CarAudioRecord

@RequiresCarApi(value = 5)
abstract class CarAudioRecord

The CarAudioRecord class manages access car microphone audio.

This is done by reading the data via calls to read.

The size of the internal buffer for audio data is defined by AUDIO_CONTENT_BUFFER_SIZE. Data should be read from this in chunks of sizes smaller or equal to this value.

The sample rate is defined by AUDIO_CONTENT_SAMPLING_RATE.

The content mime tipe is defined by AUDIO_CONTENT_MIME.

Whenever the user dismisses the microphone on the car screen, the next call to read will return -1. When the read call returns -1, it means the user has dismissed the microphone and the data can be ignored

CarAudioRecord car = CarAudioRecord.create(carContext);
car.startRecording();

byte[] data = new byte[CarAudioRecord.AUDIO_CONTENT_BUFFER_SIZE];
while(car.read(data, 0, CarAudioRecord.AUDIO_CONTENT_BUFFER_SIZE) >= 0) {
    // Use data array
    // Potentially calling car.stopRecording() if your processing finds end of speech
}
car.stopRecording();

CarAudioRecord record = CarAudioRecord.create(carContext);
// Take audio focus so that user's media is not recorded
AudioAttributes audioAttributes =
        new AudioAttributes.Builder()
                .setContentType(AudioAttributes.CONTENT_TYPE_SPEECH)
                .setUsage(USAGE_ASSISTANCE_NAVIGATION_GUIDANCE)
                .build();

AudioFocusRequest audioFocusRequest =
        new AudioFocusRequest.Builder(AudioManager.AUDIOFOCUS_GAIN_TRANSIENT_EXCLUSIVE)
                .setAudioAttributes(audioAttributes)
                .setOnAudioFocusChangeListener(state -> {
                    if (state == AudioManager.AUDIOFOCUS_LOSS) {
                        // Stop recording if audio focus is lost
                        record.stopRecording();
                    }
                })
                .build();

if (mCarContext.getSystemService(AudioManager.class).requestAudioFocus(audioFocusRequest)
        != AUDIOFOCUS_REQUEST_GRANTED) {
    return;
}

record.startRecording();

Summary

const val AUDIO_CONTENT_BUFFER_SIZE = 512: Int

const val AUDIO_CONTENT_MIME = "audio/l16": String!

const val AUDIO_CONTENT_SAMPLING_RATE = 16000: Int

@RequiresPermission(value = "android.permission.RECORD_AUDIO")
java-static fun create(carContext: CarContext): CarAudioRecord

fun read(audioData: ByteArray, offsetInBytes: Int, sizeInBytes: Int): Int

fun startRecording(): Unit

fun stopRecording(): Unit