Call-In (Video Call) & Loopback

Call-In Option through Video Call

Since the Telephony has not been functional since 2021, a new way has been implemented to allow listeners to call in and talk with the host during broadcast via video call programs like Zoom, Telegram, Jitsi, etc.

For this setup to work, an application called Loopback is installed in the studio's Mac Mini which allows virtual audio routing. A default patch named "Call-in Routing" is created to connect audio for Call-in session. This patch should be enabled at all time.

Workflow

1. Guest(s) call in via video call (e.g. Zoom) to the studio's Mac Mini

2. Audio from the guest(s) are routed to the studio mixer and mixed to the broadcasted audio stream with other materials (music, host talking, etc.)

3. A separate mix EXCLUDING the call-in guests' audio is route back from the mixer to the video call application (e.g. Zoom), so that call-in guest can hear what is broadcasted at the moment excluding their voices and react to the situation.

Setup

Before starting to mix, please make sure:

1. studio's Mac Mini

• Make sure the computer's default audio output device is set to "X-USB" (which is the mixer). It can be done by clicking the speaker icon on the top right part of the computer.

1. Loopback

• Device on the left "Call-in Routing" is enabled.

• In the device "Call-in Routing" at the "Sources" column on the left, please enable the application you are using for video call (e.g. Zoom, Telegram, Brave Browser (if you are using a browser based video call like Google Meet in this browser)), make sure it is connected to the "Channels 3 & 4" in the middle column called "Output Channels" and nothing else, and press the drop down "Option" of this source and make sure "Mute when capturing" is CHECKED

• If your application used for video call is not already displayed, make sure your application is open, and then press the "+" button next to "Sources" and select it. The new source you selected will appear below. Disconnect it from "Channels 1 & 2" and connect it to "Channels 3 & 4"

• Make sure all the other applications in the "Sources" EXCLUDING "X-USB" is disabled

• The Loopback application does not need to be opened during the session, but the device "Call-in Routing" needs to be enabled even when you close the application

1. Video call application

• Set the Audio Input in your call to "Call-in Routing"

• The output doesn't really matter since Loopback will mute it, you can set it to the "Mac mini Speakers" just to be safe

Mixing

During the session, the audio engineer should prepare and manage two separate mixes - 1) one mix for the broadcast stream (what the listener will actually hear), and 2) a separate mix for the call-in guest(s) via video call application (e.g. Zoom).

The broadcast stream (sending to the MAIN stream) should include:

• Music being played (e.g. from the studio's Mac Mini (input ch. 17-18 of the mixer), microphone of the host and people in the room (e.g. input ch. 1-8 of the mixer), etc.)

• Audio from call-in guest (video call application) - Input Channel 19-20

The mix for the call-in guest(s) (sending to output channel 9-10 on the mixer) should include:

• Music being played (e.g. from the studio's Mac Mini (input ch. 17-18 of the mixer), microphone of the host and people in the room (e.g. input ch. 1-8 of the mixer), etc.)

  • CAUTION!! - Input Channel 19-20 must NOT be included, otherwise it will cause feedback.

Monitoring

Host/guests in the Radio Studio are highly encouraged to use headphones through the Headphone amplifier to avoid any feedback between the microphones, speakers, and the call-in stream.