# AdaptiveTrackSelection

Artifact: [androidx.media3:media3-exoplayer](https://developer.android.com/jetpack/androidx/releases/media3) [View Source](https://cs.android.com/search?q=file:androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection.java+class:androidx.media3.exoplayer.trackselection.AdaptiveTrackSelection)

*** ** * ** ***

<br />

```
@UnstableApi
public class AdaptiveTrackSelection extends BaseTrackSelection
```

<br />

|---|---|---|
| [java.lang.Object](https://developer.android.com/reference/java/lang/Object.html) |||
| ↳ | [androidx.media3.exoplayer.trackselection.BaseTrackSelection](https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection) ||
|   | ↳ | [androidx.media3.exoplayer.trackselection.AdaptiveTrackSelection](https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection) |

*** ** * ** ***

A bandwidth based adaptive `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/ExoTrackSelection`, whose selected track is updated to be the highest priority track given the current network conditions and the state of the buffer.

## Summary

| ### Nested types |
|---|
| `public final class https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection.AdaptationCheckpoint` Checkpoint to determine allocated bandwidth. |
| `public class https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection.Factory implements https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/ExoTrackSelection.Factory` Factory for `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection` instances. |

| ### Constants |
|---|---|
| `static final float` | `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#DEFAULT_BANDWIDTH_FRACTION() = 0.7f` |
| `static final float` | `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#DEFAULT_BUFFERED_FRACTION_TO_LIVE_EDGE_FOR_QUALITY_INCREASE() = 0.75f` |
| `static final int` | `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#DEFAULT_MAX_DURATION_FOR_QUALITY_DECREASE_MS() = 25000` |
| `static final int` | `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#DEFAULT_MAX_HEIGHT_TO_DISCARD() = 719` |
| `static final int` | `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#DEFAULT_MAX_WIDTH_TO_DISCARD() = 1279` |
| `static final int` | `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#DEFAULT_MIN_DURATION_FOR_QUALITY_INCREASE_MS() = 10000` |
| `static final int` | `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#DEFAULT_MIN_DURATION_TO_RETAIN_AFTER_DISCARD_MS() = 25000` |

| ### Public fields |
|---|---|
| `long` | `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#latestBitrateEstimate()` |
| `int` | `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#selectedIndex()` |

| ### Protected fields |
|---|---|
| `final long` | `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#minDurationToRetainAfterDiscardUs()` |

| ### Public constructors |
|---|
| `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#AdaptiveTrackSelection(androidx.media3.common.TrackGroup,int[],androidx.media3.exoplayer.upstream.BandwidthMeter)( https://developer.android.com/reference/androidx/media3/common/TrackGroup group, int[] tracks, https://developer.android.com/reference/androidx/media3/exoplayer/upstream/BandwidthMeter bandwidthMeter )` |

| ### Protected constructors |
|---|
| `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#AdaptiveTrackSelection(androidx.media3.common.TrackGroup,int[],int,androidx.media3.exoplayer.upstream.BandwidthMeter,long,long,long,int,int,float,float,java.util.List<androidx.media3.exoplayer.trackselection.AdaptiveTrackSelection.AdaptationCheckpoint>,androidx.media3.common.util.Clock)( https://developer.android.com/reference/androidx/media3/common/TrackGroup group, int[] tracks, @https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/TrackSelection.Type int type, https://developer.android.com/reference/androidx/media3/exoplayer/upstream/BandwidthMeter bandwidthMeter, long minDurationForQualityIncreaseMs, long maxDurationForQualityDecreaseMs, long minDurationToRetainAfterDiscardMs, int maxWidthToDiscard, int maxHeightToDiscard, float bandwidthFraction, float bufferedFractionToLiveEdgeForQualityIncrease, https://developer.android.com/reference/java/util/List.html<https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection.AdaptationCheckpoint> adaptationCheckpoints, https://developer.android.com/reference/androidx/media3/common/util/Clock clock )` |
| `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#AdaptiveTrackSelection(androidx.media3.common.TrackGroup,int[],int,androidx.media3.exoplayer.upstream.BandwidthMeter,long,long,long,int,int,float,float,java.util.List<androidx.media3.exoplayer.trackselection.AdaptiveTrackSelection.AdaptationCheckpoint>,androidx.media3.common.util.Clock,java.util.Comparator<androidx.media3.common.Format>)( https://developer.android.com/reference/androidx/media3/common/TrackGroup group, int[] tracks, @https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/TrackSelection.Type int type, https://developer.android.com/reference/androidx/media3/exoplayer/upstream/BandwidthMeter bandwidthMeter, long minDurationForQualityIncreaseMs, long maxDurationForQualityDecreaseMs, long minDurationToRetainAfterDiscardMs, int maxWidthToDiscard, int maxHeightToDiscard, float bandwidthFraction, float bufferedFractionToLiveEdgeForQualityIncrease, https://developer.android.com/reference/java/util/List.html<https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection.AdaptationCheckpoint> adaptationCheckpoints, https://developer.android.com/reference/androidx/media3/common/util/Clock clock, https://developer.android.com/reference/java/util/Comparator.html<https://developer.android.com/reference/androidx/media3/common/Format> trackFormatComparator )` |

| ### Public methods |
|---|---|
| `void` | `@https://developer.android.com/reference/androidx/annotation/CallSuper https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#disable()()` Disables this track selection. |
| `void` | `@https://developer.android.com/reference/androidx/annotation/CallSuper https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#enable()()` Enables the track selection. |
| `int` | `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#evaluateQueueSize(long,java.util.List<? extends androidx.media3.exoplayer.source.chunk.MediaChunk>)(long playbackPositionUs, https://developer.android.com/reference/java/util/List.html<https://developer.android.com/reference/androidx/media3/exoplayer/source/chunk/MediaChunk> queue)` Returns the number of chunks that should be retained in the queue. |
| `long` | `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#getLatestBitrateEstimate()()` Returns the most recent bitrate estimate utilised for track selection. |
| `int` | `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#getSelectedIndex()()` Returns the index of the selected track. |
| `@https://developer.android.com/reference/androidx/annotation/Nullable https://developer.android.com/reference/java/lang/Object.html` | `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#getSelectionData()()` Returns optional data associated with the current track selection. |
| `int` | `@https://developer.android.com/reference/androidx/media3/common/C.SelectionReason https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#getSelectionReason()()` Returns the reason for the current track selection. |
| `void` | `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#onPlaybackSpeed(float)(float playbackSpeed)` Called to notify the selection of the current playback speed. |
| `void` | `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#updateSelectedTrack(long,long,long,java.util.List<? extends androidx.media3.exoplayer.source.chunk.MediaChunk>,androidx.media3.exoplayer.source.chunk.MediaChunkIterator[])( long playbackPositionUs, long bufferedDurationUs, long availableDurationUs, https://developer.android.com/reference/java/util/List.html<https://developer.android.com/reference/androidx/media3/exoplayer/source/chunk/MediaChunk> queue, MediaChunkIterator[] mediaChunkIterators )` Updates the selected track for sources that load media in discrete `https://developer.android.com/reference/androidx/media3/exoplayer/source/chunk/MediaChunk`s. |

| ### Protected methods |
|---|---|
| `boolean` | `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#canSelectFormat(androidx.media3.common.Format,int,long)(https://developer.android.com/reference/androidx/media3/common/Format format, int trackBitrate, long effectiveBitrate)` Called when updating the selected track to determine whether a candidate track can be selected. |
| `long` | `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#getMinDurationToRetainAfterDiscardUs()()` Called from `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#evaluateQueueSize(long,java.util.List<? extends androidx.media3.exoplayer.source.chunk.MediaChunk>)` to determine the minimum duration of buffer to retain after discarding chunks. |
| `boolean` | `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#shouldEvaluateQueueSize(long,java.util.List<? extends androidx.media3.exoplayer.source.chunk.MediaChunk>)(long nowMs, https://developer.android.com/reference/java/util/List.html<https://developer.android.com/reference/androidx/media3/exoplayer/source/chunk/MediaChunk> queue)` Called from `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#evaluateQueueSize(long,java.util.List<? extends androidx.media3.exoplayer.source.chunk.MediaChunk>)` to determine whether an evaluation should be performed. |

### Inherited Constants

From [androidx.media3.exoplayer.trackselection.BaseTrackSelection](https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection) `static final https://developer.android.com/reference/java/util/Comparator.html<https://developer.android.com/reference/androidx/media3/common/Format>` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection#DEFAULT_FORMAT_COMPARATOR()`

The default `https://developer.android.com/reference/androidx/media3/common/Format` comparator, which sorts formats by bitrate in descending order.
From [androidx.media3.exoplayer.trackselection.TrackSelection](https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/TrackSelection) `static final int` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/TrackSelection#TYPE_CUSTOM_BASE() = 10000`

The first value that can be used for application specific track selection types.
`static final int` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/TrackSelection#TYPE_UNSET() = 0`

An unspecified track selection type.

### Inherited fields

From [androidx.media3.exoplayer.trackselection.BaseTrackSelection](https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection) `final https://developer.android.com/reference/androidx/media3/common/TrackGroup` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection#group()`

The selected `https://developer.android.com/reference/androidx/media3/common/TrackGroup`.
`final int` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection#length()`

The number of selected tracks within the `https://developer.android.com/reference/androidx/media3/common/TrackGroup`.
`boolean` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection#playWhenReady()`

The current value of whether playback will proceed when ready.
`final int[]` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection#tracks()`

The indices of the selected tracks in `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection#group()`, in selection order.
`final int` `@https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/TrackSelection.Type
https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection#type()`

The type of the selection.

### Inherited methods

From [androidx.media3.exoplayer.trackselection.BaseTrackSelection](https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection) `void` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection#clearTrackExclusions()()`

Clears the existing track exclusions.
`boolean` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection#equals(java.lang.Object)(@https://developer.android.com/reference/androidx/annotation/Nullable https://developer.android.com/reference/java/lang/Object.html obj)` `boolean` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection#excludeTrack(int,long)(int index, long exclusionDurationMs)`

Attempts to exclude the track at the specified index in the selection, making it ineligible for selection by calls to `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/ExoTrackSelection#updateSelectedTrack(long,long,long,java.util.List<? extends androidx.media3.exoplayer.source.chunk.MediaChunk>,androidx.media3.exoplayer.source.chunk.MediaChunkIterator[])` for the specified period of time.
`final https://developer.android.com/reference/androidx/media3/common/Format` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection#getFormat(int)(int index)`

Returns the format of the track at a given index in the selection.
`final int` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection#getIndexInTrackGroup(int)(int index)`

Returns the index in the track group of the track at a given index in the selection.
`final boolean` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection#getPlayWhenReady()()`

Returns whether the playback using this track selection will proceed when ready.
`final https://developer.android.com/reference/androidx/media3/common/Format` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection#getSelectedFormat()()`

Returns the `https://developer.android.com/reference/androidx/media3/common/Format` of the individual selected track.
`final int` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection#getSelectedIndexInTrackGroup()()`

Returns the index in the track group of the individual selected track.
`final https://developer.android.com/reference/androidx/media3/common/TrackGroup` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection#getTrackGroup()()`

Returns the `https://developer.android.com/reference/androidx/media3/common/TrackGroup` to which the selected tracks belong.
`final int` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection#getType()()`

Returns an integer specifying the type of the selection, or `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/TrackSelection#TYPE_UNSET()` if not specified.
`int` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection#hashCode()()` `final int` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection#indexOf(androidx.media3.common.Format)(https://developer.android.com/reference/androidx/media3/common/Format format)`

Returns the index in the selection of the track with the specified format.
`final int` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection#indexOf(int)(int indexInTrackGroup)`

Returns the index in the selection of the track with the specified index in the track group.
`boolean` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection#isTrackExcluded(int,long)(int index, long nowMs)`

Returns whether the track at the specified index in the selection is excluded.
`final int` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection#length()()`

Returns the number of tracks in the selection.
`void` `@https://developer.android.com/reference/androidx/annotation/CallSuper
https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/BaseTrackSelection#onPlayWhenReadyChanged(boolean)(boolean playWhenReady)`

Called to notify when the playback is paused or resumed.
From [androidx.media3.exoplayer.trackselection.ExoTrackSelection](https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/ExoTrackSelection) `void` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/ExoTrackSelection#onDiscontinuity()()`

Called to notify the selection of a position discontinuity.
`void` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/ExoTrackSelection#onRebuffer()()`

Called to notify when a rebuffer occurred.
`boolean` `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/ExoTrackSelection#shouldCancelChunkLoad(long,androidx.media3.exoplayer.source.chunk.Chunk,java.util.List<? extends androidx.media3.exoplayer.source.chunk.MediaChunk>)(

long playbackPositionUs,

https://developer.android.com/reference/androidx/media3/exoplayer/source/chunk/Chunk loadingChunk,

https://developer.android.com/reference/java/util/List.html<https://developer.android.com/reference/androidx/media3/exoplayer/source/chunk/MediaChunk> queue

)`

Returns whether an ongoing load of a chunk should be canceled.

## Constants

### DEFAULT_BANDWIDTH_FRACTION

```
public static final float DEFAULT_BANDWIDTH_FRACTION = 0.7f
```

### DEFAULT_BUFFERED_FRACTION_TO_LIVE_EDGE_FOR_QUALITY_INCREASE

```
public static final float DEFAULT_BUFFERED_FRACTION_TO_LIVE_EDGE_FOR_QUALITY_INCREASE = 0.75f
```

### DEFAULT_MAX_DURATION_FOR_QUALITY_DECREASE_MS

```
public static final int DEFAULT_MAX_DURATION_FOR_QUALITY_DECREASE_MS = 25000
```

### DEFAULT_MAX_HEIGHT_TO_DISCARD

```
public static final int DEFAULT_MAX_HEIGHT_TO_DISCARD = 719
```

### DEFAULT_MAX_WIDTH_TO_DISCARD

```
public static final int DEFAULT_MAX_WIDTH_TO_DISCARD = 1279
```

### DEFAULT_MIN_DURATION_FOR_QUALITY_INCREASE_MS

```
public static final int DEFAULT_MIN_DURATION_FOR_QUALITY_INCREASE_MS = 10000
```

### DEFAULT_MIN_DURATION_TO_RETAIN_AFTER_DISCARD_MS

```
public static final int DEFAULT_MIN_DURATION_TO_RETAIN_AFTER_DISCARD_MS = 25000
```

## Public fields

### latestBitrateEstimate

```
public long latestBitrateEstimate
```

### selectedIndex

```
public int selectedIndex
```

## Protected fields

### minDurationToRetainAfterDiscardUs

```
protected final long minDurationToRetainAfterDiscardUs
```

## Public constructors

### AdaptiveTrackSelection

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

| Parameters |
|---|---|
| `https://developer.android.com/reference/androidx/media3/common/TrackGroup group` | The `https://developer.android.com/reference/androidx/media3/common/TrackGroup`. |
| `int[] tracks` | The indices of the selected tracks within the `https://developer.android.com/reference/androidx/media3/common/TrackGroup`. Must not be empty. May be in any order. |
| `https://developer.android.com/reference/androidx/media3/exoplayer/upstream/BandwidthMeter bandwidthMeter` | Provides an estimate of the currently available bandwidth. |

## Protected constructors

### AdaptiveTrackSelection

```
protected AdaptiveTrackSelection(
    TrackGroup group,
    int[] tracks,
    @TrackSelection.Type int type,
    BandwidthMeter bandwidthMeter,
    long minDurationForQualityIncreaseMs,
    long maxDurationForQualityDecreaseMs,
    long minDurationToRetainAfterDiscardMs,
    int maxWidthToDiscard,
    int maxHeightToDiscard,
    float bandwidthFraction,
    float bufferedFractionToLiveEdgeForQualityIncrease,
    List<AdaptiveTrackSelection.AdaptationCheckpoint> adaptationCheckpoints,
    Clock clock
)
```

| Parameters |
|---|---|
| `https://developer.android.com/reference/androidx/media3/common/TrackGroup group` | The `https://developer.android.com/reference/androidx/media3/common/TrackGroup`. |
| `int[] tracks` | The indices of the selected tracks within the `https://developer.android.com/reference/androidx/media3/common/TrackGroup`. Must not be empty. May be in any order. |
| `@https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/TrackSelection.Type int type` | The type that will be returned from `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/TrackSelection#getType()`. |
| `https://developer.android.com/reference/androidx/media3/exoplayer/upstream/BandwidthMeter bandwidthMeter` | Provides an estimate of the currently available bandwidth. |
| `long minDurationForQualityIncreaseMs` | The minimum duration of buffered data required for the selected track to switch to one of higher quality. |
| `long maxDurationForQualityDecreaseMs` | The maximum duration of buffered data required for the selected track to switch to one of lower quality. |
| `long minDurationToRetainAfterDiscardMs` | When switching to a video track of 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. It must be at least `minDurationForQualityIncreaseMs`. |
| `int maxWidthToDiscard` | The maximum video width that the selector may discard from the buffer to speed up switching to a higher quality. |
| `int maxHeightToDiscard` | The maximum video height that the selector may discard from the buffer to speed up switching to a higher quality. |
| `float 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. |
| `float 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. |
| `https://developer.android.com/reference/java/util/List.html<https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection.AdaptationCheckpoint> adaptationCheckpoints` | The `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection.AdaptationCheckpoint` that can be used to calculate available bandwidth for this selection. |
| `https://developer.android.com/reference/androidx/media3/common/util/Clock clock` | The `https://developer.android.com/reference/androidx/media3/common/util/Clock`. |

### AdaptiveTrackSelection

```
protected AdaptiveTrackSelection(
    TrackGroup group,
    int[] tracks,
    @TrackSelection.Type int type,
    BandwidthMeter bandwidthMeter,
    long minDurationForQualityIncreaseMs,
    long maxDurationForQualityDecreaseMs,
    long minDurationToRetainAfterDiscardMs,
    int maxWidthToDiscard,
    int maxHeightToDiscard,
    float bandwidthFraction,
    float bufferedFractionToLiveEdgeForQualityIncrease,
    List<AdaptiveTrackSelection.AdaptationCheckpoint> adaptationCheckpoints,
    Clock clock,
    Comparator<Format> trackFormatComparator
)
```

| Parameters |
|---|---|
| `https://developer.android.com/reference/androidx/media3/common/TrackGroup group` | The `https://developer.android.com/reference/androidx/media3/common/TrackGroup`. |
| `int[] tracks` | The indices of the selected tracks within the `https://developer.android.com/reference/androidx/media3/common/TrackGroup`. Must not be empty. May be in any order. |
| `@https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/TrackSelection.Type int type` | The type that will be returned from `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/TrackSelection#getType()`. |
| `https://developer.android.com/reference/androidx/media3/exoplayer/upstream/BandwidthMeter bandwidthMeter` | Provides an estimate of the currently available bandwidth. |
| `long minDurationForQualityIncreaseMs` | The minimum duration of buffered data required for the selected track to switch to one of higher quality. |
| `long maxDurationForQualityDecreaseMs` | The maximum duration of buffered data required for the selected track to switch to one of lower quality. |
| `long minDurationToRetainAfterDiscardMs` | When switching to a video track of 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. It must be at least `minDurationForQualityIncreaseMs`. |
| `int maxWidthToDiscard` | The maximum video width that the selector may discard from the buffer to speed up switching to a higher quality. |
| `int maxHeightToDiscard` | The maximum video height that the selector may discard from the buffer to speed up switching to a higher quality. |
| `float 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. |
| `float 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. |
| `https://developer.android.com/reference/java/util/List.html<https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection.AdaptationCheckpoint> adaptationCheckpoints` | The `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection.AdaptationCheckpoint` that can be used to calculate available bandwidth for this selection. |
| `https://developer.android.com/reference/androidx/media3/common/util/Clock clock` | The `https://developer.android.com/reference/androidx/media3/common/util/Clock`. |
| `https://developer.android.com/reference/java/util/Comparator.html<https://developer.android.com/reference/androidx/media3/common/Format> trackFormatComparator` | Comparator used to order selected formats. |

## Public methods

### disable

```
@CallSuper
public void disable()
```

Disables this track selection. No further dynamic changes via `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/ExoTrackSelection#updateSelectedTrack(long,long,long,java.util.List<? extends androidx.media3.exoplayer.source.chunk.MediaChunk>,androidx.media3.exoplayer.source.chunk.MediaChunkIterator[])`, `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/ExoTrackSelection#evaluateQueueSize(long,java.util.List<? extends androidx.media3.exoplayer.source.chunk.MediaChunk>)` or `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/ExoTrackSelection#shouldCancelChunkLoad(long,androidx.media3.exoplayer.source.chunk.Chunk,java.util.List<? extends androidx.media3.exoplayer.source.chunk.MediaChunk>)` will happen after this call.

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

### enable

```
@CallSuper
public void enable()
```

Enables the track selection. Dynamic changes via `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/ExoTrackSelection#updateSelectedTrack(long,long,long,java.util.List<? extends androidx.media3.exoplayer.source.chunk.MediaChunk>,androidx.media3.exoplayer.source.chunk.MediaChunkIterator[])`, `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/ExoTrackSelection#evaluateQueueSize(long,java.util.List<? extends androidx.media3.exoplayer.source.chunk.MediaChunk>)` or `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/ExoTrackSelection#shouldCancelChunkLoad(long,androidx.media3.exoplayer.source.chunk.Chunk,java.util.List<? extends androidx.media3.exoplayer.source.chunk.MediaChunk>)` will only happen after this call.

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

### evaluateQueueSize

```
public int evaluateQueueSize(long playbackPositionUs, List<MediaChunk> queue)
```

Returns the number of chunks that should be retained in the queue.

May be called by sources that load media in discrete `https://developer.android.com/reference/androidx/media3/exoplayer/source/chunk/MediaChunk` and support discarding of buffered chunks.

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.

Note that even if the source supports discarding of buffered chunks, the actual number of discarded chunks is not guaranteed. The source will call `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/ExoTrackSelection#updateSelectedTrack(long,long,long,java.util.List<? extends androidx.media3.exoplayer.source.chunk.MediaChunk>,androidx.media3.exoplayer.source.chunk.MediaChunkIterator[])` with the updated queue of chunks before loading a new chunk to allow switching to another quality.

This method will only be called when the selection is enabled and none of the `https://developer.android.com/reference/androidx/media3/exoplayer/source/chunk/MediaChunk` in the queue are currently loading.

| Parameters |
|---|---|
| `long 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. |
| `https://developer.android.com/reference/java/util/List.html<https://developer.android.com/reference/androidx/media3/exoplayer/source/chunk/MediaChunk> queue` | The queue of buffered `https://developer.android.com/reference/androidx/media3/exoplayer/source/chunk/MediaChunk`. Must not be modified. |

| Returns |
|---|---|
| `int` | The number of chunks to retain in the queue. |

### getLatestBitrateEstimate

```
public long getLatestBitrateEstimate()
```

Returns the most recent bitrate estimate utilised for track selection.

The default behavior is to return `https://developer.android.com/reference/androidx/media3/common/C#RATE_UNSET_INT()`, indicating that the bitrate estimate was not computed for the track selection decision.

### getSelectedIndex

```
public int getSelectedIndex()
```

Returns the index of the selected track.

### getSelectionData

```
public @Nullable Object getSelectionData()
```

Returns optional data associated with the current track selection.

### getSelectionReason

```
@C.SelectionReason
public int getSelectionReason()
```

Returns the reason for the current track selection.

### onPlaybackSpeed

```
public void onPlaybackSpeed(float playbackSpeed)
```

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

| Parameters |
|---|---|
| `float playbackSpeed` | The factor by which playback is sped up. |

### updateSelectedTrack

```
public void updateSelectedTrack(
    long playbackPositionUs,
    long bufferedDurationUs,
    long availableDurationUs,
    List<MediaChunk> queue,
    MediaChunkIterator[] mediaChunkIterators
)
```

Updates the selected track for sources that load media in discrete `https://developer.android.com/reference/androidx/media3/exoplayer/source/chunk/MediaChunk`s.

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

| Parameters |
|---|---|
| `long 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. |
| `long 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)`. |
| `long availableDurationUs` | The duration of media available for buffering from the current playback position, in microseconds, or `https://developer.android.com/reference/androidx/media3/common/C#TIME_UNSET()` if media can be buffered to the end of the current period. Note that if not set to `https://developer.android.com/reference/androidx/media3/common/C#TIME_UNSET()`, the position up to which media is available for buffering can be calculated as `(playbackPositionUs + availableDurationUs)`. |
| `https://developer.android.com/reference/java/util/List.html<https://developer.android.com/reference/androidx/media3/exoplayer/source/chunk/MediaChunk> queue` | The queue of already buffered `https://developer.android.com/reference/androidx/media3/exoplayer/source/chunk/MediaChunk`s. Must not be modified. |
| `MediaChunkIterator[] mediaChunkIterators` | An array of `https://developer.android.com/reference/androidx/media3/exoplayer/source/chunk/MediaChunkIterator`s providing information about the sequence of upcoming media chunks for each track in the selection. All iterators start from the media chunk which will be loaded next if the respective track is selected. Note that this information may not be available for all tracks, and so some iterators may be empty. |

## Protected methods

### canSelectFormat

```
protected boolean canSelectFormat(Format format, int trackBitrate, long effectiveBitrate)
```

Called when updating the selected track to determine whether a candidate track can be selected.

| Parameters |
|---|---|
| `https://developer.android.com/reference/androidx/media3/common/Format format` | The `https://developer.android.com/reference/androidx/media3/common/Format` of the candidate track. |
| `int trackBitrate` | The estimated bitrate of the track. May differ from `https://developer.android.com/reference/androidx/media3/common/Format#bitrate()` if a more accurate estimate of the current track bitrate is available. |
| `long effectiveBitrate` | The bitrate available to this selection. |

| Returns |
|---|---|
| `boolean` | Whether this `https://developer.android.com/reference/androidx/media3/common/Format` can be selected. |

### getMinDurationToRetainAfterDiscardUs

```
protected long getMinDurationToRetainAfterDiscardUs()
```

Called from `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#evaluateQueueSize(long,java.util.List<? extends androidx.media3.exoplayer.source.chunk.MediaChunk>)` to determine the minimum duration of buffer to retain after discarding chunks.

| Returns |
|---|---|
| `long` | The minimum duration of buffer to retain after discarding chunks, in microseconds. |

### shouldEvaluateQueueSize

```
protected boolean shouldEvaluateQueueSize(long nowMs, List<MediaChunk> queue)
```

Called from `https://developer.android.com/reference/androidx/media3/exoplayer/trackselection/AdaptiveTrackSelection#evaluateQueueSize(long,java.util.List<? extends androidx.media3.exoplayer.source.chunk.MediaChunk>)` to determine whether an evaluation should be performed.

| Parameters |
|---|---|
| `long nowMs` | The current value of `https://developer.android.com/reference/androidx/media3/common/util/Clock#elapsedRealtime()`. |
| `https://developer.android.com/reference/java/util/List.html<https://developer.android.com/reference/androidx/media3/exoplayer/source/chunk/MediaChunk> queue` | The queue of buffered `https://developer.android.com/reference/androidx/media3/exoplayer/source/chunk/MediaChunk`. Must not be modified. |

| Returns |
|---|---|
| `boolean` | Whether an evaluation should be performed. |