Global Call IP over Host-based Stack Technology User's Guide: 3.4.5. gc

3.4.5. gc_Extension( )

The gc_Extension( ) function can be used for the following purposes:

Getting notification for T.38 fax events
Retrieve call-related information
Getting notification of underlying protocol connection or disconnection state transitions
Getting notification of media streaming initiation and termination in both the transmit and receive directions
Specifying which DTMF types, when detected, provide notification to the application
Sending DTMF digits
Retrieving protocol messages (Q.931, H.245 and registration)
Sending protocol messages (Q.931, H.245 and registration)

Table 1 shows the valid extension IDs and their purpose.

Table 1. Valid Extension IDs for the gc_Extension( ) Function

Extension ID

Description

IPEXTID_FOIP Used in GCEV_EXTENSION events for notification of information related to fax. See Section 4.14, Enabling and Disabling Unsolicited Notification Events for more information.

IPEXTID_GETINFO Used to retrieve call-related information. See Section 4.5, Retrieving Current Call-Related Information for more information.

IPEXTID_IPPROTOCOL_STATE Used in GCEV_EXTENSION events for notification of intermediate protocol states, such as, Q.931 and H.245 session connections and disconnections. See Section 4.14, Enabling and Disabling Unsolicited Notification Events for more information.

IPEXTID_MEDIAINFO Used in GCEV_EXTENSION events for notification of the initiation and termination of media streaming in the transmit and receive directions. In the case of media streaming connection notification, the datatype of the parameter is IP_CAPABILITY and consists of the coder configuration that resulted from the capability exchange with the remote peer. See Section 4.14, Enabling and Disabling Unsolicited Notification Events for more information.

IPEXTID_RECEIVE_DTMF Used to select which DTMF types, when detected, provide notification to the application. See Section 4.14, Enabling and Disabling Unsolicited Notification Events for more information.

IPEXTID_RECEIVEMSG Used in GCEV_EXTENSION events when Q.931, H.245 and non-standard registration messages are received.

IPEXTID_SEND_DTMF Used to send DTMF digits. When this call is successful, the sending side receives a GCEV_EXTENSIONCMPLT event with the same ext_id. The remote side receives a GCEV_EXTENSION event with IPEXTID_RECEIV_DTMF but only when configured for notification of a specific type of DTMF. See Section 4.14, Enabling and Disabling Unsolicited Notification Events for more information.

IPEXTID_SENDMSG Used to send Q.931, H.245 and RAS messages. The supported parameter sets are:

IPSET_MSG_H245
IPSET_MSG_Q931
IPSET_MSG_RAS
When the gc_Extension( ) call completes successfully, the sending side receives a GCEV_EXTENSIONCMPLT event with the same ext_id. The remote side receives a GCEV_EXTENSION event with an ext_id field value of IPEXTID_RECEIVEMSG.

The gc_Extension( ) function is only used in the context of a call where the protocol is already known, therefore the protocol does not need to be specified. When protocol-specific information is specified and it is not of the correct protocol type, for example, attempting to send a Q.931 FACILITY message in a SIP call, the operation fails.

See the Section 4.5.2, Example of Retrieving Call-Related Information for a code example showing how to identify the type of extension event and extract the related information.

**Table 1. Valid Extension IDs for the gc_Extension( ) Function**
Extension ID	Description
IPEXTID_FOIP	Used in GCEV_EXTENSION events for notification of information related to fax. See Section 4.14, Enabling and Disabling Unsolicited Notification Events for more information.
IPEXTID_GETINFO	Used to retrieve call-related information. See Section 4.5, Retrieving Current Call-Related Information for more information.
IPEXTID_IPPROTOCOL_STATE	Used in GCEV_EXTENSION events for notification of intermediate protocol states, such as, Q.931 and H.245 session connections and disconnections. See Section 4.14, Enabling and Disabling Unsolicited Notification Events for more information.
IPEXTID_MEDIAINFO	Used in GCEV_EXTENSION events for notification of the initiation and termination of media streaming in the transmit and receive directions. In the case of media streaming connection notification, the datatype of the parameter is IP_CAPABILITY and consists of the coder configuration that resulted from the capability exchange with the remote peer. See Section 4.14, Enabling and Disabling Unsolicited Notification Events for more information.
IPEXTID_RECEIVE_DTMF	Used to select which DTMF types, when detected, provide notification to the application. See Section 4.14, Enabling and Disabling Unsolicited Notification Events for more information.
IPEXTID_RECEIVEMSG	Used in GCEV_EXTENSION events when Q.931, H.245 and non-standard registration messages are received.
IPEXTID_SEND_DTMF	Used to send DTMF digits. When this call is successful, the sending side receives a GCEV_EXTENSIONCMPLT event with the same ext_id. The remote side receives a GCEV_EXTENSION event with IPEXTID_RECEIV_DTMF but only when configured for notification of a specific type of DTMF. See Section 4.14, Enabling and Disabling Unsolicited Notification Events for more information.
IPEXTID_SENDMSG	Used to send Q.931, H.245 and RAS messages. The supported parameter sets are: IPSET_MSG_H245 IPSET_MSG_Q931 IPSET_MSG_RAS When the gc_Extension( ) call completes successfully, the sending side receives a GCEV_EXTENSIONCMPLT event with the same ext_id. The remote side receives a GCEV_EXTENSION event with an ext_id field value of IPEXTID_RECEIVEMSG.

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