在DirectX的Bin目录下有一个很好的工具-GraphEdit，通过这个工具能够很好的反映音频录制的过程。可以总结一点,DirectShow音频的录制过程就是，枚举、绑定、连接这三个步骤。接下来看看这三个步骤是如何实现的呢？
在此之前，先来介绍下几个涉及到的COM对象。
ICaptureGraphBuilder2
IBaseFilter
The IBaseFilter interface is the primary interface for DirectShow filters. All DirectShow filters must expose this interface. The Filter Graph Manager uses this interface to control filters. Applications can use this interface to enumerate pins and query for filter information, but should not use it to change the state of a filter. Instead, use the IMediaControl interface on the Filter Graph Manager.
Filter developers: Implement this interface on every DirectShow filter. The CBaseFilter base class implements this interface.
The ICaptureGraphBuilder2 interface builds capture graphs and other custom filter graphs. The Capture Graph Builder object implements this interface.
在这里主要用于获取捕获链表的管理接口，通过这个接口可以对创建的IGraphBuilder进行绑定和管理。
IGraphBuilder
The IGraphBuilder interface allows applications to call upon the filter graph manager to attempt to build a complete filter graph, or parts of a filter graph given only partial information, such as the name of a file or the interfaces of two separate pins. The filter mapper looks up filters in the registry to configure the filter graph in a meaningful way.
IGraphBuilder inherits from the IFilterGraph interface and exposes all its methods. For this reason, IFilterGraph should normally not be used directly.
通常可以通过IGraphBuilder这个COM对象，我们获取滤波器链表接口，对构建的Graph进行管理。
IMediaControl
The IMediaControl interface provides methods for controlling the flow of data through the filter graph. It includes methods for running, pausing, and stopping the graph. The Filter Graph Manager implements this interface. For more information on filter graph states, see Data Flow in the Filter Graph.
IMoniker
Enables you to use a moniker object, which contains information that uniquely identifies a COM object. An object that has a pointer to the moniker object's IMoniker interface can locate, activate, and get access to the identified object without having any other specific information on where the object is actually located in a distributed system.
Monikers are used as the basis for linking in COM. A linked object contains a moniker that identifies its source. When the user activates the linked object to edit it, the moniker is bound; this loads the link source into memory.
接下来看看实现代码，其中有相关的注释，清晰明了。
// 获取捕获链表管理器接口 CoCreateInstance(CLSID_CaptureGraphBuilder2,NULL, CLSCTX_INPROC_SERVER, IID_ICaptureGraphBuilder2, (void**)&pBuilder); // 获取滤波器借口 CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER, IID_IGraphBuilder, (void **)&pGraph); // 将获取到的滤波器接口帮定到链表管理器接口上 pBuilder->SetFiltergraph(pGraph); // 查询煤体控制接口 pGraph->QueryInterface(IID_IMediaControl,(void**)&pMC); ICreateDevEnum *pDevEnum = NULL; // 创建设备枚举接口 CoCreateInstance(CLSID_SystemDeviceEnum, NULL, CLSCTX_INPROC, IID_ICreateDevEnum, (void **)&pDevEnum); IEnumMoniker *pClassEnum = NULL; // 创建音频设备输入接口 pDevEnum->CreateClassEnumerator(CLSID_AudioInputDeviceCategory, &pClassEnum, 0); ULONG cFetched; if (pClassEnum->Next(1, &pMoniker, &cFetched) == S_OK) { // 绑定到基类滤波器，以作为捕获滤波器 pMoniker->BindToObject(0, 0, IID_IBaseFilter, (void**)&pSrc); pMoniker->Release(); } pClassEnum->Release(); // 创建CLSID_WavDest CoCreateInstance(CLSID_WavDest, NULL, CLSCTX_ALL, IID_IBaseFilter, (void **)&pWaveDest); // 创建CLSID_FileWriter CoCreateInstance(CLSID_FileWriter, NULL, CLSCTX_ALL, IID_IBaseFilter, (void **)&pWriter); // 添加滤波器 pGraph->AddFilter(pSrc,L"Wav"); pGraph->AddFilter(pWaveDest,L"WavDest"); pGraph->AddFilter(pWriter,L"FileWriter"); // 枚举查询文件设置接口 pWriter->QueryInterface(IID_IFileSinkFilter2,(void**)&pSink); pSink->SetFileName(strName.AllocSysString(),NULL); IPin* pOutpin = FindPin(pSrc,PINDIR_OUTPUT); IPin* pInpin,*pOut; pOut= FindPin(pWaveDest,PINDIR_OUTPUT); AM_MEDIA_TYPE type; type.majortype = MEDIATYPE_Stream; type.subtype =MEDIASUBTYPE_WAVE; type.formattype = FORMAT_None; type.bFixedSizeSamples = FALSE; type.bTemporalCompression = FALSE; type.pUnk = NULL; //查找滤波器引脚 pInpin = FindPin(pWaveDest,PINDIR_INPUT); IPin* pInpin2= FindPin(pWriter,PINDIR_INPUT); //连接滤波器的引脚 pGraph->ConnectDirect(pOutpin,pInpin,NULL); pGraph->ConnectDirect(pOut,pInpin2,NULL); pMC->Run();
