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mso-bidi-font-size:12.0pt;color:#993366'>6</span></i><span lang=EN-US
style='color:#993366'><o:p></o:p></span></b></p>
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src="./6-4.files/image002.jpg" align=left hspace=12 v:shapes="_x0000_s1609"><![endif]><b><span
style='font-size:24.0pt;mso-bidi-font-size:12.0pt;font-family:黑体;mso-ascii-font-family:
"Times New Roman";color:navy'>输入</span></b><b><span lang=EN-US
style='font-size:24.0pt;mso-bidi-font-size:12.0pt;mso-fareast-font-family:黑体;
color:navy'>/</span></b><b><span style='font-size:24.0pt;mso-bidi-font-size:
12.0pt;font-family:黑体;mso-ascii-font-family:"Times New Roman";color:navy'>输出管理</span></b><b><span
lang=EN-US style='font-size:16.0pt;mso-bidi-font-size:12.0pt;mso-fareast-font-family:
黑体;color:navy'><span style="mso-spacerun: yes"> </span></span></b></p>
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<p class=MsoNormal><a name="_Toc16587483"><span lang=EN-US> </span></a></p>
<h2><span style='mso-bookmark:_Toc16587483'><a name="_Toc41901943"><span
lang=EN-US style='mso-bidi-font-family:宋体'>6.4<span style="mso-spacerun:
yes"> </span>Linux声音设备编程</span></a></span><span style='mso-bookmark:_Toc16587483'><span
lang=EN-US style='mso-bidi-font-family:宋体'><o:p></o:p></span></span></h2>
<p class=MsoNormal align=center style='text-align:center'><span
style='mso-bookmark:_Toc16587483'><span lang=EN-US>(</span></span><span
style='mso-bookmark:_Toc16587483'><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>实验估计时间：</span><span
lang=EN-US>120</span></span><span style='mso-bookmark:_Toc16587483'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>分钟</span><span lang=EN-US>)</span></span></p>
<p class=MsoNormal><span style='mso-bookmark:_Toc16587483'><span lang=EN-US> </span></span></p>
<p class=MsoNormal style='margin-left:21.0pt;text-indent:-21.0pt;mso-list:l0 level1 lfo2;
tab-stops:list 21.0pt'><span style='mso-bookmark:_Toc16587483'><![if !supportLists]><span
lang=EN-US style='font-family:Wingdings;mso-bidi-font-weight:bold'>Ø<span
style='font:7.0pt "Times New Roman"'>
</span></span><![endif]></span><a href="#_背景知识"><span style='mso-bookmark:_Toc16587483'><b><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>背景知识</span></b></span><span style='mso-bookmark:_Toc16587483'></span></a><span
style='mso-bookmark:_Toc16587483'><b><span lang=EN-US><o:p></o:p></span></b></span></p>
<p class=MsoNormal style='margin-left:21.0pt;text-indent:-21.0pt;mso-list:l0 level1 lfo2;
tab-stops:list 21.0pt'><span style='mso-bookmark:_Toc16587483'><![if !supportLists]><span
lang=EN-US style='font-family:Wingdings;mso-bidi-font-weight:bold'>Ø<span
style='font:7.0pt "Times New Roman"'>
</span></span><![endif]></span><a href="#_实验目的"><span style='mso-bookmark:_Toc16587483'><b><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>实验目的</span></b></span><span style='mso-bookmark:_Toc16587483'></span></a><span
style='mso-bookmark:_Toc16587483'><b><span lang=EN-US><o:p></o:p></span></b></span></p>
<p class=MsoNormal style='margin-left:21.0pt;text-indent:-21.0pt;mso-list:l0 level1 lfo2;
tab-stops:list 21.0pt'><span style='mso-bookmark:_Toc16587483'><![if !supportLists]><span
lang=EN-US style='font-family:Wingdings;mso-bidi-font-weight:bold'>Ø<span
style='font:7.0pt "Times New Roman"'>
</span></span><![endif]></span><a href="#_工具/准备工作"><span style='mso-bookmark:
_Toc16587483'><b><span style='font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>工具</span><span lang=EN-US>/</span></b></span><span
style='mso-bookmark:_Toc16587483'><b><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>准备工作</span></b></span><span
style='mso-bookmark:_Toc16587483'></span></a><span style='mso-bookmark:_Toc16587483'><b><span
lang=EN-US><o:p></o:p></span></b></span></p>
<p class=MsoNormal style='margin-left:21.0pt;text-indent:-21.0pt;mso-list:l0 level1 lfo2;
tab-stops:list 21.0pt'><span style='mso-bookmark:_Toc16587483'><![if !supportLists]><span
lang=EN-US style='font-family:Wingdings;mso-bidi-font-weight:bold'>Ø<span
style='font:7.0pt "Times New Roman"'>
</span></span><![endif]></span><a href="#_实验内容与步骤"><span style='mso-bookmark:
_Toc16587483'><b><span style='font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>实验内容与步骤</span></b></span><span
style='mso-bookmark:_Toc16587483'></span></a><span style='mso-bookmark:_Toc16587483'><b><span
lang=EN-US><o:p></o:p></span></b></span></p>
<p class=MsoNormal><span style='mso-bookmark:_Toc16587483'><span lang=EN-US> </span></span></p>
<h3><span style='mso-bookmark:_Toc16587483'><a name="_Toc41901944"></a><a
name="_背景知识"></a><span style='mso-bookmark:_Toc41901944'><span
style='mso-bidi-font-family:宋体'>背景知识</span></span></span><span
style='mso-bookmark:_Toc16587483'><span lang=EN-US style='mso-bidi-font-family:
宋体'><o:p></o:p></span></span></h3>
<p class=MsoNormal style='text-indent:21.0pt'><span style='mso-bookmark:_Toc16587483'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>在</span><span lang=EN-US>Linux</span></span><span
style='mso-bookmark:_Toc16587483'><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>环境下对声音设备进行编程比大多数人想象的要简单得多。常用的声音设备是内部扬声器和声卡，它们对应</span><span
lang=EN-US> /dev</span></span><span style='mso-bookmark:_Toc16587483'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>目录下的一个或多个设备文件，我们可以像打开普通文件一样打开它们，用</span><span lang=EN-US>ioctl()
</span></span><span style='mso-bookmark:_Toc16587483'><span style='font-family:
宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Roman"'>函数设置一些参数，然后对这些打开的特殊文件进行写操作。</span></span></p>
<p class=MsoNormal style='text-indent:21.0pt'><span style='mso-bookmark:_Toc16587483'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>由于这些文件并非普通文件，所以不能用</span><span lang=EN-US>ANSI C (</span></span><span
style='mso-bookmark:_Toc16587483'><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>标准</span><span
lang=EN-US>C) </span></span><span style='mso-bookmark:_Toc16587483'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>的</span><span lang=EN-US>fopen</span></span><span
style='mso-bookmark:_Toc16587483'><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>、</span><span
lang=EN-US>fclose</span></span><span style='mso-bookmark:_Toc16587483'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>等来操作文件，而应该使用系统文件</span><span lang=EN-US>I/O</span></span><span
style='mso-bookmark:_Toc16587483'><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>处理函数</span><span
lang=EN-US> (open</span></span><span style='mso-bookmark:_Toc16587483'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>、</span><span lang=EN-US>read</span></span><span
style='mso-bookmark:_Toc16587483'><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>、</span><span
lang=EN-US>write</span></span><span style='mso-bookmark:_Toc16587483'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>、</span><span lang=EN-US>lseek</span></span><span
style='mso-bookmark:_Toc16587483'><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>和</span><span
lang=EN-US>close)</span></span><span style='mso-bookmark:_Toc16587483'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>来处理这些设备文件。</span><span lang=EN-US>ioctl() </span></span><span
style='mso-bookmark:_Toc16587483'><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>或许是</span><span
lang=EN-US>Linux</span></span><span style='mso-bookmark:_Toc16587483'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>下最庞杂的函数，它可以控制各种文件的属性，在</span><span lang=EN-US>Linux</span></span><span
style='mso-bookmark:_Toc16587483'><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>声音设备编程中，最重要的就是使用此函数正确设置必要的参数。</span></span></p>
<p class=MsoNormal style='text-indent:21.0pt'><span style='mso-bookmark:_Toc16587483'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>在本实验中，我们通过来学习如何实现</span><span lang=EN-US>Linux</span></span><span
style='mso-bookmark:_Toc16587483'><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>下对机器内部扬声器的编程。由于此类编程涉及到系统设备的读写，所以，很多时候需要有</span><span
lang=EN-US>root</span></span><span style='mso-bookmark:_Toc16587483'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>权限，如果将实验例子编译后不能正确执行，那么，首先请检查是否因为没有操纵某个设备的权限。</span></span></p>
<p class=MsoNormal style='text-indent:21.0pt'><span style='mso-bookmark:_Toc16587483'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>内部扬声器是控制台的一部分，所以它对应的设备文件为</span><span lang=EN-US>
/dev/console</span></span><span style='mso-bookmark:_Toc16587483'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>。变量</span><span lang=EN-US>KIOCSOUND</span></span><span
style='mso-bookmark:_Toc16587483'><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>在头文件</span><span
lang=EN-US> /usr/include/linux/kd.h</span></span><span style='mso-bookmark:
_Toc16587483'><span style='font-family:宋体;mso-ascii-font-family:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>中声明，使用</span><span lang=EN-US>ioctl() </span></span><span
style='mso-bookmark:_Toc16587483'><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>函数可以来控制扬声器的发声，使用规则为：</span></span></p>
<p class=MsoNormal><span style='mso-bookmark:_Toc16587483'><span lang=EN-US><span
style="mso-spacerun: yes"> </span>ioctl(fd,
KIOCSOUND, (int) tone) ;</span></span></p>
<p class=MsoNormal style='text-indent:21.0pt'><span style='mso-bookmark:_Toc16587483'><span
lang=EN-US>fd</span></span><span style='mso-bookmark:_Toc16587483'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>为文件设备号，</span><span lang=EN-US>tone</span></span><span
style='mso-bookmark:_Toc16587483'><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>是音频值。当</span><span
lang=EN-US>tone</span></span><span style='mso-bookmark:_Toc16587483'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>为</span><span lang=EN-US>0</span></span><span
style='mso-bookmark:_Toc16587483'><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>时，终止发声。但是，这里的音频和我们平常认为的音频是不同的。由于计算机主板定时器的时钟频率为</span><span
lang=EN-US>1.19MHz</span></span><span style='mso-bookmark:_Toc16587483'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>，所以要进行正确的发声，必须进行如下的转换：</span></span></p>
<p class=MsoNormal style='text-indent:21.0pt'><span style='mso-bookmark:_Toc16587483'><span
lang=EN-US><span style="mso-spacerun: yes"> </span></span></span><span
style='mso-bookmark:_Toc16587483'><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>扬声器音频值</span><span
lang=EN-US> = 1190000/</span></span><span style='mso-bookmark:_Toc16587483'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>期望的音频值</span></span></p>
<p class=MsoNormal style='text-indent:21.0pt'><span style='mso-bookmark:_Toc16587483'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>扬声器发声时间的长短通过函数</span><span lang=EN-US>usleep(unsigned long
usec) </span></span><span style='mso-bookmark:_Toc16587483'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>来控制，它在头文件</span><span lang=EN-US> /usr/include/unistd.h</span></span><span
style='mso-bookmark:_Toc16587483'><span style='font-family:宋体;mso-ascii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>中定义，让程序睡眠</span><span
lang=EN-US>usec</span></span><span style='mso-bookmark:_Toc16587483'><span
style='font-family:宋体;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:
"Times New Roman"'>微秒。</span></span><a href="#_top"><span style='mso-bookmark:
_Toc16587483'><span lang=EN-US style='text-decoration:none;text-underline:none'><!--[if gte vml 1]><v:shape
id="_x0000_i1025" type="#_x0000_t75" style='width:45pt;height:17.25pt'>
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</v:shape><![endif]--><![if !vml]><img border=0 width=60 height=23
src="./6-4.files/image003.gif" v:shapes="_x0000_i1025"><![endif]></span></span><span
style='mso-bookmark:_Toc16587483'></span></a><span style='mso-bookmark:_Toc16587483'></span></p>
<h3><span style='mso-bookmark:_Toc16587483'><a name="_Toc41901945"></a><a
name="_实验目的"></a><span style='mso-bookmark:_Toc41901945'><span
style='mso-bidi-font-family:宋体'>实验目的</span></span></span><span
style='mso-bookmark:_Toc16587483'><span lang=EN-US style='mso-bidi-font-family:
宋体'><o:p></o:p></span></span></h3>
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