org.deepsymmetry.beatlink

Class BeatFinder

java.lang.Object

org.deepsymmetry.beatlink.BeatFinder

public class BeatFinder
extends Object

Watches for devices to report new beats by broadcasting beat packets on port 50001, and passes them on to registered listeners. When players are actively playing music, they send beat packets at the start of each beat which, in addition to announcing the start of the beat, provide information about where the beat falls within a measure of music (assuming that the track was properly configured in rekordbox, and is in 4/4 time), the current BPM of the track being played, and the current player pitch adjustment, from which the actual effective BPM can be calculated.

When players are stopped, they do not send beat packets, but the mixer continues sending them at the last BPM reported by the master player, so it acts as the most reliable synchronization source. The mixer does not make any effort to keep its notion of measures (down beats) consistent with any player, however. So systems which want to stay in sync with measures as well as beats will want to use the VirtualCdj to maintain awareness of which player is the master player.

Author:

James Elliott

Field Summary

Fields

Modifier and Type	Field and Description
static int	BEAT_PORT The port to which devices broadcast beat messages.

Constructor Summary

Constructors

Constructor and Description
BeatFinder()

Method Summary

Modifier and Type	Method and Description
static void	addBeatListener(BeatListener listener) Adds the specified beat listener to receive beat announcements when DJ Link devices broadcast them on the network.
static Set<BeatListener>	getBeatListeners() Get the set of beat listeners that are currently registered.
static boolean	isActive() Check whether we are presently listening for beat packets.
static void	removeBeatListener(BeatListener listener) Removes the specified beat listener so that it no longer receives beat announcements when DJ Link devices broadcast them to the network.
static void	start() Start listening for beat announcements.
static void	stop() Stop listening for beats.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

BEAT_PORT

public static final int BEAT_PORT

The port to which devices broadcast beat messages.

See Also:

Constant Field Values

Constructor Detail

BeatFinder

public BeatFinder()

Method Detail

isActive

public static boolean isActive()

Check whether we are presently listening for beat packets.

Returns:

true if our socket is open and monitoring for DJ Link beat packets on the network

start

public static void start()
                  throws SocketException

Start listening for beat announcements. If already listening, has no effect.

Throws:

SocketException - if the socket to listen on port 50001 cannot be created

stop

public static void stop()

Stop listening for beats.

addBeatListener

public static void addBeatListener(BeatListener listener)

Adds the specified beat listener to receive beat announcements when DJ Link devices broadcast them on the network. If listener is null or already present in the list of registered listeners, no exception is thrown and no action is performed.

To reduce latency, beat announcements are delivered to listeners directly on the thread that is receiving them them from the network, so if you want to interact with user interface objects in listener methods, you need to use javax.swing.SwingUtilities.invokeLater(Runnable) to do so on the Event Dispatch Thread. Even if you are not interacting with user interface objects, any code in the listener method must finish quickly, or it will add latency for other listeners, and beat announcements will back up. If you want to perform lengthy processing of any sort, do so on another thread.

Parameters:

listener - the beat listener to add

removeBeatListener

public static void removeBeatListener(BeatListener listener)

Removes the specified beat listener so that it no longer receives beat announcements when DJ Link devices broadcast them to the network. If listener is null or not present in the list of registered listeners, no exception is thrown and no action is performed.

Parameters:

listener - the beat listener to remove

getBeatListeners

public static Set<BeatListener> getBeatListeners()

Get the set of beat listeners that are currently registered.

Returns:

the currently registered beat listeners