★★★★请问如何获取MPEG-2文件第一帧的图象并保存或使用.★★★★

Question

现正在编写MPEG-2素材入库程序,
不知如何获取MPEG-2文件第一帧的图象并保存或使用.
请各位大虾帮帮忙!

Answer 1

directshow 的ISampleGrabber接口GetCurrentBuffer方法捕获帧数据例子：
SampleGrabber: ISampleGrabber;procedure TMainForm.OpenFile(const FileName: string);
var
  PFileName: array [0..255] of WideChar;
  Filter: IBaseFilter;
  MediaType: TAM_MEDIA_TYPE;
begin
  CoCreateInstance(CLSID_FilterGraph, nil, CLSCTX_INPROC_SERVER,
    IID_IGraphBuilder, GraphBuilder);  CoCreateInstance(CLSID_SampleGrabber, nil, CLSCTX_INPROC_SERVER,
    IID_IBaseFilter, Filter);
  Filter.QueryInterface(IID_ISampleGrabber, SampleGrabber);
  GraphBuilder.AddFilter(Filter, 'Grabber');
  Filter:=nil;
  ZeroMemory(@MediaType, SizeOf(TAM_MEDIA_TYPE));
  MediaType.majortype:=MEDIATYPE_Video;
  MediaType.subtype:=MEDIASUBTYPE_RGB24;
  MediaType.formattype:=FORMAT_VideoInfo;
  SampleGrabber.SetMediaType(MediaType);
  SampleGrabber.SetBufferSamples(True);  StringToWideChar(FileName, PFileName, 255);
  GraphBuilder.RenderFile(PFileName, nil);  GraphBuilder.QueryInterface(IID_IVideoWindow, VideoWindow);
  VideoWindow.put_Owner(DisplayPanel.Handle);
  VideoWindow.put_WindowStyle(WS_CHILD or WS_CLIPSIBLINGS);
  VideoWindow.put_Visible(True);
  DisplayPanelResize(nil);  GraphBuilder.QueryInterface(IID_IMediaSeeking, MediaSeek);
  MediaSeek.SetTimeFormat(Time_Format_Frame);  GraphBuilder.QueryInterface(IID_IMediaControl, MediaControl);  GraphBuilder.QueryInterface(IID_IMediaEventEx, MediaEvent);
  MediaEvent.SetNotifyWindow(Handle, WM_GraphNotify, 0);
end;
procedure TMainForm.SpeedButton7Click(Sender: TObject);
var
  MediaType: TAM_MEDIA_TYPE;
  VideoInfoHeader: TVideoInfoHeader;
  BitmapInfo: TBitmapInfo;
  Bitmap: HBitmap;
  Buffer: Pointer;
  BufferSize: Integer;
begin
  SampleGrabber.GetConnectedMediaType(MediaType);  ZeroMemory(@VideoInfoHeader, SizeOf(TVideoInfoHeader));
  CopyMemory(@VideoInfoHeader, MediaType.pbFormat, SizeOf(VideoInfoHeader));  ZeroMemory(@BitmapInfo, SizeOf(TBitmapInfo));
  CopyMemory(@BitmapInfo, @VideoInfoHeader.bmiHeader, SizeOf(VideoInfoHeader.bmiHeader));  Bitmap:=CreateDIBSection(0, BitmapInfo, DIB_RGB_COLORS, Buffer, 0, 0);
  SampleGrabber.GetCurrentBuffer(BufferSize, Buffer);  Image1.Picture.Bitmap.Handle:=Bitmap
end;