com.google.android.exoplayer.util

Class SlidingPercentile

java.lang.Object

com.google.android.exoplayer.util.SlidingPercentile

public final class SlidingPercentile
extends Object

Calculate any percentile over a sliding window of weighted values. A maximum total weight is configured. Once the maximum weight is reached, the oldest value is reduced in weight until it reaches zero and is removed. This maintains a constant total weight at steady state.

SlidingPercentile can be used for bandwidth estimation based on a sliding window of past download rate observations. This is an alternative to sliding mean and exponential averaging which suffer from susceptibility to outliers and slow adaptation to step functions.

See Also:

Wiki: Moving average, Wiki: Selection algorithm

Constructor Summary

Constructors

Constructor and Description
SlidingPercentile(int maxWeight)

Method Summary

Modifier and Type	Method and Description
void	addSample(int weight, float value) Record a new observation.
float	getPercentile(float percentile) Compute the percentile by integration.

Methods inherited from class java.lang.Object

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

Constructor Detail

SlidingPercentile

public SlidingPercentile(int maxWeight)

Method Detail

addSample

public void addSample(int weight,
                      float value)

Record a new observation. Respect the configured total weight by reducing in weight or removing the oldest observations as required.

Parameters:

weight - The weight of the new observation.

value - The value of the new observation.

getPercentile

public float getPercentile(float percentile)

Compute the percentile by integration.

Parameters:

percentile - The desired percentile, expressed as a fraction in the range (0,1].

Returns:

The requested percentile value or Float.NaN.