Overview

Multicast Switching changes the multicast IP address—called a Channel—that a Decoder subscribes to, so it displays the selected Encoder. This enables fast, reliable source switching without rewiring or reconfiguring routes.

Channel changes can be triggered by a control system, user interface, or API/CLI. Two system modes are available:

• Unified Mode: Audio, video, and USB share the same Channel.
• Flexible Mode: Audio, video, and USB may use unique Channels.

All devices must use the same Mode.

Requirements

1. Compatible with Omega, Ultra, and MaxColor Series devices
2. justOS firmware version B2.1.0 or newer
3. All devices on the same VLAN and within the same IP scheme

For network setup guidance, see Multicast Switching for Single VLAN Implementations.

Concept

In a Multicast Switching system, audio, video, and USB are routed by multicast IP addresses. Each multicast IP maps to a Channel number for simple control and configuration.

• Audio and Video use separate multicast IPs, enabling independent routing in Flexible Mode.
• Each Encoder transmits on its own multicast IP.
• Each Decoder changes its Channel to match the desired Encoder.

Default Multicast IPs

Unified Mode — Audio, video, and USB switch together

• Video — 239.92.0.0
• Audio — 239.92.0.0
• USB — 239.92.0.0

Flexible Mode — Audio, video, and USB can switch together or independently

Omega & Ultra Series

• Video — 239.92.0.0
• Audio — 239.93.0.0
• USB — 239.94.0.0

MaxColor Series

• Video — 239.92.0.0
• Audio — 239.93.0.0
• USB — 239.97.0.0

Multicast IP to Channel Translation

The multicast IP structure defines how Channels are derived:

• The first two octets must match on all devices.
  • The first octet may be changed but must be consistent across the system.
  • The second octet defines the service (e.g., audio/video).
• The last two octets uniquely identify each Encoder and map directly to its Channel number.
• Channel numbers range from 0–9999.

Channel	Multicast IP
0000	239.92.00.00
0099	239.92.00.99
0100	239.92.01.00
9999	239.92.99.99

How It Works

Each Encoder continuously broadcasts on its Channel (multicast IP). A Decoder receives a Channel by joining its multicast group. When the system switches sources, the Decoder leaves one group and joins another, displaying the new Encoder instantly. The switch is triggered by a control command (API, CLI, or UI), so no stream restarts or rewiring are required.

Firewall & Ports

• Telnet (CLI): TCP 23 — Encoder/Decoder configuration (Unified/Flexible selection, astparam).
• HTTP API (justAPI): TCP 80 — Control calls such as POST /cgi-bin/api/command/channel.

Best practice: place devices on a management VLAN, allow only required ports from authorized controller IPs, and block external access.

Control Methods

You can trigger Channel changes via Telnet (CLI), the HTTP API, or the Web Interface. Use Unified or Flexible Mode commands appropriate to your design.

Telnet Protocol

Telnet provides direct CLI access to Encoders and Decoders for channel control, IP configuration, and mode selection.

• Protocol: Telnet
• Port: 23 (default)
• Authentication: None (local network only)
• Session type: Plain-text command interface

Connect with PuTTY (Windows) or the built-in telnet command (macOS/Linux). Send each command as a full line and press Enter.

Security: Telnet is clear-text. Use a trusted VLAN/management network and avoid exposing port 23 to untrusted segments.

Unified Mode — CLI Commands

AMP v1.6.0 and later default to Flexible Mode. Use the commands below only when manually configuring or converting to Unified Mode. All commands are case-sensitive.

Function	Command	Notes
Set Unified Mode	channel mode basic	Applies once system-wide. All services switch together.
Set Channel (Audio & Video)	channel $ChannelNumber	Replace $ChannelNumber with a value from 0–9999.
Set Management IP	astparam s ip_mode static astparam s ipaddr 172.17.128.1 astparam s netmask 255.255.0.0 astparam s gatewayip 172.17.255.254 astparam s save	Send via Telnet/PuTTY only. Do not use web interface for CLI strings.

Flexible Mode — CLI Commands

Default Mode: AMP v1.6.0 and later configure systems in Flexible Mode automatically.

Function	Command	Notes
Set Flexible Mode	channel mode advanced	Apply once, then reboot all devices.
Set Audio Channel	channel -a $ChannelNumber	Replace $ChannelNumber with a value from 0–9999.
Set Video Channel	channel -v $ChannelNumber	Replace $ChannelNumber with a value from 0–9999.
Set USB Channel	channel -u $ChannelNumber	Replace $ChannelNumber with a value from 0–9999.
Set Management IP	astparam s ip_mode static astparam s ipaddr 172.17.128.1 astparam s netmask 255.255.0.0 astparam s gatewayip 172.17.255.254 astparam s save	Send via Telnet/PuTTY only.

HTTP API

The complete HTTP API for justOS is documented here.

HTTP API Channel Command

Unified Mode only. POST /cgi-bin/api/command/channel switches a Decoder to a specific Channel, changing audio, video, and USB together. This Control method does not operate in Flexible Mode (AMP v1.6.0 default configuration).

Endpoint Details

• Method: POST
• URI: /cgi-bin/api/command/channel
• Content-Type: application/json (or text/plain)
• Return: application/json ({"data":...} on success, {"error":...} on failure)
• Port: 80 (HTTP)
• Firmware: justOS B2.1.0 or greater

Request Body

Provide the Channel number (integer 0–9999) the Decoder should join:

{
  "cmd": "set",
  "channel": 100
}

Example Request

POST http://172.17.128.25/cgi-bin/api/command/channel
Content-Type: application/json

{
  "cmd": "set",
  "channel": 100
}

Responses

{"data":"ok"}

{"error":"invalid request"}

All justAPI responses use JSON envelopes:

• "data" — indicates success
• "error" — indicates a problem (invalid parameter or Channel number outside 0–9999)

Usage notes: Applies only to Unified Mode; command executes immediately; send one request at a time and wait for a response; ideal for Crestron, Control4, and Q-SYS.

Web Interface

Set Audio & Video Channel

On an Encoder or Decoder, open Network and enter a Channel (0–9999), then click Apply. The change takes effect immediately.

Set Management IP (Encoder & Decoder)

On the Network tab, enter the IP address, subnet mask, and default gateway. Example: IP 172.17.128.1, Mask 255.255.0.0, Gateway 172.17.255.254.

Verification

• Confirm Decoder Channel assignments in AMP Software.
• Check switch IGMP tables for joins/leaves on expected multicast groups.
• Observe near-instant video transitions when switching sources.