Audio

expo-av allows you to implement audio playback and recording in your app.

Note that audio automatically stops if headphones / bluetooth audio devices are disconnected.

Try the playlist example app (source code is on GitHub) to see an example usage of the media playback API, and the recording example app (source code is on GitHub) to see an example usage of the recording API.

Platform Compatibility

Android Device	Android Emulator	iOS Device	iOS Simulator	Web

Installation

Terminal

- expo install expo-av

If you're installing this in a bare React Native app, you should also follow these additional installation instructions.

Usage

Playing sounds

import * as React from 'react';
import { Text, View, StyleSheet, Button } from 'react-native';
import { Audio } from 'expo-av';

export default function App() {
  const [sound, setSound] = React.useState();

  async function playSound() {
    console.log('Loading Sound');
    const { sound } = await Audio.Sound.createAsync( require('./assets/Hello.mp3')
    );
    setSound(sound);

    console.log('Playing Sound');
    await sound.playAsync();
  }

  React.useEffect(() => {
    return sound
      ? () => {
          console.log('Unloading Sound');
          sound.unloadAsync();
        }
      : undefined;
  }, [sound]);

  return (
    <View style={styles.container}>
      <Button title="Play Sound" onPress={playSound} />
    </View>
  );
}

%%placeholder-start%%const styles = StyleSheet.create({ ... }); %%placeholder-end%%const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    backgroundColor: '#ecf0f1',
    padding: 10,
  },
});

Recording sounds

import * as React from 'react';
import { Text, View, StyleSheet, Button } from 'react-native';
import { Audio } from 'expo-av';

export default function App() {
  const [recording, setRecording] = React.useState();

  async function startRecording() {
    try {
      console.log('Requesting permissions..');
      await Audio.requestPermissionsAsync();
      await Audio.setAudioModeAsync({
        allowsRecordingIOS: true,
        playsInSilentModeIOS: true,
      });

      console.log('Starting recording..');
      const { recording } = await Audio.Recording.createAsync( Audio.RECORDING_OPTIONS_PRESET_HIGH_QUALITY
      );
      setRecording(recording);
      console.log('Recording started');
    } catch (err) {
      console.error('Failed to start recording', err);
    }
  }

  async function stopRecording() {
    console.log('Stopping recording..');
    setRecording(undefined);
    await recording.stopAndUnloadAsync();
    const uri = recording.getURI();
    console.log('Recording stopped and stored at', uri);
  }

  return (
    <View style={styles.container}>
      <Button
        title={recording ? 'Stop Recording' : 'Start Recording'}
        onPress={recording ? stopRecording : startRecording}
      />
    </View>
  );
}

%%placeholder-start%%const styles = StyleSheet.create({ ... }); %%placeholder-end%%const styles = StyleSheet.create({
  container: {
    flex: 1,
    justifyContent: 'center',
    backgroundColor: '#ecf0f1',
    padding: 10,
  },
});

API

import { Audio } from 'expo-av';

Request recording permissions

`Audio.requestPermissionsAsync()`

Asks the user to grant permissions for audio recording.

Returns

A promise that resolves to an object of type PermissionResponse.

`Audio.getPermissionsAsync()`

Checks user's permissions for audio recording.

Returns

A promise that resolves to an object of type PermissionResponse.

Enabling Audio and customizing Audio Mode

`Audio.setIsEnabledAsync(value)`

Audio is enabled by default, but if you want to write your own Audio API in a bare workflow app, you might want to disable the Audio API.

Arguments

value (boolean) -- true enables Audio, and false disables it.

Returns

A Promise that will reject if audio playback could not be enabled for the device.

`Audio.setAudioModeAsync(mode)`

We provide this API to customize the audio experience on iOS and Android.

Arguments

mode (object) --

A dictionary with the following key-value pairs:
- playsInSilentModeIOS : a boolean selecting if your experience's audio should play in silent mode on iOS. This value defaults to false.
- allowsRecordingIOS : a boolean selecting if recording is enabled on iOS. This value defaults to false. NOTE: when this flag is set to true, playback may be routed to the phone receiver instead of to the speaker.
- staysActiveInBackground : a boolean selecting if the audio session (playback or recording) should stay active even when the app goes into background. This value defaults to false. This is not available in Expo Go for iOS, it will only work in standalone apps. To enable it for standalone apps, follow the instructions below to add UIBackgroundModes to your app configuration.
- interruptionModeIOS : an enum selecting how your experience's audio should interact with the audio from other apps on iOS:
  - INTERRUPTION_MODE_IOS_MIX_WITH_OTHERS : This is the default option. If this option is set, your experience's audio is mixed with audio playing in background apps.
  - INTERRUPTION_MODE_IOS_DO_NOT_MIX : If this option is set, your experience's audio interrupts audio from other apps.
  - INTERRUPTION_MODE_IOS_DUCK_OTHERS : If this option is set, your experience's audio lowers the volume ("ducks") of audio from other apps while your audio plays.
- shouldDuckAndroid : a boolean selecting if your experience's audio should automatically be lowered in volume ("duck") if audio from another app interrupts your experience. This value defaults to true. If false, audio from other apps will pause your audio.
- interruptionModeAndroid : an enum selecting how your experience's audio should interact with the audio from other apps on Android:
  - INTERRUPTION_MODE_ANDROID_DO_NOT_MIX : If this option is set, your experience's audio interrupts audio from other apps.
  - INTERRUPTION_MODE_ANDROID_DUCK_OTHERS : This is the default option. If this option is set, your experience's audio lowers the volume ("ducks") of audio from other apps while your audio plays.
- playThroughEarpieceAndroid : a boolean selecting if the audio is routed to earpiece (on Android). This value defaults to false.

Returns

A Promise that will reject if the audio mode could not be enabled for the device. Note that these are the only legal AudioMode combinations of (playsInSilentModeIOS, allowsRecordingIOS, staysActiveInBackground, interruptionModeIOS), and any other will result in promise rejection:

false, false, false, INTERRUPTION_MODE_IOS_DO_NOT_MIX
false, false, false, INTERRUPTION_MODE_IOS_MIX_WITH_OTHERS
true, true, true, INTERRUPTION_MODE_IOS_DO_NOT_MIX
true, true, true, INTERRUPTION_MODE_IOS_DUCK_OTHERS
true, true, true, INTERRUPTION_MODE_IOS_MIX_WITH_OTHERS
true, true, false, INTERRUPTION_MODE_IOS_DO_NOT_MIX
true, true, false, INTERRUPTION_MODE_IOS_DUCK_OTHERS
true, true, false, INTERRUPTION_MODE_IOS_MIX_WITH_OTHERS
true, false, true, INTERRUPTION_MODE_IOS_DO_NOT_MIX
true, false, true, INTERRUPTION_MODE_IOS_DUCK_OTHERS
true, false, true, INTERRUPTION_MODE_IOS_MIX_WITH_OTHERS
true, false, false, INTERRUPTION_MODE_IOS_DO_NOT_MIX
true, false, false, INTERRUPTION_MODE_IOS_DUCK_OTHERS
true, false, false, INTERRUPTION_MODE_IOS_MIX_WITH_OTHERS

Playing or recording audio in background (iOS)

On iOS, audio playback and recording in background is only available in standalone apps, and it requires some extra configuration. On iOS, each background feature requires a special key in UIBackgroundModes array in your Info.plist file. In standalone apps this array is empty by default, so in order to use background features you will need to add appropriate keys to your app.json configuration.

See an example of app.json that enables audio playback in background:

{
  "expo": {
    ...
    "ios": {
      ...
      "infoPlist": {
        ...
        "UIBackgroundModes": [
          "audio"
        ]
      }
    }
  }
}

Playing sounds

`Audio.Sound`

This class represents a sound corresponding to an Asset or URL.

Returns

A newly constructed instance of Audio.Sound.

Example

const sound = new Audio.Sound();
try {
  await sound.loadAsync(require('./assets/sounds/hello.mp3'));
  await sound.playAsync();
  // Your sound is playing!

  // Don't forget to unload the sound from memory
  // when you are done using the Sound object
  await sound.unloadAsync();
} catch (error) {
  // An error occurred!
}

A static convenience method to construct and load a sound is also provided:

Audio.Sound.createAsync(source, initialStatus = {}, onPlaybackStatusUpdate = null, downloadFirst = true)

Creates and loads a sound from source, with optional initialStatus, onPlaybackStatusUpdate, and downloadFirst.
```
const { sound } = await Audio.Sound.createAsync(
  source,
  initialStatus,
  onPlaybackStatusUpdate,
  downloadFirst
);

// Which is equivalent to the following:
const sound = new Audio.Sound();
sound.setOnPlaybackStatusUpdate(onPlaybackStatusUpdate);
await sound.loadAsync(source, initialStatus, downloadFirst);
```
Parameters
- source (object / number / Asset) -- The source of the sound. The following forms are supported:
  - A dictionary of the form { uri: string, headers?: { [string]: string }, overrideFileExtensionAndroid?: string } with a network URL pointing to a media file on the web, an optional headers object passed in a network request to the uri and an optional Android-specific overrideFileExtensionAndroid string overriding extension inferred from the URL. The overrideFileExtensionAndroid property may come in handy if the player receives an URL like example.com/play which redirects to example.com/player.m3u8. Setting this property to m3u8 would allow the Android player to properly infer the content type of the media and use proper media file reader.
  - require('path/to/file') for an audio file asset in the source code directory.
  - An Asset object for an audio file asset.
- initialStatus (PlaybackStatusToSet) -- The initial intended PlaybackStatusToSet of the sound, whose values will override the default initial playback status. This value defaults to {} if no parameter is passed. See the AV documentation for details on PlaybackStatusToSet and the default initial playback status.
- onPlaybackStatusUpdate (function) -- A function taking a single parameter PlaybackStatus. This value defaults to null if no parameter is passed. See the AV documentation for details on the functionality provided by onPlaybackStatusUpdate
- downloadFirst (boolean) -- If set to true, the system will attempt to download the resource to the device before loading. This value defaults to true. Note that at the moment, this will only work for sources of the form require('path/to/file') or Asset objects.
Returns

A Promise that is rejected if creation failed, or fulfilled with the following dictionary if creation succeeded:
- sound : the newly created and loaded Sound object.
- status : the PlaybackStatus of the Sound object. See the AV documentation for further information.
Example
```
try {
  const { sound: soundObject, status } = await Audio.Sound.createAsync(
    require('./assets/sounds/hello.mp3'),
    { shouldPlay: true }
  );
  // Your sound is playing!
} catch (error) {
  // An error occurred!
}
```

On the soundObject reference, the following API is provided:

soundObject.setOnMetadataUpdate(onMetadataUpdate) [iOS only] Sets a function to be called whenever the metadata (of type AVMetadata, details below) of the sound object, if any, changes.

Parameters
- onMetadataUpdate (function) -- A function taking a single object of type AVMetadata (described below) as a parameter.
soundObject.setOnAudioSampleReceived(callback) Sets a function to be called during playback, receiving the audio sample as parameter.

Parameters
- callback (function) - A function taking a single object of type AudioSample (described below) as a parameter.

The rest of the API for Audio.Sound is the same as the imperative playback API for Video-- see the AV documentation for further information:

soundObject.loadAsync(source, initialStatus = {}, downloadFirst = true)
soundObject.unloadAsync()
soundObject.getStatusAsync()
soundObject.setOnPlaybackStatusUpdate(onPlaybackStatusUpdate)
soundObject.setStatusAsync(statusToSet)
soundObject.playAsync()
soundObject.replayAsync()
soundObject.pauseAsync()
soundObject.stopAsync()
soundObject.setPositionAsync(millis)
soundObject.setRateAsync(value, shouldCorrectPitch, pitchCorrectionQuality)
soundObject.setVolumeAsync(value)
soundObject.setIsMutedAsync(value)
soundObject.setIsLoopingAsync(value)
soundObject.setProgressUpdateIntervalAsync(millis)

`AVMetadata`

Object passed to the onMetadataUpdate function. It has the following keys:

title: a string with the title of the sound object. This key is optional.

`AudioSample`

Object passed to the onAudioSampleReceived function. Represents a single sample from an audio source. The sample contains all frames (PCM Buffer values) for each channel of the audio, so if the audio is stereo (interleaved), there will be two channels, one for left and one for right audio.

channels - an array representing the data from each channel in PCM Buffer format. Array elements are objects in the following format: { frames: number[] }, where each frame is a number in PCM Buffer format (-1 to 1 range).
timestamp - a number representing the timestamp of the current sample in seconds, relative to the audio track's timeline.

Known issue: When using the ExoPlayer Android implementation, the timestamp is always -1.

Recording sounds

Notes on web usage:

A MediaRecorder issue on Chrome produces WebM files missing the duration metadata. See the open Chromium issue

MediaRecorder encoding options and other configurations are inconsistent across browsers, utilising a Polyfill such as kbumsik/opus-media-recorder or ai/audio-recorder-polyfill in your application will improve your experience. Any options passed to prepareToRecordAsync will be passed directly to the MediaRecorder API and as such the polyfill.

Web browsers require sites to be served securely in order for them to listen to a mic. See MediaDevices#getUserMedia Security for more details.

`Audio.Recording`

This class represents an audio recording. After creating an instance of this class, prepareToRecordAsync must be called in order to record audio. Once recording is finished, call stopAndUnloadAsync. Note that only one recorder is allowed to exist in the state between prepareToRecordAsync and stopAndUnloadAsync at any given time.

Note that your experience must request audio recording permissions in order for recording to function. See the Permissions module for more details. Additionally, audio recording is not supported in the iOS Simulator.

Returns

A newly constructed instance of Audio.Recording.

Example

const recording = new Audio.Recording();
try {
  await recording.prepareToRecordAsync(Audio.RECORDING_OPTIONS_PRESET_HIGH_QUALITY);
  await recording.startAsync();
  // You are now recording!
} catch (error) {
  // An error occurred!
}

A static convenience method to construct and start a recording is also provided:

Audio.Recording.createAsync(options, onRecordingStatusUpdate = null, progressUpdateIntervalMillis = null)

Creates and starts a recording using the given options, with optional onRecordingStatusUpdate and progressUpdateIntervalMillis.
```
const { recording, status } = await Audio.Recording.createAsync(
  options,
  onRecordingStatusUpdate,
  progressUpdateIntervalMillis
);

// Which is equivalent to the following:
const recording = new Audio.Recording();
await recording.prepareToRecordAsync(options);
recording.setOnRecordingStatusUpdate(onRecordingStatusUpdate);
await recording.startAsync();
```
Parameters
- options (RecordingOptions) -- Options for the recording, including sample rate, bitrate, channels, format, encoder, and extension. If no options are passed to, the recorder will be created with options Audio.RECORDING_OPTIONS_PRESET_LOW_QUALITY. See below for details on RecordingOptions.
- onRecordingStatusUpdate (function) -- A function taking a single parameter status (a dictionary, described in getStatusAsync).
- progressUpdateIntervalMillis (number) -- The interval between calls of onRecordingStatusUpdate. This value defaults to 500 milliseconds.
Returns

A Promise that is rejected if creation failed, or fulfilled with the following dictionary if creation succeeded:
- recording : the newly created and started Recording object.
- status : the RecordingStatus of the Recording object. See the AV documentation for further information.
Example
```
try {
  const { recording: recordingObject, status } = await Audio.Recording.createAsync(
    Audio.RECORDING_OPTIONS_PRESET_HIGH_QUALITY
  );
  // You are now recording!
} catch (error) {
  // An error occurred!
}
```
recordingInstance.getStatusAsync()

Gets the status of the Recording.

Returns

A Promise that is resolved with the status of the Recording: a dictionary with the following key-value pairs.

Before prepareToRecordAsync is called, the status will be as follows:
- canRecord : a boolean set to false.
- isDoneRecording : a boolean set to false.
After prepareToRecordAsync() is called, but before stopAndUnloadAsync() is called, the status will be as follows:
- canRecord : a boolean set to true.
- isRecording : a boolean describing if the Recording is currently recording.
- durationMillis : the current duration of the recorded audio.
- metering : a number that's the most recent reading of the loudness in dB. The value ranges from –160 dBFS, indicating minimum power, to 0 dBFS, indicating maximum power. Present or not based on Recording options. See RecordingOptions for more information.
- mediaServicesDidReset : (iOS only) a boolean indictating whether media services were reset during recording. This may occur if the active input ceases to be available during recording (example: airpods are the active input and they run out of batteries during recording.)
After stopAndUnloadAsync() is called, the status will be as follows:
- canRecord : a boolean set to false.
- isDoneRecording : a boolean set to true.
- durationMillis : the final duration of the recorded audio.
recordingInstance.setOnRecordingStatusUpdate(onRecordingStatusUpdate)

Sets a function to be called regularly with the status of the Recording. See getStatusAsync() for details on status.

onRecordingStatusUpdate will be called when another call to the API for this recording completes (such as prepareToRecordAsync(), startAsync(), getStatusAsync(), or stopAndUnloadAsync()), and will also be called at regular intervals while the recording can record. Call setProgressUpdateInterval() to modify the interval with which onRecordingStatusUpdate is called while the recording can record.

Parameters
- onRecordingStatusUpdate (function) -- A function taking a single parameter status (a dictionary, described in getStatusAsync).
recordingInstance.setProgressUpdateInterval(millis)

Sets the interval with which onRecordingStatusUpdate is called while the recording can record. See setOnRecordingStatusUpdate for details. This value defaults to 500 milliseconds.

Parameters
- millis (number) -- The new interval between calls of onRecordingStatusUpdate.
recordingInstance.prepareToRecordAsync(options)

Loads the recorder into memory and prepares it for recording. This must be called before calling startAsync(). This method can only be called if the Recording instance has never yet been prepared.

Parameters
- options (RecordingOptions) -- Options for the recording, including sample rate, bitrate, channels, format, encoder, and extension. If no options are passed to prepareToRecordAsync(), the recorder will be created with options Audio.RECORDING_OPTIONS_PRESET_LOW_QUALITY. See below for details on RecordingOptions.
Returns

A Promise that is fulfilled when the recorder is loaded and prepared, or rejects if this failed. If another Recording exists in your experience that is currently prepared to record, the Promise will reject. If the RecordingOptions provided are invalid, the Promise will also reject. The promise is resolved with the status of the recording (see getStatusAsync() for details).
recordingInstance.getAvailableInputs()

Returns a list of available recording inputs. This method can only be called if the Recording has been prepared.

Returns

A Promise that is fulfilled with an array of RecordingInput objects with name, uid and type params.
recordingInstance.getCurrentInput()

Returns a the currently-selected recording input. This method can only be called if the Recording has been prepared.

Returns

A Promise that is fulfilled with a RecordingInput objects with name, uid and type params.
recordingInstance.setInput(inputUid)

Sets the current recording input.

Parameters
- inputUid (string) -- The uid of a RecordingInput.
Returns

A Promise that is resolved if successful or rejected if not.
recordingInstance.startAsync()

Begins recording. This method can only be called if the Recording has been prepared.

Returns

A Promise that is fulfilled when recording has begun, or rejects if recording could not start. The promise is resolved with the status of the recording (see getStatusAsync() for details).
recordingInstance.pauseAsync()

Pauses recording. This method can only be called if the Recording has been prepared.

NOTE: This is only available on Android API version 24 and later.

Returns

A Promise that is fulfilled when recording has paused, or rejects if recording could not be paused. If the Android API version is less than 24, the Promise will reject. The promise is resolved with the status of the recording (see getStatusAsync() for details).
recordingInstance.stopAndUnloadAsync()

Stops the recording and deallocates the recorder from memory. This reverts the Recording instance to an unprepared state, and another Recording instance must be created in order to record again. This method can only be called if the Recording has been prepared.

NOTE: On Android this method may fail with E_AUDIO_NODATA when called too soon after startAsync and no audio data has been recorded yet. In that case the recorded file will be invalid and should be discarded.

Returns

A Promise that is fulfilled when recording has stopped, or rejects if recording could not be stopped. The promise is resolved with the status of the recording (see getStatusAsync() for details).
recordingInstance.getURI()

Gets the local URI of the Recording. Note that this will only succeed once the Recording is prepared to record. On web, this will not return the URI until the recording is finished.

Returns

A string with the local URI of the Recording, or null if the Recording is not prepared to record (or, on Web, if the recording has not finished).
recordingInstance.createNewLoadedSoundAsync()

Creates and loads a new Sound object to play back the Recording. Note that this will only succeed once the Recording is done recording (once stopAndUnloadAsync() has been called).

Parameters
- initialStatus (PlaybackStatusToSet) -- The initial intended PlaybackStatusToSet of the sound, whose values will override the default initial playback status. This value defaults to {} if no parameter is passed. See the AV documentation for details on PlaybackStatusToSet and the default initial playback status.
- onPlaybackStatusUpdate (function) -- A function taking a single parameter PlaybackStatus. This value defaults to null if no parameter is passed. See the AV documentation for details on the functionality provided by onPlaybackStatusUpdate
Returns

A Promise that is rejected if creation failed, or fulfilled with the following dictionary if creation succeeded:
- sound : the newly created and loaded Sound object.
- status : the PlaybackStatus of the Sound object. See the AV documentation for further information.

`RecordingOptions`

The recording extension, sample rate, bitrate, channels, format, encoder, etc can be customized by passing a dictionary of options to prepareToRecordAsync().

We provide the following preset options for convenience, as used in the example above. See below for the definitions of these presets.

Audio.RECORDING_OPTIONS_PRESET_HIGH_QUALITY
Audio.RECORDING_OPTIONS_PRESET_LOW_QUALITY

We also provide the ability to define your own custom recording options, but we recommend you use the presets, as not all combinations of options will allow you to successfully prepareToRecordAsync(). You will have to test your custom options on iOS and Android to make sure it's working. In the future, we will enumerate all possible valid combinations, but at this time, our goal is to make the basic use-case easy (with presets) and the advanced use-case possible (by exposing all the functionality available in native). As always, feel free to ping us on the forums or Slack with any questions.

In order to define your own custom recording options, you must provide a dictionary of the following key value pairs.

isMeteringEnabled : a boolean that determines whether audio level information will be part of the status object under the "metering" key.
keepAudioActiveHint : a boolean that hints to keep the audio active after prepareToRecordAsync completes. Setting this value can improve the speed at which the recording starts. Only set this value to true when you call startAsync immediately after prepareToRecordAsync. This value is automatically set when using Audio.recording.createAsync().
android : a dictionary of key-value pairs for the Android platform. This key is required.
- extension : the desired file extension. This key is required. Example valid values are .3gp and .m4a. For more information, see the Android docs for supported output formats.
- outputFormat : the desired file format. This key is required. See the next section for an enumeration of all valid values of outputFormat.
- audioEncoder : the desired audio encoder. This key is required. See the next section for an enumeration of all valid values of audioEncoder.
- sampleRate : the desired sample rate. This key is optional. An example valid value is 44100.
  
  Note that the sampling rate depends on the format for the audio recording, as well as the capabilities of the platform. For instance, the sampling rate supported by AAC audio coding standard ranges from 8 to 96 kHz, the sampling rate supported by AMRNB is 8kHz, and the sampling rate supported by AMRWB is 16kHz. Please consult with the related audio coding standard for the supported audio sampling rate.
- numberOfChannels : the desired number of channels. This key is optional. Example valid values are 1 and 2.
  
  Note that prepareToRecordAsync() may perform additional checks on the parameter to make sure whether the specified number of audio channels are applicable.
- bitRate : the desired bit rate. This key is optional. An example valid value is 128000.
  
  Note that prepareToRecordAsync() may perform additional checks on the parameter to make sure whether the specified bit rate is applicable, and sometimes the passed bitRate will be clipped internally to ensure the audio recording can proceed smoothly based on the capabilities of the platform.
- maxFileSize : the desired maximum file size in bytes, after which the recording will stop (but stopAndUnloadAsync() must still be called after this point). This key is optional. An example valid value is 65536.
ios : a dictionary of key-value pairs for the iOS platform
- extension : the desired file extension. This key is required. An example valid value is .caf.
- outputFormat : the desired file format. This key is optional. See the next section for an enumeration of all valid values of outputFormat.
- audioQuality : the desired audio quality. This key is required. See the next section for an enumeration of all valid values of audioQuality.
- sampleRate : the desired sample rate. This key is required. An example valid value is 44100.
- numberOfChannels : the desired number of channels. This key is required. Example valid values are 1 and 2.
- bitRate : the desired bit rate. This key is required. An example valid value is 128000.
- bitRateStrategy : the desired bit rate strategy. This key is optional. See the next section for an enumeration of all valid values of bitRateStrategy.
- bitDepthHint : the desired bit depth hint. This key is optional. An example valid value is 16.
- linearPCMBitDepth : the desired PCM bit depth. This key is optional. An example valid value is 16.
- linearPCMIsBigEndian : a boolean describing if the PCM data should be formatted in big endian. This key is optional.
- linearPCMIsFloat : a boolean describing if the PCM data should be encoded in floating point or integral values. This key is optional.

Following is an enumeration of all of the valid values for certain RecordingOptions keys.

Note Not all of the iOS formats included in this list of constants are currently supported by iOS, in spite of appearing in the Apple source code. For an accurate list of formats supported by iOS, see Core Audio Codecs and iPhone Audio File Formats.

android :
- outputFormat :
  - Audio.RECORDING_OPTION_ANDROID_OUTPUT_FORMAT_DEFAULT
  - Audio.RECORDING_OPTION_ANDROID_OUTPUT_FORMAT_THREE_GPP
  - Audio.RECORDING_OPTION_ANDROID_OUTPUT_FORMAT_MPEG_4
  - Audio.RECORDING_OPTION_ANDROID_OUTPUT_FORMAT_AMR_NB
  - Audio.RECORDING_OPTION_ANDROID_OUTPUT_FORMAT_AMR_WB
  - Audio.RECORDING_OPTION_ANDROID_OUTPUT_FORMAT_AAC_ADIF
  - Audio.RECORDING_OPTION_ANDROID_OUTPUT_FORMAT_AAC_ADTS
  - Audio.RECORDING_OPTION_ANDROID_OUTPUT_FORMAT_RTP_AVP
  - Audio.RECORDING_OPTION_ANDROID_OUTPUT_FORMAT_MPEG2TS
  - Audio.RECORDING_OPTION_ANDROID_OUTPUT_FORMAT_WEBM
- audioEncoder :
  - Audio.RECORDING_OPTION_ANDROID_AUDIO_ENCODER_DEFAULT
  - Audio.RECORDING_OPTION_ANDROID_AUDIO_ENCODER_AMR_NB
  - Audio.RECORDING_OPTION_ANDROID_AUDIO_ENCODER_AMR_WB
  - Audio.RECORDING_OPTION_ANDROID_AUDIO_ENCODER_AAC
  - Audio.RECORDING_OPTION_ANDROID_AUDIO_ENCODER_HE_AAC
  - Audio.RECORDING_OPTION_ANDROID_AUDIO_ENCODER_AAC_ELD
ios :
- outputFormat :
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_LINEARPCM
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_AC3
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_60958AC3
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_APPLEIMA4
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_MPEG4AAC
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_MPEG4CELP
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_MPEG4HVXC
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_MPEG4TWINVQ
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_MACE3
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_MACE6
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_ULAW
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_ALAW
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_QDESIGN
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_QDESIGN2
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_QUALCOMM
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_MPEGLAYER1
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_MPEGLAYER2
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_MPEGLAYER3
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_APPLELOSSLESS
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_MPEG4AAC_HE
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_MPEG4AAC_LD
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_MPEG4AAC_ELD
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_MPEG4AAC_ELD_SBR
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_MPEG4AAC_ELD_V2
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_MPEG4AAC_HE_V2
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_MPEG4AAC_SPATIAL
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_AMR
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_AMR_WB
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_AUDIBLE
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_ILBC
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_DVIINTELIMA
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_MICROSOFTGSM
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_AES3
  - Audio.RECORDING_OPTION_IOS_OUTPUT_FORMAT_ENHANCEDAC3
- audioQuality :
  - Audio.RECORDING_OPTION_IOS_AUDIO_QUALITY_MIN
  - Audio.RECORDING_OPTION_IOS_AUDIO_QUALITY_LOW
  - Audio.RECORDING_OPTION_IOS_AUDIO_QUALITY_MEDIUM
  - Audio.RECORDING_OPTION_IOS_AUDIO_QUALITY_HIGH
  - Audio.RECORDING_OPTION_IOS_AUDIO_QUALITY_MAX
- bitRateStrategy :
  - Audio.RECORDING_OPTION_IOS_BIT_RATE_STRATEGY_CONSTANT
  - Audio.RECORDING_OPTION_IOS_BIT_RATE_STRATEGY_LONG_TERM_AVERAGE
  - Audio.RECORDING_OPTION_IOS_BIT_RATE_STRATEGY_VARIABLE_CONSTRAINED
  - Audio.RECORDING_OPTION_IOS_BIT_RATE_STRATEGY_VARIABLE

For reference, following are the definitions of the two preset examples of RecordingOptions, as implemented in the Audio SDK:

export const RECORDING_OPTIONS_PRESET_HIGH_QUALITY: RecordingOptions = {
  isMeteringEnabled: true,
  android: {
    extension: '.m4a',
    outputFormat: RECORDING_OPTION_ANDROID_OUTPUT_FORMAT_MPEG_4,
    audioEncoder: RECORDING_OPTION_ANDROID_AUDIO_ENCODER_AAC,
    sampleRate: 44100,
    numberOfChannels: 2,
    bitRate: 128000,
  },
  ios: {
    extension: '.caf',
    audioQuality: RECORDING_OPTION_IOS_AUDIO_QUALITY_MAX,
    sampleRate: 44100,
    numberOfChannels: 2,
    bitRate: 128000,
    linearPCMBitDepth: 16,
    linearPCMIsBigEndian: false,
    linearPCMIsFloat: false,
  },
};

export const RECORDING_OPTIONS_PRESET_LOW_QUALITY: RecordingOptions = {
  isMeteringEnabled: true,
  android: {
    extension: '.3gp',
    outputFormat: RECORDING_OPTION_ANDROID_OUTPUT_FORMAT_THREE_GPP,
    audioEncoder: RECORDING_OPTION_ANDROID_AUDIO_ENCODER_AMR_NB,
    sampleRate: 44100,
    numberOfChannels: 2,
    bitRate: 128000,
  },
  ios: {
    extension: '.caf',
    audioQuality: RECORDING_OPTION_IOS_AUDIO_QUALITY_MIN,
    sampleRate: 44100,
    numberOfChannels: 2,
    bitRate: 128000,
    linearPCMBitDepth: 16,
    linearPCMIsBigEndian: false,
    linearPCMIsFloat: false,
  },
};