How to determine how many cameras are connected to a computer and connect to and use ptz cameras

How to determine how many cameras are connected to a computer and connect to and use ptz cameras:

I figure this is a nice easy first post. This is some code I struggled with finding a couple years ago on automatically determining how many cameras are connected to a computer via directshow (this code is also useful in a ptz application as I will show right after). I use OpenCV to capture from the camera and the directshow library to use the ptz camera functions. I also used the vector and stringstream library for my own ease (#include<vector> #include<sstream>)

The DisplayError function is a generic wrapper for you to fill in, whether you use printf or a messagebox.

int getDeviceCount() {
  try {
    ICreateDevEnum *pDevEnum = NULL;
    IEnumMoniker *pEnum = NULL;
    int deviceCounter = 0;
    HRESULT hr = CoCreateInstance(CLSID_SystemDeviceEnum, NULL, CLSCTX_INPROC_SERVER, IID_ICreateDevEnum, reinterpret_cast<void**>(&pDevEnum));
    if (SUCCEEDED(hr)) {
      // Create an enumerator for the video capture category.
      hr = pDevEnum->CreateClassEnumerator(CLSID_VideoInputDeviceCategory, &pEnum, 0);
      if (hr == S_OK) {
        IMoniker *pMoniker = NULL;
        while (pEnum->Next(1, &pMoniker, NULL) == S_OK) {
          IPropertyBag *pPropBag;
          hr = pMoniker->BindToStorage(0, 0, IID_IPropertyBag, (void**)(&pPropBag));
          if (FAILED(hr)) {
            pMoniker->Release();
            continue; // Skip this one, maybe the next one will work.
          }
          pPropBag->Release();
          pPropBag = NULL;
          pMoniker->Release();
          pMoniker = NULL;
          deviceCounter++;
        }
        pEnum->Release();
        pEnum = NULL;
      }
      pDevEnum->Release();
      pDevEnum = NULL;
    }
    return deviceCounter;
  } catch(Exception & e) {
    DisplayError(e.ToString());
  } catch(...) {
    DisplayError("Error Caught Counting # of Devices");
  }
  return 0;
}

This can easily be modified to connect to x number of ptz cameras with a quick ptz class

Here is our ptz class:

class ptz {
public:
  struct controlVals {
  public:
    long min, max, step, def, flags;
  };
  IBaseFilter *filter;
  IAMCameraControl *camControl;
  bool valid, validMove;
  CvCapture *capture;
  bool Initialize() {
    camControl = NULL;
    controlVals panInfo = {0}, tiltInfo = {0};
    HRESULT hr = filter->QueryInterface(IID_IAMCameraControl, (void **)&camControl);
    if(hr != S_OK)
      return false;
    else
      return true;
  }
  void ptz(int instance) {

    threadNum = instance;
    // sets up a continuous capture point through the msvc driver
    capture = cvCaptureFromCAM(threadNum);
    if (!capture)
      valid = false;
    else
      valid = true;
  }
  void Destroy() {
    if(camControl) {
      camControl->Release();
      camControl = NULL;
    }
    if (filter) {
      filter->Release();
      filter = NULL;
    }
  }
};

And here is the modified getDeviceCount code which now connects to all the cameras and gets the ptz information using direct show:

int getDeviceCount(vector<ptz> &cameras) {
  try {
    ICreateDevEnum *pDevEnum = NULL;
    IEnumMoniker *pEnum = NULL;
    int deviceCounter = 0;

    HRESULT hr = CoCreateInstance(CLSID_SystemDeviceEnum, NULL, CLSCTX_INPROC_SERVER, IID_ICreateDevEnum, reinterpret_cast<void**>(&pDevEnum));
    if (SUCCEEDED(hr)) {
      // Create an enumerator for the video capture category.
      hr = pDevEnum->CreateClassEnumerator(CLSID_VideoInputDeviceCategory, &pEnum, 0);
      if (hr == S_OK) {
        IMoniker *pMoniker = NULL;
        do {
          if (pEnum->Next(1, &pMoniker, NULL) == S_OK) {
            IPropertyBag *pPropBag;
            hr = pMoniker->BindToStorage(0, 0, IID_IPropertyBag, (void**)(&pPropBag));
            if (FAILED(hr)) {
              pMoniker->Release();
              continue; // Skip this one, maybe the next one will work.
            }
            if (SUCCEEDED(hr)) {
              ptz tmp = ptz(deviceCounter);
              HRESULT hr2 = pMoniker->BindToObject(NULL, NULL, IID_IBaseFilter, (void**) & (tmp.filter));
              if (tmp.valid)
                tmp.validMove = tmp.Initialize();
            }
            pPropBag->Release();
            pPropBag = NULL;
            pMoniker->Release();
            pMoniker = NULL;
            deviceCounter++;
          } else {
            ptz tmp = ptz(deviceCounter);
            cameras.push_back(tmp);
            deviceCounter++;
            break;
          }
        }
        while (cameras[deviceCounter -1].valid);
        pEnum->Release();
        pEnum = NULL;
      }
      pDevEnum->Release();
      pDevEnum = NULL;
    }
    return deviceCounter;
  } catch(Exception & e) {
    DisplayError(e.ToString());
  } catch(...) {
    DisplayError("Error Caught Counting # of Devices");
  }
  return 0;
}

Notice now how we have integrated OpenCV into our ptz class. Now as we find cameras we can capture the camera information using OpenCV and then use directshow to grab the information used for ptz. To move the camera we can use  a pan and a tilt function like the following:

HRESULT MechanicalPan(IAMCameraControl *pCameraControl, long value) {
  HRESULT hr = 0;
  try {
    long flags = KSPROPERTY_CAMERACONTROL_FLAGS_RELATIVE | KSPROPERTY_CAMERACONTROL_FLAGS_MANUAL;
    hr = pCameraControl->Set(CameraControl_Pan, value, flags);
    if (hr == 0x800700AA)
      Sleep(1);
    else if (hr != S_OK && hr != 0x80070490) {
      stringstream tmp;
      tmp << "ERROR: Unable to set CameraControl_Pan property value to " << value << ". (Error " << std::hex << hr << ")";
      throw Exception(tmp.str().c_str());
    }
    // Note that we need to wait until the movement is complete, otherwise the next request will
    // fail with hr == 0x800700AA == HRESULT_FROM_WIN32(ERROR_BUSY).
  } catch(Exception & e) {
    DisplayError(e.ToString());
  } catch(...) {
    DisplayError("Error Caught panning camera");
  }
  return hr;
}
// ----------------------------------------------------------------------------
HRESULT MechanicalTilt(IAMCameraControl *pCameraControl, long value) {
  HRESULT hr = 0;
  try {
    long flags = KSPROPERTY_CAMERACONTROL_FLAGS_RELATIVE | KSPROPERTY_CAMERACONTROL_FLAGS_MANUAL;
    hr = pCameraControl->Set(CameraControl_Tilt, value, flags);
    if (hr == 0x800700AA)
      Sleep(1);
    else if (hr != S_OK && hr != 0x80070490) {
      stringstream tmp;
      tmp << "ERROR: Unable to set CameraControl_Tilt property value to " << value << ". (Error " << std::hex << hr << ")";
      throw Exception(tmp.str().c_str());
    }
    // Note that we need to wait until the movement is complete, otherwise the next request will
    // fail with hr == 0x800700AA == HRESULT_FROM_WIN32(ERROR_BUSY).
  } catch(Exception & e) {
    DisplayError(e.ToString());
  } catch(...) {
    DisplayError("Error Caught tilting camera");
  }
  return hr;
}

Consider donating to further my tinkering.

Places you can find me

• Facebook
• Google+
• Linkedin
• Blogspot
• Google-Code
• Github
• YouTube
• Twitter

Read More..

How to Implement Buffer Overflow

Buffer overflow exploits are commonly found problems which can cause irrevocable damage to a system if taken advantage of. The only way to prevent them is to be careful about coding practices and bounds check to make sure no kind of input, stream, file, command, encryption key, or otherwise can be used to overwrite a buffer past bounds. The problem with this is that many libraries, programs, and operating systems used by programmers already have many of these exploits in them, making prevention difficult if not impossible.

That being said, here is kind of how it works (all examples run in Windows XP using gdb):

The files used for exploit are named vulnerable_code (courtesy of Dr. Richard Brooks from Clemson University) and they can be found here: 

http://code.google.com/p/stevenhickson-code/source/browse/#svn%2Ftrunk%2FBufferOverflow

(All code is licensed under the GPL modified license included at the google-code address. It is simply the GPL v3.0 with the modifier that if you enjoyed this and run into me somewhere sometime, you are welcome to buy me a drink).

The link above also includes all the assembly files used to create shellcode, nasm to assemble it, and arwin to find the memory locations. It should have everything you need.

Note: Bear in mind that the memory locations will probably be different for you and you will have to find them yourself (probably by writing AAAA over and over again in memory).

IMPORTANT:

This tutorial is used for explanation and education only. Do not copy my examples and turn them in for a class. You will get caught and get in trouble and you wont learn anything and I will program a helicopter to hunt you down autonomously as revenge.