lineSetupConference function (tapi.h)

Article
08/23/2022

The lineSetupConference function sets up a conference call for the addition of the third party.

Syntax

LONG lineSetupConference(
  HCALL                  hCall,
  HLINE                  hLine,
  LPHCALL                lphConfCall,
  LPHCALL                lphConsultCall,
  DWORD                  dwNumParties,
  LPLINECALLPARAMS const lpCallParams
);

Parameters

hCall

Handle to the Initial call that identifies the first party of a conference call. In some environments (as described in device capabilities), a call must exist to start a conference call, and the application must be an owner of this call. In other telephony environments, no call initially exists, hCall must be left NULL, and hLine must be specified to identify the line on which the conference call is to be initiated. The call state of hCall must be connected.

hLine

Handle to the line. This handle is used to identify the line device on which to originate the conference call if hCall is NULL. The hLine parameter is ignored if hCall is non-NULL.

lphConfCall

Pointer to an HCALL handle. This location is then loaded with a handle identifying the newly created conference call. The application is the initial sole owner of this call. The call state of hConfCall is not applicable.

lphConsultCall

Pointer to an HCALL handle. When setting up a call for the addition of a new party, a new temporary call (consultation call) is automatically allocated. Initially, the application is the sole owner for this call.

dwNumParties

Expected number of parties in the conference call. This number is passed to the service provider. The service provider is free to do as it pleases with this number: ignore it, use it as a hint to allocate the right size conference bridge inside the switch, and so on.

lpCallParams

Pointer to a LINECALLPARAMS structure containing call parameters to use when establishing the consultation call. This parameter can be set to NULL if no special call setup parameters are desired.

Return value

Returns a positive request identifier if the function is completed asynchronously, or a negative error number if an error occurs. The dwParam2 parameter of the corresponding LINE_REPLY message is zero if the function succeeds or it is a negative error number if an error occurs. Possible return values are:

LINEERR_BEARERMODEUNAVAIL, LINEERR_UNINITIALIZED, LINEERR_CALLUNAVAIL, LINEERR_INVALMEDIAMODE, LINEERR_CONFERENCEFULL, LINEERR_INVALPOINTER, LINEERR_INUSE, LINEERR_INVALRATE, LINEERR_INVALADDRESSMODE, LINEERR_NOMEM, LINEERR_INVALBEARERMODE, LINEERR_NOTOWNER, LINEERR_INVALCALLHANDLE, LINEERR_OPERATIONUNAVAIL, LINEERR_INVALCALLSTATE, LINEERR_OPERATIONFAILED, LINEERR_INVALCALLPARAMS, LINEERR_RATEUNAVAIL, LINEERR_INVALLINEHANDLE, LINEERR_RESOURCEUNAVAIL, LINEERR_INVALLINESTATE, LINEERR_STRUCTURETOOSMALL, LINEERR_USERUSERINFOTOOBIG.

Remarks

If LINEERR_INVALLINESTATE is returned, the line is currently not in a state in which this operation can be performed. A list of currently valid operations can be found in the dwLineFeatures member (of the type LINEFEATURE) in the LINEDEVSTATUS structure. (Calling lineGetLineDevStatus updates the information in LINEDEVSTATUS.) If LINEERR_INVALMEDIAMODE is returned, check for supported media types on the line in the dwMediaModes member in the LINEDEVCAPS structure.

The lineSetupConference function provides two ways to establish a new conference call, depending on whether a normal two-party call is required to pre-exist or not. When setting up a conference call from an existing two-party call, the hCall parameter is a valid call handle that is initially added to the conference call by the lineSetupConference request; hLine is ignored. On switches where conference call setup does not start with an existing call, hCall must be NULL and hLine must be specified to identify the line device on which to initiate the conference call. In either case, a consultation call is allocated for connecting to the party that is to be added to the call. The application can then use lineDial to dial the address of the other party.

The conference call typically transitions into the onHoldPendingConference state, the consultation call into the dialtone state, and the initial call (if there is one) into the conferenced state.

A conference call can also be set up by a lineCompleteTransfer that is resolved into a three-way conference. The application may be able to toggle between the consultation call and the conference call using lineSwapHold.

A consultation call can be canceled by invoking lineDrop on it. When dropping a consultation call, the existing conference call typically transitions back to the connected state. The application should observe the LINE_CALLSTATE messages to determine exactly what happens to the calls. For example, if the conference call reverts back to a regular two-party call, the conference call becomes idle and the original participant call can revert to connected.

If an application specifies the handle of the original call (hCall) in a call to the lineUnhold function, both the conference call and the consultation call typically go to idle.

Requirements

Requirement	Value
Target Platform	Windows
Header	tapi.h
Library	Tapi32.lib
DLL	Tapi32.dll