How to capture live camera frames in RGB with DirectShow
- by Jonny Boy
I'm implementing live video capture through DirectShow for live processing and display. (Augmented Reality app).
I can access the pixels easily enough, but it seems I can't get the SampleGrabber to provide RGB data. The device (an iSight -- running VC++ Express in VMWare) only reports MEDIASUBTYPE_YUY2.
After extensive Googling, I still can't figure out whether DirectShow is supposed to provide built-in color space conversion for this sort of thing. Some sites report that there is no YUV<-RGB conversion built in, others report that you just have to call SetMediaType on your ISampleGrabber with an RGB subtype.
Any advice is greatly appreciated, I'm going nuts on this one. Code provided below. Please note that
The code works, except that it doesn't provide RGB data
I'm aware that I can implement my own conversion filter, but this is not feasible because I'd have to anticipate every possible device format, and this is a relatively small project
// Playback
IGraphBuilder *pGraphBuilder = NULL;
ICaptureGraphBuilder2 *pCaptureGraphBuilder2 = NULL;
IMediaControl *pMediaControl = NULL;
IBaseFilter *pDeviceFilter = NULL;
IAMStreamConfig *pStreamConfig = NULL;
BYTE *videoCaps = NULL;
AM_MEDIA_TYPE **mediaTypeArray = NULL;
// Device selection
ICreateDevEnum *pCreateDevEnum = NULL;
IEnumMoniker *pEnumMoniker = NULL;
IMoniker *pMoniker = NULL;
ULONG nFetched = 0;
HRESULT hr = CoInitializeEx(NULL, COINIT_MULTITHREADED);
// Create CreateDevEnum to list device
hr = CoCreateInstance(CLSID_SystemDeviceEnum, NULL, CLSCTX_INPROC_SERVER, IID_ICreateDevEnum, (PVOID *)&pCreateDevEnum);
if (FAILED(hr)) goto ReleaseDataAndFail;
// Create EnumMoniker to list devices
hr = pCreateDevEnum->CreateClassEnumerator(CLSID_VideoInputDeviceCategory, &pEnumMoniker, 0);
if (FAILED(hr)) goto ReleaseDataAndFail;
pEnumMoniker->Reset();
// Find desired device
while (pEnumMoniker->Next(1, &pMoniker, &nFetched) == S_OK)
{
IPropertyBag *pPropertyBag;
TCHAR devname[256];
// bind to IPropertyBag
hr = pMoniker->BindToStorage(0, 0, IID_IPropertyBag, (void **)&pPropertyBag);
if (FAILED(hr))
{
pMoniker->Release();
continue;
}
VARIANT varName;
VariantInit(&varName);
HRESULT hr = pPropertyBag->Read(L"DevicePath", &varName, 0);
if (FAILED(hr))
{
pMoniker->Release();
pPropertyBag->Release();
continue;
}
char devicePath[DeviceInfo::STRING_LENGTH_MAX] = "";
wcstombs(devicePath, varName.bstrVal, DeviceInfo::STRING_LENGTH_MAX);
if (strcmp(devicePath, deviceId) == 0)
{
// Bind Moniker to Filter
pMoniker->BindToObject(0, 0, IID_IBaseFilter, (void**)&pDeviceFilter);
break;
}
pMoniker->Release();
pPropertyBag->Release();
}
if (pDeviceFilter == NULL) goto ReleaseDataAndFail;
// Create sample grabber
IBaseFilter *pGrabberF = NULL;
hr = CoCreateInstance(CLSID_SampleGrabber, NULL, CLSCTX_INPROC_SERVER, IID_IBaseFilter, (void**)&pGrabberF);
if (FAILED(hr)) goto ReleaseDataAndFail;
hr = pGrabberF->QueryInterface(IID_ISampleGrabber, (void**)&pGrabber);
if (FAILED(hr)) goto ReleaseDataAndFail;
// Create FilterGraph
hr = CoCreateInstance(CLSID_FilterGraph,
NULL,
CLSCTX_INPROC,
IID_IGraphBuilder,
(LPVOID *)&pGraphBuilder);
if (FAILED(hr)) goto ReleaseDataAndFail;
// create CaptureGraphBuilder2
hr = CoCreateInstance(CLSID_CaptureGraphBuilder2, NULL, CLSCTX_INPROC, IID_ICaptureGraphBuilder2, (LPVOID *)&pCaptureGraphBuilder2);
if (FAILED(hr)) goto ReleaseDataAndFail;
// set FilterGraph
hr = pCaptureGraphBuilder2->SetFiltergraph(pGraphBuilder);
if (FAILED(hr)) goto ReleaseDataAndFail;
// get MediaControl interface
hr = pGraphBuilder->QueryInterface(IID_IMediaControl, (LPVOID *)&pMediaControl);
if (FAILED(hr)) goto ReleaseDataAndFail;
// Add filters
hr = pGraphBuilder->AddFilter(pDeviceFilter, L"Device Filter");
if (FAILED(hr)) goto ReleaseDataAndFail;
hr = pGraphBuilder->AddFilter(pGrabberF, L"Sample Grabber");
if (FAILED(hr)) goto ReleaseDataAndFail;
// Set sampe grabber options
AM_MEDIA_TYPE mt;
ZeroMemory(&mt, sizeof(AM_MEDIA_TYPE));
mt.majortype = MEDIATYPE_Video;
mt.subtype = MEDIASUBTYPE_RGB32;
hr = pGrabber->SetMediaType(&mt);
if (FAILED(hr)) goto ReleaseDataAndFail;
hr = pGrabber->SetOneShot(FALSE);
if (FAILED(hr)) goto ReleaseDataAndFail;
hr = pGrabber->SetBufferSamples(TRUE);
if (FAILED(hr)) goto ReleaseDataAndFail;
// Get stream config interface
hr = pCaptureGraphBuilder2->FindInterface(NULL, &MEDIATYPE_Video, pDeviceFilter, IID_IAMStreamConfig, (void **)&pStreamConfig);
if (FAILED(hr)) goto ReleaseDataAndFail;
int streamCapsCount = 0, capsSize, bestFit = -1, bestFitPixelDiff = 1000000000, desiredPixelCount = _width * _height,
bestFitWidth = 0, bestFitHeight = 0;
float desiredAspectRatio = (float)_width / (float)_height;
hr = pStreamConfig->GetNumberOfCapabilities(&streamCapsCount, &capsSize);
if (FAILED(hr)) goto ReleaseDataAndFail;
videoCaps = (BYTE *)malloc(capsSize * streamCapsCount);
mediaTypeArray = (AM_MEDIA_TYPE **)malloc(sizeof(AM_MEDIA_TYPE *) * streamCapsCount);
for (int i = 0; i < streamCapsCount; i++)
{
hr = pStreamConfig->GetStreamCaps(i, &mediaTypeArray[i], videoCaps + capsSize * i);
if (FAILED(hr)) continue;
VIDEO_STREAM_CONFIG_CAPS *currentVideoCaps = (VIDEO_STREAM_CONFIG_CAPS *)(videoCaps + capsSize * i);
int closestWidth = MAX(currentVideoCaps->MinOutputSize.cx, MIN(currentVideoCaps->MaxOutputSize.cx, width));
int closestHeight = MAX(currentVideoCaps->MinOutputSize.cy, MIN(currentVideoCaps->MaxOutputSize.cy, height));
int pixelDiff = ABS(desiredPixelCount - closestWidth * closestHeight);
if (pixelDiff < bestFitPixelDiff && ABS(desiredAspectRatio - (float)closestWidth / (float)closestHeight) < 0.1f)
{
bestFit = i;
bestFitPixelDiff = pixelDiff;
bestFitWidth = closestWidth;
bestFitHeight = closestHeight;
}
}
if (bestFit == -1) goto ReleaseDataAndFail;
AM_MEDIA_TYPE *mediaType;
hr = pStreamConfig->GetFormat(&mediaType);
if (FAILED(hr)) goto ReleaseDataAndFail;
VIDEOINFOHEADER *videoInfoHeader = (VIDEOINFOHEADER *)mediaType->pbFormat;
videoInfoHeader->bmiHeader.biWidth = bestFitWidth;
videoInfoHeader->bmiHeader.biHeight = bestFitHeight;
//mediaType->subtype = MEDIASUBTYPE_RGB32;
hr = pStreamConfig->SetFormat(mediaType);
if (FAILED(hr)) goto ReleaseDataAndFail;
pStreamConfig->Release();
pStreamConfig = NULL;
free(videoCaps);
videoCaps = NULL;
free(mediaTypeArray);
mediaTypeArray = NULL;
// Connect pins
IPin *pDeviceOut = NULL, *pGrabberIn = NULL;
if (FindPin(pDeviceFilter, PINDIR_OUTPUT, 0, &pDeviceOut) && FindPin(pGrabberF, PINDIR_INPUT, 0, &pGrabberIn))
{
hr = pGraphBuilder->Connect(pDeviceOut, pGrabberIn);
if (FAILED(hr)) goto ReleaseDataAndFail;
}
else
{
goto ReleaseDataAndFail;
}
// start playing
hr = pMediaControl->Run();
if (FAILED(hr)) goto ReleaseDataAndFail;
hr = pGrabber->GetConnectedMediaType(&mt);
// Set dimensions
width = bestFitWidth;
height = bestFitHeight;
_width = bestFitWidth;
_height = bestFitHeight;
// Allocate pixel buffer
pPixelBuffer = (unsigned *)malloc(width * height * 4);
// Release objects
pGraphBuilder->Release();
pGraphBuilder = NULL;
pEnumMoniker->Release();
pEnumMoniker = NULL;
pCreateDevEnum->Release();
pCreateDevEnum = NULL;
return true;
