I am writing an application that needs to temporarily disable the Play/Pause button that appears on multimedia keyboards.

Normally, a key can be blocked quite easily by installing a low level keyboard hook (WH_KEYBOARD_LL) where the KeyboardProc intercepts the key (in this case VK_MEDIA_PLAY_PAUSE) and returns a "1" instead of calling CallNextHookEx. I have tried this with other keys (including the Windows key VK_LWIN) and this works perfectly. I also have no problems with this method under Windows 7 where all keys, including VK_MEDIA_PLAY_PAUSE get blocked.

Windows 8 is a different story. When my application has input focus, everything works as expected, meaning the VK_MEDIA_PLAY_PAUSE key gets blocked and no other application responds to it. However, when my application loses focus, my hook procedure gets called (this was verified by sending out a OutputDebugString) but other applications respond to key even though I return a "1". As soon as my app gets focus again, everything is block as it should.

After some investigation, I found that the multimedia keys not only generate keystrokes but also generate WM_APPCOMMAND messages so I added ShellProc (WH_SHELL) hook with the following hook procedure:

LRESULT __declspec(dllexport)__stdcall CALLBACK ShellProc(int nCode,WPARAM wParam,LPARAM lParam)
// Do we have to handle this message?
OutputDebugStringX(">>>>> HSHELL_APPCOMMAND");
// Process the hook if the hNotifyWnd window handle is valid
short AppCommand = GET_APPCOMMAND_LPARAM(lParam);
switch (AppCommand)
OutputDebugString(">>>>>ShellProc got a media command");
return 1;


// Call the next handler in the chain
return CallNextHookEx (hsh, nCode, wParam, lParam);

This procedure is only getting called when my app has input focus. Whenever I have input focus and return "1" the Play/Pause command gets blocked. As soon as I lose focus the procedure does not get called/hooked.

Anyone have any idea as to what is going on? As I have mentioned, the code works for other keys, just not the multimedia keys.

Alternatively, can anyone suggest another way of blocking the multimedia keyboards Play/Pause button?