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DirectShow框架简介
DirectShow框架是多媒体播放框架上一个非常经典的框架，现在已经十多年了，在Windows平台上依然无法替代，非常值得去学习研究。个人觉得从设计模式的角度上看，directshow框架的灵活性、复用性、可维护性、可拓展性这些方面做得非常不错，也是它经久不衰历久弥新的一个原因，现在的很多第三方的decoder和filter都基于directshow框架开发，可以很灵活的移植到directshow视频框架中，例如视骏开发的HEVC/H.265解码器，都可以直接挂载在directshow框架中进行视频解码。
图形化理解DirectShow
推荐一款工具GraphStudio,了解DirectShow框架必备工具，软件截图如下：
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我们点击Graph可以插入我们在电脑系统中注册的Filter Render，默认情况下，我们将播放的视频加到GraphStudio中，会自动生成directshow的整个播放流程,然后就可以播放视频了。一般的播放效果流程如下：
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GraphStudio会自动采用系统默认的一套Filter和Render,如果安装了K-Lite Codec Pack，就可以修改系统默认的这一套，如下图:
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我们想测试我们自己的Filter和Render，都可以自定义插入，下面就以DirectShow中植入视骏的HEVC解码器为例子，了解DirecShow的整个播放流程，如下图所示：
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DirectShow播放HEVC视频
可以参考雷老师关于DirectShow的介绍，
地址：http://blog.csdn.net/leixiaohua1020/article/details/42372419
播放的流程如下：
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整个播放我们可以抽象出三个步骤：
- 注册：播放HEVC视频需要的
Strongene Mpeg-4 Demultiplexor,Lentoid HEVC Decoder,Video Renderer - 链接：相当于上面
GraphStudio图中的链接箭头 - 播放：将视频导入播放链路中，开始播放
注册Filter和Render
解码器属性
首先获取到这些Filter的Object name、CLSID、Filename和FilePath
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如果已经将filter注册进Windows的系统中,就只需要用到Object Name,为了避免重新注册导致冲突；
//Name:File Source (Async.) {E436EBB5-524F-11CE-9F53-0020AF0BA770}
/**
Windows自带File Source (Async.)，dll路径：C:\Windows\SysWOW64\quartz.dll
CLSID =
*/
//MP4 Splitter {61F47056-E400-43D3-AF1E-AB7DFFD4C4AD} Name: Strongene Mpeg-4 Demultiplexor
static const GUID CLSID_MP4Splitter = {0x61f47056,0xe400,0x43d3,{0xaf,0x1e,0xab,0x7d,0xff,0xd4,0xc4,0xad}};
//h265-HEVC Decoder {658C5E1C-58E1-43CA-9D10-13735D465576} Name:Lentoid HEVC Decoder
static const GUID CLSID_HEVCDecoder = {0x658C5E1C,0x58E1,0x43CA,{0x9D,0x10,0x13,0x73,0x5D,0x46,0x55,0x76}};
//Name:Video Mixing Renderer {B87BEB7B-8D29-423F-AE4D-6582C10175AC}
/**
Windows自带VideoRenderer，dll路径：C:\Windows\SysWOW64\quartz.dll
*/
声明DirectShow播放需要的类和变量
IGraphBuilder * mGraph;//创建一个Filter Graph Manager组件
IMediaControl * mMediaControl;//提供控制过滤器图表中多媒体数据流的方法，包括运行、暂停和停止
IMediaEventEx * mEvent;//继承自IMediaEvent接口，处理过滤器图表的事件
IBasicVideo * mBasicVideo;//用于设置视频特性，如视频显示的目的区域和源区域
IBasicAudio * mBasicAudio;//用于控制音频流的音量和平衡
IVideoWindow * mVideoWindow;//定义一个视频窗口的控制对象
IMediaSeeking * mSeeking;//提供搜索数据流位置和设置播放速率的方法
IBaseFilter *m_pSourceFilter = NULL;
IBaseFilter *m_pSplitter = NULL;
IBaseFilter *m_pSplitter = NULL;
IBaseFilter *m_pVideoHEVCDecoder = NULL;
IBaseFilter *m_pVideoRender = NULL;
DWORD mObjectTableEntry = 0;
注册Filter：
- 加载解码器并获取DllGetClassObject指针,loadFilter()
bool loadFilter(LPCSTR chAx)
{
//加载Filter所在的dll文件
m_hInst = ::LoadLibrary(chAx);
if (NULL == m_hInst)
{
return false;
}
//获取DllGetClassObject函数指针
m_pDllGetClassObject = ( DLL_GET_CLASS_OBJECT )::GetProcAddress(m_hInst, "DllGetClassObject");
if (NULL == m_pDllGetClassObject)
{
return false;
}
return true;
}
- 动态创建解码器对象,createFilter()
bool createFilter(GUID clId, IBaseFilter** pBaseFilter)
{
if (NULL == m_pDllGetClassObject)
{
return false;
}
//获取类工厂接口
IClassFactory *p_IClassFactory = NULL;
if (FAILED( m_pDllGetClassObject(clId, IID_IClassFactory, (void **)&p_IClassFactory) ))
{
return false;
}
//创建与类厂相关联的COM对象（Filter），并获取其IBaseFilter接口
p_IClassFactory->CreateInstance(NULL, IID_IBaseFilter, (void **)pBaseFilter);
p_IClassFactory->Release();
p_IClassFactory = NULL;
if ((NULL == pBaseFilter) || (NULL == *pBaseFilter))
{
return false;
}
return true;
}
- 申明一个方法函数InitRegister()，
bool InitRegister()
{
mGraph=NULL;
mMediaControl=NULL;
mEvent=NULL;
mBasicVideo=NULL;
mBasicAudio=NULL;
mVideoWindow=NULL;
mSeeking=NULL;
if(!mGraph)
{
//建立 filter graph manager
HRESULT hr = CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER,IID_IGraphBuilder, (void **)&mGraph);
if(mGraph != NULL)
{
LPCSTR splitterDll, HEVCDecoderDll;
LPCWSTR splitterName, HEVCDecoderName;
GUID splitterGuid, HEVCDecoderGuid;
//Source Filter
hr = CoCreateInstance(CLSID_AsyncReader, NULL, CLSCTX_INPROC,IID_IBaseFilter, (void **)&m_pSourceFilter);
if(hr == S_OK)
{
mGraph->AddFilter(m_pSourceFilter, L"File Source Filter");
}
else
{
cout << "load source filter failed" << endl;
return false;
}
//Splitter
splitterDll = ".\\Codec\\mp4demux.dll";
splitterName = L"Strongene Mpeg-4 Demultiplexor";
splitterGuid = CLSID_SMp4Demultiplexor;
//HEVCDecoder
HEVCDecoderDll = ".\\Codec\\hevcdecfltr.dll";
HEVCDecoderName = L"Lentoid HEVC Decoder";
HEVCDecoderGuid = CLSID_HEVCDecoder;
//Splitter
if (loadFilter(splitterDll))
{
if (createFilter(splitterGuid, &m_pSplitter))
{
mGraph->AddFilter(m_pSplitter, splitterName);
}
else
{
cout << "add spliter failed" << endl;
return false;
}
}
else
{
cout << "load splitter faild" << endl;
return false;
}
//HEVC Decoder
if (loadFilter(HEVCDecoderDll))
{
if (createFilter(HEVCDecoderGuid, &m_pVideoHEVCDecoder))
{
mGraph->AddFilter(m_pVideoHEVCDecoder, HEVCDecoderName);
}
else
{
cout << "add decoder failed" << endl
return false;
}
}
else
{
cout << "load decoder failed!" << endl;
return false;
}
//Video Renderer
hr = CoCreateInstance(CLSID_VideoMixingRenderer9, NULL, CLSCTX_INPROC,
IID_IBaseFilter, (void **)&m_pVideoRender);
if(hr == S_OK)
{
mGraph->AddFilter(m_pVideoRender, L"Video Mixing Renderer 9");
}
else
{
cout << "load video renderer failed" << endl;
return false;
}
}
}
}
链接Filter和Renderer
- 查找空闲的filter的接口
HRESULT GetUnconnectedPin( IBaseFilter *pFilter, PIN_DIRECTION PinDir, IPin **ppPin, int iNum )
{
*ppPin = NULL;
IEnumPins* pEnum = NULL;
IPin* pPin = NULL;
int nIndex = 0;
HRESULT hr = pFilter->EnumPins(&pEnum);
if (FAILED(hr))
{
return hr;
}
while(pEnum->Next(1, &pPin, NULL) == S_OK)
{
PIN_DIRECTION ThisPinDir;
pPin->QueryDirection(&ThisPinDir);
if (ThisPinDir == PinDir) //如果out/in类型符合
{
nIndex ++;
IPin *pTmp = NULL;
hr = pPin->ConnectedTo(&pTmp); //如果已经被连接
if (SUCCEEDED(hr))
{
pTmp->Release();
}
else
{
if(nIndex == iNum) //若端口号与传入端口号同
{
pEnum->Release();
*ppPin = pPin;
pPin->Release();
return S_OK;
}
}
}
pPin->Release();
}
pEnum->Release();
cout << "GetUnconnectedPin ----> Next is null" << endl;
return false;
}
- 查找空闲的splitter的空闲指针接口
HRESULT GetUnconnectedMajortypePin( IBaseFilter *pFilter, PIN_DIRECTION PinDir, IPin **ppPin, GUID myMajortype)
{
*ppPin = NULL;
IEnumPins* pEnum = NULL;
IPin* pPin = NULL;
int nIndex = 0;
IEnumMediaTypes *pType;
AM_MEDIA_TYPE *pMType;
HRESULT hr = pFilter->EnumPins(&pEnum);
if (FAILED(hr))
{
return hr;
}
while(pEnum->Next(1, &pPin, NULL) == S_OK)
{
PIN_DIRECTION ThisPinDir;
pPin->QueryDirection(&ThisPinDir);
if (ThisPinDir == PinDir) //如果out/in类型符合
{
nIndex ++;
IPin *pTmp = NULL;
hr = pPin->ConnectedTo(&pTmp);
if (SUCCEEDED(hr)) //如果已经被连接
{
pTmp->Release();
}
else
{
pPin->EnumMediaTypes(&pType);
pType->Next(1, &pMType, 0);
if(myMajortype == pMType->majortype) //类型匹配
{
pEnum->Release();
pType->Release();
*ppPin = pPin;
pPin->Release();
return S_OK;
}
pType->Release();
}
}
pPin->Release();
}
pEnum->Release();
cout << "GetUnconnectedMajortypePin failed" << endl;
return false;
}
- DirectShow提供自动搜寻Filter，我们只需要将他们链接起来
bool LinkFilter()
{
//定义pin对象
IPin *ppinOut = NULL;
IPin *ppinIn = NULL;
IPin* Pin;
//sourceOut -> Splitter
if(m_pSourceFilter != NULL && m_pSplitter != NULL)
{
hr = GetUnconnectedPin(m_pSourceFilter, PINDIR_OUTPUT, &Pin, 1); //查找Filter空闲的pin
if (SUCCEEDED(hr))
{
ppinOut = Pin;
}
hr = GetUnconnectedPin(m_pSplitter, PINDIR_INPUT, &Pin, 1);
if (SUCCEEDED(hr))
{
ppinIn = Pin;
}
if (FAILED(mGraph->Connect(ppinOut, ppinIn)))
{
cout << "link source filter and spliter failed!" <<endl;
return false;
}
}
//Spliter -> hevcdecoder//解码HEVC
if (m_pSplitter != NULL && m_pVideoHEVCDecoder != NULL)
{
hr = GetUnconnectedMajortypePin(m_pSplitter, PINDIR_OUTPUT, &Pin, MEDIATYPE_Video);//查找splitter空闲的video outpin
if (SUCCEEDED(hr))
{
ppinOut = Pin;
}
hr = GetUnconnectedPin(m_pVideoHEVCDecoder, PINDIR_INPUT, &Pin, 1);
if (SUCCEEDED(hr))
{
ppinIn = Pin;
}
if (FAILED(mGraph->Connect(ppinOut, ppinIn)))
{
return false;
cout << "link splitter and decoder failed!" << endl;
}
}
//hevcdecoder -> videorender
if (m_pVideoDecoder != NULL && m_pVideoRender != NULL)
{
hr = GetUnconnectedPin(m_pVideoHEVCDecoder, PINDIR_OUTPUT, &Pin, 1); //查找Filter空闲的pin
if (SUCCEEDED(hr))
{
ppinOut = Pin;
}
hr = GetUnconnectedPin(m_pVideoRender, PINDIR_INPUT, &Pin, 1);
if (SUCCEEDED(hr))
{
ppinIn = Pin;
}
if (FAILED(mGraph->Connect(ppinOut, ppinIn)))
{
return false;
cout<<"link decoder and video renderer failed!"<<endl;
}
}
return true;
}
播放HEVC视频
bool RenderFile(const *char MediaUri)
{
if (mGraph)
{
HRESULT hr;
WCHAR szFilePath[MAX_PATH];
//该函数映射一个字符串到一个宽字符的字符串
MultiByteToWideChar(CP_ACP, 0, MediaUri, -1, szFilePath, MAX_PATH);
//source filter与视频文件关联
IFileSourceFilter* pFSFilter = NULL;
//pFSFilter仅需要局部变量，用完释放
m_pSourceFilter->QueryInterface(&pFSFilter);
pFSFilter->Load(szFilePath, NULL); //FilePath;
pFSFilter->Release();
pFSFilter = NULL;
if(!LinkFilter())
{
cout << "link filter failed" << endl;
}
}
else
{
cout << "render file failded" << endl;
return false;
}
}
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