Opencv Capture Causes Memory Allocation Error - c

Question

I have implemented a capture code runs on OpenCV libraries. Code captures from 2 cameras order by order. But the code causes memory allocation error after a while.
I have to release a capture stream of camera1 to open a capture stream of camera2. I could not able to get two capture simultanously so I have to capture it order by order.
Why it couses memory allocation error in this scenario?
My code is located below:
#include <cv.h>
#include <highgui.h>
#include <cxcore.h>
#include <stdio.h>
CvCapture* camera; // Use the default camera
IplImage* frame;
int main(int argc, char* argv[])
{
while(1)
{
camera = cvCreateCameraCapture(0); // Use the default camera
//camera2 = cvCreateCameraCapture(1); // Use the default camera
frame = 0;
//frame2 = 0;
cvSetCaptureProperty(camera,CV_CAP_PROP_FRAME_WIDTH,1024) ;
cvSetCaptureProperty(camera,CV_CAP_PROP_FRAME_HEIGHT,768);
frame = cvQueryFrame(camera); //need to capture at least one extra frame
if (frame != NULL) {
printf("Frame extracted from CAM1\n\r");
cvSaveImage("/dev/shm/webcam1.jpg", frame,0);
printf("Frame from CAM1 saved\n\r");
} else {
printf("Null frame 1\n\r");
}
cvReleaseImage(&frame);
cvReleaseCapture(&camera);
camera = cvCreateCameraCapture(1); // Use the default camera
cvSetCaptureProperty(camera,CV_CAP_PROP_FRAME_WIDTH,1024) ;
cvSetCaptureProperty(camera,CV_CAP_PROP_FRAME_HEIGHT,768);
frame = cvQueryFrame(camera); //need to capture at least one extra frame
if (frame != NULL) {
printf("Frame extracted from CAM2\n\r");
cvSaveImage("/dev/shm/webcam2.jpg", frame,0);
printf("Frame from CAM2 saved\n\r");
} else {
printf("Null frame 2\n\r");
}
cvReleaseImage(&frame);
cvReleaseCapture(&camera);
}

Answer 1

First of all, you can start declaring out of while() statement the cameraCapture:
camera0 = cvCreateCameraCapture(0);
camera1 = cvCreateCameraCapture(1);
frame0 = 0;
frame1 = 0;
cvSetCaptureProperty(camera0,CV_CAP_PROP_FRAME_WIDTH,1024) ;
cvSetCaptureProperty(camera0,CV_CAP_PROP_FRAME_HEIGHT,768);
cvSetCaptureProperty(camera1,CV_CAP_PROP_FRAME_WIDTH,1024) ;
cvSetCaptureProperty(camera1,CV_CAP_PROP_FRAME_HEIGHT,768);
while(1) {
/* your operation */
frame0 = cvQueryFrame(camera0);
frame1 = cvQueryFrame(camera1);
/* your operation */
}
cvReleaseImage(&frame0);
cvReleaseImage(&frame1);
cvReleaseCapture(&camera0);
cvReleaseCapture(&camera1);
Edit
If you want to take first stream from A-cam and then from B-cam, you'll have a code like the this. I don't understand exactly what do you want to do, so this code simply show your stream on a window.
Remember to use cvWaitKey(...) in order to give to highgui time to process the draw requests from cvShowImage().
Also, take a look at the documentation of cvSetCaptureProperty: here is written that currently the function supports only video files:
CV_CAP_PROP_POS_MSEC;
CV_CAP_PROP_POS_FRAMES;
CV_CAP_PROP_POS_AVI_RATIO.
By the way, this is my suggest:
const char* wndName = "window";
cvNamedWindow(wndName, CV_WINDOW_NORMAL);
IplImage* frame;
CvCapture* capture;
while(true) {
capture = cvCaptureFromCAM(0);
/* Showing for a while capture in window */
while(/* your condition */) {
frame = cvQueryFrame(capture);
/* operation with A cam */
cvShowImage(wndName, frame);
cvWaitKey(30);
}
cvReleaseCapture(&capture);
cvWaitKey(100);
/* switching source cam */
capture = cvCaptureFromCAM(1);
/* Showing for a while capture in the same window */
while(/* your condition */) {
frame = cvQueryFrame(capture);
/* operation with B cam */
cvShowImage(wndName, frame);
cvWaitKey(30);
}
}
cvReleaseImage(&frame);
cvReleaseCapture(&capture);
This works for me, give me any feedback.