（二）DirectShow接口播放Mp3音频文件

首先要声明三个接口，用于声音的播放。

如果是视频还需加上:IVideoWindow

IGraphBuilder* g_pGraphBuilder=NULL;

IMediaControl* g_pMediaControl=NULL;

IMediaPosition* g_pMediaPosition=NULL;

#define SAFE_RELEASE(p) { if(p) { (p)->Release(); (p)=NULL; } }

然后在初始化函数中，

   // 初始COM

    CoInitialize(NULL);

 

    // 创建IGraphBuilder接口对象

        CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER,  IID_IGraphBuilder, (void**)&g_pGraphBuilder);

 

    // 创建IMediaControl和IMediaPosition对象

    g_pGraphBuilder->QueryInterface(IID_IMediaControl, (void**)&g_pMediaControl);

    g_pGraphBuilder->QueryInterface(IID_IMediaPosition, (void**)&g_pMediaPosition);

 

    // 加载MP3数据

g_pGraphBuilder->RenderFile(L"Mandy.mp3", NULL);

接着在渲染函数中播放声音

    if (::GetAsyncKeyState(VK_SPACE) & 0x8000f)

        g_pMediaControl->Run();                     // 播放

    if (::GetAsyncKeyState('P') & 0x8000f)

        g_pMediaControl->Pause();                   // 暂停

    if (::GetAsyncKeyState('S') & 0x8000f)         // 停止

        g_pMediaControl->Stop(), g_pMediaPosition->put_CurrentPosition(0);

 

    if (::GetAsyncKeyState(VK_LEFT) & 0x8000f)     // 快退

    {

        REFTIME refPosition = 0.0;

        g_pMediaPosition->get_CurrentPosition(&refPosition);

        refPosition -= 1.0;

        if (refPosition <= 0.0) refPosition = 0.0;

        g_pMediaPosition->put_CurrentPosition(refPosition);

    }

    if (::GetAsyncKeyState(VK_RIGHT) & 0x8000f)    // 快进

    {

        REFTIME refPosition = 0.0;

        REFTIME refDuration = 0.0;

        g_pMediaPosition->get_CurrentPosition(&refPosition);

        g_pMediaPosition->get_Duration(&refDuration);// 总长度

        refPosition += 1.0;

        if (refPosition >= refDuration) refPosition = refDuration;

        g_pMediaPosition->put_CurrentPosition(refPosition);

    }

最后释放掉相关接口

    g_pMediaControl->Stop();

    SAFE_RELEASE(g_pGraphBuilder);

    SAFE_RELEASE(g_pMediaControl);

    SAFE_RELEASE(g_pMediaPosition);

    SAFE_RELEASE(g_pd3dDevice);

    CoUninitialize();