Speechmatics Two Way Audio

Expo module for capturing and playing pcm audio data in react-native apps (iOS and Android).

The aim of the module is to facilitate creating real-time conversational apps. The following features are provided:

• Request audio recording permissions
• Get clean (applying Acoustic Echo Cancelling) microphone samples in PCM format (1 channel 16 bit at 16kHz)
• Play audio samples in PCM format (1 channel 16 bit at 16kHz). Playback happens through main speaker unless external audio sources are connected.
• Provide volume level both for the input and output samples. Float between 0 and 1.
• [iOS only] Get microphone mode and prompt user to select a microphone mode.

Check out our examples/ to see the module in action.

Installation

npm i @speechmatics/expo-two-way-audio

Usage

Please check out our examples/ to get full sample code.

1. Request permissions for recording audio

   import {useMicrophonePermissions} from "@speechmatics/expo-two-way-audio";
   
   const [micPermission, requestMicPermission] = useMicrophonePermissions();
   console.log(micPermission);

2. Initialize the module before calling any audio functionality.

   useEffect(() => {
       const initializeAudio = async () => {
           await initialize();
       };
       initializeAudio();
   }, []);

3. Play audio

   [!NOTE] The sample below uses the buffer module: npm install buffer

    import { Buffer } from "buffer";
   
    // As an example, let's play pcm data hardcoded in a variable.
    // The examples/basic-usage does this. Check it out for real base64 data.
    const audioChunk = "SOME PCM DATA BASE64 ENCODED HERE"
    const buffer = Buffer.from(audioChunk, "base64");
    const pcmData = new Uint8Array(buffer);
    playPCMData(pcmData);

4. Get microphone samples

   // Set up a function to deal with microphone sample events.
   // In this case just print the data in the console.
   useExpoTwoWayAudioEventListener(
       "onMicrophoneData",
       useCallback<MicrophoneDataCallback>((event) => {
           console.log(`MIC DATA: ${event.data}`);
       }, []),
   );
   
   // Unmute the microphone to get microphone data events
   toggleRecording(true);

Notes

Some audio features of expo-two-way-audio like Acoustic Echo Cancelling, noise reduction or microphone modes (iOS) don't work on simulator. Run the example on a real device to test these features.

# iOS
npx expo run:ios --device --configuration Release

# Android
npx expo run:android --device --variant release

For Android, the following permissions are needed: RECORD_AUDIO, MODIFY_AUDIO_SETTINGS. In Expo apps they can bee added in your app.json file:

expo.android.permissions: ["RECORD_AUDIO", "MODIFY_AUDIO_SETTINGS"]