hr = pCaptureGraphBuilder2->FindInterface(&PIN_CATEGORY_CAPTURE, &MEDIATYPE_Video, NULL, IID_IBaseFilter, (void**)&pVideoCaptureFilter);

NULL, &MEDIATYPE_Video, pSourceFilter, IID_IBaseFilter, (void**)&pVideoFilter);

This code snippet uses the function FindInterface of the CaptureGraphBuilder2 interface to find the video filter interface of a source filter. The function takes in the following parameters:

- NULL: This is the filter category used to search for the interface. In this case, we are not specifying a filter category, so we pass NULL.
- &MEDIATYPE_Video: This specifies the media type of the interface we are searching for. In this case, we are looking for the video filter interface, so we pass MEDIATYPE_Video.
- pSourceFilter: This is a pointer to the source filter for which we want to find the video filter interface.
- IID_IBaseFilter: This is the interface identifier for the IBaseFilter interface, which is the base interface for all DirectShow filters.
- (void**)&pVideoFilter: This is a pointer to the video filter interface that will be returned by the function if it succeeds. The function uses the address of this pointer to return the interface.