LAV Filter 源代码分析 2： LAV Splitter

LAV Filter 中最著名的就是 LAV Splitter，支持Matroska /WebM，MPEG-TS/PS，MP4/MOV，FLV，OGM / OGG，AVI等其他格式，广泛存在于各种视频播放器（暴风影音这类的）之中。

本文分析一下它的源代码。在分析之前，先看看它是什么样的。

使用GraphEdit随便打开一个视频文件，就可以看见LAV Filter：

可以右键点击这个Filter看一下它的属性页面，如图所示：

属性设置页面：

支持输入格式：

下面我们在 VC 2010 中看一下它的源代码：

从何看起呢？就先从directshow的注册函数看起吧，位于dllmain.cpp之中。部分代码的含义已经用注释标注上了。从代码可以看出，和普通的DirectShow Filter没什么区别。

dllmain.cpp

/* *      Copyright (C) 2010-2013 Hendrik Leppkes *      http://www.1f0.de * *  This program is free software; you can redistribute it and/or modify *  it under the terms of the GNU General Public License as published by *  the Free Software Foundation; either version 2 of the License, or *  (at your option) any later version. * *  This program is distributed in the hope that it will be useful, *  but WITHOUT ANY WARRANTY; without even the implied warranty of *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the *  GNU General Public License for more details. * *  You should have received a copy of the GNU General Public License along *  with this program; if not, write to the Free Software Foundation, Inc., *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. */// Based on the SampleParser Template by GDCL// --------------------------------------------------------------------------------// Copyright (c) GDCL 2004. All Rights Reserved. // You are free to re-use this as the basis for your own filter development,// provided you retain this copyright notice in the source.// http://www.gdcl.co.uk// --------------------------------------------------------------------------------//各种定义。。。#include "stdafx.h"// Initialize the GUIDs#include <InitGuid.h>#include <qnetwork.h>#include "LAVSplitter.h"#include "moreuuids.h"#include "registry.h"#include "IGraphRebuildDelegate.h"// The GUID we use to register the splitter media typesDEFINE_GUID(MEDIATYPE_LAVSplitter,  0x9c53931c, 0x7d5a, 0x4a75, 0xb2, 0x6f, 0x4e, 0x51, 0x65, 0x4d, 0xb2, 0xc0);// --- COM factory table and registration code --------------//注册时候的信息const AMOVIESETUP_MEDIATYPE   sudMediaTypes[] = {    { &MEDIATYPE_Stream, &MEDIASUBTYPE_NULL },};//注册时候的信息（PIN）const AMOVIESETUP_PIN sudOutputPins[] = {  {    L"Output",            // pin name      FALSE,              // is rendered?          TRUE,               // is output?      FALSE,              // zero instances allowed?      TRUE,               // many instances allowed?      &CLSID_NULL,        // connects to filter (for bridge pins)      NULL,               // connects to pin (for bridge pins)      0,                  // count of registered media types      NULL                // list of registered media types  },  {    L"Input",             // pin name      FALSE,              // is rendered?          FALSE,              // is output?      FALSE,              // zero instances allowed?      FALSE,              // many instances allowed?      &CLSID_NULL,        // connects to filter (for bridge pins)      NULL,               // connects to pin (for bridge pins)      1,                  // count of registered media types      &sudMediaTypes[0]   // list of registered media types  }};//注册时候的信息（名称等）//CLAVSplitterconst AMOVIESETUP_FILTER sudFilterReg ={  &__uuidof(CLAVSplitter),        // filter clsid  L"LAV Splitter",                // filter name  MERIT_PREFERRED + 4,            // merit  2,                              // count of registered pins  sudOutputPins,                  // list of pins to register  CLSID_LegacyAmFilterCategory};//注册时候的信息（名称等）//CLAVSplitterSourceconst AMOVIESETUP_FILTER sudFilterRegSource ={  &__uuidof(CLAVSplitterSource),  // filter clsid  L"LAV Splitter Source",         // filter name  MERIT_PREFERRED + 4,            // merit  1,                              // count of registered pins  sudOutputPins,                  // list of pins to register  CLSID_LegacyAmFilterCategory};// --- COM factory table and registration code --------------// DirectShow base class COM factory requires this table, // declaring all the COM objects in this DLL// 注意g_Templates名称是固定的CFactoryTemplate g_Templates[] = {  // one entry for each CoCreate-able object  {    sudFilterReg.strName,      sudFilterReg.clsID,      CreateInstance<CLAVSplitter>,      CLAVSplitter::StaticInit,      &sudFilterReg  },  {    sudFilterRegSource.strName,      sudFilterRegSource.clsID,      CreateInstance<CLAVSplitterSource>,      NULL,      &sudFilterRegSource  },  // This entry is for the property page.  // 属性页  {       L"LAV Splitter Properties",      &CLSID_LAVSplitterSettingsProp,      CreateInstance<CLAVSplitterSettingsProp>,      NULL, NULL  },  {      L"LAV Splitter Input Formats",      &CLSID_LAVSplitterFormatsProp,      CreateInstance<CLAVSplitterFormatsProp>,      NULL, NULL  }};int g_cTemplates = sizeof(g_Templates) / sizeof(g_Templates[0]);// self-registration entrypointSTDAPI DllRegisterServer(){  std::list<LPCWSTR> chkbytes;  // BluRay  chkbytes.clear();  chkbytes.push_back(L"0,4,,494E4458"); // INDX (index.bdmv)  chkbytes.push_back(L"0,4,,4D4F424A"); // MOBJ (MovieObject.bdmv)  chkbytes.push_back(L"0,4,,4D504C53"); // MPLS  RegisterSourceFilter(__uuidof(CLAVSplitterSource),    MEDIASUBTYPE_LAVBluRay, chkbytes, NULL);  // base classes will handle registration using the factory template table  return AMovieDllRegisterServer2(true);}STDAPI DllUnregisterServer(){  UnRegisterSourceFilter(MEDIASUBTYPE_LAVBluRay);  // base classes will handle de-registration using the factory template table  return AMovieDllRegisterServer2(false);}// if we declare the correct C runtime entrypoint and then forward it to the DShow base// classes we will be sure that both the C/C++ runtimes and the base classes are initialized// correctlyextern "C" BOOL WINAPI DllEntryPoint(HINSTANCE, ULONG, LPVOID);BOOL WINAPI DllMain(HANDLE hDllHandle, DWORD dwReason, LPVOID lpReserved){  return DllEntryPoint(reinterpret_cast<HINSTANCE>(hDllHandle), dwReason, lpReserved);}void CALLBACK OpenConfiguration(HWND hwnd, HINSTANCE hinst, LPSTR lpszCmdLine, int nCmdShow){  HRESULT hr = S_OK;  CUnknown *pInstance = CreateInstance<CLAVSplitter>(NULL, &hr);  IBaseFilter *pFilter = NULL;  pInstance->NonDelegatingQueryInterface(IID_IBaseFilter, (void **)&pFilter);  if (pFilter) {    pFilter->AddRef();    CBaseDSPropPage::ShowPropPageDialog(pFilter);  }  delete pInstance;}

接下来就要进入正题了，看一看核心的分离器（解封装器）的类CLAVSplitter的定义文件LAVSplitter.h。乍一看这个类确实了得，居然继承了那么多的父类，实在是碉堡了。先不管那么多，看看里面都有什么函数吧。主要的函数上面都加了注释。注意还有一个类CLAVSplitterSource继承了CLAVSplitter。

LAVSplitter.h

/* *      Copyright (C) 2010-2013 Hendrik Leppkes *      http://www.1f0.de * *  This program is free software; you can redistribute it and/or modify *  it under the terms of the GNU General Public License as published by *  the Free Software Foundation; either version 2 of the License, or *  (at your option) any later version. * *  This program is distributed in the hope that it will be useful, *  but WITHOUT ANY WARRANTY; without even the implied warranty of *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the *  GNU General Public License for more details. * *  You should have received a copy of the GNU General Public License along *  with this program; if not, write to the Free Software Foundation, Inc., *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. * *  Initial design and concept by Gabest and the MPC-HC Team, copyright under GPLv2 *  Contributions by Ti-BEN from the XBMC DSPlayer Project, also under GPLv2 */#pragma once#include <string>#include <list>#include <set>#include <vector>#include <map>#include "PacketQueue.h"#include "BaseDemuxer.h"#include "LAVSplitterSettingsInternal.h"#include "SettingsProp.h"#include "IBufferInfo.h"#include "ISpecifyPropertyPages2.h"#include "LAVSplitterTrayIcon.h"#define LAVF_REGISTRY_KEY L"Software\\LAV\\Splitter"#define LAVF_REGISTRY_KEY_FORMATS LAVF_REGISTRY_KEY L"\\Formats"#define LAVF_LOG_FILE     L"LAVSplitter.txt"#define MAX_PTS_SHIFT 50000000i64class CLAVOutputPin;class CLAVInputPin;#ifdef_MSC_VER#pragma warning(disable: 4355)#endif//核心解复用（分离器）//暴漏的接口在ILAVFSettings中[uuid("171252A0-8820-4AFE-9DF8-5C92B2D66B04")]class CLAVSplitter   : public CBaseFilter  , public CCritSec  , protected CAMThread  , public IFileSourceFilter  , public IMediaSeeking  , public IAMStreamSelect  , public IAMOpenProgress  , public ILAVFSettingsInternal  , public ISpecifyPropertyPages2  , public IObjectWithSite  , public IBufferInfo{public:  CLAVSplitter(LPUNKNOWN pUnk, HRESULT* phr);  virtual ~CLAVSplitter();  static void CALLBACK StaticInit(BOOL bLoading, const CLSID *clsid);  // IUnknown  //  DECLARE_IUNKNOWN;  //暴露接口，使外部程序可以QueryInterface，关键！  //翻译（“没有代表的方式查询接口”）  STDMETHODIMP NonDelegatingQueryInterface(REFIID riid, void** ppv);  // CBaseFilter methods  //输入是一个，输出就不一定了！  int GetPinCount();  CBasePin *GetPin(int n);  STDMETHODIMP GetClassID(CLSID* pClsID);  STDMETHODIMP Stop();  STDMETHODIMP Pause();  STDMETHODIMP Run(REFERENCE_TIME tStart);  STDMETHODIMP JoinFilterGraph(IFilterGraph * pGraph, LPCWSTR pName);  // IFileSourceFilter  // 源Filter的接口方法  STDMETHODIMP Load(LPCOLESTR pszFileName, const AM_MEDIA_TYPE * pmt);  STDMETHODIMP GetCurFile(LPOLESTR *ppszFileName, AM_MEDIA_TYPE *pmt);  // IMediaSeeking  STDMETHODIMP GetCapabilities(DWORD* pCapabilities);  STDMETHODIMP CheckCapabilities(DWORD* pCapabilities);  STDMETHODIMP IsFormatSupported(const GUID* pFormat);  STDMETHODIMP QueryPreferredFormat(GUID* pFormat);  STDMETHODIMP GetTimeFormat(GUID* pFormat);  STDMETHODIMP IsUsingTimeFormat(const GUID* pFormat);  STDMETHODIMP SetTimeFormat(const GUID* pFormat);  STDMETHODIMP GetDuration(LONGLONG* pDuration);  STDMETHODIMP GetStopPosition(LONGLONG* pStop);  STDMETHODIMP GetCurrentPosition(LONGLONG* pCurrent);  STDMETHODIMP ConvertTimeFormat(LONGLONG* pTarget, const GUID* pTargetFormat, LONGLONG Source, const GUID* pSourceFormat);  STDMETHODIMP SetPositions(LONGLONG* pCurrent, DWORD dwCurrentFlags, LONGLONG* pStop, DWORD dwStopFlags);  STDMETHODIMP GetPositions(LONGLONG* pCurrent, LONGLONG* pStop);  STDMETHODIMP GetAvailable(LONGLONG* pEarliest, LONGLONG* pLatest);  STDMETHODIMP SetRate(double dRate);  STDMETHODIMP GetRate(double* pdRate);  STDMETHODIMP GetPreroll(LONGLONG* pllPreroll);  // IAMStreamSelect  STDMETHODIMP Count(DWORD *pcStreams);  STDMETHODIMP Enable(long lIndex, DWORD dwFlags);  STDMETHODIMP Info(long lIndex, AM_MEDIA_TYPE **ppmt, DWORD *pdwFlags, LCID *plcid, DWORD *pdwGroup, WCHAR **ppszName, IUnknown **ppObject, IUnknown **ppUnk);  // IAMOpenProgress  STDMETHODIMP QueryProgress(LONGLONG *pllTotal, LONGLONG *pllCurrent);  STDMETHODIMP AbortOperation();  // ISpecifyPropertyPages2  STDMETHODIMP GetPages(CAUUID *pPages);  STDMETHODIMP CreatePage(const GUID& guid, IPropertyPage** ppPage);  // IObjectWithSite  STDMETHODIMP SetSite(IUnknown *pUnkSite);  STDMETHODIMP GetSite(REFIID riid, void **ppvSite);  // IBufferInfo  STDMETHODIMP_(int) GetCount();  STDMETHODIMP GetStatus(int i, int& samples, int& size);  STDMETHODIMP_(DWORD) GetPriority();  // ILAVFSettings  STDMETHODIMP SetRuntimeConfig(BOOL bRuntimeConfig);  STDMETHODIMP GetPreferredLanguages(LPWSTR *ppLanguages);  STDMETHODIMP SetPreferredLanguages(LPCWSTR pLanguages);  STDMETHODIMP GetPreferredSubtitleLanguages(LPWSTR *ppLanguages);  STDMETHODIMP SetPreferredSubtitleLanguages(LPCWSTR pLanguages);  STDMETHODIMP_(LAVSubtitleMode) GetSubtitleMode();  STDMETHODIMP SetSubtitleMode(LAVSubtitleMode mode);  STDMETHODIMP_(BOOL) GetSubtitleMatchingLanguage();  STDMETHODIMP SetSubtitleMatchingLanguage(BOOL dwMode);  STDMETHODIMP_(BOOL) GetPGSForcedStream();  STDMETHODIMP SetPGSForcedStream(BOOL bFlag);  STDMETHODIMP_(BOOL) GetPGSOnlyForced();  STDMETHODIMP SetPGSOnlyForced(BOOL bForced);  STDMETHODIMP_(int) GetVC1TimestampMode();  STDMETHODIMP SetVC1TimestampMode(int iMode);  STDMETHODIMP SetSubstreamsEnabled(BOOL bSubStreams);  STDMETHODIMP_(BOOL) GetSubstreamsEnabled();  STDMETHODIMP SetVideoParsingEnabled(BOOL bEnabled);  STDMETHODIMP_(BOOL) GetVideoParsingEnabled();  STDMETHODIMP SetFixBrokenHDPVR(BOOL bEnabled);  STDMETHODIMP_(BOOL) GetFixBrokenHDPVR();  STDMETHODIMP_(HRESULT) SetFormatEnabled(LPCSTR strFormat, BOOL bEnabled);  STDMETHODIMP_(BOOL) IsFormatEnabled(LPCSTR strFormat);  STDMETHODIMP SetStreamSwitchRemoveAudio(BOOL bEnabled);  STDMETHODIMP_(BOOL) GetStreamSwitchRemoveAudio();  STDMETHODIMP GetAdvancedSubtitleConfig(LPWSTR *ppAdvancedConfig);  STDMETHODIMP SetAdvancedSubtitleConfig(LPCWSTR pAdvancedConfig);  STDMETHODIMP SetUseAudioForHearingVisuallyImpaired(BOOL bEnabled);  STDMETHODIMP_(BOOL) GetUseAudioForHearingVisuallyImpaired();  STDMETHODIMP SetMaxQueueMemSize(DWORD dwMaxSize);  STDMETHODIMP_(DWORD) GetMaxQueueMemSize();  STDMETHODIMP SetTrayIcon(BOOL bEnabled);  STDMETHODIMP_(BOOL) GetTrayIcon();  STDMETHODIMP SetPreferHighQualityAudioStreams(BOOL bEnabled);  STDMETHODIMP_(BOOL) GetPreferHighQualityAudioStreams();  STDMETHODIMP SetLoadMatroskaExternalSegments(BOOL bEnabled);  STDMETHODIMP_(BOOL) GetLoadMatroskaExternalSegments();  STDMETHODIMP GetFormats(LPSTR** formats, UINT* nFormats);  STDMETHODIMP SetNetworkStreamAnalysisDuration(DWORD dwDuration);  STDMETHODIMP_(DWORD) GetNetworkStreamAnalysisDuration();  // ILAVSplitterSettingsInternal  STDMETHODIMP_(LPCSTR) GetInputFormat() { if (m_pDemuxer) return m_pDemuxer->GetContainerFormat(); return NULL; }  STDMETHODIMP_(std::set<FormatInfo>&) GetInputFormats();  STDMETHODIMP_(BOOL) IsVC1CorrectionRequired();  STDMETHODIMP_(CMediaType *) GetOutputMediatype(int stream);  STDMETHODIMP_(IFilterGraph *) GetFilterGraph() { if (m_pGraph) { m_pGraph->AddRef(); return m_pGraph; } return NULL; }  STDMETHODIMP_(DWORD) GetStreamFlags(DWORD dwStream) { if (m_pDemuxer) return m_pDemuxer->GetStreamFlags(dwStream); return 0; }  STDMETHODIMP_(int) GetPixelFormat(DWORD dwStream) { if (m_pDemuxer) return m_pDemuxer->GetPixelFormat(dwStream); return AV_PIX_FMT_NONE; }  STDMETHODIMP_(int) GetHasBFrames(DWORD dwStream){ if (m_pDemuxer) return m_pDemuxer->GetHasBFrames(dwStream); return -1; }  // Settings helper  std::list<std::string> GetPreferredAudioLanguageList();  std::list<CSubtitleSelector> GetSubtitleSelectors();  bool IsAnyPinDrying();  void SetFakeASFReader(BOOL bFlag) { m_bFakeASFReader = bFlag; }protected:  // CAMThread  enum {CMD_EXIT, CMD_SEEK};  DWORD ThreadProc();  HRESULT DemuxSeek(REFERENCE_TIME rtStart);  HRESULT DemuxNextPacket();  HRESULT DeliverPacket(Packet *pPacket);  void DeliverBeginFlush();  void DeliverEndFlush();  STDMETHODIMP Close();  STDMETHODIMP DeleteOutputs();  //初始化解复用器  STDMETHODIMP InitDemuxer();  friend class CLAVOutputPin;  STDMETHODIMP SetPositionsInternal(void *caller, LONGLONG* pCurrent, DWORD dwCurrentFlags, LONGLONG* pStop, DWORD dwStopFlags);public:  CLAVOutputPin *GetOutputPin(DWORD streamId, BOOL bActiveOnly = FALSE);  STDMETHODIMP RenameOutputPin(DWORD TrackNumSrc, DWORD TrackNumDst, std::vector<CMediaType> pmts);  STDMETHODIMP UpdateForcedSubtitleMediaType();  STDMETHODIMP CompleteInputConnection();  STDMETHODIMP BreakInputConnection();protected://相关的参数设置  STDMETHODIMP LoadDefaults();  STDMETHODIMP ReadSettings(HKEY rootKey);  STDMETHODIMP LoadSettings();  STDMETHODIMP SaveSettings();  //创建图标  STDMETHODIMP CreateTrayIcon();protected:  CLAVInputPin *m_pInput;private:  CCritSec m_csPins;  //用vector存储输出PIN（解复用的时候是不确定的）  std::vector<CLAVOutputPin *> m_pPins;  //活动的  std::vector<CLAVOutputPin *> m_pActivePins;  //不用的  std::vector<CLAVOutputPin *> m_pRetiredPins;  std::set<DWORD> m_bDiscontinuitySent;  std::wstring m_fileName;  std::wstring m_processName;  //有很多纯虚函数的基本解复用类  //注意：绝大部分信息都是从这获得的  //这里的信息是由其派生类从FFMPEG中获取到的  CBaseDemuxer *m_pDemuxer;  BOOL m_bPlaybackStarted;  BOOL m_bFakeASFReader;  // Times  REFERENCE_TIME m_rtStart, m_rtStop, m_rtCurrent, m_rtNewStart, m_rtNewStop;  REFERENCE_TIME m_rtOffset;  double m_dRate;  BOOL m_bStopValid;  // Seeking  REFERENCE_TIME m_rtLastStart, m_rtLastStop;  std::set<void *> m_LastSeekers;  // flushing  bool m_fFlushing;  CAMEvent m_eEndFlush;  std::set<FormatInfo> m_InputFormats;  // Settings  //设置  struct Settings {    BOOL TrayIcon;    std::wstring prefAudioLangs;    std::wstring prefSubLangs;    std::wstring subtitleAdvanced;    LAVSubtitleMode subtitleMode;    BOOL PGSForcedStream;    BOOL PGSOnlyForced;    int vc1Mode;    BOOL substreams;    BOOL MatroskaExternalSegments;    BOOL StreamSwitchRemoveAudio;    BOOL ImpairedAudio;    BOOL PreferHighQualityAudio;    DWORD QueueMaxSize;    DWORD NetworkAnalysisDuration;    std::map<std::string, BOOL> formats;  } m_settings;  BOOL m_bRuntimeConfig;  IUnknown *m_pSite;  CBaseTrayIcon *m_pTrayIcon;};[uuid("B98D13E7-55DB-4385-A33D-09FD1BA26338")]class CLAVSplitterSource : public CLAVSplitter{public:  // construct only via class factory  CLAVSplitterSource(LPUNKNOWN pUnk, HRESULT* phr);  virtual ~CLAVSplitterSource();  // IUnknown  DECLARE_IUNKNOWN;  //暴露接口，使外部程序可以QueryInterface，关键！  //翻译（“没有代表的方式查询接口”）  STDMETHODIMP NonDelegatingQueryInterface(REFIID riid, void** ppv);};

先来看一下查询接口的函数NonDelegatingQueryInterface()吧

//暴露接口，使外部程序可以QueryInterface，关键！STDMETHODIMP CLAVSplitter::NonDelegatingQueryInterface(REFIID riid, void** ppv){  CheckPointer(ppv, E_POINTER);  *ppv = NULL;  if (m_pDemuxer && (riid == __uuidof(IKeyFrameInfo) || riid == __uuidof(ITrackInfo) || riid == IID_IAMExtendedSeeking || riid == IID_IAMMediaContent)) {    return m_pDemuxer->QueryInterface(riid, ppv);  }  //写法好特别啊，意思是一样的  return    QI(IMediaSeeking)    QI(IAMStreamSelect)    QI(ISpecifyPropertyPages)    QI(ISpecifyPropertyPages2)    QI2(ILAVFSettings)    QI2(ILAVFSettingsInternal)    QI(IObjectWithSite)    QI(IBufferInfo)    __super::NonDelegatingQueryInterface(riid, ppv);}

这个NonDelegatingQueryInterface()的写法确实够特别的，不过其作用还是一样的：根据不同的REFIID，获得不同的接口指针。在这里就不多说了。

再看一下Load()函数

// IFileSourceFilter// 打开STDMETHODIMP CLAVSplitter::Load(LPCOLESTR pszFileName, const AM_MEDIA_TYPE * pmt){  CheckPointer(pszFileName, E_POINTER);  m_bPlaybackStarted = FALSE;  m_fileName = std::wstring(pszFileName);  HRESULT hr = S_OK;  SAFE_DELETE(m_pDemuxer);  LPWSTR extension = PathFindExtensionW(pszFileName);  DbgLog((LOG_TRACE, 10, L"::Load(): Opening file '%s' (extension: %s)", pszFileName, extension));  // BDMV uses the BD demuxer, everything else LAVF  if (_wcsicmp(extension, L".bdmv") == 0 || _wcsicmp(extension, L".mpls") == 0) {    m_pDemuxer = new CBDDemuxer(this, this);  } else {    m_pDemuxer = new CLAVFDemuxer(this, this);  }  //打开  if(FAILED(hr = m_pDemuxer->Open(pszFileName))) {    SAFE_DELETE(m_pDemuxer);    return hr;  }  m_pDemuxer->AddRef();  return InitDemuxer();}

在这里我们要注意CLAVSplitter的一个变量：m_pDemuxer。这是一个指向 CBaseDemuxer的指针。因此在这里CLAVSplitter实际上调用了 CBaseDemuxer中的方法。

从代码中的逻辑我们可以看出：

1.寻找文件后缀

2.当文件后缀是：".bdmv"或者".mpls"的时候，m_pDemuxer指向一个CBDDemuxer（我推测这代表目标文件是蓝光文件什么的），其他情况下m_pDemuxer指向一个CLAVFDemuxer。

3.然后m_pDemuxer会调用Open()方法。

4.最后会调用一个InitDemuxer()方法。

在这里我们应该看看m_pDemuxer->Open()这个方法里面有什么。我们先考虑m_pDemuxer指向CLAVFDemuxer的情况。

// Demuxer Functions// 打开（就是一个封装）STDMETHODIMP CLAVFDemuxer::Open(LPCOLESTR pszFileName){  return OpenInputStream(NULL, pszFileName, NULL, TRUE);}

发现是一层封装，于是果断决定层层深入。

//实际的打开,使用FFMPEGSTDMETHODIMP CLAVFDemuxer::OpenInputStream(AVIOContext *byteContext, LPCOLESTR pszFileName, const char *format, BOOL bForce){  CAutoLock lock(m_pLock);  HRESULT hr = S_OK;  int ret; // return code from avformat functions  // Convert the filename from wchar to char for avformat  char fileName[4100] = {0};  if (pszFileName) {    ret = WideCharToMultiByte(CP_UTF8, 0, pszFileName, -1, fileName, 4096, NULL, NULL);  }  if (_strnicmp("mms:", fileName, 4) == 0) {    memmove(fileName+1, fileName, strlen(fileName));    memcpy(fileName, "mmsh", 4);  }  AVIOInterruptCB cb = {avio_interrupt_cb, this};trynoformat:  // Create the avformat_context  // FFMPEG中的函数  m_avFormat = avformat_alloc_context();  m_avFormat->pb = byteContext;  m_avFormat->interrupt_callback = cb;  if (m_avFormat->pb)    m_avFormat->flags |= AVFMT_FLAG_CUSTOM_IO;  LPWSTR extension = pszFileName ? PathFindExtensionW(pszFileName) : NULL;  AVInputFormat *inputFormat = NULL;  //如果指定了格式  if (format) {  //查查有木有    inputFormat = av_find_input_format(format);  } else if (pszFileName) {    LPWSTR extension = PathFindExtensionW(pszFileName);    for (int i = 0; i < countof(wszImageExtensions); i++) {      if (_wcsicmp(extension, wszImageExtensions[i]) == 0) {        if (byteContext) {          inputFormat = av_find_input_format("image2pipe");        } else {          inputFormat = av_find_input_format("image2");        }        break;      }    }    for (int i = 0; i < countof(wszBlockedExtensions); i++) {      if (_wcsicmp(extension, wszBlockedExtensions[i]) == 0) {        goto done;      }    }  }  // Disable loading of external mkv segments, if required  if (!m_pSettings->GetLoadMatroskaExternalSegments())    m_avFormat->flags |= AVFMT_FLAG_NOEXTERNAL;  m_timeOpening = time(NULL);  //实际的打开  ret = avformat_open_input(&m_avFormat, fileName, inputFormat, NULL);  //出错了  if (ret < 0) {    DbgLog((LOG_ERROR, 0, TEXT("::OpenInputStream(): avformat_open_input failed (%d)"), ret));    if (format) {      DbgLog((LOG_ERROR, 0, TEXT(" -> trying again without specific format")));      format = NULL;  //实际的关闭      avformat_close_input(&m_avFormat);      goto trynoformat;    }    goto done;  }  DbgLog((LOG_TRACE, 10, TEXT("::OpenInputStream(): avformat_open_input opened file of type '%S' (took %I64d seconds)"), m_avFormat->iformat->name, time(NULL) - m_timeOpening));  m_timeOpening = 0;  //初始化AVFormat  CHECK_HR(hr = InitAVFormat(pszFileName, bForce));  return S_OK;done:  CleanupAVFormat();  return E_FAIL;}

看到这个函数，立马感受到了一种“拨云见日”的感觉。看到了很多FFMPEG的API函数。最重要的依据当属avformat_open_input()了，通过这个函数，打开了实际的文件。如果出现错误，则调用avformat_close_input()进行清理。

最后，还调用了InitAVFormat()函数：

//初始化AVFormatSTDMETHODIMP CLAVFDemuxer::InitAVFormat(LPCOLESTR pszFileName, BOOL bForce){  HRESULT hr = S_OK;  const char *format = NULL;  //获取InputFormat信息（，短名称，长名称）  lavf_get_iformat_infos(m_avFormat->iformat, &format, NULL);  if (!bForce && (!format || !m_pSettings->IsFormatEnabled(format))) {    DbgLog((LOG_TRACE, 20, L"::InitAVFormat() - format of type '%S' disabled, failing", format ? format : m_avFormat->iformat->name));    return E_FAIL;  }  m_pszInputFormat = format ? format : m_avFormat->iformat->name;  m_bVC1SeenTimestamp = FALSE;  LPWSTR extension = pszFileName ? PathFindExtensionW(pszFileName) : NULL;  m_bMatroska = (_strnicmp(m_pszInputFormat, "matroska", 8) == 0);  m_bOgg = (_strnicmp(m_pszInputFormat, "ogg", 3) == 0);  m_bAVI = (_strnicmp(m_pszInputFormat, "avi", 3) == 0);  m_bMPEGTS = (_strnicmp(m_pszInputFormat, "mpegts", 6) == 0);  m_bMPEGPS = (_stricmp(m_pszInputFormat, "mpeg") == 0);  m_bRM = (_stricmp(m_pszInputFormat, "rm") == 0);  m_bPMP = (_stricmp(m_pszInputFormat, "pmp") == 0);  m_bMP4 = (_stricmp(m_pszInputFormat, "mp4") == 0);  m_bTSDiscont = m_avFormat->iformat->flags & AVFMT_TS_DISCONT;  WCHAR szProt[24] = L"file";  if (pszFileName) {    DWORD dwNumChars = 24;    hr = UrlGetPart(pszFileName, szProt, &dwNumChars, URL_PART_SCHEME, 0);    if (SUCCEEDED(hr) && dwNumChars && (_wcsicmp(szProt, L"file") != 0)) {      m_avFormat->flags |= AVFMT_FLAG_NETWORK;      DbgLog((LOG_TRACE, 10, TEXT("::InitAVFormat(): detected network protocol: %s"), szProt));    }  }  // TODO: make both durations below configurable  // decrease analyze duration for network streams  if (m_avFormat->flags & AVFMT_FLAG_NETWORK || (m_avFormat->flags & AVFMT_FLAG_CUSTOM_IO && !m_avFormat->pb->seekable)) {    // require at least 0.2 seconds    m_avFormat->max_analyze_duration = max(m_pSettings->GetNetworkStreamAnalysisDuration() * 1000, 200000);  } else {    // And increase it for mpeg-ts/ps files    if (m_bMPEGTS || m_bMPEGPS)      m_avFormat->max_analyze_duration = 10000000;  }  av_opt_set_int(m_avFormat, "correct_ts_overflow", !m_pBluRay, 0);  if (m_bMatroska)    m_avFormat->flags |= AVFMT_FLAG_KEEP_SIDE_DATA;  m_timeOpening = time(NULL);  //获取媒体流信息  int ret = avformat_find_stream_info(m_avFormat, NULL);  if (ret < 0) {    DbgLog((LOG_ERROR, 0, TEXT("::InitAVFormat(): av_find_stream_info failed (%d)"), ret));    goto done;  }  DbgLog((LOG_TRACE, 10, TEXT("::InitAVFormat(): avformat_find_stream_info finished, took %I64d seconds"), time(NULL) - m_timeOpening));  m_timeOpening = 0;  // Check if this is a m2ts in a BD structure, and if it is, read some extra stream properties out of the CLPI files  if (m_pBluRay) {    m_pBluRay->ProcessClipLanguages();  } else if (pszFileName && m_bMPEGTS) {    CheckBDM2TSCPLI(pszFileName);  }  SAFE_CO_FREE(m_stOrigParser);  m_stOrigParser = (enum AVStreamParseType *)CoTaskMemAlloc(m_avFormat->nb_streams * sizeof(enum AVStreamParseType));  if (!m_stOrigParser)    return E_OUTOFMEMORY;  for(unsigned int idx = 0; idx < m_avFormat->nb_streams; ++idx) {    AVStream *st = m_avFormat->streams[idx];    // Disable full stream parsing for these formats    if (st->need_parsing == AVSTREAM_PARSE_FULL) {      if (st->codec->codec_id == AV_CODEC_ID_DVB_SUBTITLE) {        st->need_parsing = AVSTREAM_PARSE_NONE;      }    }    if (m_bOgg && st->codec->codec_id == AV_CODEC_ID_H264) {      st->need_parsing = AVSTREAM_PARSE_FULL;    }    // Create the parsers with the appropriate flags    init_parser(m_avFormat, st);    UpdateParserFlags(st);#ifdef DEBUG    AVProgram *streamProg = av_find_program_from_stream(m_avFormat, NULL, idx);    DbgLog((LOG_TRACE, 30, L"Stream %d (pid %d) - program: %d, codec: %S; parsing: %S;", idx, st->id, streamProg ? streamProg->pmt_pid : -1, avcodec_get_name(st->codec->codec_id), lavf_get_parsing_string(st->need_parsing)));#endif    m_stOrigParser[idx] = st->need_parsing;    if ((st->codec->codec_id == AV_CODEC_ID_DTS && st->codec->codec_tag == 0xA2)     || (st->codec->codec_id == AV_CODEC_ID_EAC3 && st->codec->codec_tag == 0xA1))      st->disposition |= LAVF_DISPOSITION_SECONDARY_AUDIO;    UpdateSubStreams();    if (st->codec->codec_type == AVMEDIA_TYPE_ATTACHMENT && (st->codec->codec_id == AV_CODEC_ID_TTF || st->codec->codec_id == AV_CODEC_ID_OTF)) {      if (!m_pFontInstaller) {        m_pFontInstaller = new CFontInstaller();      }      m_pFontInstaller->InstallFont(st->codec->extradata, st->codec->extradata_size);    }  }  CHECK_HR(hr = CreateStreams());  return S_OK;done:  //关闭输入  CleanupAVFormat();  return E_FAIL;}

该函数通过avformat_find_stream_info()等获取到流信息，这里就不多说了。