Unknown Media Mode

Even when the service provider does not know the exact media mode of the call, it might still know which media modes are possible. In this case, the service provider sets a combination of likely media mode bit flags, including LINEMEDIAMODE_UNKNOWN and passes the call to TAPI. The service provider sets these bits both in the dwMediaMode field of the LINECALLINFO record and in the dwParam3 parameter of the first LINE_CALLSTATE message it sends to TAPI.

The service provider considers only the media modes for which applications have opened the line with owner privileges (it becomes aware of these media modes through the TSPI_SetDefaultMediaDetection call) and which it is capable of handling. TAPI informs the provider about the union of all the lines that have been opened with a specified media mode. The provider can use this union to enable only the appropriate media mode detections for which applications are interested. If no applications have opened the line for ownership, the provider will not consider any media modes. Incoming calls are still delivered to TAPI, but no initial owner is possible. In this case, monitoring applications will still be informed of the call, and if none of them changes their privilege to owner and answers the call, the call will remain unanswered.

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