Black screen using DirectShow SDK on PS3eye usb camera - camera

Question

I just figured out the problem that DirectShow cannot detect PS3eye camera when another problem comes to me.
It was tested that the PS3eye camera can be read by AMcap and by OpenCV using constructor VideoCapture cap(1). When I tried to use function QueryFrame() to grab frames from camera and show it in computer, it returned me a black screen. The codes are as following:
IplImage* CCameraDS::QueryFrame()
{
HRESULT hr;
if (!m_IsOpen)
{
return NULL;
}
long evCode;
long size = 0;
hr = m_pGraph->QueryInterface(IID_IMediaControl, (void **)&m_pMediaControl);
if (SUCCEEDED(hr)) {
hr = m_pMediaControl->Run();
if (FAILED(hr))
m_pMediaControl->Stop();
m_pMediaControl->Release();
}
else {
printf("Cannot preview graph.\n");
return false;
}
m_pMediaEvent->WaitForCompletion(INFINITE, &evCode);
m_pSampleGrabber->GetCurrentBuffer(&size, NULL);
//if the buffer size changed
if (size != m_nBufferSize)
{
if (m_pFrame)
cvReleaseImage(&m_pFrame);
m_nBufferSize = size;
m_pFrame = cvCreateImage(cvSize(m_nWidth, m_nHeight), IPL_DEPTH_8U, 3);
}
if (m_pFrame->imageData == NULL)
{
return 0;
}
hr = m_pSampleGrabber->GetCurrentBuffer(&m_nBufferSize, (long*)m_pFrame->imageData);
if (FAILED(hr))
return NULL;
cvFlip(m_pFrame);
return m_pFrame;
}
What's the problem? Am I missing something?