As I am completely new to OpenCV, I tried following a tutorial to capture video from a webcam. I used the following code:
#include "opencv2\opencv.hpp"
#include <stdint.h>
using namespace cv;
using namespace std;
int main(int argv, char** argc) {
Mat frame;
VideoCapture vid(0); //0 if we only have one camera
if (!vid.isOpened()) { //check camera has been initialized
cout << "ERROR: Cannot open the camera";
return -1;
}
while (vid.read(frame)) {
imshow("webcam", frame);
if (waitKey(30) >= 0) break;
}
return 0;
}
When I run the program, a window that shows the video feed opens, but it then almost immediately closes. I get this snippet from the Debug output:
SETUP: Device is setup and ready to capture.
Event: Code: 0x0d Params: 0, 0
Event: Code: 0x0e Params: 0, 0
Exception thrown at 0x000007FEFCBAA06D in test.exe: Microsoft C++ exception: cv::Exception at memory location 0x000000000026EB10.
SETUP: Disconnecting device 0
I don't know what could be wrong with my code or even how to begin debugging this. Any advice? Thank you!
Related
I build OpenCV 3.4 with Gstreamer MSVC 1.16.1, using Cmake and Visual Studio 10.
I have include bin directory to the system path variable, added all additional include and library to Visual Studio.
Now when I am trying to read an Image to test if OpenCV is correctly installed it throws an error as:
OpenCV Error: Assertion failed (size.width>0 && size.height>0) in imshow, file .../opencv/modules/highgui/src/window.cpp
The code was:
Mat image1;
image1 = imread("D:\\Capture2.JPG");
if(! image1.data ) // Check for invalid input
{
cout << "Could not open or find the image" << std::endl ;
}
imshow("Image",image1);
cvWaitKey(0);
return 0;
Now I tried to play a video using demo code from openCV site:
// opencv_3.4_test.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include "opencv2/opencv.hpp"
#include <iostream>
using namespace std;
using namespace cv;
int _tmain(int argc, _TCHAR* argv[])
{
// Create a VideoCapture object and open the input file
// If the input is the web camera, pass 0 instead of the video file name
VideoCapture cap("Wildlife.mp4");
// Check if camera opened successfully
if(!cap.isOpened()){
cout << "Error opening video stream or file" << endl;
return -1;
}
while(1){
Mat frame;
// Capture frame-by-frame
cap >> frame;
// If the frame is empty, break immediately
if (frame.empty())
break;
// Display the resulting frame
imshow( "Frame", frame );
// Press ESC on keyboard to exit
char c=(char)waitKey(25);
if(c==27)
break;
}
// When everything done, release the video capture object
cap.release();
// Closes all the frames
destroyAllWindows();
return 0;
}
The program is building correctly but I am getting following error while running it:
warning: Error opening file (/build/opencv/modules/videoio/src/cap_ffmpeg_impl.hpp:808)
warning: ?Wildlife.mp4 (/build/opencv/modules/videoio/src/cap_ffmpeg_impl.hpp:809)
GStreamer: error opening bin syntax error
Where can be the error as they both are simplest OpenCV program.
So the error was, there was an invisible character ('\u202A') present just after " of the filename. Once I deleted it, everything runs fine.
I found this from the warning C4566: character represented by universal-character-name '\u202A' cannot be represented in the current code page (1252)
So I have played around in OpenCV a bunch before and never run into this problem. I am implementing a MeanShift algorithm and trying to do it on video devices, images, and videos. Devices and images work; however, no matter what I try, when I run VideoCapture on my filename (whether setting it in the Constructor or using the VideoCapture::open() method, and whether local or with a full path) I always get stuck in my error check.
Thoughts? Ideas? code below. running in Visual Studio 2012
#include "opencv2\highgui\highgui.hpp"
#include "opencv2\core\core.hpp"
#include "opencv2\opencv.hpp"
#include "opencv2\video\video.hpp"
#include <string>
using cv::Mat;
using std::string;
enum Filetype{Image, Video};
int main(int argc, char* argv[])
{
string filename = "short_front.avi";// "C:\\Users\\Jonathan\\Videos\\short_front.mp4"; //"hallways.jpg";
Mat cv_image; //convert to unsigned char * with data
Mat filtImage_;
Mat segmImage_;
Mat whiteImage_;
cv::VideoCapture vid;
vid.open("C:/Users/Jonathan/Desktop/TestMeanShift/TestMeanShift/short_front.avi");
cv::waitKey(1000);
if ( !vid.isOpened() ){
throw "Error when reading vid";
cv::waitKey(0);
return -1;
}
// cv_image = cv::imread(filename);//, CV_LOAD_IMAGE_COLOR);
// if(! cv_image.data){
// std::cerr << "Image Failure: " << std::endl;
// system("pause");
// return -1;
// }
//Mat cv_image_gray;
//cv::cvtColor(cv_image,cv_image_gray,CV_RGB2GRAY);
for (;;)
{
vid >> cv_image;
if ( !cv_image.data)
continue;
cv::imshow("Input",cv_image); //add a normal window here to resizable
}
EDIT: This is a distinct problem from the one listed here because it deals with a specific corner case: VideoCapture and ImageCapture both work, only not VideoCapture with a file. When it doesn't work, the code runs properly, except that the "video" it creates is incomplete as it didn't open properly. Therefore, as the code above does not crash in compile time or run time, the only indicator is bad output (6KB video output file). If you are having issues not with the corner case I am describing but general issues with the above functions in OpenCV, the aforementioned link could help you.
I use this code and it just displays the video into a frame but when I execute this code I gets this Unhandled exception.
#include <opencv/cv.h>
#include <opencv/highgui.h>
using namespace cv;
int main()
{
Mat image;
VideoCapture cap;
cap.open(0);
namedWindow("Window",1);
while (1)
{
cap>>image;
imshow("Window",image);
waitKey(100);
}
return 0;
}
Unhandled exception at at 0x00007FFF945FAB78 in ConsoleApplication2.exe: Microsoft C++ exception: cv::Exception at memory location 0x00000099DFC1F3B0.
What can I do to escape from this unhandled exception & display the video correctly?
Note : Using OpenCv 2.4.8 , V.S.2012 x64
check VS dependencies,
project/projectname configuration/ linke/input
in address check lib name.
I am trying to display the video feed from IP camera getting the following error
warning: Could not find codec parameters
(../../modules/highgui/src/cap_ffmpeg_impl.hpp:540)
Here's the code for the same.
#include <stdio.h>
#include <opencv2/opencv.hpp>
#include <iostream>
using namespace cv;
using namespace std;
int main(int, char**)
{
VideoCapture vcap;
Mat image;
// This works on a D-Link CDS-932L
const string videoStreamAddress = "http://admin:admin123#172.41.20.55:80/? action=stream?dummy=param.mjpg";//From mjpeg streamer
//const string videoStreamAddress = "http://192.168.1.13:8080/videofeed? dummy=param.mjpg"; // Streaming from android using ip-cam
//open the video stream and make sure it's opened
if(!vcap.open(videoStreamAddress)) {
cout << "Error opening video stream or file" << std::endl;
return -1;
}
for(;;) {
if(!vcap.read(image)) {
cout << "No frame" << std::endl;
waitKey();
}
cv::imshow("Output Window", image);
if(cv::waitKey(1) >= 0) break;
}
}
First i got different error so I installed K-Lite codec. Now I am getting this error.
Can some one please tell me what is the error related to.
I have gone through many post from stackoverflow and opencv also but could manage to get a satisfactory answer.
Please help me.
Thanks in advance.
I was able to Solve the problem with the following code.
#include <stdio.h>
#include <opencv2/opencv.hpp>
int main(){
CvCapture *camera=cvCaptureFromFile("http://username:password#ipOfCamera/axis-cgi/mjpg/video.cgi?resolution=640x480&req_fps=30&.mjpg");
if (camera==NULL)
printf("camera is null\n");
else
printf("camera is not null");
cvNamedWindow("img");
while (cvWaitKey(10)!=atoi("q")){
double t1=(double)cvGetTickCount();
IplImage *img=cvQueryFrame(camera);
/*if(img){
cvSaveImage("C:/opencv.jpg",img);
}*/
double t2=(double)cvGetTickCount();
printf("time: %gms fps: %.2g\n",(t2-t1)/(cvGetTickFrequency()*1000.), 1000./((t2-t1)/(cvGetTickFrequency()*1000.)));
cvShowImage("img",img);
}
cvReleaseCapture(&camera);
}
Would be good if it helps someone like me.
Also Thanks #karlphillip for giving your time.
Warnings are not errors! Relax.
In this case FFmpeg is complaining and not OpenCV. The reason is probably because the mjpg format that is specified on the URL doesn't really require an actual codec.
I am getting video frames using cvQueryframes, but in few videos of avi file I get :
Unhandled exception at 0x715c14f0 0xC0000005:
Access violation reading location 0x02f509f0.
I am using visual studio 2010 with OpenCV 2.4.5 and Qt5
CvCapture* cap= cvCaptureFromFile(file);
frame = cvQueryFrame(capture);
There could be multiple reasons for this, link wrong file name, codec not found etc. Try putting debug printf before opening file to see if file name is proper also check for cap if it is not NULL. You can try something like this
int main(int argc, char*argv[])
{
char *my_file = "C:\\vid_an2\\desp_me.avi";
std::cout<<"Video File "<<my_file<<std::endl;
cv::VideoCapture input_video;
if(input_video.open(my_file))
{
std::cout<<"Video file open "<<std::endl;
}
else
{
std::cout<<"Not able to Video file open "<<std::endl;
}
namedWindow("My_Win",1);
namedWindow("Segemented", 1);
Mat cap_img;
for(;;)
{
input_video >> cap_img;
imshow("My_Win", cap_img);
waitKey(0);
}
return 0;
}