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This message is sent when a change in the call's media type is detected. The sending of this message is controlled with the lineMonitorMedia function.

    hDevice = (DWORD) hCall;
    dwCallbackInstance = (DWORD) hCallback;
    dwParam1 = (DWORD) MediaMode;
    dwParam2 = (DWORD) 0;
    dwParam3 = (DWORD) TickCount;


Handle to the call.


Callback instance supplied when opening the line.


New media type (or mode). This parameter must be one and only one of the LINEMEDIAMODE constants.


Not used by this message. Value is NULL.


Tick count (the number of milliseconds since Windows started) at which the specified media was detected. For TAPI versions earlier than 2.0, this parameter is not used.

The LINE_MONITORMEDIA message is sent to the application that has enabled media monitoring for the media type detected.

Because this timestamp may have been generated on a computer other than the one on which the application is executing, it is useful only for comparison to other similarly timestamped messages generated on the same line device (LINE_GATHERDIGITS, LINE_MONITORDIGITS (TAPI), LINE_MONITORMEDIA), in order to determine their relative timing (separation between events). The tick count can wrap around after approximately 49.7 days; applications must take this into account when performing calculations.

If the service provider does not generate the timestamp (for example, if it was created using an earlier version of TAPI), TAPI provides a timestamp at the point closest to the service provider generating the event so that the synthesized timestamp is as accurate as possible.



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