linux上面摄像头有专用的接口V4L和V4L2，这里分享一个V4L2接口采集图片的示例，这里硬件野火的imx开发板，摄像头为uvc摄像头，pcl上ubuntu也运行通过
1、先要确定/dev/video*设备文件是否存在，不存在就需要修改内核启用摄像头支持
Device Drivers --->
<*> Multimedia support --->
[*] Video capture adapters --->
[*]V4L USB devices --->
<*> USB Video Class (UVC)
[*] UVC input events device support
2、打开设备文件
video_dev = open("\dev\video0",O_RDWR));
3、获取摄像头信息
ioctl(video_dev,VIDIOCGCAP,&video_cap)
4、获取摄像头通道
ioctl(video_dev,VIDIOCGCHAN,&video_chan)
5、获取捕捉属性
ioctl(video_dev,VIDIOCGPICT,&video_pic)
6、设置捕捉属性
ioctl(video_dev,VIDIOCSPICT,&video_pic)
7、映射地址
ioctl(video_dev,VIDIOCGMBUF,&mbuf)
mmap(0,mbuf.size,PROT_READ|PROT_WRITE,MAP_SHARED,video_dev,0);
8、获取摄像头图像
ioctl(video_dev,VIDIOCMCAPTURE,&mmap)
9、保存
c程序
camera.c
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <sys/ioctl.h>
#include <errno.h>
#include <linux/videodev2.h>
#include <sys/mman.h>
#include <sys/time.h>
int fd;
struct v4l2_buffer buf;
struct buffer
{
void * start;
unsigned int length;
long long int timestamp;
} *buffers;
volatile int IMAGEWIDTH,IMAGEHEIGHT,FRAME_NUM;
//申请缓存并映用户空间地址
static int v4l2_mem_ops()
{
unsigned int n_buffers;
struct v4l2_requestbuffers req;
//申请帧缓冲
req.count=FRAME_NUM;
req.type=V4L2_BUF_TYPE_VIDEO_CAPTURE;
req.memory=V4L2_MEMORY_MMAP;
if(ioctl(fd,VIDIOC_REQBUFS,&req)==-1)
{
printf("request for buffers error\n");
return -1;
}
// 申请用户空间的地址列
buffers = malloc(req.count*sizeof (*buffers));
if (!buffers)
{
printf ("out of memory!\n");
return -1;
}
// 进行内存映射
for (n_buffers = 0; n_buffers < FRAME_NUM; n_buffers++)
{
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = n_buffers;
//查询
if (ioctl (fd, VIDIOC_QUERYBUF, &buf) == -1)
{
printf("query buffer error\n");
return -1;
}
//映射
buffers[n_buffers].length = buf.length;
buffers[n_buffers].start = mmap(NULL,buf.length,PROT_READ|PROT_WRITE, MAP_SHARED, fd, buf.m.offset);
if (buffers[n_buffers].start == MAP_FAILED)
{
printf("buffer map error\n");
return -1;
}
}
return 0;
}
int camera_init(char *camera_dev,int img_w,int img_h,int frame_n)
{
struct v4l2_capability cap;
struct v4l2_fmtdesc fmtdesc;
struct v4l2_format fmt;
struct v4l2_streamparm stream_para;
IMAGEWIDTH = img_h;
IMAGEWIDTH = img_w;
FRAME_NUM = frame_n;
//打开摄像头设备
fd = open(camera_dev, O_RDWR)；
if (fd == -1)
{
printf("[%s]:[%d] open camera file error\r\n", __FUNCTION__, __LINE__);
return -1;
}
//查询设备属性
if (ioctl(fd, VIDIOC_QUERYCAP, &cap) == -1)
{
printf("Error opening device %s: unable to query device.\n",FILE_VIDEO);
return -1;
}
else
{
printf("driver:\t\t%s\n",cap.driver);
printf("card:\t\t%s\n",cap.card);
printf("bus_info:\t%s\n",cap.bus_info);
printf("version:\t%d\n",cap.version);
printf("capabilities:\t%x\n",cap.capabilities);
if ((cap.capabilities & V4L2_CAP_VIDEO_CAPTURE) == V4L2_CAP_VIDEO_CAPTURE)
{
printf("Device %s: supports capture.\n",FILE_VIDEO);
}
if ((cap.capabilities & V4L2_CAP_STREAMING) == V4L2_CAP_STREAMING)
{
printf("Device %s: supports streaming.\n",FILE_VIDEO);
}
}
//显示所有支持帧格式
fmtdesc.index=0;
fmtdesc.type=V4L2_BUF_TYPE_VIDEO_CAPTURE;
printf("Support format:\n");
while(ioctl(fd,VIDIOC_ENUM_FMT,&fmtdesc)!=-1)
{
printf("\t%d.%s\n",fmtdesc.index+1,fmtdesc.description);
fmtdesc.index++;
}
//检查是否支持某帧格式
struct v4l2_format fmt_test;
fmt_test.type=V4L2_BUF_TYPE_VIDEO_CAPTURE;
fmt_test.fmt.pix.pixelformat=V4L2_PIX_FMT_RGB32;
if(ioctl(fd,VIDIOC_TRY_FMT,&fmt_test)==-1)
{
printf("not support format RGB32!\n");
}
else
{
printf("support format RGB32\n");
}
//查看及设置当前格式
printf("set fmt...\n");
fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_RGB32; //jpg格式
//fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;//yuv格式
fmt.fmt.pix.height = img_h;
fmt.fmt.pix.width = img_w;
fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
printf("fmt.type:\t\t%d\n",fmt.type);
printf("pix.pixelformat:\t%c%c%c%c\n",fmt.fmt.pix.pixelformat & 0xFF, (fmt.fmt.pix.pixelformat >> 8) & 0xFF,(fmt.fmt.pix.pixelformat >> 16) & 0xFF, (fmt.fmt.pix.pixelformat >> 24) & 0xFF);
printf("pix.height:\t\t%d\n",fmt.fmt.pix.height);
printf("pix.width:\t\t%d\n",fmt.fmt.pix.width);
printf("pix.field:\t\t%d\n",fmt.fmt.pix.field);
if(ioctl(fd, VIDIOC_S_FMT, &fmt) == -1)
{
printf("Unable to set format\n");
return -1;
}
printf("get fmt...\n");
if(ioctl(fd, VIDIOC_G_FMT, &fmt) == -1)
{
printf("Unable to get format\n");
return -1;
}
{
printf("fmt.type:\t\t%d\n",fmt.type);
printf("pix.pixelformat:\t%c%c%c%c\n",fmt.fmt.pix.pixelformat & 0xFF, (fmt.fmt.pix.pixelformat >> 8) & 0xFF,(fmt.fmt.pix.pixelformat >> 16) & 0xFF, (fmt.fmt.pix.pixelformat >> 24) & 0xFF);
printf("pix.height:\t\t%d\n",fmt.fmt.pix.height);
printf("pix.width:\t\t%d\n",fmt.fmt.pix.width);
printf("pix.field:\t\t%d\n",fmt.fmt.pix.field);
}
//设置及查看帧速率，这里只能是30帧，就是1秒采集30张图
memset(&stream_para, 0, sizeof(struct v4l2_streamparm));
stream_para.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
stream_para.parm.capture.timeperframe.denominator = 30;
stream_para.parm.capture.timeperframe.numerator = 1;
if(ioctl(fd, VIDIOC_S_PARM, &stream_para) == -1)
{
printf("Unable to set frame rate\n");
return -1;
}
if(ioctl(fd, VIDIOC_G_PARM, &stream_para) == -1)
{
printf("Unable to get frame rate\n");
return -1;
}
{
printf("numerator:%d\ndenominator:%d\n",stream_para.parm.capture.timeperframe.numerator,stream_para.parm.capture.timeperframe.denominator);
}
int ret = v4l2_mem_ops();
if(ret == -1) return ret;
return 0;
}
int camera_get_pic(char*picname, int picnum)
{
unsigned int n_buffers;
enum v4l2_buf_type type;
char file_name[100];
char index_str[10];
long long int extra_time = 0;
long long int cur_time = 0;
long long int last_time = 0;
//入队和开启采集
for (n_buffers = 0; n_buffers < FRAME_NUM; n_buffers++)
{
buf.index = n_buffers;
ioctl(fd, VIDIOC_QBUF, &buf);
}
type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
ioctl(fd, VIDIOC_STREAMON, &type);
//出队，处理，写入yuv文件，入队，循环进行
int loop = picnum/FRAME_NUM;
if(loop == 0) loop = 1;
while(loop > 0)
{
for(n_buffers = 0; n_buffers < FRAME_NUM; n_buffers++)
{
if(picnum == (n_buffers+FRAME_NUM*loop))
return 0;
//出队
buf.index = n_buffers;
ioctl(fd, VIDIOC_DQBUF, &buf);
//查看采集数据的时间戳之差，单位为微妙
buffers[n_buffers].timestamp = buf.timestamp.tv_sec*1000000+buf.timestamp.tv_usec;
cur_time = buffers[n_buffers].timestamp;
extra_time = cur_time - last_time;
last_time = cur_time;
printf("time_deta:%lld\n\n",extra_time);
printf("buf_len:%d\n",buffers[n_buffers].length);
//处理数据只是简单写入文件，名字以loop的次数和帧缓冲数目有关
printf("grab image data OK\n");
memset(file_name,0,sizeof(file_name));
memset(index_str,0,sizeof(index_str));
sprintf(index_str,"%d",loop*4+n_buffers);
strcpy(file_name, picname);
strcat(file_name, index_str);
strcat(file_name,".jpg");
//strcat(file_name,".yuv");
FILE *fp2 = fopen(file_name, "wb");
if(!fp2)
{
printf("open %s error\n",file_name);
return (-1);
}
fwrite(buffers[n_buffers].start, IMAGEHEIGHT*IMAGEWIDTH*2,1,fp2);
fclose(fp2);
printf("save %s OK\n",file_name);
//入队循环
ioctl(fd, VIDIOC_QBUF, &buf);
}
loop--;
}
}
int close_camera()
{
unsigned int n_buffers;
enum v4l2_buf_type type;
//关闭流
type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
ioctl(fd, VIDIOC_STREAMON, &type);
//关闭内存映射
for(n_buffers=0;n_buffers<FRAME_NUM;n_buffers++)
{
munmap(buffers[n_buffers].start,buffers[n_buffers].length);
}
//释放自己申请的内存
free(buffers);
//关闭设备
close(fd);
return 0;
}
main.c
#include <stdio.h>
#include "camera.h"
int main()
{
printf("init camera\n");
camera_init("/dev/video0", 640, 480, 4);
printf("read camera\n");
camera_get_pic("/img/mypic", 20);
printf("finish,close\n");
close_camera();
return 0;
}
运行程序之前先建一个img目录用来存照片