This project is a quick start guide for revealing Alango DSP algorithms bundled into Respeaker library. Basically, it allows sending pre-processed audio stream to custom ASR engine via WebSockets.

Make sure you installed all the required dependencies on your Respeaker Core V2 board (assuming you already have their official debian distribution):

sudo apt-get update && sudo apt-get -y upgrade
sudo apt-get install -y \
  cmake \
  mraa-tools \
  zlib1g-dev \
  librespeaker-dev \
  libsndfile1-dev \
  libasound2-dev

Don't forget to reboot your board after installation!

This project also depends on IXWebSocket library. You can build it the following way:

git clone https://github.com/machinezone/IXWebSocket.git
cd IXWebSocket && mkdir build && cd build
cmake ..
make -j
sudo make install

Setup Vosk ASR server. We'll use this server later for sending audio chunks from ReSpeaker board.

Pull source code:

git clone https://github.com/sskorol/respeaker-websockets.git
cd respeaker-websockets && mkdir build

Adjust config.json with required values. Note that it'll be automatically copied to the build folder.

{
  "webSocketAddress": "ws://127.0.0.1:2700",
  "respeaker": {
    "kwsModelName": "snowboy.umdl",
    "kwsSensitivity": "0.6",
    "listeningTimeout": 8000,
    "wakeWordDetectionOffset": 300,
    "gainLevel": 10,
    "singleBeamOutput": false,
    "enableWavLog": false,
    "agc": true
  },
  "pixelRing": {
    "ledBrightness": 20,
    "onIdle": true,
    "onListen": true,
    "onSpeak": true,
    "toMute": true,
    "toUnmute": true,
    "idleColor": "teal",
    "listenColor": "blue",
    "speakColor": "purple",
    "muteColor": "yellow",
    "unmuteColor": "green",
    "isMutedOnStart": false
  },
  "hardware": {
    "model": "Respeaker Core V2",
    "ledsAmount": 12,
    "spiBus": 0,
    "spiDev": 0,
    "power": {
      "gpioPin": 66,
      "gpioVal": 0
    }
  }
}

You can use any of the hotwords located in models folder.

Build source code:

cd build
cmake ..
make -j

This script will produce respeaker_core executable in the build folder.

Make sure you have VOSK or other ASR server running. By default respeaker_core uses localhost address trying to establish connection with WS server. You may want to change it to the actual server's address.

Use the following commands to start a speech streaming process:

./respeaker_core

You should see a configuration log and a message about successfull connectivity to WS server and Pixel Ring (implemented based on snips-respeaker-skill sources).

Current app's logic assumes the following chain:

• Apply rate conversion, beamforming, acoustic echo cancellation, noise suppression and automatic gain control to the input audio stream.
• Wake word detection ("snowboy" is a default one). You can change it in config.json.
• When wake word is detected, you will see it in log, as well as the direction which is tracked by DOA (direction of arrival) algorithm. Moreover, a Pixel Ring color state is changed to notify user so that they can start dictating.
• Then we check if the pre-processed chunk is not a hotword to prevent sending it to the WS server. It's required for the hotword's filtering which we don't wanna get a transcribe for.
• Send audio chunks to WS server until we receive a final transcribe or reach a 8s timeout. Transcibe or timeout event also changes Pixel Ring state, which becomes idle.

It's recommended you'll check main.cpp source code and comments to understand what's going on there, and customize it for your own needs.

Install nodejs:

curl -sL https://deb.nodesource.com/setup_14.x | sudo bash -
sudo apt-get install -y nodejs

Install pm2:

sudo npm install pm2@latest -g

Create pm2 startup script:

pm2 startup -u respeaker --hp /home/respeaker
sudo env PATH=$PATH:/usr/bin pm2 startup systemd -u respeaker --hp /home/respeaker

Open pm2 service for editing:

sudo nano /etc/systemd/system/pm2-respeaker.service

Adjust Unit block with the following options:

Wants=network-online.target
After=network.target network-online.target

Adjust Service block with the following option:

LimitRTPRIO=99

It's very important to set this limit (also known as ulimit -r). Otherwise, you won't be able to start this service on boot.

Adjust Install block with the following option:

WantedBy=multi-user.target network-online.target

Restart pm2 service:

sudo systemctl daemon-reload
sudo systemctl restart pm2-respeaker

Add respeaker_core binary to pm2:

pm2 start respeaker_core --watch --name asr --time

Save current process list:

pm2 save

• Refactor code in an object-oriented manner.
• Implement Google / Echo patterns to control Pixel Ring.