PRB: MCI Fails to Read a File Using a Custom mmio Procedure (155703)
The information in this article applies to:
- Microsoft Windows Software Development Kit (SDK) 4.0
- Microsoft Visual C++ 4.1
This article was previously published under Q155703
4.00
WINDOWS
kbprg kbprb
SYMPTOMS
On the Windows 95 platform, the Media Control Interface (MCI) returns
MMSYSTEM348 error when using a custom mmio procedure to read a wave or an
avi file (device element). The text description for MMSYSTEM348 is "Cannot
read this file. Make sure the file hasn't been deleted, or check your disk
or network connection."
CAUSE
The value in the adwInfo[2] member of the MMIOINFO structure is used by
MCIWAVE and MCIAVI drivers. Therefore, its content cannot be trusted when
the custom mmio procedure is invoked to read the custom device element. The
stated problem occurs when a custom mmio procedure uses adwInfo[2] to store
the pointer to the data to be read.
RESOLUTION
A simple workaround is to use a static local variable to retain information
between invocations of the custom procedure. For instance:
static DWORD dwMyLocalVar;
MORE INFORMATION
MCI allows the use of a custom mmio procedure to open a wave or an avi
device. When the custom procedure is invoked, the first argument is a
pointer to MMIOINFO structure. One field in MMIOINFO is adwInfo. In
general, a custom mmio procedure can use adwInfo for state information.
However, if the custom procedure is to be used by MCI drivers, it should
use other local variables to store information. Please note that this
problem only occurs for 32-bit applications running on Windows 95 operating
system.
| Modification Type: | Major | Last Reviewed: | 2/4/2000 |
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| Keywords: | kbmm KB155703 |
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