The following code illustrates how to update header attributes.

   HMMIO hmmio1;
   MMAUDIOHEADER mmAudioHeader;
   LONG lBytesWritten;
   ULONG ulReserved = 0L;
   ULONG ulFlags = 0L;
   ULONG rc;
    ...

   memset( &mmAudioHeader, '\0', sizeof(MMAUDIOHEADER));
    ...

   rc = mmioSetHeader( hmmio1,
                       (PVOID)&mmAudioHeader,
                       (LONG)sizeof(MMAUDIOHEADER),
                       &lBytesWritten,
                       ulReserved,
                       ulFlags);
   if (rc)
     /* error */
   else
    ...