c 摄像头生成yuv未压缩图片

播发yuv格式图片：ffplay -f rawvideo -video_size 1920X1080 -pixel_format  yuyv422  my.yuv

此图片是没有进行过任何压缩处理的图片，是摄像头最高分辨率的图片。

 
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <linux/videodev2.h>  //v4l2 头文件
#include <string.h>
#include <sys/mman.h>
 
 
int main(void)
{
	//1.打开设备
	int fd = open("/dev/video0", O_RDWR);
	if(fd < 0)
	{
		perror("打开设备失败");
		return -1;
	}
	
	//设置采集格式	
	struct v4l2_format {
		enum v4l2_buf_type {
			V4L2_BUF_TYPE_VIDEO_CAPTURE        = 1,
			V4L2_BUF_TYPE_VIDEO_OUTPUT         = 2,
			V4L2_BUF_TYPE_VIDEO_OVERLAY        = 3,
			
			
		}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 */
			
			
			struct v4l2_pix_format {
				__u32			width;
				__u32			height;
				__u32			pixelformat;
				__u32			field;		/* enum v4l2_field */
				__u32			bytesperline;	/* for padding, zero if unused */
				__u32			sizeimage;
				__u32			colorspace;	/* enum v4l2_colorspace */
				__u32			priv;		/* private data, depends on pixelformat */
				__u32			flags;		/* format flags (V4L2_PIX_FMT_FLAG_*) */
				union {
					/* enum v4l2_ycbcr_encoding */
					__u32			ycbcr_enc;
					/* enum v4l2_hsv_encoding */
					__u32			hsv_enc;
				};
				__u32			quantization;	/* enum v4l2_quantization */
				__u32			xfer_func;	/* enum v4l2_xfer_func */
			}pix;
			
		} fmt;
	}vfmt;
 
	vfmt.type=1;	
	vfmt.fmt.pix.width=1920;         //720p=1280*720  1080p=1920*1080
	vfmt.fmt.pix.pixelformat=v4l2_fourcc('Y','U','Y','V');         //生成不压缩的图片
	                                                              //播发yuv格式图片：ffplay -f rawvideo -video_size 1920X1080 -pixel_format  yuyv422  my.yuv
 
	int ret = ioctl(fd, VIDIOC_S_FMT, &vfmt);
	if(ret < 0)
	{
		perror("设置格式失败");
	}
	
	//4.申请内核缓冲区个数
	
	struct v4l2_requestbuffers {
		__u32			count;     //申请个数
		__u32			type;		/* enum v4l2_buf_type */
		__u32			memory;		/* enum v4l2_memory */
		__u32			capabilities;
		__u32			reserved[1];
	}reqbuffer;
	
	reqbuffer.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
	reqbuffer.count = 1; //申请4个缓冲区
	reqbuffer.memory=V4L2_BUF_CAP_SUPPORTS_MMAP;      //映射方式
	ret  = ioctl(fd, VIDIOC_REQBUFS, &reqbuffer);
	if(ret < 0)
	{
		perror("申请队列空间失败");
	}
	
	//设置 设备映射到内存的选项
	struct v4l2_buffer {
		__u32			index;
		__u32			type;
		__u32			bytesused;
		__u32			flags;
		__u32			field;
		struct timeval		timestamp;
		struct v4l2_timecode	timecode;
		__u32			sequence;
		
		/* memory location */
		__u32			memory;
		union {
			__u32           offset;
			unsigned long   userptr;
			struct v4l2_plane *planes;
			__s32		fd;
		} m;
		__u32			length;
		__u32			reserved2;
		union {
			__s32		request_fd;
			__u32		reserved;
		};
	}mapbuffer;
	unsigned char *mptr;
	unsigned int  size;
	mapbuffer.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
	mapbuffer.index = 0;
	
	ret = ioctl(fd, VIDIOC_QUERYBUF, &mapbuffer);//查询缓冲区状态
	if(ret < 0)
	{
		perror("查询内核空间队列失败");
	}
	
	int type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
	ret = ioctl(fd, VIDIOC_STREAMON, &type);     //启动流
	if(ret < 0)
	{
		perror("开启失败");
	}
	
	mptr= (unsigned char *)mmap(NULL, mapbuffer.length, PROT_READ|PROT_WRITE, 
		MAP_SHARED, fd, mapbuffer.m.offset);       //设备映射到缓冲区内存
	size=mapbuffer.length;
	
	ret  = ioctl(fd, VIDIOC_QBUF, &mapbuffer);    //把缓冲区数据放入读队列中
	if(ret < 0)                                   
	{
		perror("放回失败");
	}
	
 
	ret = ioctl(fd, VIDIOC_DQBUF, &mapbuffer);       //读当前队列缓冲区的数据
	if(ret < 0)
	{
		perror("提取数据失败");
	}
	
	FILE *file=fopen("my.yuv", "w+");
	
	fwrite(mptr,mapbuffer.length, 1, file);
	fclose(file);
		
	munmap(mptr, size);
	
	close(fd);
	
	return 0;
}