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Global Call IP Technology Guide — November 2007 363
Dialogic Corporation
Third Party Call Control (3PCC) Operations and Multimedia Support
Figure 73. Successfully Modifying the Coder (part one)
IPML
Library A
Application A
Global Call
Library A
(IPCCLIB)
Application B
Global Call
Library B
(IPCCLIB)
IPML
Library B
gc_MakeCall
SDP Offer 1
GCEV_DIALING
ipm_StartMedia
(RCV_ONLY)
INVITE
SDP Offer 1
GCEV_OFFERED
SDP Offer 1
IPMEV_START_MEDIA
RTP
gc_SetUserInfo
SDP Answer 1
IPMEV_START_MEDIA
180 Ringing
SDP Answer 1
ipm_ModifyMedia
(TxRx)
RTP
IPMEV_MODIFY
_MEDIA
200 OK
SDP Answer 1
GCEV_ANSWERED
GCEV_SIP_ACK
gc_SipAck
ACK
GCEV_REQ
_MODIFY_CALL
SDP Offer 2
ipm_StartMedia(TxRx)
re-INVITE
SDP Offer 2
RTP
SDP added by the application
in a provisional response will be
automatically included in
the dialog's final response.
Duplicate SDPs will not be
delivered to the application.
GCEV_ACCEPT
GCEV_ALERTING
SDP Answer 1
gc_AnswerCall
GCEV_SIP_ACK_OK
ipm_ModifyMedia
(TxRx)
IPMEV_MODIFY
_MEDIA
If the application executes ipm_ModifyMedia( )
when the re-INVITEis transmitted
or when the GCEV_MODIFY_CALL_ACK is
received, there will alway be a short media drop.
This is a limitation in the IPML library.
continued in the
Successfully Modifying the Coder (part two)
figure
GCEV_CONNECTED
gc_ReqModifyCall
SDP Offer 2
gc_AcceptCall
GCEV_SIP_200OK
SDP offer has only one
receive coder specified,
allowing IPML to "start early"
on the offering side.