Add the ISampleGrabberCB to the main class of your app:
TForm1 = class(TForm, ISampleGrabberCB)

You have to create the following in your main class:
Private
FSampleGrabber : IBaseFilter
m_SampleGrabber: ISampleGrabber

function SampleCB(SampleTime: Double　pSample: IMediaSample): HResult　stdcall
function BufferCB(SampleTime: Double　pBuffer: PByte　BufferLen: longint): HResult　stdcall
.. etc
end
function TForm1.SampleCB(SampleTime: Double　pSample: IMediaSample): HResult
begin
Result := E_NOTIMPL
end
,Add the ISampleGrabberCB to the main class of your app:
TForm1 = class(TForm, ISampleGrabberCB)

You have to create the following in your main class:
Private
FSampleGrabber : IBaseFilter
m_SampleGrabber: ISampleGrabber

function SampleCB(SampleTime: Double　pSample: IMediaSample): HResult　stdcall
function BufferCB(SampleTime: Double　pBuffer: PByte　BufferLen: longint): HResult　stdcall
.. etc
end
function TForm1.SampleCB(SampleTime: Double　pSample: IMediaSample): HResult
begin
Result := E_NOTIMPL
end