This message is sent before first mmioRead or mmioWrite streamed at optimum rate to the file.

pmmioinfo (PMMIOINFO)

A pointer to an MMIOINFO data structure.

usMsg (USHORT)

Set to MMIOM_BEGINSTREAM.

lParam1 (LONG)

Contains one of the following values:

STREAM_READ

Read stream from server to client.
STREAM_WRITE
Write stream from client to server.

pParam2 (PQOSInfo)

A pointer to a QOSInfo structure. This structure contains a variable length array of QOS structures. Each QOS structure contains one quality of service parameter (specified in the lQOSParmId field of the QOS structure) which is of one of the following:

SERVICE_REQUEST

This requests the type of service required for this stream. The lQOSValue field of the QOS structure contains the type of service: GUARANTEED, DONTCARE, or DONTRESERVE.
MAX_EE_JITTER
The number of stream buffers for handling jitter. Buffers needed to store a single unit of data are separate. The lQOSValue field of the QOS structure contains the number of buffers.
MAX_DATA_RATE
Maximum data rate in bytes per second. The lQOSValue field of the QOS structure contains this information.
AVG_DATA_RATE
Average data rate in bytes per second. The lQOSValue field of the QOS structure contains this information.

rc (ULONG)

Return codes indicating success or failure:

MMIO_SUCCESS

The file is in streaming mode.
MMIOERR_UNSUPPORTED_MESSAGE
IOProc does not support this message.
MMIOERR_QOSUNAVAILABLE
Quality of service is unavailable.
MMIO_ERROR
Streaming was unsuccessful due to other errors.

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