Extracting fragments from audio and video content

Yesterday my sweetheart asked me to help her with extracting fragments from video and audio content. I hadn't any tasks at my job today, so I begin my working day with searching for soft which can do this.

First of all, I want to mention that there is a nice tool which can do both of this tasks - Vidmex, but 1) a trial version can work with 3sec fragments 2) crack is very hard task to find - there are many cracks available but to download any of them you must register at crack site, which is not free.

I have chosen on 2 products (both are shareware but have trial period - 30 days. Easy workaround - before installing and running for the first time add a few years to current system time's year, after this set the valid time).

For video I have chosen Advanced X Video Converter 4.7.1
For audio - Acoustica 4.0 from Acon Digital Media

Telling the truth I have looked through the catalog of multimedia soft and simply choosed the first available soft which can help me to achieve my goals somehow, that's why both product names begin with 'A' :D

Turning monitor off - my WinAPI experience

Having some free-of-tasks time at my job I decided to create a simple utility which can turn off the my laptop display. I needed such a tool because sometimes display light is very annoying - for example when you are high and want just to listen for a music. It annoys me with ilumination even with "Blank screen" screensaver.

Of course there are plenty of such a soft available on the Internet (however it is all shareware), but as I already have said I had a free time at my job and strong interest to low-level programming (it is really low-level comparing to my everyday tasks).

Here is requirements for utility I need:
- It must turn off the display when launched
- It must turn it on back when ESC key is pressed

Very simple isn't it?

I have no problems with turning display on/off:

//Turn off
SendMessage(HWND_TOPMOST, WM_SYSCOMMAND, SC_MONITORPOWER, 2);
//Turn on
SendMessage(HWND_TOPMOST, WM_SYSCOMMAND, SC_MONITORPOWER, -1);

Btw, as the window handle you can pass any valid handle

The only problem I had was Windows hooks. Some experience gathered
- If you want to register global hook you MUST define its function in separate DLL
- When registering global hook (registration code can be in the hook DLL or in the calling process, it doesn't matter) use the following code:
SetWindowsHookEx(WH_KEYBOARD, HookFunction, hDLLInstance, 0);
- If you want to store any data in the DLL process namespace think if it must be shared between all your-DLL-and-process connections - because Windows allocates separate memory space for DLL data for each process that uses this DLL. For example, in my case, as DLL contained system-wide keyboard hook, it will have separate space
for data for each process where hook event occured. But, I need to store HWND variable for my utility hidden window - to send WM_DISPOSE event to it when user press ESC key (it is the best way I know to close application. May be there are better ways, simply I don't know them). So the solution will be to store this HWND value in shared DLL memory space - in this case it doesn't matter which process will "execute" the hook - HWND value will be the same for all the DLL instances.
Here is code example how to define shared-variable section:

//Will store main window handle at shared DLL memory space
#pragma data_seg(".SHARED")
HWND hWnd = NULL;
//hook management
HHOOK hhookKeyboardHook;
#pragma data_seg()
#pragma comment(linker, "/section:.SHARED,rws")

And here is the hook function code:

LRESULT __stdcall HookFunction(int nCode, WPARAM wParam, LPARAM lParam)
{
    if (nCode < 0){ // do not process message 
      return CallNextHookEx((HHOOK)HookFunction, nCode, wParam, lParam);  
    } else if (VK_ESCAPE == wParam){
      //Turn on the monitor
      SendMessage(HWND_TOPMOST, WM_SYSCOMMAND, SC_MONITORPOWER, -1); 
    
      //Release hook
      if(NULL != hhookKeyboardHook ){
          UnhookWindowsHookEx(hhookKeyboardHook );
      }

      //Send message to close application
      SendMessage(hWnd, WM_DESTROY, 0, 0);  
    }

    //calling next hook which may exist
    return CallNextHookEx((HHOOK)HookFunction, nCode, wParam, lParam);  
}

And code which sets the hook:

__declspec(dllexport) void __stdcall SetHook(HWND windowHandle){
    hWnd = windowHandle;
    SendMessage(HWND_TOPMOST, WM_SYSCOMMAND, SC_MONITORPOWER, 2);
    SetWindowsHookEx(WH_KEYBOARD, HookFunction, hInst, 0);
}

Both functions are located at separate DLL, SetHook is marked as __declspec(dllexport) to be able to dynamically call it from dynamically loaded DLL library. I used Microsoft Visual Studio 2003 to work on this problem.