How to open the registered CD playing application on Windows

“I need to run whatever is registered to handle audio CDs”

Background

I make all sorts of pieces of software, some on CD-ROM and occasionally that CD can contain Audio tracks. Occasionally, I need to be able to open the local CD playing application – whatever that is (often Windows Media Player). Turns out, getting this to load and auto play can be rather tricky.

“Can’t you just play the .CDA files?”

Not on a CD-ROM. Whilst an Audio CD under Windows appears as a set of .CDA files (pointers to the actual audio tracks), on a CD-ROM, Windows decides that the data volume takes precedence over the audio tracks. They aren’t shown and you can’t find them in Windows Explorer.

(As a point of interest, OS X does mount CD-ROMs that contains audio tracks as a separate Audio track volume and a Data volume).

Time to break out the Windows C++ compiler

Whilst we don’t want to dive too far into the mess that is Windows programming, we do need to do a tiny bit and look at a useful function called ShellExecuteEx (used for asking the Shell to Execute External programs), and the information structure ShellExecuteInfo.

Whilst the ShellExecuteInfo structure looks hideous, it turns out we only need a few bits to open the CD playing app.

The main points to note here are lpFile = NULL, and the lpClass = _T(“AudioCD”) – We don’t need to specify a file, e.g. X:\Track01.cda (because we can’t see it anyway). We also pass in the “play” verb – lpVerb = _T(“play”) asking the system to run the “play” action against the AudioCD entry in the registry. Finally we pass in the lpDirectory = _T(“d:”) – which is the letter of the drive containing the audio CD. In reality the CD Drive may not be on drive D: and this should be a variable.

#include "stdafx.h"
#include <shlobj.h>

int _tmain(int argc, _TCHAR* argv[])
{
    CoInitializeEx(NULL, COINIT_APARTMENTTHREADED | COINIT_DISABLE_OLE1DDE);

    // split the program name into two chunks by :
    char* p = strtok((char*)argv[0], ":");
    char drive[3]={"d:"};
    sprintf(drive, "%s:", p);
  
    // Create and clear out the shellexecuteinfo structure
    SHELLEXECUTEINFO ShExecInfo;
    memset(&ShExecInfo, 0, sizeof(SHELLEXECUTEINFO));

    // Set all the parameters
    ShExecInfo.cbSize = sizeof(SHELLEXECUTEINFO);
    ShExecInfo.fMask = SEE_MASK_CLASSNAME;
    ShExecInfo.lpClass = _T("AudioCD");
    ShExecInfo.lpVerb = _T("play");
    ShExecInfo.hwnd = NULL;
    ShExecInfo.lpFile = NULL;
    ShExecInfo.lpParameters = NULL;
    ShExecInfo.lpDirectory = (LPCWSTR)drive;  // drive letter
    ShExecInfo.nShow = SW_SHOW;   // show the app on screen
    ShExecInfo.hInstApp = NULL;

    BOOL result = ShellExecuteEx(&ShExecInfo);
    if (!result)
    {
	DWORD error = GetLastError();
	return error;
    }
    return 0;
}