Bridges

Bridges connect livematrix to audio hardware: an analog interface, a Dante Virtual Soundcard or Dante interface, a radio, another intercom or a mixing desk. Each bridge line patches one hardware channel to an external user, party line or feed, or to and from a user directly.

There are three ways to bring hardware in:

• Built-in: the sound cards of the server machine itself. Nothing to install.
• Remote: the livematrix bridge, installed on another computer where the hardware is, for example at the desk or in a rack.
• Federation: a link to another livematrix server, whose channels you patch like a sound card.

Patch the server’s own sound cards

Open Bridges, tab Built-in. The built-in bridge is always on; each line’s Enabled box says whether that line runs. The Device lists offer the sound cards the server sees. After you plug one in, open the ⋮ menu next to Add line and choose Rescan audio devices. The Bridges guide button at the top of the page opens this page.

The lines are a table, one line per row. Press Add line, name it, and choose its Target: an external user, a party line or feed, or To / from a user. Each line has an input leg, an output leg, or both:

• Input sends one hardware channel into the target.
• Output plays the target’s audio on one hardware channel, without what this line’s own input sends.
• Both make a four-wire. The two legs may use paired sides of the same interface or different devices.

Choose each leg’s Device and channel (Ch); channels are numbered from

1. Set a leg’s device to Off for a line that only goes one way. Tone plays a test tone instead of the output’s audio, so you can check the hardware path without changing what the line is connected to.

Every change saves as you make it: a list or a box as you choose, a number or the name when you press Enter or leave the field. A new line saves once it has a target and its devices. The next line you add starts on the same devices, one channel further on, so patching a run of channels is choosing a target per row. Remove (the bin) deletes a line without asking.

On a phone the table shows each line’s name, target and levels. Tap the arrow at the start of a row to open the rest: Enabled, the devices, channels and gains, the test tone, the state, and the buttons to move or remove the line.

Connect a remote bridge

Install the livematrix bridge on the computer with the hardware. The installers for Windows, macOS and Linux are on the Download page. The bridge runs as a service and has its own web page on port 5678.

1. In the admin, open Bridges, tab Remote, and press New bridge key. Name it, for example Studio A bridge, and press Generate key. Press Copy.
2. On the bridge computer, open http://localhost:5678 (or http://<bridge computer>:5678 from elsewhere).
3. On the Server tab, under Server Connection, enter the Server URL, for example ws://192.168.1.100:9080/ws, and paste the Bridge Key. Press Save Connection.

The bridge shows Connected on the Remote tab once it is in. Press Configure to edit its lines from the admin, with the same editor as the built-in bridge. The lines are stored on the bridge and apply as soon as it has them. A remote bridge looks for new audio devices by itself every few seconds. The bridge’s own page has the same editor on its Lines tab, with level meters and every line’s state. Its Server tab holds the connection settings and updates, and says how the connection stands: connected and for how long, or why it is not, such as a refused key or an unreachable server, and when it tries again.

All lines of a bridge travel over one encrypted connection. Adding, changing or removing one line does not interrupt the others; only a lost connection interrupts every line of that bridge until it reconnects.

Manage bridge keys

Copy key copies the key again. Revoke disconnects the bridge and keeps it out until you press Activate. Delete removes the key for good; the bridge then needs a new one.

Guard a bridge key like an administrator password. Whoever has it can connect a bridge that talks as any user and listens to any user’s mix.

If the bridge page doesn’t open

The bridge page listens on TCP port 5678. If another machine cannot open it, allow the livematrix bridge through the Windows or macOS firewall, or open port 5678 in ufw or firewalld on Linux.

livematrix-bridge-ctl (with sudo on Linux, and from an administrator command prompt in the bridge’s installation folder on Windows) can set the server URL (--set-server-url), restart the bridge (--restart) and reset the page’s password (--reset-ui-password). On a Mac, the bridge’s menu bar icon can restart the bridge, reset the page’s password and change the page’s port (Configure Port…); set the server URL on the bridge page.

Allow microphone access on macOS

When a bridge first opens an input, macOS asks for microphone access on the computer running that bridge. The affected lines show Waiting for permission. Choose Allow in the macOS dialog; the inputs start automatically. Client connections and playback remain available while the dialog is waiting.

If the lines show Microphone access blocked, enable access for livematrix in System Settings → Privacy & Security → Microphone on that computer. For the built-in bridge, this is the server computer.

Connect hardware as an external user

Choose a user under External users when the hardware is how that person takes part, for example a panel or beltpack of another intercom, or a headset on the interface. The line acts as one more device of that user. Its output plays the user’s mix. Its input talks as the user, with their keys.

All of a user’s devices share one microphone. A sole live bridge input becomes the microphone automatically. Connecting or renegotiating a bridge does not take the microphone away from another live device. If another device owns it, the bridge input is gated; use Take over mic once when you intend to move ownership to the bridge.

Connect hardware to and from a user directly

Choose To / from a user when the hardware should reach that user’s ears or take their microphone without being one of their devices: a talkback or IFB into a presenter’s earpiece, or an iso of their voice to a recorder.

• Input plays in the user’s ears at all times, at the leg’s gain. No key needs to be pressed, and nobody else hears it, not even someone listening to the user.
• Output carries the user’s microphone whenever it is unmuted, whatever keys they press. It carries nothing else.

The line never takes over the user’s microphone, and it shows no Take over mic.

Connect hardware to a party line or feed

A bridge line targeting a party line contributes its input to that line and plays the other contributors on its output. It never returns its own input. Two bridge lines on the same party line are separate participants, so each hears the other.

A feed works the same way for bridge hardware: an input contributes audio and an output monitors all other contributors without returning itself. Feed keys in the app remain listen-only.

Set a leg’s gain and watch its level

Each leg that is on has a gain in dB, from −60 to +24 (0.1 dB steps), in the dB column next to its channel. The input gain sets how loud the hardware channel reaches its target; the output gain sets how loud the line plays on its hardware channel, test tone included. The change is saved and heard as soon as you press Enter. The line keeps running, and no other line is touched.

In the Levels column a meter per leg shows its level after the gain, with a peak hold. Two dots at its end light for a few seconds when the leg clips:

• Red means clipping after the gain. Lower the gain.
• Amber means clipping before the gain. The signal arrives at full scale already. Lower the source (the interface’s preamp, or whatever feeds the line); the gain cannot fix it.

A dimmed meter means the leg is not measured. Either it is not running, or, on an output, its audio has not arrived yet. The line’s status says why. The management UI shows meters for the built-in bridge. A standalone bridge shows its meters in its own web UI, and the management UI shows its gains without meters.

Pair duplex devices

When the operating system reports the capture and playback sides of one interface as a pair, choosing the input side preselects its playback side for the output, even when the output leg is off. An output you selected explicitly is never replaced. Channels are not chosen for you, except on a federation link, where the output follows the input’s channel. On Windows, the computer’s own built-in devices and loopback (recording of an output) devices are never paired. Check the device and channel on both legs before saving.

Read line status

Each row reports the running state of its input and output: Running, Waiting, Device missing, Channel missing, Link down, Would loop, Disabled, Failed, Refused or Target missing. For a line on an external user, Mic live, Mic gated or Mic owned by another device shows whether its input is heard. A missing target, unavailable device, licence refusal, or media failure stays on that line. Other lines on the same bridge remain connected.

• Refused means the server turned the line down, usually because the licence has no free ports. The row shows the reason and a Retry button.
• Target missing means the user, party line, or feed it targets was deleted. The line keeps its settings; select another target, disable it, or delete it.
• Link down means the federation link the line uses is not connected. The line carries silence until it is back.
• Would loop means that, together with another channel of the same federation link, this line would patch the same two targets to each other and send audio around in a circle. Both servers refuse the line on the later channel. Change the patch on either server.

Nothing retries a refused line on a timer. It is tried again when you press Retry. The built-in bridge also tries every refused line again whenever its lines change; a standalone bridge does when that line’s target or legs change, or when the bridge reconnects. A missing or failing audio device is different: the bridge retries it by itself.

Licence ports

Every enabled bridge line with a target uses licence ports while it runs, on the built-in bridge exactly as on a standalone one. A line targeting a party line or feed, or to / from a user, uses one port per leg: one for input, one for output, two for both. A line on an external user counts as one more device of that user. The test tone uses no extra port. See Console and licence.

Link two servers

Federation links this server to another livematrix server, for example a truck to the broadcast centre. A link shows up on the Built-in tab as a device named Link: and the link’s name. Patch its channels here like a sound card’s; see Federation for a worked example.