KIOSRecognizer Class Reference

Inherits from	NSObject
Declared in	KIOSRecognizer.h KIOSRecognizer.mm

Overview

An instance of the KIOSRecognizer class, called recognizer, manages recognizer resources and provides speech recognition capabilities to your application.

You typically initialize the engine at the app startup time by calling initWithASRBundle: or initWithASRBundleAtPath: method, and then use sharedInstance method when you need to access the recognizer.

Recognition results are provided via callbacks. To obtain results one of your classes will need to adopt a KIOSRecognizerDelegate protocol, and implement some of its methods.

In order to properly handle audio interrupts you will need to implement [KIOSRecognizerDelegate recognizerReadyToListenAfterInterrupt:] callback method in which you need to perform audio play cleanup (stop playing audio). This allows KeenASR SDK to properly deactivate audio session before app goes to background.

You can optionally implement [KIOSRecognizerDelegate recognizerReadyToListenAfterInterrupt:] callback method, which will trigger after KIOSRecognizer is fully setup after app comes to the foreground. This is where you may refresh the UI state of the app.

Initialization example:

 if (! [KIOSRecognizer sharedInstance]) {
     [KIOSRecognizer initWithASRBundle:@"librispeechQT-nnet2-en-us"];
 }
 // for convenience our class keeps a local reference of the recognizer
 self.recognizer = [KIOSRecognizer sharedInstance];

 // this class will also be implementing methods from KIOSRecognizerDelegate 
 // protocol
 self.recognizer.delegate = self;

 // recordings will be saved on the device
 self.recognizer.createAudioRecordings = YES;

 // after 0.8sec of silence, recognizer will automatically stop listening
 [self.recognizer setVADParameter:KIOSVadTimeoutEndSilenceForGoodMatch toValue:.8];

 // define callbacks for KIOSRecognizerDelegate

After initialization, audio data from all sessions when recognizer is listening will be used for online speaker adaptation. You can name speaker adaptation profiles via adaptToSpeakerWithName:, persist profiles in the filesystem via saveSpeakerAdaptationProfile, and reset via resetSpeakerAdaptation.

Warning: Only a single instance of the recognizer can exist at any given time.

Properties

`+ sharedInstance`

Returns shared instance of the recognizer

+ (nullable KIOSRecognizer *)sharedInstance

Return Value

The shared recognizer instance

Discussion

Warning: if the engine has not been initialized by calling initWithASRBundle:, this method will return nil

Declared In

KIOSRecognizer.h

`delegate`

Delegate, which handles KIOSRecognizerDelegate protocol methods

@property (nonatomic, weak, nullable) id<KIOSRecognizerDelegate> delegate

Declared In

KIOSRecognizer.h

`recognizerState`

State of the recognizer, a read-only property that takes one of KIOSRecognizerState values

@property (assign, readonly) KIOSRecognizerState recognizerState

Declared In

KIOSRecognizer.h

`asrBundlePath`

Absolute path to the ASR bundle where acoustic models, config, etc. reside

@property (nonatomic, readonly, nonnull) NSString *asrBundlePath

Declared In

KIOSRecognizer.h

`asrBundleName`

Name of the ASR Bundle (name of the directory that contains all the ASR resources. This will be the last component of the asrBundlePath.

@property (nonatomic, readonly, nonnull) NSString *asrBundleName

Declared In

KIOSRecognizer.h

`currentDecodingGraphName`

Name of the decoding graph currently used by the recognizer

@property (nonatomic, readonly, nullable) NSString *currentDecodingGraphName

Declared In

KIOSRecognizer.h

`recognizerType`

Type of the recognizer. It makes sense to query this property only after the recognizer has been initialized.

@property (nonatomic, assign, readonly) KIOSRecognizerType recognizerType

Declared In

KIOSRecognizer.h

`langCode`

Two-letter language code that defines language of the ASR Bundle used to initialize the recognizer. For example: @“en”, @“es”, etc.

@property (nonatomic, readonly, nonnull) NSString *langCode

Declared In

KIOSRecognizer.h

`rescore`

If set to YES, recognizer will perform rescoring for the final result, using rescoring language model provided in the custom decoding graph that’s bundled with the application.

@property (nonatomic, assign) BOOL rescore

Discussion

Default is YES.

Warning: If the resources necessary for rescoring are not available in the custom decoding graph directory bundled with the app, and rescore is set to YES, rescoring step will be skipped.

Declared In

KIOSRecognizer.h

Initialization, Preparing, Starting, and Stopping Recognition

`+ initWithASRBundle:`

Initialize ASR engine with the ASR Bundle, which provides all the resources necessary for initialization. You will use this initalization method if you included ASR bundle with your application. See also initWithASRBundleAtPath: for scenarios when ASR Bundle is not included with the app, but downloaded after the app has been installed. SDK initialization needs to occur before any other work can be performed.

+ (BOOL)initWithASRBundle:(nonnull NSString *)bundleName

Parameters

`bundleName`	name of the ASR Bundle. A directory containing all the resources necessary for the specific recognizer type. This will typically include all acoustic model related files, and configuration files. The bundle directory should contain decode.conf configuration file, which can be augmented with additional config params. Currently, that is the only way to pass various settings to the decoder. All path references in config files should be relative to the app root directory (e.g. librispeechQT-nnet2-en-us/mfcc.conf). The init method will initiallize appropriate recognizer type based on the name and content of the ASR bundle.

bundleName

name of the ASR Bundle. A directory containing all the resources necessary for the specific recognizer type. This will typically include all acoustic model related files, and configuration files. The bundle directory should contain decode.conf configuration file, which can be augmented with additional config params. Currently, that is the only way to pass various settings to the decoder. All path references in config files should be relative to the app root directory (e.g. librispeechQT-nnet2-en-us/mfcc.conf). The init method will initiallize appropriate recognizer type based on the name and content of the ASR bundle.

Return Value

TRUE if succesful, FALSE otherwise.

Discussion

Warning: When initializing the recognizer, you need to make sure that bundle directory contains all the necessary resources needed for the specific recognizer type. If your app is dynamically creating decoding graphs, ASR bundle directory needs to contain lang subdirectory with relevant resources (lexicon, etc.).

Declared In

KIOSRecognizer.h

`+ initWithASRBundleAtPath:`

Initialize ASR engine with the ASR Bundle located at provided path. This is an alternative method to initialize the SDK, which you would use if you did not package ASR Bundle with your application but instead downloaded it after the app has been installed. SDK initialization needs to occur before any other work can be performed.

+ (BOOL)initWithASRBundleAtPath:(nonnull NSString *)pathToASRBundle

Parameters

`pathToASRBundle`	full path to the ASR Bundle. For more details about ASR Bundles see initWithASRBundle:

Return Value

TRUE if succesful, FALSE otherwise.

Discussion

Warning: When initializing the recognizer, make sure that the bundle directory contains all the necessary resources needed for the specific recognizer type. If your app is dynamically creating decoding graphs, ASR bundle directory needs to contain lang subdirectory with relevant resources (lexicon, etc.).

Declared In

KIOSRecognizer.h

`+ teardown`

Teardown recognizer and all the related resources. This method would typically be called when you want to create a new recognizer that uses different ASR Bundle (currently the SDK supports only one recognizer instance at the time). For example, if you are using English recognizer and want to switch to a Spanish recognizer you would teardown the English recognizer, and then create a Spanish recognizer.

+ (BOOL)teardown

Return Value

TRUE if the singletone instance of the recognizer was succesfully tore down or if sharedInsance is already nil, FALSE otherwise.

Discussion

Warning: This method will return FALSE if recognizer is in KIOSRecognizerStateListening or KIOSRecognizerStateFinalProcessing state. Any application level references to sharedInstance will become invalid if the teardown is successful.

Declared In

KIOSRecognizer.h

`– prepareForListeningWithCustomDecodingGraphWithName:`

Prepare for recognition by loading custom decoding graph that was prepared via [KIOSDecodingGraph createDecodingGraphFromSentences:forRecognizer:andSaveWithName:] or [KIOSDecodingGraph createDecodingGraphFromArpaFileAtURL:forRecognizer:andSaveWithName:] methods.

- (BOOL)prepareForListeningWithCustomDecodingGraphWithName:(nonnull NSString *)dgName

Parameters

`dgName`	name of the custom decoding graph

Return Value

TRUE if successful, FALSE otherwise

Discussion

After calling this method, recognizer will load the decoding graph into memory and it will be ready to start listening via startListening method.

Declared In

KIOSRecognizer.h

`– prepareForListeningWithCustomDecodingGraphAtPath:`

Prepare for recognition by loading custom decoding graph that was bundled with the application. You will typically use this approach for large vocabulary tasks, where it would take too long to build the decoding graph on the mobile device.

- (BOOL)prepareForListeningWithCustomDecodingGraphAtPath:(nonnull NSString *)pathToDecodingGraphDirectory

Parameters

`pathToDecodingGraphDirectory`	absolute path to the custom decoding graph directory which was created ahead of time and packaged with the app.

Return Value

TRUE if successful, FALSE otherwise.

Discussion

After calling this method, recognizer will load the decoding graph into memory and it will be ready to start listening via startListening method.

Warning: If custom decoding graph was built with rescoring capability, all the resources will be loaded regardless of how rescore paramater is set.

Declared In

KIOSRecognizer.h

`– startListening`

Start processing incoming audio.

- (BOOL)startListening

Return Value

TRUE if successful, FALSE otherwise

After calling this method, recognizer will listen to and decode audio coming through the microphone using decoding graph you specified via one of the prepareForListening methods. The listening process will stop either by: a) an explicit call to stopListening or b) if one of the Voice Activity Detection module rules are triggered (for example, max duration without speech, or end-silence, etc.), c) if audio interrupt occurs (phone call, audible notification, app goes to background, etc.).

When the recognizer stops listening due to VAD triggering, it will call recognizerFinalResult:forRecognizer: callback method.

When the recognizer stops listening due to audio interrupt, no callback methods will be triggered until audio interrupt is over.

If decoding graph was created with the trigger phrase support recognizer will listen continuously until the trigger phrase is recognized, then it will switch over to the standard mode with partial results being reported via recognizerPartialResult:forRecognizer: callback.

VAD settings can be modified via setVADParameter:toValue: method.

Discussion

Warning: You will need to call either prepareForListeningWithCustomDecodingGraphWithName or prepareForListeningWithCustomDecodingGraphAtPath before calling this method. You will also need to make sure that user has granted audio recording permission before calling this method; see AVAudioSessionRecordPermission and [AVAudioSession requestRecordPermission:] in AVFoundation framework for details.

Declared In

KIOSRecognizer.h

`– startListeningFromAudioFile:`

Performs speech recognition on the audio file. This is an asynchronious method, which will perform basic validation (valid wav file, sampling frequency of the audio matches that of the ASR Bundle), and then start recognition in the background and return. Recognition results can be obtained via recognizerFinalResult:forRecognizer: and recognizerPartialResult:forRecognizer: methods.

- (BOOL)startListeningFromAudioFile:(nonnull NSString *)pathToAudioFile

Parameters

`pathToAudioFile`	full path to the audio file in WAV format. Files should be mono (single channel) and its sampling frequency should match the sampling frequency used for the ASR bundle training (typically 16kHz).

Return Value

TRUE if the audio file is valid WAV file, its sampling frequency matches the one in ASR Bundle, and recording duration is less than 100ms, FALSE otherwise.

Discussion

Note: The whole audio file will be loaded in the memory, thus we currently limit the length to 200sec. If file is longer than 200sec no processing will occur and the method will return FALSE.

Declared In

KIOSRecognizer.h

`– stopListening`

Stop the recognizer from processing incoming audio.

- (void)stopListening

Discussion

Warning: Calling this method will not trigger recognizerFinalResult delegate call. Use stopListeningAndReturnFinalResult if you are interested in obtaining the final result directly.

Declared In

KIOSRecognizer.h

`– stopListeningAndReturnFinalResult`

Stop the recognizer from processing incoming audio and return the final result.

- (nullable KIOSResult *)stopListeningAndReturnFinalResult

Return Value

Final result of the recognition.

Discussion

Warning: This method runs synchroniously. For large decoding graphs there may be noticable delay (few hundred ms) on lower-end devices. This method will return nil if recognizer is already in KIOSRecognizerStateFinalProcessing (due to VAD rules automatically triggering for example).

Declared In

KIOSRecognizer.h

Speaker Adaptation

`– adaptToSpeakerWithName:`

Defines the name that will be used to uniquely identify speaker adaptation profile. When recognizer starts to listen, it will try to find a matching speaker profile in the filesystem (profiles are matched based on speakername, asrbundle, and audio route). When saveSpeakerAdaptationProfile method is called, it uses the name to uniquely identify the profile file that will be saved in the filesystem.

- (void)adaptToSpeakerWithName:(nonnull NSString *)speakerName

Parameters

`speakerName`	(pseduo)name of the speaker for which adaptation is to be performed. Default value is ‘default’. The name used here does not have to correspond to the real name of user (thus we call it pseudo name). The exact value does not matter as long as you can match the value to the specific user in your app. For example, you could use ‘user1’, ‘user2’, etc..

speakerName

(pseduo)name of the speaker for which adaptation is to be performed. Default value is ‘default’.

The name used here does not have to correspond to the real name of user (thus we call it pseudo name). The exact value does not matter as long as you can match the value to the specific user in your app. For example, you could use ‘user1’, ‘user2’, etc..

Discussion

Warning: If you cannot match names to your users, it’s recommended to not use this method, and to not save adaptation profiles between sessions. Adaptation will still be performed throughout the session, but each new session (activity after initialization of recognizer) will start from the baseline models.

In-memory speaker adaptation profile can always be reset by calling resetSpeakerAdaptation.

If this method is called while recognizer is listening, it will only affect subsequent calls to startListening methods.

Declared In

KIOSRecognizer.h

`– resetSpeakerAdaptation`

Resets speaker adaptation profile in the current recognizer session. Calling this method will also reset the speakerName to ‘default’. If the corresponding speaker adaptation profile exists in the filesystem for ‘default’ speaker, it will be used. If not, initial models from the ASR Bundle will be the baseline.

- (void)resetSpeakerAdaptation

Discussion

You would typically use this method id there is a new start of a certain activity in your app that may entail new speaker. For example, a practice view is started and there is a good chance a different user may be using the app.

If speaker (pseudo)identities are known, you don’t need to call this method, you can just switch speakers by calling adaptToSpeakerWithName: with the appropriate speakerName

Following are the tradeoffs when using this method:

the downside of resetting user profile for the existing user is that ASR performance will be reset to the baseline (no adaptation), which may slightly degrade performance in the first few interactions
the downside of NOT resetting user profile for a new user is that, depending on the characteristics of the new user’s voice, ASR performance may initially be degraded slightly (when comparing to the baseline case of no adaptation)

Calls to this method will be ignored if recognizer is in LISTENING state.

If you are resetting adaptation profile and you know user’s (pseudo)identity, you may want to call saveSpeakerAdaptationProfile method prior to calling this method so that on subsequent user switches, adaptation profiles can be reloaded and recognition starts with the speaker profile trained on previous sessions audio.

Declared In

KIOSRecognizer.h

`– saveSpeakerAdaptationProfile`

Saves speaker profile (used for adaptation) in the filesystem.

- (void)saveSpeakerAdaptationProfile

Discussion

Speaker profile will be saved in the file system, in Caches/KaldiIOS-speaker-profiles/ directory. Profile filename is composed of the speakerName, asrBundle, and audioRoute.

Declared In

KIOSRecognizer.h

`+ removeAllSpeakerAdaptationProfiles`

Remove all adaptation profiles for all speakers.

+ (BOOL)removeAllSpeakerAdaptationProfiles

Declared In

KIOSRecognizer.h

`+ removeSpeakerAdaptationProfiles:`

Removes all adaptation profiles for the speaker with name speakerName.

+ (BOOL)removeSpeakerAdaptationProfiles:(nonnull NSString *)speakerName

Parameters

`speakerName`	name of the speaker whose profiles should be removed

Declared In

KIOSRecognizer.h

File Audio Recording Management

`createAudioRecordings`

Set to true if you want to keep audio recordings in the file system. Default is FALSE.

@property (nonatomic, assign) BOOL createAudioRecordings

Declared In

KIOSRecognizer.h

`createJSONMetadata`

Set to FALSE if you do NOT want to keep response metadata in the file system.

@property (nonatomic, assign) BOOL createJSONMetadata

Discussion

When set to TRUE, KIOSRecognizer instance will store a JSON file with various metadata (speech recognition result, basic device info, etc.) on device filesystem. If you are using Keen Dashboard cloud service via KIOSUploader this flag needs to be set to true, otherwise no data will be stored locally on the device, and consequently pushed to the cloud.

Default is FALSE.

Declared In

KIOSRecognizer.h

`recordingsDir`

Directory in which recordings and JSON metadata will be stored. Default is Library/Cache/keenasr-data/

@property (nonatomic, copy, readonly, nonnull) NSString *recordingsDir

Declared In

KIOSRecognizer.h

`lastRecordingFilename`

Filename of the last recording. If createAudioRecordings was set to TRUE, you can read the filename of the latest recording via this property.

@property (nonatomic, readonly, nullable) NSString *lastRecordingFilename

Discussion

This value is set upon calling startListening, if createAudioRecordings was set to true. Audio file is created as soon as recognizer starts listening, it’s continuosly updated while recognizer is listening, and closed after recogizer stopped listening. Accessing or modifying current audio file while recognizer is listening can result in unpredictable behavior.

Declared In

KIOSRecognizer.h

`lastJSONMetadataFilename`

Filename of the last JSON metadata file. If createJSONMetadata was set to TRUE, you can read the filename of the latest JSON metadata file via this property.

@property (nonatomic, readonly, nullable) NSString *lastJSONMetadataFilename

Discussion

This value is set upon calling startListening, if createJSONMetadata was set to true. JSON file is created only after recognizer stops listening, when all the relevant information is available.

Declared In

KIOSRecognizer.h

Audio Handling

`handleNotifications`

If set to YES (default behavior), SDK will handle various notifications related to app activity. When app goes to background, or a phone call or a audio interrupt comes through, the SDK will stop listening, teardown internal audio stack, and then upon app coming back to foreground/interrupt ending it will reinitialize internal audio stack.

@property (nonatomic, assign, setter=setHandleNotifications:) BOOL handleNotifications

Discussion

If set to NO, it is developer’s responsibility to handle notifications that may affect audio capture. In this case, you will need to stop listening and deactivate KeenASR audio stack if an audio interrupt comes through, and then reinit the audio stack when the interrupt is over. Setting handleNotifications to NO allows the SDK to work in the background mode; you will still need to properly handle audio interrupts using deactivateAudioStack, activateAudioStack or reinitAudioStack, and stopListening methods.

Declared In

KIOSRecognizer.h

`– inputLevel`

The most recent signal input level in dB

- (float)inputLevel

Return Value

signal input level in dB

Declared In

KIOSRecognizer.h

`+ echoCancellationAvailable`

Provides information about echo cancellation support on the device.

+ (BOOL)echoCancellationAvailable

Return Value

YES if echo cancellation is supported, NO otherwise

Declared In

KIOSRecognizer.h

`– performEchoCancellation:`

EXPERIMENTAL Specifies if echo cancellation should be performed. If value is set to YES and the device supports echo cancellation, then audio played by the application will be removed from the audio captured via the microphone.

- (BOOL)performEchoCancellation:(BOOL)value

Parameters

`value`	set to YES to turn on echo cancellation processing, NO to turn it off. Default is NO.

Return Value

TRUE if value was successfully set, FALSE otherwise. If the device does not support echo cancellatio and you pass YES to this method, it will return FALSE.

Discussion

Warning: Calls to this method while the recognizer is listening will be ignored end the method will return FALSE.

Declared In

KIOSRecognizer.h

`– enableBluetoothA2DPOutput:`

Enables bluetooth output via AVAudioSessionCategoryOptionAllowBluetoothA2DP category option of AVAudioSession.

- (void)enableBluetoothA2DPOutput:(BOOL)value

Declared In

KIOSRecognizer.h

`– deactivateAudioStack`

Deactivates audio session and KeenASR audio stack. If handleNotifications is set to YES, you will not need to use this method and its counterpart activateAudioStack; KeenASR Framework will handle audio interrupts and notifications when the app goes to background/foreground.

- (BOOL)deactivateAudioStack

Return Value

TRUE if audio stack was successfully deactivated, FALSE otherwise.

@warning: It’s recommended that any audio IO (playing audio, video, etc.) is stopped before calling this method.

Discussion

If your app is handling notifications explicitly (handleNotifications is set to NO), you may want to call this method when an audio interrupt occurs. If recognizer is listening, this method will automatically stop listening, and then deactivate the audio stack. When the app comes active or audio interrupt finishes, you will need to call the activateAudioStack.

Declared In

KIOSRecognizer.h

`– activateAudioStack`

Activates audio stack that was previously deactivated using deactivateAudioStack method. This method should be called after all other audio systems have been setup to make sure AVAudioSession is properly initialized for audio capture.

- (BOOL)activateAudioStack

Return Value

TRUE if audio stack was successfully activated, FALSE otherwise.

Declared In

KIOSRecognizer.h

`– reinitAudioStack`

Reinitializes audio stack. Calling this method is equaivalent to calling deactivateAudioStack followed by activateAudioStack method.

- (void)reinitAudioStack

Declared In

KIOSRecognizer.h

Other

`+ version`

Version of the KeenASR framework.

+ (nonnull NSString *)version

Declared In

KIOSRecognizer.h

`+ setLogLevel:`

Set log level for the framework.

+ (void)setLogLevel:(KIOSRecognizerLogLevel)logLevel

Parameters

`logLevel`	one of KIOSRecognizerLogLevel Default value is KIOSRecognizerLogLevelWarning.

logLevel

one of KIOSRecognizerLogLevel

Default value is KIOSRecognizerLogLevelWarning.

Declared In

KIOSRecognizer.h

Config Parameters

`– setVADParameter:toValue:`

Set any of KIOSVadParameter Voice Activity Detection parameters. These parameters can be set at any time and they will go into effect immediately.

- (void)setVADParameter:(KIOSVadParameter)parameter toValue:(float)value

Parameters

`parameter`	one of KIOSVadParameter
`value`	duration in seconds for the parameter

Discussion

Warning: Setting VAD rules in the config file within the ASR bundle will NOT have any effect. Values for these parameters are set to their defaults upon initialization of KIOSRecognizer. They can only be changed programmatically, using this method.

Declared In

KIOSRecognizer.h

Deprecated methods and properties

`listening`

Is recognizer listening to and decoding the incoming audio. This property has been deprecated and replaced by recognizerState.

@property (assign, readonly) BOOL listening

Declared In

KIOSRecognizer.h

Other Methods

`– setVADParameter:toValue:forceUpdate:updateCache:`

@param parameter @param value @param forceUpdate @param updateCache

- (void)setVADParameter:(KIOSVadParameter)parameter toValue:(float)value forceUpdate:(BOOL)forceUpdate updateCache:(BOOL)updateCache

Declared In

KIOSRecognizer.mm