opencv c ++ VideoCapture open（）错误

Question

我正在尝试在OS X上的opencv c ++中读取网络摄像头流，但是当我尝试打开该Feed时出现以下错误：

Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 0 beyond bounds for empty array'

堆栈跟踪：

*** First throw call stack:
(
0   CoreFoundation                      0x00007fff86cfee7b __exceptionPreprocess + 171
1   libobjc.A.dylib                     0x00007fff9b8e8cad objc_exception_throw + 48
2   CoreFoundation                      0x00007fff86c181dc -[__NSArrayM objectAtIndex:] + 204
3   libopencv_highgui.2.4.dylib         0x0000000104b09280 _ZN13CvCaptureFileC2EPKc + 350
4   libopencv_highgui.2.4.dylib         0x0000000104b07cf2 _Z32cvCreateFileCapture_AVFoundationPKc + 34
5   libopencv_highgui.2.4.dylib         0x0000000104afb7ee cvCreateFileCapture + 14
6   libopencv_highgui.2.4.dylib         0x0000000104afba9e _ZN2cv12VideoCapture4openERKNSt3__112basic_stringIcNS1_11char_traitsIcEENS1_9allocatorIcEEEE + 64
7   classification.bin                  0x0000000104031842 main + 370
8   libdyld.dylib                       0x00007fff9c1cc255 start + 1
9   ???                                 0x0000000000000005 0x0 + 5
)
libc++abi.dylib: terminating with uncaught exception of type NSException
Abort trap: 6

代码：

VideoCapture cap;
printf("vidcap created\n"); // This message is printed
cap.open("http://192.168.1.155:80/video.cgi?dummy=.mjpg");
printf("feed opened\n"); // this one is not

出现此错误的原因是什么？