制的值

1）struct v4l2_requestbuffers

struct v4l2_requestbuffers {
	__u32		     count;
	enum v4l2_buf_type      type;
	enum v4l2_memory        memory;
	__u32		     reserved[2];
};

2）struct v4l2_capability cap

struct v4l2_capability {
	__u8	 driver[16];	/* i.e. "bttv" */
	__u8	 card[32];	/* i.e. "Hauppauge WinTV" */
	__u8	 bus_info[32];	/* "PCI:" + pci_name(pci_dev) */
	__u32      version;        /* should use KERNEL_VERSION() */
	__u32	 capabilities;	/* Device capabilities */
	__u32	 reserved[4];
};

3）struct v4l2_input input;

struct v4l2_input {
	__u32	     index;		/*  Which input */
	__u8	     name[32];		/*  Label */
	__u32	     type;		/*  Type of input */
	__u32	     audioset;		/*  Associated audios (bitfield) */
	__u32          tuner;             /*  Associated tuner */
	v4l2_std_id    std;
	__u32	     status;
	__u32	     reserved[4];
};

4）struct v4l2_standard std;

struct v4l2_standard {
	__u32		     index;
	v4l2_std_id          id;
	__u8		     name[24];
	struct v4l2_fract    frameperiod; /* Frames, not fields */
	__u32		     framelines;
	__u32		     reserved[4];
};

5）struct v4l2_format fmt;                            //帧的格式，比如宽度，高度等

struct v4l2_format {
	enum v4l2_buf_type type;
	union {
		struct v4l2_pix_format		pix;     /* V4L2_BUF_TYPE_VIDEO_CAPTURE */
		struct v4l2_window		win;     /* V4L2_BUF_TYPE_VIDEO_OVERLAY */
		struct v4l2_vbi_format		vbi;     /* V4L2_BUF_TYPE_VBI_CAPTURE */
		struct v4l2_sliced_vbi_format	sliced;  /* V4L2_BUF_TYPE_SLICED_VBI_CAPTURE */
		__u8	raw_data[200];                   /* user-defined */
	} fmt;
};

6）struct v4l2_buffer buf;                            //代表驱动中的一帧

struct v4l2_buffer {
	__u32			index;
	enum v4l2_buf_type      type;
	__u32			bytesused;
	__u32			flags;
	enum v4l2_field		field;
	struct timeval		timestamp;
	struct v4l2_timecode	timecode;
	__u32			sequence;

	/* memory location */
	enum v4l2_memory        memory;
	union {
		__u32           offset;
		unsigned long   userptr;
	} m;
	__u32			length;
	__u32			input;
	__u32			reserved;
};

7）struct v4l2_std_id stdid;                                   //视频制式，例如：V4L2_STD_PAL_B

typedef __u64 v4l2_std_id;

/* one bit for each */
#define V4L2_STD_PAL_B          ((v4l2_std_id)0x00000001)
#define V4L2_STD_PAL_B1         ((v4l2_std_id)0x00000002)
#define V4L2_STD_PAL_G          ((v4l2_std_id)0x00000004)
#define V4L2_STD_PAL_H          ((v4l2_std_id)0x00000008)
#define V4L2_STD_PAL_I          ((v4l2_std_id)0x00000010)
#define V4L2_STD_PAL_D          ((v4l2_std_id)0x00000020)
#define V4L2_STD_PAL_D1         ((v4l2_std_id)0x00000040)
#define V4L2_STD_PAL_K          ((v4l2_std_id)0x00000080)

#define V4L2_STD_PAL_M          ((v4l2_std_id)0x00000100)
#define V4L2_STD_PAL_N          ((v4l2_std_id)0x00000200)
#define V4L2_STD_PAL_Nc         ((v4l2_std_id)0x00000400)
#define V4L2_STD_PAL_60         ((v4l2_std_id)0x00000800)

#define V4L2_STD_NTSC_M         ((v4l2_std_id)0x00001000)
#define V4L2_STD_NTSC_M_JP      ((v4l2_std_id)0x00002000)
#define V4L2_STD_NTSC_443       ((v4l2_std_id)0x00004000)
#define V4L2_STD_NTSC_M_KR      ((v4l2_std_id)0x00008000)

#define V4L2_STD_SECAM_B        ((v4l2_std_id)0x00010000)
#define V4L2_STD_SECAM_D        ((v4l2_std_id)0x00020000)
#define V4L2_STD_SECAM_G        ((v4l2_std_id)0x00040000)
#define V4L2_STD_SECAM_H        ((v4l2_std_id)0x00080000)
#define V4L2_STD_SECAM_K        ((v4l2_std_id)0x00100000)
#define V4L2_STD_SECAM_K1       ((v4l2_std_id)0x00200000)
#define V4L2_STD_SECAM_L        ((v4l2_std_id)0x00400000)
#define V4L2_STD_SECAM_LC       ((v4l2_std_id)0x00800000)

/* ATSC/HDTV */
#define V4L2_STD_ATSC_8_VSB     ((v4l2_std_id)0x01000000)
#define V4L2_STD_ATSC_16_VSB    ((v4l2_std_id)0x02000000)

/* FIXME:
   Although std_id is 64 bits, there is an issue on PPC32 architecture that
   makes switch(__u64) to break. So, there's a hack on v4l2-common.c rounding
   this value to 32 bits.
   As, currently, the max value is for V4L2_STD_ATSC_16_VSB (30 bits wide),
   it should work fine. However, if needed to add more than two standards,
   v4l2-common.c should be fixed.
 */

/* some merged standards */
#define V4L2_STD_MN	(V4L2_STD_PAL_M|V4L2_STD_PAL_N|V4L2_STD_PAL_Nc|V4L2_STD_NTSC)
#define V4L2_STD_B	(V4L2_STD_PAL_B|V4L2_STD_PAL_B1|V4L2_STD_SECAM_B)
#define V4L2_STD_GH	(V4L2_STD_PAL_G|V4L2_STD_PAL_H|V4L2_STD_SECAM_G|V4L2_STD_SECAM_H)
#define V4L2_STD_DK	(V4L2_STD_PAL_DK|V4L2_STD_SECAM_DK)

/* some common needed stuff */
#define V4L2_STD_PAL_BG		(V4L2_STD_PAL_B		|\
				 V4L2_STD_PAL_B1	|\
				 V4L2_STD_PAL_G)
#define V4L2_STD_PAL_DK		(V4L2_STD_PAL_D		|\
				 V4L2_STD_PAL_D1	|\
				 V4L2_STD_PAL_K)
#define V4L2_STD_PAL		(V4L2_STD_PAL_BG	|\
				 V4L2_STD_PAL_DK	|\
				 V4L2_STD_PAL_H		|\
				 V4L2_STD_PAL_I)
#define V4L2_STD_NTSC           (V4L2_STD_NTSC_M	|\
				 V4L2_STD_NTSC_M_JP     |\
				 V4L2_STD_NTSC_M_KR)
#define V4L2_STD_SECAM_DK      	(V4L2_STD_SECAM_D	|\
				 V4L2_STD_SECAM_K	|\
				 V4L2_STD_SECAM_K1)
#define V4L2_STD_SECAM		(V4L2_STD_SECAM_B	|\
				 V4L2_STD_SECAM_G	|\
				 V4L2_STD_SECAM_H	|\
				 V4L2_STD_SECAM_DK	|\
				 V4L2_STD_SECAM_L       |\
				 V4L2_STD_SECAM_LC)

#define V4L2_STD_525_60		(V4L2_STD_PAL_M		|\
				 V4L2_STD_PAL_60	|\
				 V4L2_STD_NTSC		|\
				 V4L2_STD_NTSC_443)
#define V4L2_STD_625_50		(V4L2_STD_PAL		|\
				 V4L2_STD_PAL_N		|\
				 V4L2_STD_PAL_Nc	|\
				 V4L2_STD_SECAM)
#define V4L2_STD_ATSC           (V4L2_STD_ATSC_8_VSB    |\
				 V4L2_STD_ATSC_16_VSB)

#define V4L2_STD_UNKNOWN        0
#define V4L2_STD_ALL            (V4L2_STD_525_60	|\
				 V4L2_STD_625_50)

8）struct v4l2_queryctrl query;                   //查询的控制

/*  Used in the VIDIOC_QUERYCTRL ioctl for querying controls */
struct v4l2_queryctrl {
	__u32		     id;
	enum v4l2_ctrl_type  type;
	__u8		     name[32];	/* Whatever */
	__s32		     minimum;	/* Note signedness */
	__s32		     maximum;
	__s32		     step;
	__s32		     default_value;
	__u32                flags;
	__u32		     reserved[2];
};

9）struct v4l2_control control;                    //具体控制的值

/*
 *	C O N T R O L S
 */
struct v4l2_control {
	__u32		     id;
	__s32		     value;
};