cvCaptureFromCAM 分析

CV_IMPL CvCapture * cvCaptureFromCAM (int index){    int  domains[] = {CV_CAP_IEEE1394,   // identical to CV_CAP_DC1394 CV_CAP_STEREO, CV_CAP_VFW,        // identical to CV_CAP_V4LCV_CAP_MIL, CV_CAP_QT,-1 };    // interpret preferred interface (0 = autodetect)    int pref = (index / 100) * 100;    if (pref) {domains[0]=pref;index %= 100;domains[1]=-1;    }    // try every possibly installed camera API    for (int i = 0; domains[i] >= 0; i++) {// local variable to memorize the captured deviceCvCapture *capture;switch (domains[i]) {#ifdef HAVE_TYZXcase CV_CAP_STEREO:capture = cvCaptureFromCAM_TYZX (index);if (capture)return capture;#endif#if   defined (HAVE_VFW)case CV_CAP_VFW:capture = cvCaptureFromCAM_VFW (index);if (capture) return capture;#elif defined (HAVE_CAMV4L) || defined (HAVE_CAMV4L2)case CV_CAP_V4L:capture = cvCaptureFromCAM_V4L (index);if (capture) return capture;#endif#if   defined (HAVE_DC1394)case CV_CAP_DC1394:capture = cvCaptureFromCAM_DC1394 (index);if (capture)return capture;#elif defined (HAVE_CMU1394)        case CV_CAP_IEEE1394:capture = cvCaptureFromCAM_CMU (index);if (capture)return capture;#endif#ifdef HAVE_MILcase CV_CAP_MIL:capture = cvCaptureFromCAM_MIL (index);if (capture) return capture;#endif#ifdef HAVE_QUICKTIMEcase CV_CAP_QT:capture = cvCaptureFromCAM_QT (index);if (capture)return capture;#endif        }    }// failed open a camera    return 0;}