Class: shaka.media.SegmentPrefetch

This class manages segment prefetch operations. Called by StreamingEngine to prefetch next N segments ahead of playhead, to reduce the chances of rebuffering.

Constructor

new SegmentPrefetch(prefetchLimit, stream, fetchDispatcher, reverse, shouldPrefetchNextSegmentnullable, getPlaybackRatenullable, allowReferencenullable)

This class manages segment prefetch operations. Called by StreamingEngine to prefetch next N segments ahead of playhead, to reduce the chances of rebuffering.

Parameters:
Name Type Attributes Description
prefetchLimit number
stream shaka.extern.Stream
fetchDispatcher shaka.media.SegmentPrefetch.FetchDispatcher
reverse boolean
shouldPrefetchNextSegment function <nullable>
getPlaybackRate function <nullable>
allowReference function <nullable>
 If provided and it returns false for a reference, that reference is not prefetched but iteration continues with the following one.
Source:

Members

allowReference_ :function(!shaka.media.SegmentReference): boolean

Type:
  • function(!shaka.media.SegmentReference): boolean
Source:

fetchDispatcher_ :shaka.media.SegmentPrefetch.FetchDispatcher

Type:
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getPlaybackRate_ :function(): number

Type:
  • function(): number
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initSegmentPrefetchMap_ :Map<!shaka.media.InitSegmentReference, !shaka.media.SegmentPrefetchOperation>

Type:
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iterator_ :shaka.media.SegmentIterator

Type:
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prefetchLimit_ :number

Type:
  • number
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reverse_ :boolean

Type:
  • boolean
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segmentPrefetchMap_ :Map<!shaka.media.SegmentReference, !shaka.media.SegmentPrefetchOperation>

Type:
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shouldPrefetchNextSegment_ :function(!shaka.media.SegmentReference, !shaka.extern.Stream): boolean

Type:
  • function(!shaka.media.SegmentReference, !shaka.extern.Stream): boolean
Source:

stream_ :shaka.extern.Stream

Type:
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Methods

logPrefix_(stream) → {string}

The prefix of the logs that are created in this class.
Parameters:
Name Type Description
stream shaka.extern.Stream
Source:
Returns:
Type
string

abortPrefetchedSegment_(referencenon-null)

Remove a segment from prefetch map and abort it.
Parameters:
Name Type Description
reference shaka.media.SegmentReference | shaka.media.InitSegmentReference
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clearAll(clearInitSegmentsopt)

Clear all segment data.
Parameters:
Name Type Attributes Default Description
clearInitSegments boolean <optional>
 true
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clearInitSegments_()

Remove all init segments that don't have associated segments in the segment prefetch map. If we don't have segments, but we have initialization segments, it is not cleaned. By default, with delete on get, the init segments should get removed as they are used. With deleteOnGet set to false, we need to clear them every so often once the segments that are associated with each init segment is no longer prefetched.
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clearMap_(mapnon-null)

Clear All Helper
Parameters:
Name Type Description
map Map<T, !shaka.media.SegmentPrefetchOperation>
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dispatchFetch_(prefetchMapnon-null, reference, segmentPrefetchOperationnon-null) → {Promise}

Starts a prefetch operation that is about to be added to |prefetchMap|. If it fails, it is removed from the map, so that a later request for the same reference, such as one made when streaming is retried, fetches it again instead of getting the same failure.
Parameters:
Name Type Description
prefetchMap Map<T, !shaka.media.SegmentPrefetchOperation>
reference T
segmentPrefetchOperation shaka.media.SegmentPrefetchOperation
Source:
Returns:
Type
Promise

evict(time, clearInitSegmentsopt)

Parameters:
Name Type Attributes Default Description
time number
clearInitSegments boolean <optional>
 false
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getPrefetchedSegment(referencenon-null, streamDataCallbacknullable) → {shaka.net.NetworkingEngine.PendingRequest}

Get the result of prefetched segment if already exists.
Parameters:
Name Type Attributes Description
reference shaka.media.SegmentReference | shaka.media.InitSegmentReference
streamDataCallback ?function(BufferSource): !Promise= <nullable>
Source:
Returns:
op
Type
shaka.net.NetworkingEngine.PendingRequest

getStream() → {shaka.extern.Stream}

Get the current stream.
Source:
Returns:
Type
shaka.extern.Stream

prefetchInitSegment(initSegmentReferencenon-null) → {Promise}

Fetch init segment.
Parameters:
Name Type Description
initSegmentReference shaka.media.InitSegmentReference
Source:
Returns:
Type
Promise

prefetchSegmentsByTime(currTime, skipFirstopt) → {Promise}

Fetch next segments ahead of current time.
Parameters:
Name Type Attributes Default Description
currTime number
skipFirst boolean <optional>
 false
Source:
Returns:
Type
Promise

removeReference(referencenon-null)

Remove a reference of prefetched segment if already exists.
Parameters:
Name Type Description
reference shaka.media.SegmentReference | shaka.media.InitSegmentReference
Source:

replaceFetchDispatcher(fetchDispatcher)

Parameters:
Name Type Description
fetchDispatcher shaka.media.SegmentPrefetch.FetchDispatcher
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resetLimit(newPrefetchLimit)

Reset the prefetchLimit and clear all internal states. Called by StreamingEngine when configure() was called.
Parameters:
Name Type Description
newPrefetchLimit number
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resetPosition()

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setReverse(reverse)

Parameters:
Name Type Description
reverse boolean
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switchStream(stream)

Called by Streaming Engine when switching variant.
Parameters:
Name Type Description
stream shaka.extern.Stream
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Type Definitions

FetchDispatcher

A callback function that fetches a segment.
Type:
Source: