Trouble in GMFPreview sample

Question

I use the PreviewController class of GMFPreview sample.

My source filter is based on PushSource.

I can see a preview video, but I cannot record it.

When I pressed a record button, I met an error 'VFW_E_NO_ALLOCATOR' in line:

HRESULT hr = m_pBridge->BridgeGraphs(m_pSourceGraphSinkFilter, m_pCaptureGraphSourceFilter);

I traced it, and I found the error is in the below line:

Function: HRESULT BridgeStream::Bridge(BridgeSinkInput* pInputPin, BridgeSourceOutput* pOutputPin)

Line: hr = pOutputPin->GetConnectionAllocator(&pAlloc);

'm_pAllocator' of output pin is NULL.

Debugging messages:

2: Added stream 1: video, Mux Inputs, Discard mode
85: Sink 0x418af88 has 1 pins
86: Sink filter 0x418afd8 in graph 0x12fd30
1496: Source 0x41c4108 has 1 pins
1497: Source filter 0x41c4158 in graph 0xc6f3bc8
1578: Source 0x41c4108 pause from 0
1578: Source 0x41c4108 run from 1, latency 10 ms
1579: Bridging 0x418afd8 to 0x41c4158
1579: Pin 0x418b678 disconnect
1580: Source 0x41c4108 new connection, base 0
226228: Source 0x41c4108 stop from 2
226231: Sink 0x418af88 Stop
226232: Sink 0x418af88 ResetEOSCount
226250: Bridging 0x0 to 0x0

How can I fix this error?

Please, help me.