UAC 双向终端类型设备（Bi-directional Terminal Types）

在UAC的终端描述符里除了常见的输入终端和输出终端，也存在一些看起来很高级的类型，如双向终端类型设备（Bi-directional Terminal Types）、电话终端类型（Telephony Terminal Types）和额外扩展的终端类型（External Terminal Types）。
关于这几个比较高级的终端类型，具体的应用，我也没有仔细的研究过，不过最近说为了过一个认证，需要将MIC的设备类型该为这些高级终端类型中的一个，所以本人也试了一下，看一下效果。

这里本人将虚拟的UAC设备的输入终端类型从Microphone 0x0201改为了 Headset 0x0402。这里在设备管理器中的效果对比如下：

原始的数据配置如下：

    USB_AC_IT_DESCRIPTOR* pACITDesc = (USB_AC_IT_DESCRIPTOR*)((char*)pACHeaderDesc + pACHeaderDesc->bLength);
    pACITDesc->bLength = 0x0C;
    pACITDesc->bDescriptorType = 0x24;
    pACITDesc->bDescriptorSubtype = 0x02;
    pACITDesc->bTerminalID = 0x01;
    pACITDesc->wTerminalType = 0x0201;
    pACITDesc->bAssocTerminal = 0x00;
    pACITDesc->bNrChannels = 0x02; // XXX: 0x01
    pACITDesc->wChannelConfig = 0x03; // XXX: 0x0000
    pACITDesc->iChannelNames = 0x00;
    pACITDesc->iTerminal = 0x00;
    // Output Terminal Descriptor
    USB_AC_OT_DESCRIPTOR* pACOTDesc = (USB_AC_OT_DESCRIPTOR*)((char*)pACITDesc + pACITDesc->bLength);
    pACOTDesc->bLength = 0x09;
    pACOTDesc->bDescriptorType = 0x24;
    pACOTDesc->bDescriptorSubtype = 0x03;
    pACOTDesc->bTerminalID = 0x03;
    pACOTDesc->wTerminalType = 0x0101;
    pACOTDesc->bAssocTerminal = 0x00;
    pACOTDesc->bSourceID = 0x01;
    pACOTDesc->iTerminal = 0x00;

改为0X0402后：

  USB_AC_IT_DESCRIPTOR* pACITDesc = (USB_AC_IT_DESCRIPTOR*)((char*)pACHeaderDesc + pACHeaderDesc->bLength);
    pACITDesc->bLength = 0x0C;
    pACITDesc->bDescriptorType = 0x24;
    pACITDesc->bDescriptorSubtype = 0x02;
    pACITDesc->bTerminalID = 0x01;
    pACITDesc->wTerminalType = 0x0402;
    pACITDesc->bAssocTerminal = 0x00;
    pACITDesc->bNrChannels = 0x02; // XXX: 0x01
    pACITDesc->wChannelConfig = 0x03; // XXX: 0x0000
    pACITDesc->iChannelNames = 0x00;
    pACITDesc->iTerminal = 0x00;
    // Output Terminal Descriptor
    USB_AC_OT_DESCRIPTOR* pACOTDesc = (USB_AC_OT_DESCRIPTOR*)((char*)pACITDesc + pACITDesc->bLength);
    pACOTDesc->bLength = 0x09;
    pACOTDesc->bDescriptorType = 0x24;
    pACOTDesc->bDescriptorSubtype = 0x03;
    pACOTDesc->bTerminalID = 0x03;
    pACOTDesc->wTerminalType = 0x0101;
    pACOTDesc->bAssocTerminal = 0x00;
    pACOTDesc->bSourceID = 0x01;
    pACOTDesc->iTerminal = 0x00;

从效果上来看，就好像图标变了，别的具体还有什么变化，没在仔细的研究，不过测试了一下，也可以用。