I get no video from the camera that is connected with firewire.

edit

(Edit reassembling some comments)

I haven't a firewire cam to test but, to grab from them your OpenCV binaries should have IEEE1394 capturing support enabled. By default isn't (check HAVE_DC1394 in your /include/opencv2/cvconfig.h)

To enable IEEE1394 you should rebuild OpenCV enabling HAVE_DC1394 in CMAKE. This requires libdc1394 3rd party libs available on you PC. But it does not work for all cameras.

Is a common case for FireWire (or GigE IP) industrial cameras to have its own SDK/DLL for C++. In this case you have to create your own function that grabs using the SDK and write the image into a cv::Mat. Camera manufactures provide rich examples for free.

As alternative, if your firewire camera has a driver which provides a layer for Video For Windows (VFW) or DirectShow layer, you should be able to open it using standard VideoCapture cap(deviceID); where deviceID is the ID assigned to the cam. To know this ID is a bit difficult but you can search (if it exists) with a brute force using code as below.

have fun!

/** \brief Test all grabbing drivers and fills a vector of all available cameras CAPdrivers+ID
 * 
 * For each CAPdrivers+ID, opens the device. If success, push CAP+ID in \c camIdx
 * A grabbing test is done just to inform the user.
 * \param camIdx[out] a vector of all readable cameras CAP+ID
 * \note remove some cout to use as function
 */
bool EnumerateCameras(vector<int> &camIdx)
{
    camIdx.clear();
    struct CapDriver{
        int enumValue; string enumName; string comment;
    };
    // list of all CAP drivers (see highgui_c.h)
    vector<CapDriver> drivers;
    drivers.push_back({ CV_CAP_MIL, "CV_CAP_MIL", "MIL proprietary drivers" });
    drivers.push_back({ CV_CAP_VFW, "CV_CAP_VFW", "platform native" });
    drivers.push_back({ CV_CAP_FIREWARE, "CV_CAP_FIREWARE", "IEEE 1394 drivers" });
    drivers.push_back({ CV_CAP_STEREO, "CV_CAP_STEREO", "TYZX proprietary drivers" });
    drivers.push_back({ CV_CAP_QT, "CV_CAP_QT", "QuickTime" });
    drivers.push_back({ CV_CAP_UNICAP, "CV_CAP_UNICAP", "Unicap drivers" });
    drivers.push_back({ CV_CAP_DSHOW, "CV_CAP_DSHOW", "DirectShow (via videoInput)" });
    drivers.push_back({ CV_CAP_MSMF, "CV_CAP_MSMF", "Microsoft Media Foundation (via videoInput)" });
    drivers.push_back({ CV_CAP_PVAPI, "CV_CAP_PVAPI", "PvAPI, Prosilica GigE SDK" });
    drivers.push_back({ CV_CAP_OPENNI, "CV_CAP_OPENNI", "OpenNI (for Kinect)" });
    drivers.push_back({ CV_CAP_OPENNI_ASUS, "CV_CAP_OPENNI_ASUS", "OpenNI (for Asus Xtion)" });
    drivers.push_back({ CV_CAP_ANDROID, "CV_CAP_ANDROID", "Android" });
    drivers.push_back({ CV_CAP_ANDROID_BACK, "CV_CAP_ANDROID_BACK", "Android back camera" }),
    drivers.push_back({ CV_CAP_ANDROID_FRONT, "CV_CAP_ANDROID_FRONT","Android front camera"}),
    drivers.push_back({ CV_CAP_XIAPI, "CV_CAP_XIAPI", "XIMEA Camera API" });
    drivers.push_back({ CV_CAP_AVFOUNDATION, "CV_CAP_AVFOUNDATION", "AVFoundation framework for iOS" });
    drivers.push_back({ CV_CAP_GIGANETIX, "CV_CAP_GIGANETIX", "Smartek Giganetix GigEVisionSDK" });
    drivers.push_back({ CV_CAP_INTELPERC, "CV_CAP_INTELPERC", "Intel Perceptual Computing SDK" });

    std::string winName,driverName,driverComment;
    int driverEnum;
    Mat frame;
    bool found;
    std::cout << "Searching for cameras IDs..." << endl << endl;
    for (int drv = 0; drv < drivers.size(); drv++)
    {
        driverName = drivers[drv].enumName;
        driverEnum = drivers[drv].enumValue;
        driverComment = drivers[drv].comment;
        std::cout << "Testing driver " << driverName << "..." ;
        found = false;

        int maxID = 100; //100 IDs between drivers
        if (driverEnum == CV_CAP_VFW)
            maxID = 10; //VWF opens same camera after 10 ?!?
        else if (driverEnum == CV_CAP_ANDROID)
            maxID = 98; //98 and 99 are front and back cam
        else if ((driverEnum == CV_CAP_ANDROID_FRONT) || (driverEnum == CV_CAP_ANDROID_BACK))
            maxID = 1; 

        for (int idx = 0; idx <maxID; idx++)
        {
            VideoCapture cap(driverEnum + idx);  // open the camera
            if (cap.isOpened())                  // check if we ...