/**
 * This interface defines several useful constants used throughout
 * the mobile client code for ultrasound detection.
 *
 * @author Tony Offer
 * @author Chris Palistrant
 * @version 1.0
 */
public interface Constants {
	// The sampling rate used for recording and used by the
	// ultrasound detection algorithm for various calculations.
	public static final float SAMPLING_RATE = 44100.0F;

	// A default target frequency for the ultrasound detection
	// algorithm.  The target frequency is the frequency that the
	// ultrasound detection algorithm looks for in the audio signal.
	public static final float TARGET_FREQUENCY = 21000.0F;

	// The block size used by the Goertzel algorithm.  This number
	// represents the amount of samples necessary to make a decision
	// as to the presence of the target frequency.
	public static final int N = 420;

	// The size, in bits, of the audio samples that will be recorded
	// while listening for ultrasound.  Note that reading from a
	// Java data line for the purposes of recording audio returns a
	// stream of bytes, which do not necessarily contain the same
	// number of bits as the samples themselves.
	public static final int SAMPLE_SIZE = 16;

	// The number of channels used for recording is not listed here
	// as a constant because different systems may support different
	// channels.
	
	// Whether or not the recorded samples are signed.
	public static final boolean SIGN = true;

	// Whether or not the samples employ big endian encoding.
	public static final boolean BIGEND = false;

	// The multicast group that the DatagramListener thread's socket
	// should join in order to receive datagram broadcasts.
	public static final String GROUPADDR = "235.255.255.254";

	// The port number on which the DatagramListener thread should
	// listen for datagram broadcasts.
	public static final int PORTNUM = 8019;

	// The maximum datagram message size that could be received by
	// the DatagramListener thread.  This essentially defines the
	// maximum size of room messages.
	public static final int MAXMSGSIZE = 1000;

	// The number of positive ultrasound detections in a row that
	// are required before a positive ultrasound identification can
	// be made.
	public static final int DEBOUNCE_VAL = 5;
	
	// The number of UltrasoundAnalyzer threads to use in the
	// UltrasoundListener object's thread pool.  This value can
	// be tweaked to improve performance since a greater number of
	// threads means more parallelism while too many threads means
	// wasted resources.  Peak performance is achieved when each
	// of the threads in the thread pool are always busy but the
	// UltrasoundListener object does not have to wait for any
	// thread to become available when it has data to analyze.  See
	// the UltrasoundListener class for more details.
	public static final int NUMTHREADS = 20;

	// The number of entries to keep in the recent history of room
	// determinations.  When ultrasound is detected for a certain
	// room, the room string will be placed in a history of this
	// length.  A larger history means that room determinations will
	// be more accurate, while a smaller history means that room
	// determinations will occur more quickly.
	public static final int HISTORY_SIZE = 20;

	// The average amount of time it takes for ultrasound to be
	// detected after receiving an 802.11 message (assuming the
	// ultrasound was generated concurrently with the 802.11).  This
	// value was determined experimentally.  It is in ms.
	public static final int AVG_DETECT_TIME = 410;

	// The maximum amount of time it takes for ultrasound to be
	// detected after receiving an 802.11 message (assuming the
	// ultrasound was generated concurrently with the 802.11).  This
	// value was determined experimentally.  It is in ms.
	public static final int MAX_DETECT_TIME = 839;

	// The number of received datagram messages to store while
	// waiting to receive ultrasound.
	public static final int ROOM_MSG_BUF = 10;

	// The number of room determinations for the same room that must
	// occur in a row before the confidence magnitude for that room is
	// boosted.  The idea here is to quickly increase confidence
	// that a device is in a given room if multiple room decisions
	// occur in a sequence for that room.
	public static final int SEQUENCE = 3;

	// The additional confidence magnitude boost that should be
	// given to a room if it has been decided upon at least SEQUENCE
	// times in a row.
	public static final int WEIGHT = 50;
}