In this section:
The SBC supports Text over Internet Protocol (ToIP), including the inter-working between ToIP and the Text Telephone (TTY) protocols employed in Code Division Multiple Access (CDMA) wireless networks and wire-line VoIP networks (using Baudot).
The support is applicable to SBC 5400, 7000, SWe (virtual and cloud environments), and CNe.
The T.140 protocol supports the following codecs: AMR-WB, AMR-NB, EVS, G.711, G.722, and Opus.
The following interworkings and related transcodings are also supported:
Based on PSP configuration, the SBC has the capability to generate RTCP for T.140 pass-through media streams if RTCP is not received from other peer. The interval for which the SBC monitors the RTCP packets for T140 stream from endpoints are also defined. If RTCP is not received within the interval, the SBC starts RTCP generation.
For more information, refer to Packet Service Profile - CLI.
Users can control text transcoding using the flag g711T140BaudotAdapt.
|
Parameter | Default | Description | M/O |
---|---|---|---|
| Disable | When this flag is enabled, the SBC can introduce a DSP resource into the call path when the audio codecs are same and while the RTT to Baudot interworking is needed.
Note
This flag only affects the behavior for G.711-G.711 calls for which one leg has T.140 (one m-line with T.140) with a valid port. | O |
set profiles media packetServiceProfile MY_PSP> flags g711T140BaudotAdapt enable commit
In the following example, the Caller (UA-A) provides two streams in its SDP: one for the audio and one for the Real-Time Text media line. Their respective media description is also provided: audio G.729 is specified as the first codec in the intersected Pack Service Profile, and text with t140 subtype on the second stream, but the user could choose ANY codec whose RRT the SBC does not support). A list of codecs could follow G.729. When the Call Recipient rejects the T.140 (using port 0), the SBC knows that it must set the DSP to perform transcoding and that no adaptation can take place (no Baudot to/from T.140 adaptation is possible since G.729 does not support T.140).
For this scenario, the DSP is inserted even though there is no text adaptation. In order to have text adaptation, the offer will always start (first codec in the intersected PSP) with a codec for which the SBC supports T.140 (e.g. AMR, AMR-WB, etc.).