4.6.1. Specifying DTMF Support

Global Call can be used to configure which DTMF modes (UII Alphanumeric, RFC 2833, or Inband) are supported by the application. The DTMF mode can be specified:

• For all line devices simultaneously using gc_SetConfigData( ).
• On a per line device basis using gc_SetUserInfo( ) with a duration parameter value of GC_ALLCALLS.
• On a per call basis using gc_SetUserInfo( ) with a duration parameter value of GC_SINGLECALL.

The GC_PARM_BLK associated with the gc_SetConfigData( ) or gc_SetUserInfo( ) function identifies which DTMF modes are supported. The GC_PARM_BLK includes the following parameter set ID and parameter ID:

• IPSET_DTMF - The parameter set specific to DTMF.
  • IPPARM_SUPPORT_DTMF_BITMASK - Parameter ID that specifies the DTMF transmission mode(s). The possible values are:
    • IP_DTMF_TYPE_ALPHANUMERIC - This is the default.
      - For H.323, DTMF digits are sent and received in H.245 User Input Indication (UII) Alphanumeric messages.
      - For SIP, this value is not supported, therefore, one of the two options following must be explicitly specified.
    • IP_DTMF_TYPE_INBAND_RTP - DTMF digits are sent and received inband via standard RTP transcoding.
    • IP_DTMF_TYPE_RFC_2833 - DTMF digits are send and received in the RTP stream as defined in RFC 2833.

Note: The IPPARM_SUPPORT_DTMF_BITMASK can only be replaced; it cannot be modified. For each gc_SetConfigData( ) or gc_SetUserInfo( ) call, the IPPARM_SUPPORT_DTMF_BITMASK parameter is overwritten.

The mode in which DTMF is transmitted (Tx) is determined by the intersection of the mode values specified by the IPPARM_SUPPORT_DTMF_BITMASK and the receive capabilities of the remote endpoint. When this intersection includes multiple modes, the selected mode is based on the following priority:

1. RFC 2833
2. H.245 UII Alphanumeric (H.323 only)
3. Inband

The mode in which DTMF is received (Rx) is based on the selection of transmission mode from the remote endpoint, however RFC 2833 can only be received if RFC 2833 is specified by the IPPARM_SUPPORT_DTMF_BITMASK parameter.

Table 10 summarizes the DTMF mode settings and associated behavior.

Table 10. Summary of DTMF Mode Settings and Behavior

IP_DTMF_ TYPE_ RFC_2833	IP_DTMF_ TYPE_ ALPHA NUMERIC †	IP_DTMF_ TYPE_ INBAND	Transmit (Tx) DTMF Mode	Receive (Rx) DTMF Mode
1 (enabled)	0 (disabled)	0 (disabled)	RFC 2833 if supported by remote endpoint, otherwise UII Alphanumeric †	RFC 2833, UII Alphanumeric † or Inband as chosen by the remote endpoint
0 (disabled)	1 (enabled)	0 (disabled)	UII Alphanumeric †	UII Alphanumeric † or Inband as chosen by the remote endpoint
0 (disabled)	0 (disabled)	1 (enabled)	Inband	UII Alphanumeric † or Inband as chosen by the remote endpoint
0 (disabled)	1 (enabled)	1 (enabled)	UII Alphanumeric †	UII Alphanumeric † or Inband as chosen by the remote endpoint
1 (enabled)	1 (enabled)	0 (disabled)	RFC 2833 if supported by remote endpoint, otherwise UII Alphanumeric †	RFC 2833, UII Alphanumeric † or Inband as chosen by the remote endpoint
1 (enabled)	0 (disabled)	1 (enabled)	RFC 2833 if supported by the remote endpoint, otherwise Inband	RFC 2833, UII Alphanumeric † or Inband as chosen by the remote endpoint
1 (enabled)	1 (enabled)	1 (enabled)	RFC 2833 if supported by the remote endpoint, otherwise UII Alphanumeric †	RFC 2833, UII Alphanumeric † or Inband as chosen by the remote endpoint
† Applies to H.323 only.

When using RFC 2833, the payload type is specified using the following parameter set and parameter ID:

• IPSET_DTMF
  • IPPARM_DTMF_RFC2833_PAYLOAD_TYPE - Identifies the payload type. Possible values are:
    • IP_USE_STANDARD_PAYLOADTYPE (default payload type, 101)
    • A value in the range 96 to 127 (dynamic payload type)

Click here to contact Telecom Support Resources