Dialogic 6.2 - Manual (Page 195)

Making Two-Channel Call Transfers (Tromboning)
November 2009 195
When the application creates a two-channel call transfer, the two
callers become sources of the reflected data. The application must
configure the echo cancellation portion of the channel resource to
remove repeated input from two sources by using its reference signal
slot (the channel’s reference number is 1). The application must also
call the BfvSpeechEchoCancelControl() function to configure the
channel to accept an input reference signal on slot #1.
For example, your application could create a connection from the
output slot of Network resource 1 to the reference input slot of
Channel 0 by calling the BfvSpeechEchoCancelControl() and
BfvCallSWConnect() functions with the following arguments:
BT_ZERO(speech_args);
/* Configure channel to get its input reference signal from slot #1. */
Speech_args.echoc_op = ECHOC_OP_ALT_INPUT_ENABLE;
BfvSpeechEchoCancelControl (lp, &speech_args);
BT_ZERO(args);
args.conn_mode = CALL_SW_TRANSMIT_ONLY_DEF;
args.src_port_class = CALL_SW_PORT_NETWORK_DEF;
args.src_port_unit = 0;
args.src_stream = 0;
args.src_slot = 1; /* Network Timeslot */
args.dest_port_class = CALL_SW_PORT_CHANNEL_DEF;
args.dest_port_unit = 2; /* Logical DSP Channel Number */
args.dest_stream = 0;
args.dest_slot = 1; /* Reference Slot */
BfvCallSWConnect (lp, &args);