Programming Guide (iOS)

In this chapter, we explain how to use HKWirelessHD APIs to create an app controlling HK Omni speakers. The sample codes explained in this section are copied from HKWPlayer app.

All APIs can be accessed through the singleton object pointer of HKWControlHandler. The first thing you have to do is create an instance of HKWControlHandler and use it to invoke the APIs you want to use.

In HKWirelessHD SDK, all the APIs are defined in Objective-C. However, the examples in this document are written in Swift. In case you use Swift for app development, you need to create a Swift bridging header file to make Objective-C APIs visible to Swift code.

For setting up a project with HKWirelessHD SDK, please refer to Getting Started Guide.


Initialize HKWirelessHD Control Handler and start the Wireless Audio

Controlling HK Omni speakers are done by calling APIs provided by HKWControlHandler. So, the first thing to do to use HKWirelessHD APIs is to acquire the singleton object of HKWControlHandler and initialize it.

Once you acquire the HKWControlHandler object, you need to initialize it by calling initializeHKWirelessController(). initializeHKWirelessController() takes a string of license key as parameter. Every developer who signs up for Harman developer community will receive a license key. If you have not received it yet, then just use the license key specified in the sample code for temporary use until your own license key is delivered to you.

This API requires a boolean parameter that specifies if all speakers in the network will be added right after initialzation. If it is true, then all speakers will be added to session, so you can play music without adding speakers separately. If it is false, none of speakers will be added to playback session, so you need to add speakers separately to session to play music using APIs like AddDeviceToSession().

if HKWControlHandler.sharedInstance().isInitialized() == false {
        // HKWControlHandler has not been initialized before. Initialize it now.
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), {
                if HKWControlHandler.sharedInstance().initializeHKWirelessController(g_licenseKey, withSpeakersAdded:true) != 0 {
                        println("initializeHKWirelessControl failed")



Note that intializeHKWirelessController() is a blocking call. So, it will not return until the caller initializes HKWireless Controller. If the phone is not connected to a Wi-Fi network, or any other app on the same phone is already using the HKWireless controller, then the call will wait until the app releases the controller. If you want non-blocking behavior, you should call this function asynchronously by running it in a separate thread, not within the main thread. So, it would be nice to present a dialog to user before calling initializeHKWirelessController() to notice that the app will wait until HKWirelessHD network is available.


Note that even after a successful call to initializeHKWirelessController(), it takes a little time (a few hundreds milliseconds) to get the information of all the speakers available for streaming audio.

Getting the information of speakers

HKWControlHandler maintains the list of speakers available in the network. The list changes every time a speaker is added to the network or removed from the network. Whenever a speaker is added to or removed from the network, the hkwDeviceStateUpdated() delegate function is called. So developer needs to check which speaker has been added or removed, and handle the case accordingly, such as update the UI of speaker list, and so on.

Device Information

Each speaker information contains a list of attributes that specify its static information such as speaker name, group name, IP address, etc. and also dynamic information such as volume level, boolean value indicating if it is playing or not, Wi-Fi signal strength, etc.

You can retrieve all the attributes of device (speaker) information through DeviceInfo object, and it is specified in DeviceInfo.h. The following table shows the list of information that DeviceInfo provides.

In the table, “Fixed/Variable” column means if the attribute value is a fixed value during the execution, or can be changed by itself or by calling APIs. “Set by API” column means whether the value of the attribute can be changed by API calls.

Note that all the attributes in DeviceInfo.h are “readonly”. So, you can only read the value of each attribute. You need to use corresponding API functions to change the values of the attributes.

Attribute Type in Swift Description Fixed/Variable Set by API
deviceId CLongLong the unique ID of the speaker Fixed (in manufacturing) No
deviceName String the name of the speaker Variable Yes
groupId CLongLong the unique ID of the group that the speaker belongs to Variable (set when a group is created) No
groupName String the name of the group that the speaker belongs to Variable (set when a group is created) Yes
modelName String the name of the Model of the speaker Fixed (in manufacturing) No
ipAddress String the IP address as String Fixed (when network setup) No
port String the port number Fixed (when network setup) No
macAddress String the mac address as String Fixed (in manufacturing) No
volume Int the volume level value (0 to 50) Variable Yes
active Bool indicates if added to the current playback session Variable Yes
wifiSignalStrength Int Wi-Fi strength in dBm scale, -100 (low) to 0 (high) Variable No
role Int the role definition (stereo or 5.1 channel) Variable Yes
version String the firmware version number as String Fixed (when firmware update) No
balance Int the balance value in stereo mode. -6 to 6, 0 is neutral Variable Yes
isPlaying Bool indicates whether the speaker is playing or not Variable No
channelType Int the channel type: 1 is stereo. Variable Yes
isMaster Bool indicates if it is the master in stereo or group mode Variable Yes

As shown in the table above, some of the attributes can be set by the APIs. And some attributes change during the runtime, so the app should keep the latest value of the attributes by calling corresponding APIs or by callback functions.

The following is an example of retrieving some of attributes of a speaker information.

let deviceInfo: DeviceInfo = HKWControlHandler.sharedInstance().getDeviceInfoByGroupIndexAndDeviceIndex(groupIndex, deviceIndex:deviceIndex)

println("deviceName: \(deviceInfo.deviceName")
println("groupName: \(deviceInfo.groupName")
println("volume: \(deviceInfo.volume")
println("deviceId: \(deviceInfo.deviceId")
println("deviceActive: \(")
println("deviceModel: \(deviceInfo.modelName")

Getting a speaker (device) information

HKWControlHandler maintains the list of speaker internally. Each speaker information can be retrieved either by specifying the index in the table, or by specifying the index of group and the index of member inside of the group.

Get the speaker information from the table

You can retrieve a speaker information (as DeviceInfo object) by specifying the index in the table.

- (DeviceInfo *) getDeviceInfoByIndex:(NSInteger)deviceIndex;

Here, the range of deviceIndex is 0 to the number of speakers (deviceCount) minus 1.

This function is useful when you need to show all the speakers in ordered list in TableViewCell.

Get a speaker information from the group list

You can retrieve a speaker information by specifying a group index and the index of the speaker in the group.

- (DeviceInfo *) getDeviceInfoByGroupIndexAndDeviceIndex:(NSInteger) groupIndex

Here, groupIndex represents the index of the group where the device belong to. deviceIndex means the index of the device in the group.

This function is useful to find the device information (DeviceInfo object) that will be shown in a TableViewCell. For example, to show a speaker information in two section TableView, the groupIndex can correspond to the section number, and deviceIndex can correspond to the row number.

Get a speaker information with deviceId

If you already knows the deviceId (device unique identifier) of a speaker, then you can retrieve the deviceInfo object with the following function.

- (DeviceInfo *) getDeviceInfoById:(long long) deviceId;

Refreshing device status information

If any change happens on a speaker, the speaker sends an event with updated information to HKWControlHandler and then the speaker information stored in HKWControlHandler is updated. Then, HKWControlHandler calls corresponding delegate protocol functions registered by the app to make it processed by the event handler.

However, in our current implementation, the event dispatching initiated by speaker takes a little more time than the app polling to check if there is any update on speakers. To reduce the time of status update, we provide a pair of functions to refresh device status, which is a kind of polling speakers to check the update. Especially, if you need to show a list of speakers with the latest information, you’d better force to refresh the speaker information, not just waiting updates from speakers.

To discover and update the status of speakers immediately, you can use the following functions:

// start to refresh devices ...

... ...

// stop to refresh devices

startRefreshDeviceInfo() will refresh and update every 2 seconds the status of the devices in the current Wi-Fi network.

Add or remove a speaker to/from a playback session

To play a music on a specific speaker, the speaker should be added to the current playback session.

You can check whether or not a speaker is currently added to the current playback session by check the “active” attribute of DeviceInfo object (in DeviceInfo.h).

/*! Indicates if the speaker is active (added to the current playback session) */
@property (nonatomic, readonly) BOOL active;

Add a speaker to a session (to play on)

Use addDeviceToSession() to add a speaker to the current playback session.

- (BOOL) addDeviceToSession:(long long) deviceid;

For example,

// add the speaker to the current playback session

If the execution is successful, then the attribute “active” of the speaker is set to “true”.


A speaker can be added to the current on-going playback session anytime, even the playbach is started already. It usually takes a couple of seconds for the added speaker to start to play audio.

Remove a speaker from a session

Use removeDeviceFromSession() to remove a speaker from current playback session. The removed speaker will stop playing audio immediately.

- (BOOL) removeDeviceFromSession:(long long) deviceid;

For example,

// remove a speaker from the current playback session

If the execution is successful, then the attribute “active” of the speaker is set to “false”.


A speaker can be removed from the current on-going playback session anytime.


After a speaker was removed from the session and there is no speaker remaining in the session, then the current playback stops automatically.

Play Audio File

Play CAF file (MP3, WAV, etc.)

If one or more speakers are available to the session, or if there is at least one speaker active, you can start to play a song.

The playback is based on the Apple Core Audio framework. So, the supported audio file and data formats by HKWirelessHDSDK are the same as those supported by Apple’s Core Audio framework. The detailed information is available at iOS audio file formats. According to the Apple developer documentation, CAF supports AIFF (.aif, .aiff), CAF (.caf), MPEG-1, Layer 3 (.mp3), MPEG-2 or MPEG-4 ADTS (.aac), MPEG-4 Audio (.mp4, .m4a), and WAVE (.wav).

- (BOOL) playCAF:(NSURL *)assetURL songName:(NSString*)songName resumeFlag:(BOOL)resumeFlag;

To play a song, you should prepare a AssetURL using NSURL first. Here is an example:

let assetUrl = NSURL(fileURKWithPath: nsPath)

HKWControlHandler.sharedInstance().playCAF(assetUrl, songName: songTitle, resumeFlag: false)

Here, resumeFlag is false, if you start the song from the beginning. If you want to resume to play the current song, then resumeFlag should be true. songTitle is a string, representing the song name. (This is only internally used as a file name to store converted PCM data in the memory temporarily.)

If you want to specify a starting point of the audio stream, then you can use playCAFFromCertainTime() to start the playback from a specified time.

- (bool) playCAFFromCertainTime:(NSURL *)assetURL

Here, startTime is in second.

playCAF() and playCAFFromCertainTime() can play both WAV and MP3 audio file. In case of WAV, it is played without conversion. In case of MP3, it is converted to PCM format first, and then played.

To play WAF audio file, use playWAV().

- (bool) playWAV:(NSString*)wavPath;

The following example shows how to play a WAV file stored in the application bundle.

nsWavPath = NSBundle.mainBundle().bundlePath.stringByAppendingPathComponent(songTitle)



playCAF() and playCAFFromCertainTime() cannot play an audio file in Apple’s iTunes Match service. Songs should reside locally on the device for playback. So, it would be nice to check if the song resides on the device when your app gets the MPMediaItem of a song from MediaPicker.

You can check the playback status anytime, that is, before and after as well as in the middle of the playback. You can get the player status by calling getPlayerState(). (HKPlayerState is defined in HKWControlHandler.h)

- (HKPlayerState)getPlayerState;

If you just want to check if the player is playing audio now, then use isPlaying().

- (bool) isPlaying;

Play Web Streaming Music


This API is NOT supported by HKWirelessHDSDKlw (lightweight version of HKWirelessHDSDK). It is only supported by HKWirelessHD SDK.

Use playStreamingMedia() to playt a streaming media. It uses a parameter of streamingMediaUrl to specify the URL of the media file in the streaming service. It starts with a protocol name, such as “http://” or “rtps://”. Currently, http:, rtps:, and mms: are supported. The supported file format is mp3, m4a, wav.

completedCallback is a callback that returns the result of the call, that is, if the call is successful or not. If it cannot find the media file on the server or some other errors occur, then it return false.

- (void)playStreamingMedia:(NSString *)streamingMediaUrl withCallback:(void (^)(bool result))completedCallback;


When you stop playing the streaming music, you must use stop(), not pause().

Playback controls

Stop playback

To stop the current playback, use stop(). As a result. the playback status is changed to EPlayerState_Stop, and hkwPlaybackStateChanged() delegate protocol is called if implemented.

- (void) stop;

For example,


It is safe to call stop() even if there is no on-going playback. Actually, we recommand to call stop() before you start to play a new audio stream.


If the current playback is stopped by calling stop(), the playback cannot be resumed. Resuming is only possible when the playback is paused by calling pause().

Pause playback

To pause the current play, use pause(). As a result, the playback status is changed to EPlayerState_Pause, and hkwPlaybackStateChanged() delegate protocol is called if implemented.

The playback paused by calling pause() can be resumed.

- (void) pause;

For example,


Resume playback

To resume the paused playback, use playCAF() with the parameter resumeFlag set to true. The API is described earlier in this section.

Volume Control

You can set volumes in two ways – one is set volume for an individual speaker, and the other is set volume for all speakers with the same volume level. The volume level ranges from 0 (mute) to 50 (max).


Volume change funcions are all asynchronous call. That is, it takes a little time (a few milli second) for a volue change to take effect on the speakers.


When setVolumeDevice() is called, the average volume can be also changed. So, it is safe to retrieve the speaker volumes using VolumeLevelChanged callback (explained later) when your app calls volume control APIs.

Set volume to all speakers

Use setVolume() to set the same volume level to all speakers.

- (void) setVolume:(NSInteger)volume;

For example,

// set volume level to 25 to all speakers
var volume  = 25

Set volume to a particular speaker

Use setVolumeDevice() to set volume to a particular speaker. You need to specify the deviceId for the speaker.

- (void) setVolumeDevice:(long long)deviceId volume:(NSInteger)volume;

For example,

// set volume level to 25 to a speaker
var volume  = 25
HKWControlHandler.sharedInstance().setVolumeDevice(deviceId volume:volume)

Get volume of all speakers

Use getVolume() to get the average volume level fro all speakers.

- (NSInteger) getVolume;

For example,

var averageVolume = HKWControlHandler.sharedInstance().getVolume()

Get volume of a particular speaker

Use getDeviceVolume() to get the volume level of a particular speaker.

For example,

var volume = HKWControlHandler.sharedInstance().getDeviceVolume(deviceId)

Mute and Unmute

Use mute() to mute the current playback. The volume level turns to 0.

Use unmute() to unmute the current muted playback. After unmute(), the volume level returns to the original volume level before mute() is called.

Use isMuted() to check if the current playback is muted or not.

Speakers and Groups

In HKWirelessHD SDK, a group is a collection of speakers. A group is defined as below:

  • The group of a speaker is defined by specifying a group name in the speaker information as attribute.
  • A speaker can join only one group at a time. The meaning of “joining a group” is to have the group name in its attribute.
  • All the speakers with the same group name belong to the same group associated with the group name.
  • The group ID is determined by following the device ID of the initial member of a group. For example, there is no group with the name “Group-A”, and Speaker-A sets the group as “Group-A”, then the GroupID is created with the deviceID of Speaker-A. After that, if Speaker-B joins Group-A, then the group name and the group ID are set by the ones that Speaker-A has.

Change speaker name

Use setDeviceName() to change the speaker name.


You cannot set the device name by setting deviceName property value directly. The property is read-only.

- (void) setDeviceName:(long long)deviceId deviceName:(NSString *)deviceName;

For example,

HKWControlHandler.sharedInstance().setDeviceName(deviceId, deviceName:”My Omni10”)


While a speaker is playing audio, if the name of the speaker is changed, then the current playback is interrupted (stopped) with error. The error code and message are returned by hkwErrorOccurred() delegate defined in HKWDeviceEventHandlerDelegate protocol.

Set the group for a speaker

To set a group for a speaker (in other words, to join a speaker to a group), use setDeviceGroupName() as below:

- (void) setDeviceGroupName:(long long)deviceId groupName:(NSString *)groupName;

For example,

HKWControlHandler.sharedInstance().setDeviceGroupName(deviceId, groupName:”Living Room”)


If you change the group name of a speaker, then the list of speakers of the group automatically changes.

Remove a speaker from a group

Use removeDeviceFromGroup() to remove the speaker from the currently belonged group. After being removed from a group, the name of group of the speaker is set to harman, which is a default group name implying that the speaker does not belong to any group.

- (void)removeDeviceFromGroup:(long long)deviceId;

For example,


Delegate APIs for events handling

In HKWirelessHD, the communication between user’s phone and speakers are done in asynchronous way. Therefore, some API calls from HKWControlHandler can take a little time to take effects on the speaker side. Similarly, any change of status on the speaker side are reported to the phone a little time later. For example, the status of availability of a speaker can be updated a few seconds later after a speaker turns on or off.

All the status update from the speaker side are reported to the phone via delegate protocols. So, your app needs to implement the delegate protocols accordingly to receive and handle the events from HKWControlHandler.

There are two kinds of delegate protocols for event handling.

  • HKWDeviceEventHandlerDelegate (defined in HKWDeviceEventHandlerSingleton.h)
    • This delegate protocol defines several APIs for receiving events about status changes or error from speakers.
  • HKWPlayerEventHandlerDelegate (defined in HKWPlayerEventHandlerSingleton.h)
    • This delegate protocol defines several APIs for receiving events about playback status and volume control.


hkwDeviceStateUpdated (required)

This function is invoked when some of device information have been changed on a particular speaker. The information being monitored incudes device status (active or inactive), model name, group name, and wifi signal strengths, etc. The parameter reason specifies what the update is about. The reason code is defined in HKWControlHandler.h.

Note that volume level change does not trigger this call. The volume update is reported by hkwVolumeLevelChanged() callback.

-(void) hkwDeviceStateUpdated:(long long)deviceId withReason:(NSInteger) reason;

This callback is essential to retrieve and update the speaker information in timely manner. If your app has a screen that shows a list of speakers available in the network with latest information, you can receive the event via this function and update the list.

A most common usage for this function is to invole tableView.reloadData() to update the list of speakers in a table view controller, as shown below.

func hkwDeviceStateUpdated(deviceId: CLongLong, withReason reason:Int) {

hkwErrorOccured (required)

This function is invoked when an error occurs during the execution. The callback returns the error code, and also corresponding error message for detailed description. The error codes are defined in HKWCOntrolHandler.h.

-(void) hkwErrorOccurred:(NSInteger)errorCode withErrorMessage:(NSString*)errorMesg;

A most common usage of this function is to show an alert dialog to notice the user of the error.


hkwPlayEnded (required)

This function is invoked when the current playback has ended.


This function is useful to take any actioin when the current playback has ended.

hkwDeviceVolumeChanged (optional)

This function is invoked when volume level is changed for any speakers. It is called asynchronously right after any of SetVolume APIs are called by apps.

The function delivers the device ID of the speaker with volume changed, a new device volume level, and average volume level value, as below:

-(void)hkwDeviceVolumeChanged:(long long)deviceId deviceVolume:(NSInteger)deviceVolume withAverageVolume:(NSInteger)avgVolume;


When speaker volume is changed by a call to setVolume(), then all the speakers are set to a new volume level, and this function can be used to get the new volume level value.

hkwPlaybackStateChanged (optional) This function is invoked when playback state is changed during the playback. The callback delivers the playState value as parameter.


hkwPlaybackTimeChanged (optional)

This function is invoked when the current playback time is changed. It is called every one second. The function parameter timeElapsed returns the time (in second) elapsed since the start of the playback. This function is useful when your app update the progress bar of the current playback.


How to implement the delegate protocols

To make your ViewController as delegate, that is, to receive the events from HKWControlHandler in your ViewController, your ViewController class has to implement the protocol by specifying the delegate protocol name in the class definition as below:

class SpeakerListViewController: UIViewController, UITableViewDataSource,
        SpeakerTableCellDelegate, HKWDeviceEventHandlerDelegate  {
        ... ...

And then, the ViewController class should set itself to delegate attribute of the handler singleton class as below:

HKDeviceEventHandlerSingleton.sharedInstance().delegate = self

Note that during the runtime, only one instance of the event handler for HKWControlHandler is instantiated, so it is designed as a singleton. It can be retrieved by calling sharedInstance() to the class.

For device event handler


For player event handler



Since there is only one instance of delegator for each delegate, if you set delegate in several different places of your app, then the latest setting will override the delegate value, and the previous setting will be overridden. So, you need to set the delegate every time you show a ViewController, and one right place to set the delegate is inside viewDidAppear() in ViewController class as shown below.

override func viewDidAppear(animated: Bool) {
        HKWDeviceEventHandlerSingleton.sharedInstance().delegate = self
        HKWPlayerEventHandlerSingleton.sharedInstance().delegate = self