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 types
DEFINE_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 nameFALSE,              // 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 typesNULL                // list of registered media types},{L"Input",             // pin nameFALSE,              // 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）
//CLAVSplitter
const AMOVIESETUP_FILTER sudFilterReg =
{&__uuidof(CLAVSplitter),        // filter clsidL"LAV Splitter",                // filter nameMERIT_PREFERRED + 4,            // merit2,                              // count of registered pinssudOutputPins,                  // list of pins to registerCLSID_LegacyAmFilterCategory
};
//注册时候的信息（名称等）
//CLAVSplitterSource
const AMOVIESETUP_FILTER sudFilterRegSource =
{&__uuidof(CLAVSplitterSource),  // filter clsidL"LAV Splitter Source",         // filter nameMERIT_PREFERRED + 4,            // merit1,                              // count of registered pinssudOutputPins,                  // list of pins to registerCLSID_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 entrypoint
STDAPI DllRegisterServer()
{std::list<LPCWSTR> chkbytes;// BluRaychkbytes.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"); // MPLSRegisterSourceFilter(__uuidof(CLAVSplitterSource),MEDIASUBTYPE_LAVBluRay, chkbytes, NULL);// base classes will handle registration using the factory template tablereturn AMovieDllRegisterServer2(true);
}STDAPI DllUnregisterServer()
{UnRegisterSourceFilter(MEDIASUBTYPE_LAVBluRay);// base classes will handle de-registration using the factory template tablereturn 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
// correctly
extern "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);// IMediaSeekingSTDMETHODIMP 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);// IAMStreamSelectSTDMETHODIMP 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);// IAMOpenProgressSTDMETHODIMP QueryProgress(LONGLONG *pllTotal, LONGLONG *pllCurrent);STDMETHODIMP AbortOperation();// ISpecifyPropertyPages2STDMETHODIMP GetPages(CAUUID *pPages);STDMETHODIMP CreatePage(const GUID& guid, IPropertyPage** ppPage);// IObjectWithSiteSTDMETHODIMP SetSite(IUnknown *pUnkSite);STDMETHODIMP GetSite(REFIID riid, void **ppvSite);// IBufferInfoSTDMETHODIMP_(int) GetCount();STDMETHODIMP GetStatus(int i, int& samples, int& size);STDMETHODIMP_(DWORD) GetPriority();// ILAVFSettingsSTDMETHODIMP 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();// ILAVSplitterSettingsInternalSTDMETHODIMP_(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 helperstd::list<std::string> GetPreferredAudioLanguageList();std::list<CSubtitleSelector> GetSubtitleSelectors();bool IsAnyPinDrying();void SetFakeASFReader(BOOL bFlag) { m_bFakeASFReader = bFlag; }
protected:// CAMThreadenum {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;// TimesREFERENCE_TIME m_rtStart, m_rtStop, m_rtCurrent, m_rtNewStart, m_rtNewStop;REFERENCE_TIME m_rtOffset;double m_dRate;BOOL m_bStopValid;// SeekingREFERENCE_TIME m_rtLastStart, m_rtLastStop;std::set<void *> m_LastSeekers;// flushingbool 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 factoryCLAVSplitterSource(LPUNKNOWN pUnk, HRESULT* phr);virtual ~CLAVSplitterSource();// IUnknownDECLARE_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returnQI(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 LAVFif (_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FFMPEG
STDMETHODIMP 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 avformatchar 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 requiredif (!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AVFormatCHECK_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AVFormat
STDMETHODIMP 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 streamsif (m_avFormat->flags & AVFMT_FLAG_NETWORK || (m_avFormat->flags & AVFMT_FLAG_CUSTOM_IO && !m_avFormat->pb->seekable)) {// require at least 0.2 secondsm_avFormat->max_analyze_duration = max(m_pSettings->GetNetworkStreamAnalysisDuration() * 1000, 200000);} else {// And increase it for mpeg-ts/ps filesif (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 filesif (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 formatsif (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 flagsinit_parser(m_avFormat, st);UpdateParserFlags(st);#ifdef DEBUGAVProgram *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)));
#endifm_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。

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