Using the Remote Control Device with Windows

Microsoft Corporation

September 2002

Applies to:
    Microsoft® Windows® XP
    Microsoft Windows XP Media Center Edition

Summary: Learn about the infrared remote control system supported by some Microsoft operating systems and how applications can retrieve input from the remote control device. (11 printed pages)

Introduction
Infrared Input System
Remote Control Buttons
Retrieving Infrared Commands
Handling the Play and Pause Commands
For More Information

Beginning with Microsoft® Windows® XP Service Pack 1, the Microsoft Windows XP Professional Edition and Microsoft Windows XP Media Center Edition operating systems will support input from an infrared remote control device. This device enhances the personal computer's capability to become part of a home entertainment system.

This article provides information about how this remote control system can be used by software developers. It contains the following topics:

• Infrared Input System. Describes the remote control device and its connection to the computer.
• Remote Control Buttons. Describes the standard and optional buttons on the remote control.
• Retrieving Infrared Commands. Describes how an application retrieves commands from the remote control, and which commands are associated with the remote control buttons.
• Handling the Play and Pause Commands. Describes how to handle commands from the Play and Pause buttons on the remote control in combination with Play/Pause commands from the keyboard.
• For More Information. Gives sources of related information.

The following illustration shows a remote control designed for use with a Media Center PC.

Figure 1. Remote control device

The appearance of the remote control may vary from manufacturer to manufacturer. However, the core functionality is constant.

The remote control interacts with an infrared sensor, which consists of the following hardware:

• A receiver component that processes input from the remote control
• A circuit for learning infrared commands
• A universal serial bus (USB) connection that sends input notifications to software running on the computer
• Two emitter ports

In addition, the sensor requires a device driver that supports the Plug and Play specification. A default driver is installed with the versions of the Microsoft Windows operating system that support the infrared sensor.

The USB cable enables users to place the sensor near the monitor so they can point the remote at the monitor when sending commands to the computer. Alternatively, the sensor might be mounted in the front panel of the computer by the manufacturer.

Input from the remote control is processed as follows:

1. The sensor receives the signal and forwards it to a device driver on the computer.
2. The device driver converts the input into a WM_INPUT, WM_APPCOMMAND, WM_KEYDOWN, WM_KEYPRESS, or WM_KEYUP message.
3. Windows places these messages in the message queue to be processed by a program's main window procedure.
4. The foreground program processes messages of interest. For example, a digital media streaming program could process the messages corresponding to the transport buttons (Pause, Play, Stop, Fast Forward, and Rewind) but ignore messages from the numeric keypad.

Remote control design may vary by manufacturer. However, all devices are required to have a set of standard buttons that fall into four categories.

Navigation buttons:

• eHome
• Up
• Down
• Left
• Right
• OK
• Back
• Details
• Guide
• TV/Jump

Transport buttons:

• Play
• Pause
• Stop
• Record
• Fast Forward
• Rewind
• Skip
• Replay

AV and Power Control buttons:

• Volume +
• Volume -
• Chan/Page +
• Chan/Page -
• Mute
• DVD Menu
• Standby

Data Entry buttons:

• 0
• 1
• 2 ABC
• 3 DEF
• 4 GHI
• 5 JKL
• 6 MNO
• 7 PQRS
• 8 TUV
• 9 WXYZ
• Clear
• Enter

In addition to the required buttons, a manufacturer may incorporate the following optional buttons, which are divided into four categories. Applications should not rely on the presence of these buttons.

Shortcut buttons:

• My TV
• My Music
• Recorded TV
• My Pictures
• My Videos

DVD buttons:

• DVD Angle
• DVD Audio
• DVD Subtitle

Keypad buttons:

• #
• *

OEM-specific buttons:

• OEM 1
• OEM 2

This section describes the Windows commands generated by the remote control device driver and how to retrieve them so that your application can respond appropriately to input.

The following table shows the associated messages and keyboard equivalents for the compulsory and optional buttons on the remote control.

Buttons that generate WM_INPUT messages are defined according to the Human Interface Device (HID) specification. The following table shows the HID mapping of these buttons.

In order to process WM_INPUT messages, the application must first register the devices from which it receives data. You can do this by using the Win32® function RegisterRawInputDevices. Each RAWINPUTDEVICE structure passed to this function specifies one usage page and usage.

The following example C++ code registers the device to receive input from the controls defined on the vendor-defined usage page that have a usage of 0x88:

RAWINPUTDEVICE Rid[1];

Rid[0].usUsagePage = 0xFFBC;
Rid[0].usUsage = 0x88; 
Rid[0].dwFlags = 0;

if (RegisterRawInputDevices(Rid, 1, sizeof(Rid[0])) == FALSE) 
{
    ErrorExit();  // Add error-handling code here.
}

To identify the event that triggered a WM_INPUT message, your application must parse the data passed to the window procedure as the lParam parameter.

If you are using the Microsoft .NET Framework, you must implement the WndProc method to retrieve messages. The WndProc method is a member of the NativeWindow class found in the System.Windows.Forms namespace. The overridden method is called each time a new message is placed in the form's message queue. Before returning, the method must call the base WndProc method to ensure that unprocessed messages are handled properly.

The following C# code shows how to use the WndProc method to retrieve WM_KEYDOWN messages:

using System.Windows.Forms;
.
.
.
class Form1Window : NativeWindow
{ 
  private const int WM_KEYDOWN = 0x0100;
  private int iChar;
  public Form1 form;
 
  protected override void WndProc(ref Message message)
  {
    // Handle the navigation and numeric buttons.
 
    if (message.Msg == WM_KEYDOWN)
    {
      iChar = message.WParam.ToInt32();
 
      switch(iChar)
      {
        case (int)Keys.D0:
          // Handle 0 key here.  
          break;
       // Insert more cases here.
.
.
.
      }  // End switch.
    }    // End key messages.
    base.WndProc(ref message);
  }      // End WndProc
}        // End class.

In the initialization code for the main form, you must create an instance of the Form1Window class and assign the main form to it, as follows:

public Form1()
{
  InitializeComponent();
  Form1Window win = new Form1Window();
  win.form = this;
  win.AssignHandle(this.Handle);
} 

The Play and Pause buttons on the remote control generate separate commands, APPCOMMAND_MEDIA_PLAY and APPCOMMAND_MEDIA_PAUSE, respectively. In addition, some keyboards use a single button to switch between the playing and paused states, generating an APPCOMMAND_MEDIA_PLAY_PAUSE message. Applications should be able to process messages from either the remote control or the keyboard, while keeping track of the current playback state and responding appropriately.

The following table shows the playback state, the keyboard or remote control command, and the recommended action an application should take in response to these messages.

To learn more about Human Interface Device (HID) and the structure of HID data, see the USB home page (https://www.usb.org).

To learn more about how to retrieve HID data from a WM_INPUT message, see the Raw Input page at MSDN.