org.xiph.speex
Class Vbr

java.lang.Object
  org.xiph.speex.Vbr

public class Vbr

extends java.lang.Object

This class analyses the signal to help determine what bitrate to use when the Varible BitRate option has been selected.

Version:

$Revision: 1.3 $

Author:

Marc Gimpel, Wimba S.A. (marc@wimba.com)

Field Summary

private float	accum_sum
private float	average_energy
private int	consec_noise
private float	energy_alpha
static float[][]	hb_thresh Wideband threshhold table.
private float	last_energy
private float[]	last_log_energy
private float	last_pitch_coef
private float	last_quality
static int	MIN_ENERGY
static float[][]	nb_thresh Narrowband threshhold table.
private float	noise_accum
private float	noise_accum_count
private float	noise_level
static float	NOISE_POW
private float	soft_pitch
static float[][]	uhb_thresh Ultra-wideband threshhold table.
static int	VBR_MEMORY_SIZE

Constructor Summary

Vbr()
Constructor

Method Summary

float

analysis(float[] sig, int len, int pitch, float pitch_coef) This function should analyse the signal and decide how critical the coding error will be perceptually.

Methods inherited from class java.lang.Object

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

Field Detail

VBR_MEMORY_SIZE

public static final int VBR_MEMORY_SIZE

See Also:

Constant Field Values

MIN_ENERGY

public static final int MIN_ENERGY

See Also:

Constant Field Values

NOISE_POW

public static final float NOISE_POW

See Also:

Constant Field Values

nb_thresh

public static final float[][] nb_thresh

Narrowband threshhold table.

hb_thresh

public static final float[][] hb_thresh

Wideband threshhold table.

uhb_thresh

public static final float[][] uhb_thresh

Ultra-wideband threshhold table.

energy_alpha

private float energy_alpha

average_energy

private float average_energy

last_energy

private float last_energy

last_log_energy

private float[] last_log_energy

accum_sum

private float accum_sum

last_pitch_coef

private float last_pitch_coef

soft_pitch

private float soft_pitch

last_quality

private float last_quality

noise_level

private float noise_level

noise_accum

private float noise_accum

noise_accum_count

private float noise_accum_count

consec_noise

private int consec_noise

Constructor Detail

Vbr

public Vbr()

Constructor

Method Detail

analysis

public float analysis(float[] sig,
                      int len,
                      int pitch,
                      float pitch_coef)

This function should analyse the signal and decide how critical the coding error will be perceptually. The following factors should be taken into account:

• Attacks (positive energy derivative) should be coded with more bits
• Stationary voiced segments should receive more bits
• Segments with (very) low absolute energy should receive less bits (maybe only shaped noise?)
• DTX for near-zero energy?
• Stationary fricative segments should have less bits
• Temporal masking: when energy slope is decreasing, decrease the bit-rate
• Decrease bit-rate for males (low pitch)?
• (wideband only) less bits in the high-band when signal is very non-stationary (harder to notice high-frequency noise)???

Parameters:

sig - - signal.

len - - signal length.

pitch - - signal pitch.

pitch_coef - - pitch coefficient.

Returns: