com.google.android.exoplayer2.trackselection

Class AdaptiveTrackSelection

java.lang.Object

com.google.android.exoplayer2.trackselection.BaseTrackSelection

com.google.android.exoplayer2.trackselection.AdaptiveTrackSelection

All Implemented Interfaces:

TrackSelection

public class AdaptiveTrackSelection
extends BaseTrackSelection

A bandwidth based adaptive TrackSelection, whose selected track is updated to be the one of highest quality given the current network conditions and the state of the buffer.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	AdaptiveTrackSelection.Factory Factory for AdaptiveTrackSelection instances.

Field Summary

Fields

Modifier and Type	Field and Description
static float	DEFAULT_BANDWIDTH_FRACTION
static float	DEFAULT_BUFFERED_FRACTION_TO_LIVE_EDGE_FOR_QUALITY_INCREASE
static int	DEFAULT_MAX_DURATION_FOR_QUALITY_DECREASE_MS
static int	DEFAULT_MIN_DURATION_FOR_QUALITY_INCREASE_MS
static int	DEFAULT_MIN_DURATION_TO_RETAIN_AFTER_DISCARD_MS
static long	DEFAULT_MIN_TIME_BETWEEN_BUFFER_REEVALUTATION_MS

Fields inherited from class com.google.android.exoplayer2.trackselection.BaseTrackSelection

group, length, tracks

Constructor Summary

Constructors

Constructor and Description
AdaptiveTrackSelection(TrackGroup group, int[] tracks, BandwidthMeter bandwidthMeter)
AdaptiveTrackSelection(TrackGroup group, int[] tracks, BandwidthMeter bandwidthMeter, long minDurationForQualityIncreaseMs, long maxDurationForQualityDecreaseMs, long minDurationToRetainAfterDiscardMs, float bandwidthFraction, float bufferedFractionToLiveEdgeForQualityIncrease, long minTimeBetweenBufferReevaluationMs, Clock clock)

Method Summary

Modifier and Type	Method and Description
void	enable() Enables the track selection.
int	evaluateQueueSize(long playbackPositionUs, java.util.List<? extends MediaChunk> queue) May be called periodically by sources that load media in discrete MediaChunks and support discarding of buffered chunks in order to re-buffer using a different selected track.
int	getSelectedIndex() Returns the index of the selected track.
java.lang.Object	getSelectionData() Returns optional data associated with the current track selection.
int	getSelectionReason() Returns the reason for the current track selection.
void	onPlaybackSpeed(float playbackSpeed) Called to notify the selection of the current playback speed.
void	updateSelectedTrack(long playbackPositionUs, long bufferedDurationUs, long availableDurationUs) Updates the selected track.

Methods inherited from class com.google.android.exoplayer2.trackselection.BaseTrackSelection

blacklist, disable, equals, getFormat, getIndexInTrackGroup, getSelectedFormat, getSelectedIndexInTrackGroup, getTrackGroup, hashCode, indexOf, indexOf, isBlacklisted, length

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_MIN_DURATION_FOR_QUALITY_INCREASE_MS

public static final int DEFAULT_MIN_DURATION_FOR_QUALITY_INCREASE_MS

See Also:

Constant Field Values

DEFAULT_MAX_DURATION_FOR_QUALITY_DECREASE_MS

public static final int DEFAULT_MAX_DURATION_FOR_QUALITY_DECREASE_MS

See Also:

Constant Field Values

DEFAULT_MIN_DURATION_TO_RETAIN_AFTER_DISCARD_MS

public static final int DEFAULT_MIN_DURATION_TO_RETAIN_AFTER_DISCARD_MS

See Also:

Constant Field Values

DEFAULT_BANDWIDTH_FRACTION

public static final float DEFAULT_BANDWIDTH_FRACTION

See Also:

Constant Field Values

DEFAULT_BUFFERED_FRACTION_TO_LIVE_EDGE_FOR_QUALITY_INCREASE

public static final float DEFAULT_BUFFERED_FRACTION_TO_LIVE_EDGE_FOR_QUALITY_INCREASE

See Also:

Constant Field Values

DEFAULT_MIN_TIME_BETWEEN_BUFFER_REEVALUTATION_MS

public static final long DEFAULT_MIN_TIME_BETWEEN_BUFFER_REEVALUTATION_MS

See Also:

Constant Field Values

Constructor Detail

AdaptiveTrackSelection

public AdaptiveTrackSelection(TrackGroup group,
                              int[] tracks,
                              BandwidthMeter bandwidthMeter)

Parameters:

group - The TrackGroup.

tracks - The indices of the selected tracks within the TrackGroup. Must not be empty. May be in any order.

bandwidthMeter - Provides an estimate of the currently available bandwidth.

AdaptiveTrackSelection

public AdaptiveTrackSelection(TrackGroup group,
                              int[] tracks,
                              BandwidthMeter bandwidthMeter,
                              long minDurationForQualityIncreaseMs,
                              long maxDurationForQualityDecreaseMs,
                              long minDurationToRetainAfterDiscardMs,
                              float bandwidthFraction,
                              float bufferedFractionToLiveEdgeForQualityIncrease,
                              long minTimeBetweenBufferReevaluationMs,
                              Clock clock)

Parameters:

group - The TrackGroup.

tracks - The indices of the selected tracks within the TrackGroup. Must not be empty. May be in any order.

bandwidthMeter - Provides an estimate of the currently available bandwidth.

minDurationForQualityIncreaseMs - The minimum duration of buffered data required for the selected track to switch to one of higher quality.

maxDurationForQualityDecreaseMs - The maximum duration of buffered data required for the selected track to switch to one of lower quality.

minDurationToRetainAfterDiscardMs - When switching to a track of significantly higher quality, the selection may indicate that media already buffered at the lower quality can be discarded to speed up the switch. This is the minimum duration of media that must be retained at the lower quality.

bandwidthFraction - The fraction of the available bandwidth that the selection should consider available for use. Setting to a value less than 1 is recommended to account for inaccuracies in the bandwidth estimator.

bufferedFractionToLiveEdgeForQualityIncrease - For live streaming, the fraction of the duration from current playback position to the live edge that has to be buffered before the selected track can be switched to one of higher quality. This parameter is only applied when the playback position is closer to the live edge than minDurationForQualityIncreaseMs, which would otherwise prevent switching to a higher quality from happening.

minTimeBetweenBufferReevaluationMs - The track selection may periodically reevaluate its buffer and discard some chunks of lower quality to improve the playback quality if network condition has changed. This is the minimum duration between 2 consecutive buffer reevaluation calls.

Method Detail

enable

public void enable()

Description copied from interface: TrackSelection

Enables the track selection.

This method may not be called when the track selection is already enabled.

Specified by:

enable in interface TrackSelection

Overrides:

enable in class BaseTrackSelection

onPlaybackSpeed

public void onPlaybackSpeed(float playbackSpeed)

Description copied from interface: TrackSelection

Called to notify the selection of the current playback speed. The playback speed may affect adaptive track selection.

Specified by:

onPlaybackSpeed in interface TrackSelection

Overrides:

onPlaybackSpeed in class BaseTrackSelection

Parameters:

playbackSpeed - The playback speed.

updateSelectedTrack

public void updateSelectedTrack(long playbackPositionUs,
                                long bufferedDurationUs,
                                long availableDurationUs)

Description copied from interface: TrackSelection

Updates the selected track.

This method may only be called when the selection is enabled.

Parameters:

playbackPositionUs - The current playback position in microseconds. If playback of the period to which this track selection belongs has not yet started, the value will be the starting position in the period minus the duration of any media in previous periods still to be played.

bufferedDurationUs - The duration of media currently buffered from the current playback position, in microseconds. Note that the next load position can be calculated as (playbackPositionUs + bufferedDurationUs).

availableDurationUs - The duration of media available for buffering from the current playback position, in microseconds, or C.TIME_UNSET if media can be buffered to the end of the current period. Note that if not set to C.TIME_UNSET, the position up to which media is available for buffering can be calculated as (playbackPositionUs + availableDurationUs).

getSelectedIndex

public int getSelectedIndex()

Description copied from interface: TrackSelection

Returns the index of the selected track.

getSelectionReason

public int getSelectionReason()

Description copied from interface: TrackSelection

Returns the reason for the current track selection.

getSelectionData

@Nullable
public java.lang.Object getSelectionData()

Description copied from interface: TrackSelection

Returns optional data associated with the current track selection.

evaluateQueueSize

public int evaluateQueueSize(long playbackPositionUs,
                             java.util.List<? extends MediaChunk> queue)

Description copied from interface: TrackSelection

May be called periodically by sources that load media in discrete MediaChunks and support discarding of buffered chunks in order to re-buffer using a different selected track. Returns the number of chunks that should be retained in the queue.

To avoid excessive re-buffering, implementations should normally return the size of the queue. An example of a case where a smaller value may be returned is if network conditions have improved dramatically, allowing chunks to be discarded and re-buffered in a track of significantly higher quality. Discarding chunks may allow faster switching to a higher quality track in this case. This method may only be called when the selection is enabled.

Specified by:

evaluateQueueSize in interface TrackSelection

Overrides:

evaluateQueueSize in class BaseTrackSelection

Parameters:

playbackPositionUs - The current playback position in microseconds. If playback of the period to which this track selection belongs has not yet started, the value will be the starting position in the period minus the duration of any media in previous periods still to be played.

queue - The queue of buffered MediaChunks. Must not be modified.

Returns:

The number of chunks to retain in the queue.