TForm1 = class(TForm, ISampleGrabberCB)

{ 从回调中获取图像,应尽快处理,否则会影响 DirectShow 返回数据,此处代码应进行优化处理 }
function TForm1.SampleCB(SampleTime: Double; pSample: IMediaSample): HResult;
var
  BufferLen: Integer;
  ppBuffer : PByte;
  btTime   : Double;
begin
  Result := S_OK;
 
  BufferLen := pSample.GetSize;
  if BufferLen <= 0 then
    Exit;
 
  { 计算帧率 }
  Inc(FintCount);
  if FbakSampleTime = 0 then
  begin
    FbakSampleTime := SampleTime;
  end
  else
  begin
    btTime  := SampleTime - FbakSampleTime;
    Caption := Format('%d f/s', [Round(FintCount / btTime)]);
  end;
 
  { 获取图像 }
  pSample.GetPointer(ppBuffer);
  case FourCC of
    FourCC_YUY2, FourCC_YUYV, FourCC_YUNV: { YUV 数据格式 }
      begin
        YUY2_to_RGB(FBMP, ppBuffer);
        img1.Picture.Bitmap.Assign(FBMP);
      end;
    FourCC_MJPG: { JPEG 数据格式 }
      begin
        FMemStream.Clear;
        FMemStream.SetSize(BufferLen);
        FMemStream.Position := 0;
        FMemStream.WriteBuffer(ppBuffer^, BufferLen);
        FMemStream.Position := 0;
 
        if GDIPlusAvailable then
        begin
          GDIPlus_LoadBMPStream2(FMemStream, FBMP);
          img1.Picture.Bitmap.Assign(FBMP);
        end
        else
        begin
          FJPG.Grayscale := False;
          FJPG.LoadFromStream(FMemStream);
          FBMP.Width  := FJPG.Width;
          FBMP.Height := FJPG.Height;
          FBMP.Canvas.Draw(0, 0, FJPG);
          img1.Picture.Bitmap.Assign(FBMP);
        end;
      end;
  end;
end;