//========================================================================
//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*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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