Features

Dual media streams

Some call scenarios require the outbound INVITE to offer two separate audio media streams rather than the single stream that jambonz normally generates. For example, a carrier, gateway, or recording system on the far end may expect the inbound and outbound audio to be delivered on distinct RTP streams.

jambonz supports this through the dual_streams parameter on the REST create call endpoint (POST /v1/Accounts/{AccountSid}/Calls).

dual_streams is supported only when placing an outbound call through the REST API. It is not available as a property of the dial verb.

How it works

When you set dual_streams: true in the request body, jambonz:

  1. Allocates two media endpoints instead of one.
  2. Merges the SDP from both endpoints into a single offer, producing an INVITE whose SDP contains two m=audio lines (two media streams).
  3. When the far end answers, splits the answering SDP back into its two audio streams, connects each one to its corresponding media endpoint, and bridges the two endpoints together.

The result is a single established call in which the SDP negotiated two audio media streams.

Usage

Set dual_streams to true in the body of the create-call request:

1{
2  "from": "16175551212",
3  "to": {
4    "type": "phone",
5    "number": "15085551000",
6    "trunk": "My Carrier"
7  },
8  "application_sid": "f4790f7e-...-7e75c8c0d9c1",
9  "dual_streams": true
10}
dual_streams
boolean

If true, the outbound INVITE’s SDP offer will contain two audio media streams (two m=audio lines) instead of one. Defaults to false.

Notes and limitations

  • This feature depends on the far end accepting and answering an SDP offer that contains two audio media streams. Not all carriers, gateways, or SIP endpoints support multi-stream offers, so you should test it with your specific provider before relying on it in production.
  • dual_streams only affects how the outbound call’s SDP is generated; it does not change the dialed destination or the application logic that runs on the call.