AudioCodes Mediant 2000, User Manual

Page: 358 / 418

SIP User's Manual 358 Document #: LTRT-68808
Mediant 2000
Below is an example of media descriptions of an SDP indicating support for V.152.
v=0
o=- 0 0 IN IPV4 <IPAdressA>
s=-
t=0 0
p=+1
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 u-law as the VBD codec) as well as the voice codecs G.711
μ -law and
G.729.
Instead of using VBD transport mode, the V.152 implementation can use alternative relay
fax transport methods (e.g., 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.
To configure T.38 mode, use the CoderName parameter.
7.6 Event Notification using X-Detect Header
The device 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 device configurations need to be performed. The table
below lists the support event types (and subtypes) and the corresponding device
configurations, if required:
Table 7-2: Supported X-Detect Event Types
Events Type Subtype Required Configuration
AMD
voice
automatic
silence
unknown
EnableDSPIPMDetectors = 1
AMDTimeout = 2000 (msec)
CPT
SIT SITDetectorEnable = 1
UserDefinedToneDetectorEnable = 1
FAX
CED (IsFaxUsed ≠ 0) or (IsFaxUsed = 0, and
FaxTransportMode ≠ 0)
modem VxxModemTransportType = 3
PTT
voice-start
voice-end
EnableDSPIPMDetectors = 1