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C++:
HRESULT GetIMediaSample(IMediaSample ** pSample)
{
    *pSample = [your IMediaSample address]
    return S_OK;
}

C#:
[PreserveSig]
int GetIMediaSample(out IMediaSample pSample)

兩邊有一邊宣告錯誤就會拿到NULL

C# 中使用範例:

IMediaSample sample = null;
if (GetIMediaSample(out sample)==0)
{
    // do something with the sample you got
}

最近重灌工作機器，DirectShow SDK要重灌
由於實在不想灌多灌一個Platform SDK，選擇使用 DirectX SDK 9.0b裡面附的

由於使用VS2005，所以必需做一些修正。這邊順手把修正記錄一下

• 關於c:\program files\microsoft visual studio 8\vc\platformsdk\include\winnt.h(222) : error C2146: syntax error : missing ';' before identifier 'PVOID64' 錯誤訊息:

在 winnt.h 中加入 #define POINTER_64 __ptr64

• c:\program files\microsoft visual studio 8\vc\platformsdk\include\winnt.h(222) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int

在project setting->C++項目下的command line裡加上 /wd4430 忽略之

• 修正Count及iDone兩個變數找不到的問題(重新宣告即可)

以上修正完應可順利使用 VS2005 來編譯 BaseClasses

補充，DXSDK9裡附的filter的sample在編譯時需在 library 中增加 strmiids.lib 方可順利編譯

一般DirectShow Graph在運行的時候，會選定一個reference clock做為撥放的基準(一般會在render上)。但是同時要轉檔(transcoding)以及預覽(preview)轉換後的結果時，會變成transcoding的速度會被render限制住，這時候就需要把reference clock取消，讓transcoding全速執行。

// C# IMediaFilter  mf = (IMediaFilter)gb; // use IMediaFilter::SetSyncSource // to remove reference clock mf.SetSyncSource(null);

In Visual Studio

• [F5] (Start Debug)
• Choose excutable: graphedit.exe
• Generate your filter in graphedit, and do something.
• Debug ....:P

今天請了 leader 來幫忙看，算是解決了
不是我的 filter 有問題，是Windows內建的某 filter 有問題 ORZ
接上那個問題 filter ，接在它後面的 filter 完全收不到訊號

不過後來發現那邊比較像是接錯了，手動換成正確的 filter 就沒問題了

If the pin is connected, this method copies the media type into the AM_MEDIA_TYPE structure specified by pmt. The caller must free the media type's format block. You can use the MicrosoftR Win32R CoTaskMemFree function, or the FreeMediaType helper function.

If the pin is not connected, this method clears the media type specified by pmt and returns an error code.

• DirectShow filter is a win32 DLL.
• Use regsvr32.exe to register filter, then u can find it in GraphEdit.
• For building a DirectShow filter

1. First, build base classes of DirectShow in the "DXSDK/Sample/DirectShow/BaseClasses".
2. Include <streams.h> in BaseClasses dir.
3. Use __stdcall in "calling convention" of VC++ project setting.
4. Use multithread rulltime library.
5. Add a xxx.def file into your project dir. The fomat should like below:

   LIBRARY xxx.ax EXPORTS DllMain PRIVATE DllGetClassObject PRIVATE DllCanUnloadNow PRIVATE DllRegisterServer PRIVATE DllUnregisterServer PRIVATE

6. Link these libraries to project.
   

   Debug: Strmbasd.lib, Msvcrtd.lib, Winmm.lib Release: Strmbas.lib, Msvcrtd.lib, Winmm.lib

7. Choose "ignore default library" in linker options of project setting.
8. Declear a DLL Entry as follow

   extern "C" BOOL WINAPI DllEntryPoint(HINSTANCE, ULONG, LPVOID); BOOL APIENTRY DllMain(HANDLE hModule, DWORD dwReason, LPVOID lpReserved) { return DllEntryPoint((HINSTANCE)(hModule), dwReason, lpReserved); }

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