Problem reading a recorded file.

Question

4.50/5 (2 votes)

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Hello, I am doing an audio recording application. I am writing the audio data to a file. I am trying to read the data in the file and add it to a buffer. During debugging, I find the error is pointing to:

ASSERT(AfxIsValidAddress(lpBuf, nCount));

of the

CFile::Read

function. Here is the code:

C#

void CWaveIn::WriteWaveFile()
{
    CString* databuf;   //buffer to hold the data from the file.
    databuf = NULL;
    databuf = new CString;
    CFile my_file,f1;
    if(my_file.Open(m_strFile,CFile::modeRead|CFile::shareDenyNone,NULL))
    {   
       unsigned int x =  ;
       int iRead = my_file.Read((void*)databuf, my_file.GetLength());//error here
       .....

If you think, I have problem with my recording, I am pasting that code as well:
(I am using a callback thread, for recording. The thread's function is written below)

DWORD WINAPI CWaveIn::ThreadProc(LPVOID lpParameter)
{
    CWaveIn* pWaveIn     = (CWaveIn*)lpParameter;
    MSG msg;
    DWORD dwWait      = 0;
    DWORD dwUser      = 0;
    WAVEHDR *pWaveHdr = NULL;
    if (pWaveIn == NULL)
    {
        return -1;
    }
    while ((dwWait = WaitForSingleObject(pWaveIn->m_hEventKill, 5)) != 0)
    {
        // Handle MMAPI wave capturing thread messages
        while (PeekMessage(&msg, 0, 0, 0, PM_REMOVE))
        {
            switch (msg.message)
            {
            case MM_WIM_DATA:
                EnterCriticalSection(&pWaveIn->m_critSecRtp);
                pWaveHdr = (WAVEHDR*)msg.lParam;      
                // Unprepare header, initialize with the next buffer position, prepare the header
                //  again and add it to the wave capture device.
                if (pWaveHdr)
                {
                    waveInUnprepareHeader(pWaveIn->m_hWaveIn, pWaveHdr, sizeof(WAVEHDR));
                    dwUser = pWaveHdr->dwUser;
                    //m_fRecord is a FILE* in CWaveIn class                       
                    fwrite(pWaveHdr->lpData, 1, pWaveHdr->dwBytesRecorded, pWaveIn->m_fRecord);
                    ZeroMemory(pWaveHdr, sizeof(WAVEHDR));                       
                    pWaveHdr->dwBufferLength = BYTES_PER_HDR;
                    pWaveHdr->lpData = (char*)pWaveIn->m_HdrBuffer[dwUser];
                    pWaveHdr->dwUser = dwUser;
                    waveInPrepareHeader(pWaveIn->m_hWaveIn, pWaveHdr, sizeof(WAVEHDR));
                    waveInAddBuffer(pWaveIn->m_hWaveIn, pWaveHdr, sizeof(WAVEHDR));
                }
                LeaveCriticalSection(&pWaveIn->m_critSecRtp);
                break;
            default:
                break;
            }
        }
    }
    CloseHandle(pWaveIn->m_thread);
    pWaveIn->m_thread = NULL;
    return 0;
}

Posted 3-Jul-12 18:52pm

stib_markc

Updated 3-Jul-12 18:56pm

v3

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OriginalGriff · Accepted Answer · 2012-07-03T18:59:00

Why are you assigning a new, empty CString to the buffer and then reading into it?

C#

CString* databuf;   //buffer to hold the data from the file.
databuf = NULL;
databuf = new CString;
...
int iRead = my_file.Read((void*)databuf, my_file.GetLength());//error here

Surely, assigning a buffer that was big enough to hold the data in the file would be a better idea? An empty CString is not going to "magically" expand itself to cope with the file data just because you have assigned it and cast it to a pointer-to-void! Have a look at the CFile.Read function, and allocate a buffer instead: http://msdn.microsoft.com/en-us/library/ctka0kks(v=vs.80).aspx[^]

barneyman · Accepted Answer · 2012-07-03T19:03:00

Solution 2

you're using CString incorrectly

It does not represent an object with a buffer that you can scribble into ...

change it to

char *databuf=new char[my_file.GetLength()];

inside the .Open clause

and make sure you delete it on the way out

Posted 3-Jul-12 19:03pm

barneyman

Comments

stib_markc 4-Jul-12 1:23am

Thank you.