amcap sample code 分析初步 --学习通用filter graph的构建技术
学习通用filter graph的构建技术
1 构造filter
我们现在要向Filter Graph中加入一个AVI Mux Filter代码如
IBaseFilter *pMux;
hr=AddFilterByCLSXD(pGraph, CLSID_Avidest, L"AVI Mux", ipMux);
if {SUCCEEDED(hr))
/* …•/
pMux->Release{);
}
并不是所有的Filter都能通过CoCreatcInstance函數来创建，大部分注册在Audio Canpressore 目录下的 Filter (它们使用 了CLSID__ACMWrapper包装 Filter).
大部分注册在 Video Compressors 下的 Filter (它们用 CLSID_AV1Co包装Filter), 以及代表硬件（WDM或VFW)的包裝Filter,必须通过枚举的方式来创建.
构造filter情景分析
看看代码里，搜索所有的CoCreateInstance，在amcap.cpp里，有一处知道，其他待续
amcap.cpp(893): HRESULT hr = CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC, amcap.cpp(2802): hr = CoCreateInstance(CLSID_SystemDeviceEnum, NULL, CLSCTX_INPROC_SERVER, amcap.cpp(3907): hr = CoCreateInstance((REFCLSID)CLSID_CaptureGraphBuilder2,
todo:关于使用枚举的类型
后续补充
2 得到filter未连接pin
代码里暂时没使用，略过
2.5 【重要】补充filter的基础知识
补充一个陆其明推荐的 mpeg合成的filter设计
这里先不上图，直接一句话。
Video stream --> mpeg video encoder --> mpeg mux filter (合成)--> file writer
音频前两个是独立的，后续合并到mux
3 连接两个filter
关键词 addfilter
首先看搜索结果,没有使用书上addfilterbyclsid,基本都是封装的addfilter
关注前面搜索结果
| amcap.cpp(1104): hr = gcap.pFg->AddFilter(gcap.pVCap, gcap.wachFriendlyName); amcap.cpp(1294): hr = gcap.pFg->AddFilter(gcap.pACap, wachAudioFriendlyName); SampleCGB.cpp(335): hr = graph_->AddFilter( pMPEG2Demux_, L"Dump" ); SampleCGB.cpp(640): return graph_->AddFilter( static_cast<IBaseFilter *>( pMPEG2Demux_ ),L"MPEG2 Demux" ); SampleCGB.cpp(846): hr = graph_->AddFilter( pFilter, L"Encoder" ); SampleCGB.cpp(901): hr = graph_->AddFilter( pEncoder, L"Encoder" ); SampleCGB.cpp(1112): hr = graph_->AddFilter( pFilter, NULL ); SampleCGB.cpp(1255): hr = graph_->AddFilter( pEncoder, L"Audio Encoder" ); SampleCGB.cpp(1276): hr = graph_->AddFilter( pEncoder, L"Audio Encoder" ); SampleCGB.cpp(1311): hr = graph_->AddFilter( pFilter, L"Audio Encoder" ); SampleCGB.cpp(1393): hr = graph_->AddFilter( pVMR, L"VMR" ); SampleCGB.cpp(1500): hr = graph_->AddFilter( pAudioRenderer, L"Audio renderer" );
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以下为例，有个问题，就是第二个参数，待分解。
| // Add the video capture filter to the graph with its friendly name hr = gcap.pFg->AddFilter(gcap.pVCap,gcap.wachFriendlyName); if(hr != NOERROR) { ErrMsg(TEXT("Error %x: Cannot add vidcap to filtergraph"), hr); goto InitCapFiltersFail; } |
分析connectfilter
再次分析connectfilter,搜索代码，只有samplergb.cpp有，主程序没有
结果是
| SampleCGB.h(190): HRESULT ConnectFilters(CComPtr<IBaseFilter> pUpFilter, SampleCGB.cpp(1018): HRESULT hr = ConnectFilters( SampleCGB.cpp(1121): hr = ConnectFilters( pEncoder, pFilter ); SampleCGB.cpp(1131): hr = ConnectFilters( pFilter, pMPEG2Demux_ ); SampleCGB.cpp(1258): SUCCEEDED( ConnectFilters( pEncoder, pMultiplexer ) ) SampleCGB.cpp(1279): SUCCEEDED( ConnectFilters( pEncoder, pMultiplexer ) ) SampleCGB.cpp(1324): hr = ConnectFilters( pFilter, pMultiplexer );
|
分析是
| SampleCGB.h(190): HRESULT ConnectFilters(CComPtr<IBaseFilter> pUpFilter, SampleCGB.cpp(1018): HRESULT hr = ConnectFilters( pEncoder，pMPEG2Demux_ //try adirectconnection between codec and MPEG2Demux //意图尝试，函数位置同下，如果不成功，就分别连接。 SampleCGB.cpp(1121): hr = ConnectFilters( pEncoder, pFilter ); //在ISampleCaptureGraphBuilder::ConnectMultiplexerToMPEG2Demux( SampleCGB.cpp(1131): hr = ConnectFilters( pFilter, pMPEG2Demux_ ); //在ISampleCaptureGraphBuilder::ConnectMultiplexerToMPEG2Demux(
SampleCGB.cpp(1258): SUCCEEDED( ConnectFilters( pEncoder, pMultiplexer ) ) SampleCGB.cpp(1279): SUCCEEDED( ConnectFilters( pEncoder, pMultiplexer ) ) SampleCGB.cpp(1324): hr = ConnectFilters( pFilter, pMultiplexer ); |
小结
回到基础上，
Video stream -->mpeg video encoder --> mpeg mux filter (合成)--> file writer
当前只看到encoder和mux的连接，其他写文件等filter connect 后续待发现。
4 【大量需要分析，未完成】寻找接口初步QueryInterface
以queryInterface为关键词，看到大量使用的地方，一句话来说，这是一个使用频率很高的api,必须要懂。
| amcap.cpp(146): STDMETHODIMP QueryInterface(REFIID iid, void **p) amcap.cpp(804): if(S_OK == punk->QueryInterface(IID_IBaseFilter, (void **) &pf)) amcap.cpp(1204): if(pP->QueryInterface(IID_IKsPropertySet, amcap.cpp(1441): hr = gcap.pRender->QueryInterface(IID_IConfigAviMux, (void **)&gcap.pConfigAviMux); amcap.cpp(1514): gcap.pSink->QueryInterface( IID_IBaseFilter, reinterpret_cast<void **>( &sink ) ); amcap.cpp(1575): hr = gcap.pFg->QueryInterface(IID_IVideoWindow, (void **)&gcap.pVW); amcap.cpp(1625): hr = gcap.pFg->QueryInterface(IID_IMediaEventEx, (void **)&gcap.pME); amcap.cpp(1771): hr = gcap.pFg->QueryInterface(IID_IVideoWindow, (void **)&gcap.pVW); amcap.cpp(1844): hr = gcap.pFg->QueryInterface(IID_IMediaEventEx, (void **)&gcap.pME); amcap.cpp(1883): HRESULT hr = gcap.pFg->QueryInterface(IID_IMediaControl, (void **)&pMC); amcap.cpp(1917): HRESULT hr = gcap.pFg->QueryInterface(IID_IMediaControl, (void **)&pMC); amcap.cpp(1976): hr = gcap.pFg->QueryInterface(IID_IMediaControl, (void **)&pMC); //以上分别有start stop catpute等
//void MakeMenuOptions()以下 amcap.cpp(2081): HRESULT hr = gcap.pFg->QueryInterface(IID_IMediaControl, (void **)&pMC); amcap.cpp(2228): hr = gcap.pACap->QueryInterface(IID_ISpecifyPropertyPages, (void **)&pSpec); amcap.cpp(2262): hr = gcap.pVCap->QueryInterface(IID_ISpecifyPropertyPages, (void **)&pSpec); amcap.cpp(2289): hr = pSC->QueryInterface(IID_ISpecifyPropertyPages, (void **)&pSpec); amcap.cpp(2319): hr = pSC->QueryInterface(IID_ISpecifyPropertyPages, (void **)&pSpec); amcap.cpp(2349): hr = pX->QueryInterface(IID_IBaseFilter, (void **)&pXF); amcap.cpp(2352): hr = pX->QueryInterface(IID_ISpecifyPropertyPages, (void **)&pSpec); amcap.cpp(2370): hr = pX2->QueryInterface(IID_ISpecifyPropertyPages, (void **)&pSpec); amcap.cpp(2402): hr = pTV->QueryInterface(IID_ISpecifyPropertyPages, (void **)&pSpec); amcap.cpp(2430): hr = pSC->QueryInterface(IID_ISpecifyPropertyPages, (void **)&pSpec); amcap.cpp(2453): hr = pTVA->QueryInterface(IID_ISpecifyPropertyPages, (void **)&pSpec);
//以下： //AppCommand()Process all of our WM_COMMAND messages. amcap.cpp(3346): hr = gcap.pVCap->QueryInterface(IID_ISpecifyPropertyPages, amcap.cpp(3396): hr = pSC->QueryInterface(IID_ISpecifyPropertyPages, amcap.cpp(3472): hr = pSC->QueryInterface(IID_ISpecifyPropertyPages, amcap.cpp(3508): hr = pX->QueryInterface(IID_ISpecifyPropertyPages, amcap.cpp(3537): hr = pTV->QueryInterface(IID_ISpecifyPropertyPages, amcap.cpp(3557): hr = gcap.pACap->QueryInterface(IID_ISpecifyPropertyPages, amcap.cpp(3586): hr = pSC->QueryInterface(IID_ISpecifyPropertyPages, amcap.cpp(3618): hr = pX->QueryInterface(IID_IBaseFilter, (void **)&pXF); amcap.cpp(3626): hr = pX2->QueryInterface(IID_ISpecifyPropertyPages, amcap.cpp(3653): hr = pTVA->QueryInterface(IID_ISpecifyPropertyPages,
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关键词 findFilter
寻找FindPin为关键词,增加findfilter
本质上，是使用queryInterface函数寻找
结果很多，尤其在amcap函数中，
以关键词FindPin搜索，结果如下，画出重点分析区域
| AMCap\SampleCGB.h(96): STDMETHOD(FindPin)( IUnknown *pSource, AMCap\SampleCGB.h(136): HRESULT FindPin( AMCap\amcap.cpp(1320): hr = gcap.pBuilder->FindPin(gcap.pVCap, PINDIR_OUTPUT, &PIN_CATEGORY_VBI, AMCap\amcap.cpp(1323): hr = gcap.pBuilder->FindPin(gcap.pVCap, PINDIR_OUTPUT, &PIN_CATEGORY_CC, AMCap\SampleCGB.cpp(199):ISampleCaptureGraphBuilder::FindPin( IUnknown *pSource, AMCap\SampleCGB.cpp(207): return graphBuilder2_->FindPin( pSource, pindir, pCategory, pType, AMCap\SampleCGB.cpp(508):HRESULT ISampleCaptureGraphBuilder::FindPin( AMCap\SampleCGB.cpp(804): hr = FindPin( pFilter, pinMedium, PINDIR_INPUT, TRUE, pPin ); AMCap\SampleCGB.cpp(1419): hr = graphBuilder2_->FindPin( AMCap\SampleCGB.cpp(1507): hr = graphBuilder2_->FindPin(
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当前分析以上findpin，发现主要集中在寻找pin，执行关闭操作
// create the capture filters of the graph. We need to keep them loaded from
// the beginning, so we can set parameters on them and have them remembered
//
BOOL InitCapFilters()
{
//********//
SkipAudio:
// Can this filter do closed captioning?
IPin *pPin;
hr = gcap.pBuilder->FindPin(gcap.pVCap, PINDIR_OUTPUT, &PIN_CATEGORY_VBI,
NULL, FALSE, 0, &pPin);//------------------请关注此
if(hr != S_OK)
hr = gcap.pBuilder->FindPin(gcap.pVCap, PINDIR_OUTPUT, &PIN_CATEGORY_CC,
NULL, FALSE, 0, &pPin);
if(hr == S_OK)
{
pPin->Release();
gcap.fCCAvail = TRUE;
}
else
{
gcap.fCapCC = FALSE; // can't capture it, then
}
方法小结：
以上都是以局部api来看使用，这样脱离功能的学习，有点片面。
最好从功能角度上出发.下一步结合amcap的变更出发