Event Notification Using X-Detect Header - 3Com V7122 User Manual

c=IN IP4 <IPAddressA
m=audio <udpPort A> RTP/AVP 18 0
a=ptime:10
a=rtpmap:96 PCMU/8000
a=gpmd: 96 vbd=yes
In the example above, V.152 implementation is supported (using the dynamic payload type
96 and G.711 mu-law as the VBD codec) as well as the voice codecs G.711 mu-law and
G.729.
Instead of using VBD transport mode, the V.152 implementation can use alternative relay fax
transport methods (for example, fax relay over IP using T.38). The preferred V.152 transport
method is indicated by the SDP 'pmft' attribute. Omission of this attribute in the SDP content
means that VBD mode is the preferred transport mechanism for voice-band data.

Event Notification using X-Detect Header

The gateway supports the sending of notifications to a remote party notifying the occurrence
(or detection) of certain events on the media stream. Event detection and notifications is
performed using the X-Detect SIP message header, and only when establishing a SIP
dialog.
For supporting some events, certain gateway configurations need to be performed. The table
below lists the support event types (and subtypes) and the corresponding gateway
configurations, if required:
Supported X-Detect Event Types
Table 50
Events
Type Subtype
AMD voice
automata
silence
unknown
CPT SIT
FAX
CED
modem
PTT voice-start
voice-end
252
Required Gateway Configuration
EnableDSPIPMDetectors = 1
AMDTimeout = 2000 (msec)
SITDetectorEnable = 1
UserDefinedToneDetectorEnable = 1
Note: Differentiation of SIT is not supported in 5.0.
(IsFaxUsed ≠ 0) or (IsFaxUsed = 0 and FaxTransportMode ≠ 0)
VxxModemTransportType = 3
EnableDSPIPMDetectors = 1
V7122 GatewayUser Guide