DirectShow播放视频流程

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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：
GraphStudio
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：
directshow框图

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:
K-Lite
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：
Hevc-VideoPlay

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：

direcshow

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
FilterInfo
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；

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//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

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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()
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    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()
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    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()，
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    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

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    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

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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
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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

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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;
	}
}