Caution

This library is still in very early development.

Kotlin Multiplatform Audio Library

Kodio is a Kotlin Multiplatform library for straightforward audio recording and playback. It leverages coroutines and Flow to provide a modern, asynchronous API for handling audio streams across JVM, Android, Web (JS/Wasm), and iOS.

Usage Example

Here’s a simple loopback example that records audio for 5 seconds and then plays it back.

suspend fun main() {
   // Record some audio for 5 seconds
   val recording = SystemAudioSystem.createRecordingSession()
   recording.start()
   delay(5000)
   recording.stop()
   val audioFlow = recording.audioflow.value
       ?: error("Audio flow should not be null")
   // Playback the recorded audio
   val playback = SystemAudioSystem.createPlaybackSession()
   playback.load(audioFlow)
   playback.play()
}

You can also write it to a file (using kotlinx.io)

 audioFlow.writeToFile(
     format = AudioFileFormat.Wav,
     path = Path("test.wav")
 )

Setup

It is best to fork/clone the repo and build it locally at this point in development. But releases are also published to Maven Central semi-frequently.

Gradle

dependencies {
    implementation("space.kodio:core:0.0.6")
}

Platform-Specific Setup

Android

1. Manifest permission: Add the RECORD_AUDIO permission to your AndroidManifest.xml:

       <uses-permission android:name="android.permission.RECORD_AUDIO" />

   You are also responsible for handling the runtime permission request dialog. If permission is denied, the library will throw an AudioPermissionDeniedException.
2. Initialization: Before using the library, you must initialize the AndroidAudioSystem with an application Context and an Activity (which is used to launch the permission request dialog). This is typically done in your Application or MainActivity's onCreate method.

       // In your MainActivity or Application class
       AndroidAudioSystem.setApplicationContext(applicationContext)
       AndroidAudioSystem.setMicrophonePermissionRequestActivity(this)

3. Handle runtime permission requests: The library will automatically handle runtime permission requests when a RecordingSession is created. If the user denies the permission, the library will throw AudioPermissionDeniedException. In your MainActivity override the following:

       override fun onRequestPermissionsResult(
           requestCode: Int,
           permissions: Array<out String?>,
           grantResults: IntArray,
           deviceId: Int
       ) {
           //...
           AndroidAudioPermissionManager.onRequestPermissionsResult(requestCode, grantResults)
       }

iOS

1. Permissions: You must provide a description for microphone usage in your Info.plist file. Add the NSMicrophoneUsageDescription key with a string explaining why your app needs microphone access.
2. Device Selection: On iOS, it is not possible to programmatically select a specific audio output device. The PlaybackSession will always use the system's current default output.

JVM

No special setup is required. The library should work out of the box on any system with available audio input and output devices.

MacOs (Experimental)

TODO (not sure if additional setup is required).

Credits

This project is inspired by https://github.com/theolm/kmp-record