Capturing audio to be used by a publisher

The BaseAudioDevice.startCapturer method is called when the audio device should start capturing audio to be published. The NoiseAudioDevice implementation of this method starts the capturer thread to be run in the queue after 1 second:

override fun startCapturer(): Boolean {
    capturerStarted = true
    capturerHandler?.postDelayed(capturer, capturerIntervalMillis)
    return true
}

The capturer thread produces a buffer containing samples of random data (white noise). It then calls the writeCaptureData method of the AudioBus object, which sends the samples to the audio bus. The publisher in the application uses the samples sent to the audio bus to transmit as audio in the published stream. Then if a capture is still in progress (if the app is publishing), the capturer thread is run again after another second:

private val capturer: Runnable = object : Runnable {
    override fun run() {
        capturerBuffer?.rewind()
        val rand = Random()
        rand.nextBytes(capturerBuffer?.array())
        audioBus.writeCaptureData(capturerBuffer, SAMPLING_RATE)
        if (capturerStarted && !audioDriverPaused) {
            capturerHandler?.postDelayed(this, capturerIntervalMillis)
        }
    }
}

The AudioDevice class includes other methods that are implemented by the NoiseAudioDevice class. However, this sample does not do anything of interest in these methods, so they are not included in this guide.