写一个filter,把系统时间叠加在视频捕捉的视频流上并写入文件，200分(200分)

怎么写这个filter，又如何实现PIN的连接？

begin

// Activate the filter graph, at this stage the source filters are added to the graph
CaptureGraph.Active := true;

// configure output Audio media type + source
if AudioSourceFilter.FilterGraph <> nil then

begin

PinList := TPinList.Create(AudioSourceFilter as IBaseFilter);
i := 0;
while i < PinList.Countdo

if PinList.PinInfo.dir = PINDIR_OUTPUT then

begin

if AudioFormats.ItemIndex <> -1 then

with (PinList.Items as IAMStreamConfig)do

SetFormat(AudioMediaTypes.Items[AudioFormats.ItemIndex].AMMediaType^);
PinList.Delete(i);
end else
inc(i);
if InputLines.ItemIndex <> -1 then

with (PinList.Items[InputLines.ItemIndex] as IAMAudioInputMixer)do

put_Enable(true);
PinList.Free;
end;


// configure output Video media type
if VideoSourceFilter.FilterGraph <> nil then

begin

PinList := TPinList.Create(VideoSourceFilter as IBaseFilter);
if VideoFormats.ItemIndex <> -1 then

with (PinList.First as IAMStreamConfig)do

SetFormat(VideoMediaTypes.Items[VideoFormats.ItemIndex].AMMediaType^);
PinList.Free;
end;



// now render streams
with CaptureGraph as IcaptureGraphBuilder2do

begin

CheckDSError(RenderStream(@PIN_CATEGORY_PREVIEW, nil, VideoSourceFilter as IBaseFilter, nil, VideoWindow as IBaseFilter));
CheckDSError(RenderStream(@PIN_CATEGORY_CAPTURE, nil, VideoSourceFilter as IBaseFilter, nil, ASFWriter as IBaseFilter));
CheckDSError(RenderStream(nil, nil, AudioSourceFilter as IBaseFilter, nil, ASFWriter as IBaseFilter));

end;