A problem with mmioOpen API

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I am trying to make an audio player that plays .wav files. I wrote a function ReadWaveFile(CString szFilename) for reading the wave data of the file into the WAVEHDR structure. In this function

<pre>
BOOL CWavePlay::ReadWaveFile(CString szFilename)
{
	hmmio = mmioOpen((LPTSTR)&szFilename,NULL,MMIO_READ);
	ASSERT(hmmio);		//error here: hmmio=0x00000000
	if(hmmio==0)
		return FALSE;
        ....
}

mmioOpen is always returning 0 whenever I pass a filepath to this function for opening the specified file. And what baffles me is when i pass the filepath explicitly in mmioOpen API the code works; i.e., a valid handle is returned.
can some body explain why is this happening??

Posted 28-Mar-12 19:17pm

stib_markc

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«_Superman_» · Accepted Answer · 2012-03-28T19:44:00

Solution 1

Try this - hmmio = mmioOpen((LPTSTR)szFilename,NULL,MMIO_READ);
You could also use the PlaySound API with the SND_FILENAME flag.

Posted 28-Mar-12 19:44pm

«_Superman_»

Comments

stib_markc 29-Mar-12 1:50am

That is what i actually did, please see my code...
PlaySound works only with small files. As I said I am trying to make an audio player, not trying to add (small)sounds to my program.

«_Superman_» 29-Mar-12 2:07am

If you look carefully you will see that an & is missing in my post.
Are you sure PlaySound only works with small files. I'm not aware of this limitation. Please check with multiple files.

stib_markc 29-Mar-12 2:58am

error C2440: 'type cast' : cannot convert from 'class CString' to 'char *' the code doent build... and yes the PlaySound function doesn't play the file fully(if it is larger than normal windows sound files). I checked it with multiple files.

«_Superman_» 29-Mar-12 3:30am

Try this - hmmio = mmioOpen((LPTSTR)(LPCTSTR)szFilename,NULL,MMIO_READ);

stib_markc 29-Mar-12 3:39am

Thank you <<_Superman_>> the problem is solved.... but why this type of casting is needed, I mean what is difference?

«_Superman_» 29-Mar-12 3:47am

The CString class has an overloaded LPCTSTR operator which returns a const TCHAR*.
So the inner cast is an explicit call to this overloaded operator which we then cast to a LPTSTR which is nothing but a TCHAR*.

stib_markc · Accepted Answer · 2012-03-28T22:40:00

Solution 2

the solution is:

<pre>hmmio = mmioOpen((LPTSTR)(LPCTSTR)szFilename,NULL,MMIO_READ);

Posted 28-Mar-12 22:40pm

stib_markc