Delphi Change resolution of webcam in directshow - delphi

Question

i am trying to change the resolution of the frames to 320x240 because my webcam is providing frames in 640x480 and the encoder i am using is not working right with higher resolution, i do it this way
procedure OnDevieStart()
begin
FilterGraph.ClearGraph;
FilterGraph.Active := False;
Filter.BaseFilter.Moniker := SysDev.GetMoniker(TMenuItem(Sender).tag);
FilterGraph.Active := true;
SetVideoProperties(Filter as iBaseFilter);
with FilterGraph as ICaptureGraphBuilder2 do
try
RenderStream(#PIN_CATEGORY_PREVIEW, nil, Filter as IBaseFilter, SampleGrabber as IBaseFilter, VideoWindow as IbaseFilter);
FilterGraph.Play;
except
ShowMessage('Unable to use specified device!')
end;
end;
function SetVideoProperties(pVideoCapture: IBaseFilter):Boolean;
var
hr:HRESULT;
pStreamConfig: IAMStreamConfig;
pAM_Media: PAMMediaType;
pvih: PVIDEOINFOHEADER;
pICGP2: ICaptureGraphBuilder2;
begin
pICGP2 := FilterGraph as ICaptureGraphBuilder2;
hr := pICGP2.FindInterface(#PIN_CATEGORY_CAPTURE, nil, pVideoCapture,
IID_IAMStreamConfig, pStreamConfig);
if (SUCCEEDED(hr)) then begin
pStreamConfig.GetFormat(pAM_Media);
pvih := pAM_Media.pbFormat ;
pAM_Media.subtype := MEDIASUBTYPE_RGB24;
pvih.bmiHeader.biWidth := 320;
pvih.bmiHeader.biHeight := 240;
pvih.AvgTimePerFrame := 10000000 div 15;
pStreamConfig.SetFormat(pAM_Media^);
DeleteMediaType(pAM_Media);
pStreamConfig := nil;
end;
end;
But the resolution stays the same when grabbing the frames through the sample grabber
Is there anything wrong with this approach?
UPDATE
Ok i think i am now updating all the members
function SetVideoProperties(pVideoCapture: IBaseFilter):Boolean;
var
hr:HRESULT;
pStreamConfig: IAMStreamConfig;
pAM_Media: PAMMediaType;
pvih: PVIDEOINFOHEADER;
pICGP2: ICaptureGraphBuilder2;
begin
pICGP2 := FilterGraph as ICaptureGraphBuilder2;
hr := pICGP2.FindInterface(#PIN_CATEGORY_CAPTURE, nil, pVideoCapture,
IID_IAMStreamConfig, pStreamConfig);
if (SUCCEEDED(hr)) then begin
pStreamConfig.GetFormat(pAM_Media);
pAM_Media.subtype := MEDIASUBTYPE_RGB24;
pAM_Media.majortype := MEDIATYPE_Video;
pAM_Media.bFixedSizeSamples := True;
pAM_Media.bTemporalCompression := False;
pAM_Media.lSampleSize := 230400;
pAM_Media.formattype := FORMAT_VideoInfo;
pAM_Media.pUnk := nil;
pAM_Media.cbFormat := 88;
pvih := pAM_Media.pbFormat;
pvih.dwBitRate := 6912000;
pvih.AvgTimePerFrame := 10000000 div 15;
pvih.bmiHeader.biSize := 40;
pvih.bmiHeader.biWidth := 320;
pvih.bmiHeader.biHeight := 240;
pvih.bmiHeader.biPlanes := 1;
pvih.bmiHeader.biBitCount := 24;
pvih.bmiHeader.biCompression := 0;
pvih.bmiHeader.biSizeImage := 230400;
pvih.bmiHeader.biXPelsPerMeter := 0;
pvih.bmiHeader.biYPelsPerMeter := 0;
pvih.bmiHeader.biClrUsed := 0;
pvih.bmiHeader.biClrImportant := 0;
hr := pStreamConfig.SetFormat(pAM_Media^);
If Succeeded(hr) then ShowMessage('SUCCEED') else ShowMessage(IntToStr(hr));
DeleteMediaType(pAM_Media);
pStreamConfig := nil;
end;
end;

Answer 1

Your initialization of new media type with new resolution is incorrect/incomplete: update other members as well
You should be checking SetFormat result to detect failures in format settings
The code itself appears to be incomplete, there is no evidence you are at all changing the format and the source filter exists and added to the filter graph

Answer 2

See DSPack demo "...\dspack2.3.4\Demos\D6-D7\videocap"
You need to enumerate all availible formats of webcam, and then set one.
Thats the code from there:
(button Start OnClick handler)
VideoMediaTypes,
AudioMediaTypes: TEnumMediaType;
.......
// 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;
Here
SetFormat(VideoMediaTypes.Items[VideoFormats.ItemIndex].AMMediaType^);
VideoMediaTypes is a list of available formats that populated when user selects the Source.
VideoFormat is GUI control (ListBox) for selecting the format