fi.helsinki.cs.ohtu.mpeg2.audio.mpa
Class ScaleFactors

java.lang.Object
  fi.helsinki.cs.ohtu.mpeg2.audio.mpa.ScaleFactors

public class ScaleFactors
extends java.lang.Object

Implements scale factor calculations for MPEG-1 Layer I and II audio. The scale factors are used in the encoding process to implement an application specific (read 'home-made') floating-point representation of sub-band samples: The scale factor indices are coded along the scaled (and quantized) sub-band samples. Thus the scaling can be reversed while decoding.

Nested Class Summary

private static class

ScaleFactors.TxPattern Transmission pattern defines how the three scale factors of a single sub-band are coded into the output stream.

Field Summary

private static double[]	SCALEFACTORS Scalefactors, taken from table 3-B.1 of ISO 11172-3.
private static ScaleFactors.TxPattern[][]	TRANS_PATTERN Transmission patterns tabulated in 3-C.4 of the 11172

Constructor Summary

private

ScaleFactors()

Method Summary

static int	calcScale(double[] samples) Calculates scale factor index for an array of samples.
static int[]	calcScale(double[][] samples) Calculates scale factor indices for an array of sample arrays.
static int	calcScfsi(int[] scfis) Calculates scale factor select information for given three scale factor indices and adjusts the indices accordingly.
static double	scale(double sample, int scfi) Scales the given sample with the scale factor indicated by the scale factor select index.
static int	search(double max) Finds next largest scalefactor for a given value from SCALEFACTORS.

Methods inherited from class java.lang.Object

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

Field Detail

SCALEFACTORS

private static final double[] SCALEFACTORS

Scalefactors, taken from table 3-B.1 of ISO 11172-3.

TRANS_PATTERN

private static final ScaleFactors.TxPattern[][] TRANS_PATTERN

Transmission patterns tabulated in 3-C.4 of the 11172

Constructor Detail

ScaleFactors

private ScaleFactors()

Method Detail

calcScale

public static int calcScale(double[] samples)

Calculates scale factor index for an array of samples.

Parameters:

samples - The array of samples

Returns:

The scale factor index

calcScale

public static int[] calcScale(double[][] samples)

Calculates scale factor indices for an array of sample arrays.

Parameters:

samples - The array of sample arrays [CHANNEL][SUBBAND]

Returns:

The array of scale factor indices [SBSLIMIT]

calcScfsi

public static int calcScfsi(int[] scfis)

Calculates scale factor select information for given three scale factor indices and adjusts the indices accordingly.

Parameters:

scfis - The array of three scale factor indices, contents adjusted to match with the select information

Returns:

The scale factor select information

search

public static int search(double max)

Finds next largest scalefactor for a given value from SCALEFACTORS. Uses binary search.

Parameters:

max - A value that is compared to the scalefactors

Returns:

Index of the next largest scalefactor

scale

public static double scale(double sample,
                           int scfi)

Scales the given sample with the scale factor indicated by the scale factor select index.

Parameters:

sample - The sample to scale

scfi - The scale factor index

Returns:

The scaled sample