# Enabling Acoustic Echo Cancellation

Acoustic Echo Cancellation (AEC) is a type of sound processing used to cancel out the noise coming out of your speaker and going into your mic. In LVA this functionality can be useful to allow LVA to listen to wake words even when audio is playing, particularly when a timer is playing. PulseAudio and PipeWire already provide built-in modules for AEC.

## Enabling AEC

### PulseAudio
```sh
pactl load-module module-echo-cancel source_name=aec_mic aec_method=webrtc
```

To make permanent, add to `/etc/pulse/default.pa`:
```
load-module module-echo-cancel source_name=aec_mic aec_method=webrtc
```

### PipeWire
```sh
pw-cli load-module libpipewire-module-echo-cancel '{ source.props={ node.name=aec_mic } }'
```

To make permanent, add the following to the `context.modules` section of `/etc/pipewire/pipewire.conf`:
```
{ name = libpipewire-module-echo-cancel
    args = {
      source.props = { node.name = aec_mic }
    }
}
```

Or if you are using a standard PipeWire installation without a custom `pipewire.conf`, create a new file inside `pipewire.conf.d/`:
```
context.modules = [
  { name = libpipewire-module-echo-cancel
    args = {
      source.props = { node.name = aec_mic }
    }
  }
]
```

## Using the AEC Input

In the `.env` file:
```
AUDIO_INPUT_DEVICE="aec_mic"
```

## Changing Source and Sink for AEC

### PulseAudio
```sh
pactl load-module module-echo-cancel source_name=aec_mic aec_method=webrtc source_master=<mic-source> sink_master=<sink>
```

### PipeWire
```sh
pw-cli load-module libpipewire-module-echo-cancel '{ source.props={ node.name=aec_mic node.description="Echo Cancelled Mic" } sink.props={ node.name=aec_sink } capture.props={ node.name=<your-mic-node-name> } playback.props={ node.name=<your-speaker-node-name> } }'
```

To make permanent, add to `context.modules` in `/etc/pipewire/pipewire.conf` or a file in `pipewire.conf.d/`:
```
{ name = libpipewire-module-echo-cancel
    args = {
      source.props = {
        node.name = aec_mic
        node.description = "Echo Cancelled Mic"
      }
      sink.props = {
        node.name = aec_sink
      }
      capture.props = {
        node.name = <your-mic-node-name>
      }
      playback.props = {
        node.name = <your-speaker-node-name>
      }
    }
}
```