edgealgorithmen bei opencv liefern leeres bild

[DocJunioR]

hi hallo, es gibt mich noch! ^^

ich habe folgendes Problem:

/*
 * main.cpp
 *
 *  Created on: 30.08.2010
 *      Author: tecdroid
 */
#include <opencv/cv.h>
#include <opencv/highgui.h>
#include <stdio.h>

// A Simple Camera Capture Framework
int main() {

	CvCapture* capture = cvCaptureFromCAM(CV_CAP_ANY);
	if (!capture) {
		fprintf(stderr, "ERROR: capture is NULL \n");
		getchar();
		return -1;
	}

	// Create a window in which the captured images will be presented
	cvNamedWindow("mywindow", CV_WINDOW_AUTOSIZE);

	// Show the image captured from the camera in the window and repeat
	while (1) {
		// Get one frame
		IplImage* frame = cvQueryFrame(capture);
		if (!frame) {
			fprintf(stderr, "ERROR: frame is null...\n");
			getchar();
			break;
		}

		// despeckle

		// grayscale
		IplImage *gray = cvCreateImage(cvGetSize(frame), IPL_DEPTH_8U, 1);
		cvCvtColor(frame, gray, CV_RGB2GRAY);
//		cvEqualizeHist(gray, gray);

		// sobel
		IplImage *edged = cvCreateImage(cvGetSize(frame), IPL_DEPTH_16S, 1);
		cvSobel(gray, edged, 0 , 1);

		cvShowImage("mywindow", edged);

		// Do not release the frame!
		// but the rest
		cvReleaseImage(&edged);
		cvReleaseImage(&gray);

		//If ESC key pressed, Key=0x10001B under OpenCV 0.9.7(linux version),
		//remove higher bits using AND operator
		if ((cvWaitKey(10) & 255) == 27)
			break;
	}

	// Release the capture device housekeeping
	cvReleaseCapture(&capture);
	cvDestroyWindow("mywindow");
	return 0;
}

Das gargestellte Bild ist komplett grau. Das direkte Kamerabild, sowie das gegraute Bild sind sichtbar. Kann mir wer erklären, warum?