wince下用DirectShow播放音频和视频

//========================================================================
//TITLE:
// wince下用DirectShow播放音频和视频
//AUTHOR:
// norains
//DATE:
// Monday 14-May-2007
//Environment:
// WinCE 5.0
//========================================================================

虽然网上关于wince下如何使用DirectShow播放多媒体文件的资料不多,但WinCE毕竟还属于windows,而桌面系统的DirectShow例子网上信手拈来,并且其中DirectShow的功能方法与之WinCE下差别不大,又本人实在没有信心比他们的轮子造得更为华丽,所以这篇文章就直接切入正题,不介绍DirectShow的结构功能,直接来看看怎么用吧.(其实还是自己懒惰的原因大一些,恩,不过这个和本文的主题没多大关系:-)).

为了方便代码的移植,所以我将DirectShow的操作封装成CMedia类,只要直接调用该类,就可以相当简便地调用DirectShow来播放多媒体文件了

好,闲话至此,我们以具体代码看看是如何: //获取CMedia的实例
CMedia *m_pMedia = CMedia::GetInstance();

//设置播放的窗口
m_pMedia->SetVideoWindow(hWnd);

//打开媒体文件
m_pMedia->Open(TEXT("A.AVI"));

//播放
m_pMedia->Play();

...

//播放结束后,调用Close释放资源
m_pMedia->Open();
没错,就是六行代码,就这么简单,可以顺利播放媒体文件.在这里要说一下的是,因为我们播放的是视频,需要有一个窗口显示,所以需要调用SetVideoWindow()函数来设置播放窗口.这个播放视频的窗口,可以是普通的窗口,也可以是Picture控件.当然咯,如果是播放音频文件,那么则完全可以无视这个函数.

还有一个最值得注意的地方,当调用Open()成功之后,一定要调用Close()来释放资源,然后才能打开另一个媒体文件.否则,不释放的资源可能会导致很多莫名其妙的后果哦.

等等,代码似乎还不完美,比如说,我想在文件播放之后再接着播放另外一个文件,那么我如何知道什么时候文件已经播放完毕了呢?这时候我们就需要请出SetNotifyWindow().

该函数的作用是设置一个接受消息的窗口,当DirectShow有事件变更时,就会发送指定的消息到指定的窗口,原型如下:

SetNotifyWindow(HWND hWnd, UINT wMsg,long lInstanceData)

hWnd:接收消息的窗口句柄.

wMsg:指定的自定义消息

lInstanceData:消息的参数.


那么,现在以接收一个视频播放结束事件的代码片段为例子: //自定义一个消息
#define WM_GRAPHNOTIFY (WM_USER + 13)

//设置接收消息窗口和消息
m_pMedia->SetVideoWindow(hWnd,WM_GRAPHNOTIFY,NULL);

...

//这个是消息循环函数
LRESULT CMainWnd::WndProc(HWND hWnd, UINT wMsg, WPARAM wParam, LPARAM lParam)
...{
switch(wMsg)
...{

...

case WM_GRAPHNOTIFY:
...{
LONG evCode,evParam1,evParam2;

//获取此时的DirectShow事件
if(m_pMedia->GetEvent(&evCode,&evParam1,&evParam2) == TRUE)
...{
if(evCode == EC_COMPLETE)
...{
MessageBox(NULL,TEXT("播放完毕"),TEXT(""),MB_OK);
}
}
return 0;
}
}

...

}

好了,知道播放完毕,就这么简单.恩,还很复杂..?呵呵,我觉得已经很简单了.

文章的最后,让我们再来看看CMedia的其它几个有用的函数吧:

CheckVisibility()
描述:判断文件的种类
当返回值为TRUE时,为视频文件;反之为只是音频文件.


SetVolume(LONG lVolume, LONG lBalance)
描述:设置音量.
lVolume:设置音量的大小,范围为–10,000 到 0.
lBalance:设置左右音量的均衡,范围是–10,000 到 10,000,默认是0.


SetDisplayMode(DISPLAYMODE mode)
描述:设置播放模式.
DISP_FIT:按比例拉伸至视屏窗口.
DISP_STRETCH:不按比例拉伸至视屏窗口.
DISP_NATIVE:如果视频原本尺寸小于屏幕,则以原视频文件大小播放.否则,将和DISP_FIT相同
DISP_FULLSCREEN:全屏

/**//////////////////////////////////////////////////////////////////////
//Media.h: interface for the CMedia class.
//
//Version:
// 1.2.0
//Date:
// 2007.05.08
/**///////////////////////////////////////////////////////////////////////
#ifndef MEDIA_H
#define MEDIA_H

#include <mmsystem.h>
#include <streams.h>

//--------------------------------------------------------------------
//Macro define

//The volume value
#define MAX_VOLUME 0
#define MIN_VOLUME -10000

//The balance value
#define MAX_BALANCE 10000
#define MIN_BALANCE -10000

//--------------------------------------------------------------------
//Enum value

enum DISPLAYMODE
...{
//Fit to the play window size. How wide (height) the window is, how
//is the move. Keep aspect ratio.
DISP_FIT,

//Stretch to the play window size. Don't keep the aspect ratio.
DISP_STRETCH,

//Full screen play.
DISP_FULLSCREEN,

//When the size of video is smaller than the play window, it displayes
//as the video size. If it's bigger , it just like the DISP_FIT mode.
DISP_NATIVE
};
//--------------------------------------------------------------------

//The media file property
typedef struct
...{
//The volume range is –10,000 to 0.
//Divide by 100 to get equivalent decibel value (for example –10,000 = –100 dB).
LONG lVolume;

//The value from –10,000 to 10,000 indicating the stereo balance
//As with the Volume property, units correspond to .01 decibels (multiplied by –1 when plBalance is a positive value).
//For example, a value of 1000 indicates –10 dB on the right channel and –90 dB on the left channel.
LONG lBalance;

//Width of the video
LONG lWidth;

//Height of the video
LONG lHeight;

//Approximate bit rate
LONG lBitRate;

}MEDIAPROPERTY,*PMEDIAPROPERTY;
//--------------------------------------------------------------------
class CMedia
...{
public:
BOOL GetEvent(LONG *plEvCode, LONG *plParam1, LONG *plParam2);
BOOL SetNotifyWindow(HWND hWnd, UINT wMsg,long lInstanceData);
BOOL SetVolume(LONG lVolume, LONG lBalance = 0);
BOOL SetDisplayMode(DISPLAYMODE mode);
BOOL GetMediaProperty(PMEDIAPROPERTY pOutProperty);
static CMedia * GetInstance();
void Close();
BOOL CheckVisibility();
void SetVideoWindow(HWND hWndVideo);
BOOL Open(TCHAR * pszFileName);
BOOL Stop();
BOOL Pause();
BOOL Play();
virtual ~CMedia();

protected:

CMedia();

// Collection of interfaces
IGraphBuilder *m_pGB;
IMediaControl *m_pMC;
IMediaEventEx *m_pME;
IVideoWindow *m_pVW;
IBasicAudio *m_pBA;
IBasicVideo *m_pBV;
IMediaSeeking *m_pMS;

TCHAR m_szFileName[MAX_PATH];
HWND m_hWndVideo; //The window play video
HWND m_hWndNotify; //The window notify
BOOL m_bExitThrd;
BOOL m_bThrdRunning;
static CMedia * m_pInstance;
DISPLAYMODE m_DispMode;

};

#endif //#ifndef MEDIA_H

/**///////////////////////////////////////////////////////////////////////
// Media.cpp: implementation of the CMedia class.
//
/**///////////////////////////////////////////////////////////////////////

#include "stdafx.h"
#include "Media.h"

//----------------------------------------------------------------------------------------------
//Macro define

//Default play mode
#define DEFAULT_DISPLAY_MODE DISP_NATIVE

//----------------------------------------------------------------------
//Initialize
CMedia *CMedia::m_pInstance = NULL;
//------------------------------------------------------------------------

/**///////////////////////////////////////////////////////////////////////
// Construction/Destruction
/**///////////////////////////////////////////////////////////////////////

CMedia::CMedia():
m_pGB(NULL),
m_pMC(NULL),
m_pME(NULL),
m_pVW(NULL),
m_pBA(NULL),
m_pBV(NULL),
m_pMS(NULL),
m_hWndVideo(NULL),
m_bExitThrd(TRUE),
m_bThrdRunning(FALSE),
m_DispMode(DEFAULT_DISPLAY_MODE),
m_hWndNotify(NULL)
...{
memset(m_szFileName,0,sizeof(m_szFileName));
}

CMedia::~CMedia()
...{
if(m_pInstance != NULL)
...{
delete m_pInstance;
m_pInstance = NULL;
}

}

//------------------------------------------------------------
//Description:
// Play the media file
// When you call the function,you should call Open() before.
//
//-------------------------------------------------------------
BOOL CMedia::Play()
...{
// Run the graph to play the media file

if(m_pMC == NULL)
...{
return FALSE;
}

m_pMC->Run();

return TRUE;
}

//------------------------------------------------------------
//Description:
// Pause.
// When you call the function,you should call Open() before.
//
//-------------------------------------------------------------
BOOL CMedia::Pause()
...{

if(m_pMC == NULL)
...{
return FALSE;
}

m_pMC->Pause();

return TRUE;
}

//------------------------------------------------------------
//Description:
// Stop.
// When you call the function,you should call Open() before.
//
//-------------------------------------------------------------
BOOL CMedia::Stop()
...{

if(m_pMC == NULL || m_pMS == NULL)
...{
return FALSE;
}

m_pMC->Stop();
m_pMS->SetPositions(0, AM_SEEKING_AbsolutePositioning,NULL,AM_SEEKING_NoPositioning);

return TRUE;
}

//--------------------------------------------------------------------------
//Description:
// Open the media file. When succeed in calling the function ,
//you should call the Close() to release the resource
//
//-------------------------------------------------------------------------
BOOL CMedia::Open(TCHAR *pszFileName)
...{
BOOL bResult = FALSE;

if(_tcslen(pszFileName) >= MAX_PATH)
...{
goto END;
}
else
...{
_tcscpy(m_szFileName,pszFileName);

//Check the file existing
HANDLE hdFile = CreateFile(m_szFileName,GENERIC_READ,FILE_SHARE_READ,NULL,OPEN_EXISTING,NULL,NULL);
if(hdFile == INVALID_HANDLE_VALUE)
...{
//The file doesn't exist
goto END;
}
else
...{
CloseHandle(hdFile);
}
}

// Initialize COM
if(CoInitializeEx(NULL, COINIT_MULTITHREADED) != S_OK)
...{
goto END;
}

// Get the interface for DirectShow's GraphBuilder
if(CoCreateInstance(CLSID_FilterGraph, NULL, CLSCTX_INPROC_SERVER, IID_IGraphBuilder, (void **)&m_pGB) != S_OK)
...{
goto END;
}

// Have the graph construct its the appropriate graph automatically
if(m_pGB->RenderFile(m_szFileName, NULL) != NOERROR)
...{
goto END;
}

// QueryInterface for DirectShow interfaces
if(m_pGB->QueryInterface(IID_IMediaControl, (void **)&m_pMC) != NOERROR)
...{
goto END;
}
if(m_pGB->QueryInterface(IID_IMediaEventEx, (void **)&m_pME) != NOERROR)
...{
goto END;
}
if(m_pGB->QueryInterface(IID_IMediaSeeking, (void **)&m_pMS) != NOERROR)
...{
goto END;
}

// Query for video interfaces, which may not be relevant for audio files
if(m_pGB->QueryInterface(IID_IVideoWindow, (void **)&m_pVW) != NOERROR)

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