关于opencv更改摄像头参数（帧率，分辨率，曝光度……）的几个问题

1，适用于VideoCapture打开的摄像头

VideoCapture capture(0); 设置摄像头参数不要随意修改

capture.set(CV_CAP_PROP_FRAME_WIDTH, 1080);//宽度

capture.set(CV_CAP_PROP_FRAME_HEIGHT, 960);//高度

capture.set(CV_CAP_PROP_FPS, 30);//帧率帧/秒

capture.set(CV_CAP_PROP_BRIGHTNESS, 1);//亮度

capture.set(CV_CAP_PROP_CONTRAST,40);//对比度 40

capture.set(CV_CAP_PROP_SATURATION, 50);//饱和度 50

capture.set(CV_CAP_PROP_HUE, 50);//色调 50

capture.set(CV_CAP_PROP_EXPOSURE, 50);//曝光 50 获取摄像头参数

得到摄像头的参数

capture.get(CV_CAP_PROP_FRAME_WIDTH);

capture.get(CV_CAP_PROP_FRAME_HEIGHT);

capture.get(CV_CAP_PROP_FPS);

capture.get(CV_CAP_PROP_BRIGHTNESS);

capture.get(CV_CAP_PROP_CONTRAST);

capture.get(CV_CAP_PROP_SATURATION);

capture.get(CV_CAP_PROP_HUE);

capture.get(CV_CAP_PROP_EXPOSURE); 获取视频参数：

capture.get(CV_CAP_PROP_FRAME_COUNT);//视频帧数

然后你会发现除了个别参数你能更改之外（如曝光度），大分布你是不能更改的，甚至都没办法得到，这种并不适用

2，不做开发，只是单纯的更改

那么推荐一个软件，amcap，百度网盘链接，百度网盘-链接不存在，很简单很容易上手。

补，现在突然想起来我的一个学长告诉我的，利用这个软件调节摄像头的曝光度，可以改变帧率，且摄像头会记住曝光度的设置（其他特性就没有这个特点）。-2019.3.12

3，修改opencv的文件，不过效果可能和第一个差不多

大概是在opencv的这个位置，找一下，modules/highgui/src/cap_v4l.cpp，里面有关于参数的设置，位置比较靠前，可以搜索，也可以直接找到

大致在200多行

4，v4l2

下面是我找到的一篇参考，可以突破帧率的限制，当然前提是摄像头支持

Jetson TX1开发笔记(六)：V4L2+OpenCV3.1以MJPG格式读取USB摄像头图像并实时显示_Jack-Cui的博客-CSDN博客

目前只适用于Linux系统，本人试验过，120帧的摄像头在只打开摄像头时可以达到100帧左右，设置的图片分辨率越小，能达到的帧率越高

#include <unistd.h>
#include <error.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <pthread.h>
#include <linux/videodev2.h>
#include <sys/mman.h>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include <math.h>
#include <iostream>
#include <iomanip>
#include <string>
using namespace std;
using namespace cv;
#define CLEAR(x) memset(&(x), 0, sizeof(x))
#define IMAGEWIDTH 3264
#define IMAGEHEIGHT 2448
#define WINDOW_NAME1 "【原始图】" //为窗口标题定义的宏
#define WINDOW_NAME2 "【图像轮廓】" //为窗口标题定义的宏
Mat g_srcImage; Mat g_grayImage;
int g_nThresh = 90;
int g_nMaxThresh = 255;
RNG g_rng(12345);
Mat g_cannyMat_output;
vector<vector<Point> > g_vContours;
vector<Vec4i> g_vHierarchy;
Point point1[100000];
Point point2[100000];
Point point3[100000];
int ii,iii;
int flag2 = 0;//避障用
float number = 0;
int fps=0;
class V4L2Capture {
public:
V4L2Capture(char *devName, int width, int height);
virtual ~V4L2Capture();
int openDevice();
int closeDevice();
int initDevice();
int startCapture();
int stopCapture();
int freeBuffers();
int getFrame(void **,size_t *);
int backFrame();
static void test();
private:
int initBuffers();
struct cam_buffer
{
void* start;
unsigned int length;
};
char *devName;
int capW;
int capH;
int fd_cam;
cam_buffer *buffers;
unsigned int n_buffers;
int frameIndex;
};
V4L2Capture::V4L2Capture(char *devName, int width, int height) {
// TODO Auto-generated constructor stub
this->devName = devName;
this->fd_cam = -1;
this->buffers = NULL;
this->n_buffers = 0;
this->frameIndex = -1;
this->capW=width;
this->capH=height;
}
V4L2Capture::~V4L2Capture() {
// TODO Auto-generated destructor stub
}
int V4L2Capture::openDevice() {
/*设备的打开*/
printf("video dev : %s\n", devName);
fd_cam = open(devName, O_RDWR);
if (fd_cam < 0) {
perror("Can't open video device");
}
return 0;
}
int V4L2Capture::closeDevice() {
if (fd_cam > 0) {
int ret = 0;
if ((ret = close(fd_cam)) < 0) {
perror("Can't close video device");
}
return 0;
} else {
return -1;
}
}
int V4L2Capture::initDevice() {
int ret;
struct v4l2_capability cam_cap; //显示设备信息
struct v4l2_cropcap cam_cropcap; //设置摄像头的捕捉能力
struct v4l2_fmtdesc cam_fmtdesc; //查询所有支持的格式：VIDIOC_ENUM_FMT
struct v4l2_crop cam_crop; //图像的缩放
struct v4l2_format cam_format; //设置摄像头的视频制式、帧格式等
/* 使用IOCTL命令VIDIOC_QUERYCAP，获取摄像头的基本信息*/
ret = ioctl(fd_cam, VIDIOC_QUERYCAP, &cam_cap);
if (ret < 0) {
perror("Can't get device information: VIDIOCGCAP");
}
printf(
"Driver Name:%s\nCard Name:%s\nBus info:%s\nDriver Version:%u.%u.%u\n",
cam_cap.driver, cam_cap.card, cam_cap.bus_info,
(cam_cap.version >> 16) & 0XFF, (cam_cap.version >> 8) & 0XFF,
cam_cap.version & 0XFF);
/* 使用IOCTL命令VIDIOC_ENUM_FMT，获取摄像头所有支持的格式*/
cam_fmtdesc.index = 0;
cam_fmtdesc.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
printf("Support format:\n");
while (ioctl(fd_cam, VIDIOC_ENUM_FMT, &cam_fmtdesc) != -1) {
printf("\t%d.%s\n", cam_fmtdesc.index + 1, cam_fmtdesc.description);
cam_fmtdesc.index++;
}
/* 使用IOCTL命令VIDIOC_CROPCAP，获取摄像头的捕捉能力*/
cam_cropcap.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if (0 == ioctl(fd_cam, VIDIOC_CROPCAP, &cam_cropcap)) {
printf("Default rec:\n\tleft:%d\n\ttop:%d\n\twidth:%d\n\theight:%d\n",
cam_cropcap.defrect.left, cam_cropcap.defrect.top,
cam_cropcap.defrect.width, cam_cropcap.defrect.height);
/* 使用IOCTL命令VIDIOC_S_CROP，获取摄像头的窗口取景参数*/
cam_crop.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
cam_crop.c = cam_cropcap.defrect; //默认取景窗口大小
if (-1 == ioctl(fd_cam, VIDIOC_S_CROP, &cam_crop)) {
//printf("Can't set crop para\n");
}
} else {
printf("Can't set cropcap para\n");
}
/* 使用IOCTL命令VIDIOC_S_FMT，设置摄像头帧信息*/
cam_format.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
cam_format.fmt.pix.width = capW;
cam_format.fmt.pix.height = capH;
cam_format.fmt.pix.pixelformat = V4L2_PIX_FMT_MJPEG; //要和摄像头支持的类型对应
cam_format.fmt.pix.field = V4L2_FIELD_INTERLACED;
ret = ioctl(fd_cam, VIDIOC_S_FMT, &cam_format);
if (ret < 0) {
perror("Can't set frame information");
}
/* 使用IOCTL命令VIDIOC_G_FMT，获取摄像头帧信息*/
cam_format.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
ret = ioctl(fd_cam, VIDIOC_G_FMT, &cam_format);
if (ret < 0) {
perror("Can't get frame information");
}
printf("Current data format information:\n\twidth:%d\n\theight:%d\n",
cam_format.fmt.pix.width, cam_format.fmt.pix.height);
ret = initBuffers();
if (ret < 0) {
perror("Buffers init error");
//exit(-1);
}
return 0;
}
int V4L2Capture::initBuffers() {
int ret;
/* 使用IOCTL命令VIDIOC_REQBUFS，申请帧缓冲*/
struct v4l2_requestbuffers req;
CLEAR(req);
req.count = 4;
req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
req.memory = V4L2_MEMORY_MMAP;
ret = ioctl(fd_cam, VIDIOC_REQBUFS, &req);
if (ret < 0) {
perror("Request frame buffers failed");
}
if (req.count < 2) {
perror("Request frame buffers while insufficient buffer memory");
}
buffers = (struct cam_buffer*) calloc(req.count, sizeof(*buffers));
if (!buffers) {
perror("Out of memory");
}
for (n_buffers = 0; n_buffers < req.count; n_buffers++) {
struct v4l2_buffer buf;
CLEAR(buf);
// 查询序号为n_buffers 的缓冲区，得到其起始物理地址和大小
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = n_buffers;
ret = ioctl(fd_cam, VIDIOC_QUERYBUF, &buf);
if (ret < 0) {
printf("VIDIOC_QUERYBUF %d failed\n", n_buffers);
return -1;
}
buffers[n_buffers].length = buf.length;
//printf("buf.length= %d\n",buf.length);
// 映射内存
buffers[n_buffers].start = mmap(
NULL, // start anywhere
buf.length, PROT_READ | PROT_WRITE, MAP_SHARED, fd_cam,
buf.m.offset);
if (MAP_FAILED == buffers[n_buffers].start) {
printf("mmap buffer%d failed\n", n_buffers);
return -1;
}
}
return 0;
}
int V4L2Capture::startCapture() {
unsigned int i;
for (i = 0; i < n_buffers; i++) {
struct v4l2_buffer buf;
CLEAR(buf);
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = i;
if (-1 == ioctl(fd_cam, VIDIOC_QBUF, &buf)) {
printf("VIDIOC_QBUF buffer%d failed\n", i);
return -1;
}
}
enum v4l2_buf_type type;
type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if (-1 == ioctl(fd_cam, VIDIOC_STREAMON, &type)) {
printf("VIDIOC_STREAMON error");
return -1;
}
return 0;
}
int V4L2Capture::stopCapture() {
enum v4l2_buf_type type;
type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if (-1 == ioctl(fd_cam, VIDIOC_STREAMOFF, &type)) {
printf("VIDIOC_STREAMOFF error\n");
return -1;
}
return 0;
}/*ok*/
int V4L2Capture::freeBuffers() {
unsigned int i;
for (i = 0; i < n_buffers; ++i) {
if (-1 == munmap(buffers[i].start, buffers[i].length)) {
printf("munmap buffer%d failed\n", i);
return -1;
}
}
free(buffers);
return 0;
}
int V4L2Capture::getFrame(void **frame_buf, size_t* len) {
struct v4l2_buffer queue_buf;
CLEAR(queue_buf);
queue_buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
queue_buf.memory = V4L2_MEMORY_MMAP;
if (-1 == ioctl(fd_cam, VIDIOC_DQBUF, &queue_buf)) {
printf("VIDIOC_DQBUF error\n");
return -1;
}
*frame_buf = buffers[queue_buf.index].start;
*len = buffers[queue_buf.index].length;
frameIndex = queue_buf.index;
return 0;
}
int V4L2Capture::backFrame() {
if (frameIndex != -1) {
struct v4l2_buffer queue_buf;
CLEAR(queue_buf);
queue_buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
queue_buf.memory = V4L2_MEMORY_MMAP;
queue_buf.index = frameIndex;
if (-1 == ioctl(fd_cam, VIDIOC_QBUF, &queue_buf)) {
printf("VIDIOC_QBUF error\n");
return -1;
}
return 0;
}
return -1;
}
void V4L2Capture::test() {
unsigned char *yuv422frame = NULL;
unsigned long yuvframeSize = 0;
string videoDev="/dev/video0";
V4L2Capture *vcap = new V4L2Capture(const_cast<char*>(videoDev.c_str()),
1920, 1080);
vcap->openDevice();
vcap->initDevice();
vcap->startCapture();
vcap->getFrame((void **) &yuv422frame, (size_t *)&yuvframeSize);
vcap->backFrame();
vcap->freeBuffers();
vcap->closeDevice();
}
void line2(Point point3[100000], int n)
{
float aa, bb, cc, dd, ee, ff, gg;
int jj = 0;
for (;jj <n;jj++)
{
aa += point3[jj].x*point3[jj].x;
bb += point3[jj].x;
cc += point3[jj].x*point3[jj].y;
dd += point3[jj].y;
}
ee = aa*n - bb*bb;
if ((int)(ee* 100) != 0)
{
ff = (n*cc - bb*dd) / ee;
gg = (dd - bb*ff) / n;
}
else {
ff = 0;
gg = 1;
}
Point point0, pointn;
point0.y = 0;
point0.x = gg;
pointn.y = (n-1);
pointn.x = ((n-1) * ff + gg);
Mat draw_ing2 = Mat::zeros(g_cannyMat_output.size(), CV_8UC3);
line(draw_ing2, point0, pointn, (255, 255, 255));
imshow("10", draw_ing2);
//cout << "\n"<<ff <<" "<< gg << endl;
float the =180*atan(ff)/3.14159;
float dis = ff * 160+gg - 160;
cout << the << " " << dis << endl;
//正中心ff=0，gg=160，逆时ff为正，顺时ff为负
}
void findcolor(cv::Mat &image)
{
cv::Mat_<cv::Vec3b>::iterator it = image.begin<cv::Vec3b>();
cv::Mat_<cv::Vec3b>::iterator itend = image.end<cv::Vec3b>();
ii = 0;
iii = 0;
int flagg = 0;
cv::Mat srcX(image.rows, image.cols , CV_32F);
cv::Mat srcY(image.rows, image.cols, CV_32F);
for (int i = 0;i < image.rows;i++)
{
for (int j = 0;j < image.cols;j++)
{
if (flagg == 0)/*这样遍历水平方向无法得到有效数据*/
{
if ((*it)[0] == 255 && (*it)[1] == 0 && (*it)[2] == 255)
{
flagg = 1;
point1[ii].x = i;
point1[ii].y = j;
ii++;
}
}
else
{
if ((*it)[0] == 255 && (*it)[1] == 0 && (*it)[2] == 255)
{
flagg = 0;
point2[iii].x = i;
point2[iii].y = j;
iii++;
}
}
if (it == itend)
break;
else it++;
}
}
IplImage pImg = IplImage(image);
CvArr* arr = (CvArr*)&pImg;
int nn = ii;
for (;ii > 0;ii--)
{
point3[ii].x = (point1[ii].x + point2[ii].x) / 2;
point3[ii].y = (point1[ii].y + point2[ii].y) / 2;
//circle(image, point3[ii], 1, (255, 255, 255));
cvSet2D(arr, point3[ii].x, point3[ii].y, Scalar(255, 255, 255));
}
line2(point3, nn);
}
void on_ThreshChange(int, void* )
{
// 使用Canndy检测边缘
Canny( g_grayImage, g_cannyMat_output, g_nThresh, g_nThresh*2, 3 );
// 找到轮廓
findContours( g_cannyMat_output, g_vContours, g_vHierarchy, RETR_TREE, CHAIN_APPROX_SIMPLE, Point(0, 0) );
// 计算矩
vector<Moments> mu(g_vContours.size() );
for(unsigned int i = 0; i < g_vContours.size(); i++ )
{ mu[i] = moments( g_vContours[i], false ); }
// 计算中心矩
vector<Point2f> mc( g_vContours.size() );
for( unsigned int i = 0; i < g_vContours.size(); i++ )
{ mc[i] = Point2f( static_cast<float>(mu[i].m10/mu[i].m00), static_cast<float>(mu[i].m01/mu[i].m00 )); }
// 绘制轮廓
Mat drawing = Mat::zeros(g_cannyMat_output.size(), CV_8UC3);
for( unsigned int i = 0; i< g_vContours.size(); i++ )
{
//Scalar color = Scalar( g_rng.uniform(0, 255), g_rng.uniform(0,255), g_rng.uniform(0,255) );//随机生成颜色值
Scalar color = Scalar(255, 0, 255);
drawContours( drawing, g_vContours, i, color, 2, 8, g_vHierarchy, 0, Point() );//绘制外层和内层轮廓
circle( drawing, mc[i], 4, color, -1, 8, 0 );;//绘制圆
}
findcolor(drawing);
//line1(point1,point2,ii,iii);
// 显示到窗口中
// namedWindow( WINDOW_NAME2, WINDOW_AUTOSIZE );
imshow( WINDOW_NAME2, drawing );
}
void findline(Mat image)
{
cv::Mat_<cv::Vec3b>::iterator it = image.begin<cv::Vec3b>();
cv::Mat_<cv::Vec3b>::iterator itend = image.end<cv::Vec3b>();
for (;it != itend;it++)
{
if ((*it)[1] == 0 && (*it)[2] >= 100)//条件可能需要改变
{
if(flag2==0)
{
flag2 = 1;
cout << "注意line1，避障"<<endl;
//向主控发送消息
}
else
{
cout << "注意line2，避障" << endl;
//向主控发送消息
//避障一与避障二中间要隔一段时间
}
}
}
}
void wave(const cv::Mat &image, cv::Mat &result)
{
cv::Mat srcX(image.rows / 2, image.cols / 2, CV_32F);
cv::Mat srcY(image.rows / 2, image.cols / 2, CV_32F);
for (int i = 0;i<image.rows /2;i++)
for (int j = 0;j < image.cols /2;j++)
{
srcX.at<float>(i, j) = 2 * j;
srcY.at<float>(i, j) = 2 * i;
}
cv::remap(image, result, srcX, srcY, cv::INTER_LINEAR);
}
void VideoPlayer() {
unsigned char *yuv422frame = NULL;
unsigned long yuvframeSize = 0;
string videoDev = "/dev/video0";
V4L2Capture *vcap = new V4L2Capture(const_cast<char*>(videoDev.c_str()), 640, 480);
vcap->openDevice();
vcap->initDevice();
vcap->startCapture();
cvNamedWindow("Capture",CV_WINDOW_AUTOSIZE);
IplImage* img;
CvMat cvmat;
double t;
clock_t start, end;
double number=0;
int fps=0;
while(1){
start=clock();
t = (double)cvGetTickCount();
vcap->getFrame((void **) &yuv422frame, (size_t *)&yuvframeSize);
cvmat = cvMat(IMAGEHEIGHT,IMAGEWIDTH,CV_8UC3,(void*)yuv422frame); //CV_8UC3
//解码
img = cvDecodeImage(&cvmat,1);
if(!img){
printf("DecodeImage error!\n");
}
cv::Mat g_srcImage = cv::cvarrToMat(img,true);
cvShowImage("Capture",img);
cvReleaseImage(&img);
vcap->backFrame();
if((cvWaitKey(1)&255) == 27){
exit(0);
}
wave(g_srcImage, g_srcImage);
findline(g_srcImage);
// 把原图像转化成灰度图像并进行平滑
cvtColor(g_srcImage, g_grayImage, COLOR_BGR2GRAY);
blur(g_grayImage, g_grayImage, Size(3, 3));
//创建滚动条并进行初始化
createTrackbar(" 阈值", WINDOW_NAME1, &g_nThresh, g_nMaxThresh, on_ThreshChange);
on_ThreshChange(0, 0);
t = (double)cvGetTickCount() - t;
printf("Used time is %g ms\n", (t / (cvGetTickFrequency() * 1000)));
end =clock();
number=number+end-start;
fps++;
if (number/ CLOCKS_PER_SEC>= 0.25)//windows10 for CLK_TCK
{
cout<<fps<<endl;
fps = 0;
number = 0;
}
}
vcap->stopCapture();
vcap->freeBuffers();
vcap->closeDevice();
}
int main() {
VideoPlayer();
return 0;
}