# Call-In (Video Call) & Loopback

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.&#x20;

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.&#x20;

**Workflow**

1. Guest(s) call in via video call (e.g. Zoom) to the studio's Mac Mini&#x20;
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&#x20;

* 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.

2. Loopback&#x20;

* Device on the left "Call-in Routing" is **enabled**.&#x20;
* 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

3. Video call application&#x20;

* 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.)&#x20;
  * **CAUTION!!** - Input Channel 19-20 **must NOT** be included, otherwise it will cause feedback.

**Monitoring**&#x20;

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.&#x20;