windows_capture_devices.cpp

#include <Python.h>

// https://msdn.microsoft.com/en-us/library/windows/desktop/dd377566(v=vs.85).aspx
#include <windows.h>
#include <dshow.h>
#include <comutil.h>

#pragma comment(lib, "strmiids")

#if PY_MAJOR_VERSION >= 3
#ifndef IS_PY3K
#define IS_PY3K 1
#endif
#endif

struct module_state {
    PyObject *error;
};

#if defined(IS_PY3K)
#define GETSTATE(m) ((struct module_state*)PyModule_GetState(m))
#else
#define GETSTATE(m) (&_state)
static struct module_state _state;
#endif

// #pragma comment(lib, "kernel32")
// #pragma comment(lib, "user32")
// #pragma comment(lib, "gdi32")
// #pragma comment(lib, "winspool")
// #pragma comment(lib, "comdlg32")
// #pragma comment(lib, "advapi32")
// #pragma comment(lib, "shell32")
// #pragma comment(lib, "ole32")
// #pragma comment(lib, "oleaut32")
// #pragma comment(lib, "uuid")
// #pragma comment(lib, "odbc32")
// #pragma comment(lib, "odbccp32")
#pragma comment(lib, "comsuppwd.lib")

HRESULT EnumerateDevices(REFGUID category, IEnumMoniker **ppEnum)
{
	// Create the System Device Enumerator.
	ICreateDevEnum *pDevEnum;
	HRESULT hr = CoCreateInstance(CLSID_SystemDeviceEnum, NULL,
		CLSCTX_INPROC_SERVER, IID_PPV_ARGS(&pDevEnum));

	if (SUCCEEDED(hr))
	{
		// Create an enumerator for the category.
		hr = pDevEnum->CreateClassEnumerator(category, ppEnum, 0);
		if (hr == S_FALSE)
		{
			hr = VFW_E_NOT_FOUND;  // The category is empty. Treat as an error.
		}
		pDevEnum->Release();
	}
	return hr;
}

PyObject* DisplayDeviceInformation(IEnumMoniker *pEnum)
{
	// Create an empty Python list
	PyObject* pyList = PyList_New(0); 

	IMoniker *pMoniker = NULL;

	while (pEnum->Next(1, &pMoniker, NULL) == S_OK)
	{
		IPropertyBag *pPropBag;
		HRESULT hr = pMoniker->BindToStorage(0, 0, IID_PPV_ARGS(&pPropBag));
		if (FAILED(hr))
		{
			pMoniker->Release();
			continue;
		}

		VARIANT var;
		VariantInit(&var);

		// Get description or friendly name.
		hr = pPropBag->Read(L"Description", &var, 0);
		if (FAILED(hr))
		{
			hr = pPropBag->Read(L"FriendlyName", &var, 0);
		}
		if (SUCCEEDED(hr))
		{
			// Append a result to Python list
			char  *pValue = _com_util::ConvertBSTRToString(var.bstrVal);
			hr = PyList_Append(pyList, Py_BuildValue("s", pValue));
			delete[] pValue;  
			if (FAILED(hr)) {
				printf("Failed to append the object item at the end of list list\n");
				return pyList;
			}

			// printf("%S\n", var.bstrVal);
			VariantClear(&var);
		}

		hr = pPropBag->Write(L"FriendlyName", &var);

		// WaveInID applies only to audio capture devices.
		hr = pPropBag->Read(L"WaveInID", &var, 0);
		if (SUCCEEDED(hr))
		{
			printf("WaveIn ID: %d\n", var.lVal);
			VariantClear(&var);
		}

		hr = pPropBag->Read(L"DevicePath", &var, 0);
		if (SUCCEEDED(hr))
		{
			// The device path is not intended for display.
			// printf("Device path: %S\n", var.bstrVal);
			VariantClear(&var);
		}

		pPropBag->Release();
		pMoniker->Release();
	}

	return pyList;
}

static PyObject *
get_capture_devices(PyObject *self, PyObject *args)
{
	PyObject* pyList = NULL; 
	
	HRESULT hr = CoInitializeEx(NULL, COINIT_MULTITHREADED);
	if (SUCCEEDED(hr))
	{
		IEnumMoniker *pEnum;

		hr = EnumerateDevices(CLSID_VideoInputDeviceCategory, &pEnum);
		if (SUCCEEDED(hr))
		{
			pyList = DisplayDeviceInformation(pEnum);
			pEnum->Release();
		}
		CoUninitialize();
	}

    return pyList;
}

static PyMethodDef Methods[] =
{
    {"get_capture_devices", get_capture_devices, METH_VARARGS, NULL},
    {NULL, NULL, 0, NULL}
};

PyMODINIT_FUNC
initdevice(void);

#if defined(IS_PY3K)

static int device_traverse(PyObject *m, visitproc visit, void *arg) {
    Py_VISIT(GETSTATE(m)->error);
    return 0;
}

static int device_clear(PyObject *m) {
    Py_CLEAR(GETSTATE(m)->error);
    return 0;
}

static struct PyModuleDef moduledef = {
    PyModuleDef_HEAD_INIT,
    "windows_capture_devices",
    NULL,
    sizeof(struct module_state),
    Methods,
    NULL,
    device_traverse,
    device_clear,
    NULL
};

#define INITERROR return NULL

PyMODINIT_FUNC
PyInit_windows_capture_devices(void)

#else
#define INITERROR return
void
initdevice(void)
#endif
{
#if defined(IS_PY3K)
    PyObject *module = PyModule_Create(&moduledef);
#else
    PyObject *module = Py_InitModule("windows_capture_devices", Methods);
#endif

    if (module == NULL)
        INITERROR;
    struct module_state *st = GETSTATE(module);

    st->error = PyErr_NewException("windows_capture_devices.Error", NULL, NULL);
    if (st->error == NULL) {
        Py_DECREF(module);
        INITERROR;
    }

#if defined(IS_PY3K)
    return module;
#endif
}