4.13.1. Specifying T.38 Coder Capability

Using Global Call, T.38 coder support is specified in the same manner as any other coder capability, that is:

• On a per line device basis using gc_SetUserInfo( ) with a duration parameter value of GC_ALLCALLS.
• On a per call basis using gc_MakeCall( ) or gc_SetUserInfo( ) with a duration parameter value of GC_SINGLECALL.

To support the initiation of a T.38-only call, the application must specifically disable audio capability. This cannot be achieved by specifying no audio capability, since specifying no audio capability is equivalent to a "don't care" condition meaning all capabilities are enabled. Consequently, the audio capabilities must be explicitly disabled by specifying a GCCAP_AUDIO_disabled capability in the capabilities list.

When specifying the capability on a line device basis or on a per call basis, a GC_PARM_BLK with the following parameter set ID and parameter ID must be set up:

• GCSET_CHAN_CAPABILITY
  • IPPARM_LOCAL_CAPABILITY

The GCPARM_LOCAL_CAPABILITY parameter is of type IP_CAPABILITY and should include the following field values:

• capability - set to GCCAP_DATA_t38UDPFax
• type - GCCAPTYPE_RDATA
• direction - IP_CAP_DIR_LCLTXRX
• payload - Not supported
• extra - A parameter of type IP_DATA_CAPABILITY with the following field values:
  • max_bit_rate - set to a value of 144 (in units of 100 bits/sec)

See Section 7.4, IP_CAPABILITY for more information.

Click here to contact Telecom Support Resources