📄 chap11_6.htm
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<title>11.6 Win 32的多媒体服务</title>
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<td width="238" bgcolor="#000000" height="20"><p align="right"></font><span style="text-decoration: none"><a href="../../index.htm"><font color="#FFFFFF">电脑报Visual
C++网络教程</font></a></span></td>
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</center></div><font FACE="Times New Roman" SIZE="3"><b><p ALIGN="CENTER"></b></font><font FACE="Times New Roman" size="4" color="#3973DE">11.6 Win 32</font><font size="4" color="#3973DE">的多媒体服务</font><font FACE="Times New Roman" size="4"></p>
<p ALIGN="JUSTIFY"></font><font FACE="Times New Roman" SIZE="3">Windows 95/NT</font><font SIZE="3">提供了丰富的多媒体服务功能，包括大量从低级到高级的多媒体</font><font FACE="Times New Roman" SIZE="3">API</font><font SIZE="3">函数。利用这些功能强大的</font><font FACE="Times New Roman" SIZE="3">API</font><font SIZE="3">，用户可以在不同层次上编写多媒体应用程序。有关多媒体服务的内容完全可以写一本书，本节只是向读者简要地介绍一些最常用的多媒体服务。</font><font FACE="Times New Roman" SIZE="3"></p>
<p ALIGN="JUSTIFY"></font><font SIZE="3">在用</font><font FACE="Times New Roman" SIZE="3">Visual C++</font><font SIZE="3">开发多媒体应用时，用户必须在所有要用到多媒体函数的源程序中包含</font><font FACE="Times New Roman" SIZE="3">MMSYSTEM.H</font><font SIZE="3">头文件，并且该文件位置应在</font><font FACE="Times New Roman" SIZE="3">WINDOWS.H</font><font SIZE="3">头文件的后面。另外，在连接程序时要用到</font><font FACE="Times New Roman" SIZE="3">WINMM.LIB</font><font SIZE="3">引入库，所以用户应该在</font><font FACE="Times New Roman" SIZE="3">Project Settings</font><font SIZE="3">对话框的</font><font FACE="Times New Roman" SIZE="3">Link</font><font SIZE="3">页的</font><font FACE="Times New Roman" SIZE="3">Object/library modules</font><font SIZE="3">栏中加入</font><font FACE="Times New Roman" SIZE="3">WINMM.LIB</font><font SIZE="3">，或者在源程序中加入下面一行：</font><font FACE="Times New Roman" SIZE="3"></p>
<p ALIGN="JUSTIFY">#pragma comment(lib, "winmm.lib")</p>
<b><p ALIGN="JUSTIFY"></b></font><font color="#3973DE" FACE="Times New Roman" SIZE="3">11.6.1
</font><font SIZE="3" color="#3973DE">高级音频函数</font><font FACE="Times New Roman" SIZE="3"></p>
<p ALIGN="JUSTIFY">Windows</font><font SIZE="3">提供了三个特殊的播放声音的高级音频函数：</font><font FACE="Times New Roman" SIZE="3">MessageBeep</font><font SIZE="3">、</font><font FACE="Times New Roman" SIZE="3">PlaySound</font><font SIZE="3">和</font><font FACE="Times New Roman" SIZE="3">sndPlaySound</font><font SIZE="3">。这三个函数可以满足播放波形声音的一般需要，但它们播放的</font><font FACE="Times New Roman" SIZE="3">WAVE</font><font SIZE="3">文件（波形声音文件）的大小不能超过</font><font FACE="Times New Roman" SIZE="3">100KB</font><font SIZE="3">，如果要播放较大的</font><font FACE="Times New Roman" SIZE="3">WAVE</font><font SIZE="3">文件，则应该使用</font><font FACE="Times New Roman" SIZE="3">MCI</font><font SIZE="3">服务。</font><font FACE="Times New Roman" SIZE="3"></p>
<p ALIGN="JUSTIFY">MessageBeep</font><font SIZE="3">读者已经用过了，该函数主要用来播放系统报警声音。系统报警声音是由用户在控制面板中的声音</font><font FACE="Times New Roman" SIZE="3">(Sounds)</font><font SIZE="3">程序中定义的，或者在</font><font FACE="Times New Roman" SIZE="3">WIN.INI</font><font SIZE="3">的</font><font FACE="Times New Roman" SIZE="3">[sounds]</font><font SIZE="3">段中指定。该函数的声明为：</p>
<blockquote>
</font><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">BOOL MessageBeep(UINT
uType);</p>
</font><font SIZE="3"><p ALIGN="JUSTIFY">参数</font><font FACE="Times New Roman" SIZE="3">uType</font><font SIZE="3">说明了告警级，如表</font><font FACE="Times New Roman" SIZE="3">11.4</font><font SIZE="3">所示。若成功则函数返回</font><font FACE="Times New Roman" SIZE="3">TRUE</font><font SIZE="3">。</p>
</font><b>
</blockquote>
<p><font SIZE="3"> </p>
<p ALIGN="CENTER">表</font><font FACE="Times New Roman" SIZE="3">11.4 </font><font SIZE="3">系统告警级</font></b></p>
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<td WIDTH="32%"><font SIZE="3"><b><p ALIGN="JUSTIFY">级别</b></font></td>
<td WIDTH="68%"><font SIZE="3"><b><p ALIGN="JUSTIFY">描述</b></font></td>
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<td WIDTH="32%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">-1</font></td>
<td WIDTH="68%"><font SIZE="3"><p ALIGN="JUSTIFY">从机器的扬声器中发出蜂鸣声。</font></td>
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<td WIDTH="32%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">MB_ICONASTERISK</font></td>
<td WIDTH="68%"><font SIZE="3"><p ALIGN="JUSTIFY">播放由</font><font FACE="Times New Roman" SIZE="3">SystemAsterisk</font><font SIZE="3">定义的声音。</font></td>
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<td WIDTH="32%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">MB_ICONEXCLAMATION</font></td>
<td WIDTH="68%"><font SIZE="3"><p ALIGN="JUSTIFY">播放由</font><font FACE="Times New Roman" SIZE="3">SystemExclamation</font><font SIZE="3">定义的声音。</font></td>
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<td WIDTH="32%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">MB_ICONHAND</font></td>
<td WIDTH="68%"><font SIZE="3"><p ALIGN="JUSTIFY">播放由</font><font FACE="Times New Roman" SIZE="3">SystemHand</font><font SIZE="3">定义的声音。</font></td>
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<td WIDTH="32%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">MB_ICONQUESTION</font></td>
<td WIDTH="68%"><font SIZE="3"><p ALIGN="JUSTIFY">播放由</font><font FACE="Times New Roman" SIZE="3">SystemQuestion</font><font SIZE="3">定义的声音。</font></td>
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<td WIDTH="32%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">MB_OK</font></td>
<td WIDTH="68%"><font SIZE="3"><p ALIGN="JUSTIFY">播放由</font><font FACE="Times New Roman" SIZE="3">SystemDefault</font><font SIZE="3">定义的声音</font></td>
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<font FACE="Times New Roman" SIZE="3"><b><p ALIGN="JUSTIFY"></b></font><font SIZE="3">在开始播放后，</font><font FACE="Times New Roman" SIZE="3">MessageBeep</font><font SIZE="3">函数立即返回。如果该函数不能播放指定的报警声音，它就播放</font><font FACE="Times New Roman" SIZE="3">SystemDefault</font><font SIZE="3">定义的系统缺省声音，如果连系统缺省声音也播放不了，那么它就会在计算机的扬声器上发出嘟嘟声。在缺省时上表的</font><font FACE="Times New Roman" SIZE="3">MB_</font><font SIZE="3">系列声音均未定义。</font><font FACE="Times New Roman" SIZE="3"></p>
<p ALIGN="JUSTIFY">MessageBeep</font><font SIZE="3">只能用来播放少数定义的声音，如果程序需要播放数字音频文件</font><font FACE="Times New Roman" SIZE="3">(*.WAV</font><font SIZE="3">文件）或音频资源，就需要使用</font><font FACE="Times New Roman" SIZE="3">PlaySound</font><font SIZE="3">或</font><font FACE="Times New Roman" SIZE="3">sndPlaySound</font><font SIZE="3">函数。</font><font FACE="Times New Roman" SIZE="3"></p>
<p ALIGN="JUSTIFY">PlaySound</font><font SIZE="3">函数的声明为：</p>
<blockquote>
<blockquote>
<blockquote>
</font><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">BOOL PlaySound(LPCSTR
pszSound, HMODULE hmod,DWORD fdwSound);</font></p>
</blockquote>
</blockquote>
</blockquote>
<p><font SIZE="3"> </p>
<p ALIGN="JUSTIFY">参数</font><font FACE="Times New Roman" SIZE="3">pszSound</font><font SIZE="3">是指定了要播放声音的字符串，该参数可以是</font><font FACE="Times New Roman" SIZE="3">WAVE</font><font SIZE="3">文件的名字，或是</font><font FACE="Times New Roman" SIZE="3">WAV</font><font SIZE="3">资源的名字，或是内存中声音数据的指针，或是在系统注册表</font><font FACE="Times New Roman" SIZE="3">WIN.INI</font><font SIZE="3">中定义的系统事件声音。如果该参数为</font><font FACE="Times New Roman" SIZE="3">NULL</font><font SIZE="3">则停止正在播放的声音。参数</font><font FACE="Times New Roman" SIZE="3">hmod</font><font SIZE="3">是应用程序的实例句柄，当播放</font><font FACE="Times New Roman" SIZE="3">WAV</font><font SIZE="3">资源时要用到该参数，否则它必须为</font><font FACE="Times New Roman" SIZE="3">NULL</font><font SIZE="3">。参数</font><font FACE="Times New Roman" SIZE="3">fdwSound</font><font SIZE="3">是标志的组合，如表</font><font FACE="Times New Roman" SIZE="3">11.5</font><font SIZE="3">所示。若成功则函数返回</font><font FACE="Times New Roman" SIZE="3">TRUE</font><font SIZE="3">，否则返回</font><font FACE="Times New Roman" SIZE="3">FALSE</font><font SIZE="3">。</font><b><font FACE="Times New Roman" SIZE="3"></p>
<p ALIGN="CENTER"></font><font SIZE="3"> </p>
<p ALIGN="CENTER">表</font><font FACE="Times New Roman" SIZE="3">11.5 </font><font SIZE="3">播放标志</font></b></p>
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<td WIDTH="27%"><font SIZE="3"><b><p ALIGN="JUSTIFY">标志</b></font></td>
<td WIDTH="73%"><font SIZE="3"><b><p ALIGN="JUSTIFY">含义</b></font></td>
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<td WIDTH="27%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">SND_APPLICATION</font></td>
<td WIDTH="73%"><font SIZE="3"><p ALIGN="JUSTIFY">用应用程序指定的关联来播放声音。</font></td>
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<td WIDTH="27%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">SND_ALIAS</font></td>
<td WIDTH="73%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">pszSound</font><font SIZE="3">参数指定了注册表或</font><font FACE="Times New Roman" SIZE="3">WIN.INI</font><font SIZE="3">中的系统事件的别名。</font></td>
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<td WIDTH="27%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">SND_ALIAS_ID</font></td>
<td WIDTH="73%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">pszSound</font><font SIZE="3">参数指定了预定义的声音标识符。</font></td>
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<td WIDTH="27%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">SND_ASYNC</font></td>
<td WIDTH="73%"><font SIZE="3"><p ALIGN="JUSTIFY">用异步方式播放声音，</font><font FACE="Times New Roman" SIZE="3">PlaySound</font><font SIZE="3">函数在开始播放后立即返回。</font></td>
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<td WIDTH="27%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">SND_FILENAME</font></td>
<td WIDTH="73%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">pszSound</font><font SIZE="3">参数指定了</font><font FACE="Times New Roman" SIZE="3">WAVE</font><font SIZE="3">文件名。</font></td>
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<td WIDTH="27%"><font FACE="Times New Roman" SIZE="3"><p ALIGN="JUSTIFY">SND_LOOP</font></td>
<td WIDTH="73%"><font SIZE="3"><p ALIGN="JUSTIFY">重复播放声音，必须与</font><font FACE="Times New Roman" SIZE="3">SND_ASYNC</font><font SIZE="3">标志一块使用。</font></td>
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