Windows 声音处理编程（基于winmm.dll）（3）

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这一篇介绍向声卡发送数据的方法。首先在C#中重写midiOutOpen和midiOutShortMsg方法：

//打开指定的MIDI输出设备进行回放

[DllImport("winmm.dll")]
public static extern uint midiOutOpen(out IntPtr lphMidiOut, uint uDeviceID, IntPtr dwCallback, IntPtr dwInstance, uint dwFlags);

//向指定的MIDI输出设备发送一条短MIDI消息

[DllImport("winmm.dll")]
public static extern uint midiOutShortMsg(IntPtr hMidiOut, uint dwMsg);

GM音色表：http://www2.gxai.edu.cn/dnyy/dnzp/ShowArticle.asp?ArticleID=488 ，声卡也可以模拟此声色表中的声音进行演奏，操作流程如下：

midiOutOpen(out handle, 0, IntPtr.Zero, IntPtr.Zero, 0); //打开设备，获取handle

midiOutShortMsg(handle, Convert.ToUInt32(0x000000C0 +音色值 * 256)); //设置音色，音色值通过GM音色表可以查到，例如：73是短笛

midiOutShortMsg(handle, Convert.ToUInt32(0x00403B90 + data * 256));//给声卡发送数据，播放声音，midiOutShortMsg参数如下：

来自百度百科：http://baike.baidu.com/view/2089748.htm

3、使用格式：
　　ret=midiOutShortMsg(midiout, &H90 + ((flip) * &H100) + (volume * &H10000) + channel)
　　说明：
　　midiout是midioutopen开启设备成功后就会提供这个Long型变量，flip是Integer型参数，代表音的高低，相邻为半音，如60和61，隔1为全音，如63和65；volume为设备的音量值，普遍使用的是0-100之间的值。channel为通道，默认使用0即可。所谓通道就是MIDI音乐中的音层，就像电子琴的16个音层，有节奏通道，和弦通道，低音通道等等。最大可以支持16层，可以取其任意一个值即可。

将以上步骤封装在一个函数中，如下：

private void playNote(IntPtr handle, uint data, int time)
{
Audio.midiOutShortMsg(handle, Convert.ToUInt32(0x000000C0 + comboBox1.SelectedIndex * 256));
if (data == 0)
{
System.Threading.Thread.Sleep(time);
return;
}
Audio.midiOutShortMsg(handle, Convert.ToUInt32(0x00403B90 + data * 256));
System.Threading.Thread.Sleep(time);
Audio.midiOutReset(handle);
}//combobox1是音色的下拉列表，data是基于3B的音阶

通过以上函数，执行下列代码，即可播放98笑傲江湖（吕颂贤）中的音调。

private void btnSample_Click(object sender, EventArgs e)
{
playNote(handle, 12, 250);
playNote(handle, 12, 250);
playNote(handle, 15, 250);
playNote(handle, 17, 250);
playNote(handle, 19, 1000);
playNote(handle, 24, 700);
playNote(handle, 19, 250);
playNote(handle, 22, 200);
playNote(handle, 00, 250);
playNote(handle, 22, 900);
playNote(handle, 19, 400);
playNote(handle, 17, 400);
playNote(handle, 19, 400);
playNote(handle, 22, 400);
playNote(handle, 24, 250);
playNote(handle, 22, 250);
playNote(handle, 19, 1500);
playNote(handle, 00, 300);
playNote(handle, 19, 1000);
playNote(handle, 24, 700);
playNote(handle, 19, 250);
playNote(handle, 22, 200);
playNote(handle, 00, 250);
playNote(handle, 22, 900);
playNote(handle, 19, 400);
playNote(handle, 17, 400);
playNote(handle, 19, 400);
playNote(handle, 22, 400);
playNote(handle, 24, 250);
playNote(handle, 22, 250);
playNote(handle, 19, 1000);
playNote(handle, 00, 300);
playNote(handle, 19, 400);
playNote(handle, 17, 250);
playNote(handle, 15, 600);
playNote(handle, 00, 100);
playNote(handle, 15, 250);
playNote(handle, 17, 400);
playNote(handle, 19, 400);
playNote(handle, 17, 100);
playNote(handle, 00, 250);
playNote(handle, 17, 500);
playNote(handle, 00, 100);
playNote(handle, 17, 400);
playNote(handle, 15, 250);
playNote(handle, 12, 250);
playNote(handle, 00, 100);
playNote(handle, 12, 250);
playNote(handle, 15, 250);
playNote(handle, 17, 400);
playNote(handle, 19, 400);
playNote(handle, 22, 600);
playNote(handle, 24, 250);
playNote(handle, 22, 400);
playNote(handle, 19, 250);
playNote(handle, 17, 250);
playNote(handle, 15, 600);
playNote(handle, 17, 600);
playNote(handle, 19, 400);
playNote(handle, 17, 150);
playNote(handle, 00, 250);
playNote(handle, 17, 600);
playNote(handle, 15, 600);
playNote(handle, 12, 300);
playNote(handle, 00, 100);
playNote(handle, 12, 250);
playNote(handle, 15, 250);
playNote(handle, 17, 250);
playNote(handle, 19, 400);
playNote(handle, 22, 250);
playNote(handle, 24, 700);
playNote(handle, 00, 100);
playNote(handle, 24, 500);
}