Source: lib/media/segment_prefetch.js

  1. /*! @license
  2.  * Shaka Player
  3.  * Copyright 2016 Google LLC
  4.  * SPDX-License-Identifier: Apache-2.0
  5.  */
  7. goog.provide('shaka.media.SegmentPrefetch');
  9. goog.require('goog.asserts');
  10. goog.require('shaka.log');
  11. goog.require('shaka.media.InitSegmentReference');
  12. goog.require('shaka.media.SegmentIterator');
  13. goog.require('shaka.media.SegmentReference');
  14. goog.require('shaka.net.NetworkingEngine');
  15. goog.require('shaka.util.Error');
  16. goog.require('shaka.util.Uint8ArrayUtils');
  19. /**
  20.  * @summary
  21.  * This class manages segment prefetch operations.
  22.  * Called by StreamingEngine to prefetch next N segments
  23.  * ahead of playhead, to reduce the chances of rebuffering.
  24.  */
  25. shaka.media.SegmentPrefetch = class {
  26.   /**
  27.    * @param {number} prefetchLimit
  28.    * @param {shaka.extern.Stream} stream
  29.    * @param {shaka.media.SegmentPrefetch.FetchDispatcher} fetchDispatcher
  30.    * @param {boolean} reverse
  31.    */
  32.   constructor(prefetchLimit, stream, fetchDispatcher, reverse) {
  33.     /** @private {number} */
  34.     this.prefetchLimit_ = prefetchLimit;
  36.     /** @private {shaka.extern.Stream} */
  37.     this.stream_ = stream;
  39.     /** @private {shaka.media.SegmentPrefetch.FetchDispatcher} */
  40.     this.fetchDispatcher_ = fetchDispatcher;
  42.     /**
  43.      * @private {!Map.<
  44.      *        !(shaka.media.SegmentReference),
  45.      *        !shaka.media.SegmentPrefetchOperation>}
  46.      */
  47.     this.segmentPrefetchMap_ = new Map();
  49.     /**
  50.      * @private {!Map.<
  51.      *        !(shaka.media.InitSegmentReference),
  52.      *        !shaka.media.SegmentPrefetchOperation>}
  53.      */
  54.     this.initSegmentPrefetchMap_ = new Map();
  56.     /** @private {?shaka.media.SegmentIterator} */
  57.     this.iterator_ = null;
  59.     /** @private {boolean} */
  60.     this.reverse_ = reverse;
  61.   }
  63.   /**
  64.    * @param {shaka.media.SegmentPrefetch.FetchDispatcher} fetchDispatcher
  65.    */
  66.   replaceFetchDispatcher(fetchDispatcher) {
  67.     this.fetchDispatcher_ = fetchDispatcher;
  68.     for (const operation of this.segmentPrefetchMap_.values()) {
  69.       operation.replaceFetchDispatcher(fetchDispatcher);
  70.     }
  71.   }
  73.   /**
  74.    * Fetch next segments ahead of current time.
  75.    *
  76.    * @param {number} currTime
  77.    * @param {boolean=} skipFirst
  78.    * @return {!Promise}
  79.    * @public
  80.    */
  81.   prefetchSegmentsByTime(currTime, skipFirst = false) {
  82.     goog.asserts.assert(this.prefetchLimit_ > 0,
  83.         'SegmentPrefetch can not be used when prefetchLimit <= 0.');
  85.     const logPrefix = shaka.media.SegmentPrefetch.logPrefix_(this.stream_);
  86.     if (!this.stream_.segmentIndex) {
  87.       shaka.log.debug(logPrefix, 'missing segmentIndex');
  88.       return Promise.resolve();
  89.     }
  90.     if (!this.iterator_) {
  91.       this.iterator_ = this.stream_.segmentIndex.getIteratorForTime(
  92.           currTime, /* allowNonIndepedent= */ true, this.reverse_);
  93.     }
  94.     if (!this.iterator_) {
  95.       shaka.log.debug(logPrefix, 'missing iterator');
  96.       return Promise.resolve();
  97.     }
  98.     if (skipFirst) {
  99.       this.iterator_.next();
  100.     }
  101.     const promises = [];
  102.     while (this.segmentPrefetchMap_.size < this.prefetchLimit_) {
  103.       const reference = this.iterator_.next().value;
  104.       if (!reference) {
  105.         break;
  106.       }
  107.       // By default doesn't prefech preload partial segments when using
  108.       // byterange
  109.       let prefetchAllowed = true;
  110.       if (reference.isPreload() && reference.endByte != null) {
  111.         prefetchAllowed = false;
  112.       }
  113.       if (reference.getStatus() ==
  114.           shaka.media.SegmentReference.Status.MISSING) {
  115.         prefetchAllowed = false;
  116.       }
  117.       if (reference.getSegmentData()) {
  118.         prefetchAllowed = false;
  119.       }
  120.       if (prefetchAllowed && reference.initSegmentReference) {
  121.         promises.push(this.prefetchInitSegment(
  122.             reference.initSegmentReference));
  123.       }
  124.       if (prefetchAllowed && !this.segmentPrefetchMap_.has(reference)) {
  125.         const segmentPrefetchOperation =
  126.           new shaka.media.SegmentPrefetchOperation(this.fetchDispatcher_);
  127.         promises.push(segmentPrefetchOperation.dispatchFetch(
  128.             reference, this.stream_));
  129.         this.segmentPrefetchMap_.set(reference, segmentPrefetchOperation);
  130.       }
  131.     }
  132.     this.clearInitSegments_();
  133.     return Promise.all(promises);
  134.   }
  136.   /**
  137.    * Fetch init segment.
  138.    *
  139.    * @param {!shaka.media.InitSegmentReference} initSegmentReference
  140.    * @return {!Promise}
  141.    */
  142.   prefetchInitSegment(initSegmentReference) {
  143.     goog.asserts.assert(this.prefetchLimit_ > 0,
  144.         'SegmentPrefetch can not be used when prefetchLimit <= 0.');
  146.     const logPrefix = shaka.media.SegmentPrefetch.logPrefix_(this.stream_);
  147.     if (!this.stream_.segmentIndex) {
  148.       shaka.log.debug(logPrefix, 'missing segmentIndex');
  149.       return Promise.resolve();
  150.     }
  152.     if (initSegmentReference.getSegmentData()) {
  153.       return Promise.resolve();
  154.     }
  156.     // init segments are ignored from the prefetch limit
  157.     const initSegments = Array.from(this.initSegmentPrefetchMap_.keys());
  158.     const someReference = initSegments.some((reference) => {
  159.       return shaka.media.InitSegmentReference.equal(
  160.           reference, initSegmentReference);
  161.     });
  162.     if (someReference) {
  163.       return Promise.resolve();
  164.     }
  165.     const segmentPrefetchOperation = new shaka.media.SegmentPrefetchOperation(
  166.         this.fetchDispatcher_);
  167.     const promise = segmentPrefetchOperation.dispatchFetch(
  168.         initSegmentReference, this.stream_);
  169.     this.initSegmentPrefetchMap_.set(
  170.         initSegmentReference, segmentPrefetchOperation);
  171.     return promise;
  172.   }
  174.   /**
  175.    * Get the result of prefetched segment if already exists.
  176.    * @param {!(shaka.media.SegmentReference|shaka.media.InitSegmentReference)}
  177.    *        reference
  178.    * @param {?function(BufferSource):!Promise=} streamDataCallback
  179.    * @return {?shaka.net.NetworkingEngine.PendingRequest} op
  180.    * @public
  181.    */
  182.   getPrefetchedSegment(reference, streamDataCallback) {
  183.     goog.asserts.assert(this.prefetchLimit_ > 0,
  184.         'SegmentPrefetch can not be used when prefetchLimit <= 0.');
  186.     const logPrefix = shaka.media.SegmentPrefetch.logPrefix_(this.stream_);
  188.     let prefetchMap = this.segmentPrefetchMap_;
  189.     if (reference instanceof shaka.media.InitSegmentReference) {
  190.       prefetchMap = this.initSegmentPrefetchMap_;
  191.     }
  193.     if (prefetchMap.has(reference)) {
  194.       const segmentPrefetchOperation = prefetchMap.get(reference);
  195.       if (streamDataCallback) {
  196.         segmentPrefetchOperation.setStreamDataCallback(streamDataCallback);
  197.       }
  198.       if (reference instanceof shaka.media.SegmentReference) {
  199.         shaka.log.debug(
  200.             logPrefix,
  201.             'reused prefetched segment at time:', reference.startTime,
  202.             'mapSize', prefetchMap.size);
  203.       } else {
  204.         shaka.log.debug(
  205.             logPrefix,
  206.             'reused prefetched init segment at time, mapSize',
  207.             prefetchMap.size);
  208.       }
  209.       return segmentPrefetchOperation.getOperation();
  210.     } else {
  211.       if (reference instanceof shaka.media.SegmentReference) {
  212.         shaka.log.debug(
  213.             logPrefix,
  214.             'missed segment at time:', reference.startTime,
  215.             'mapSize', prefetchMap.size);
  216.       } else {
  217.         shaka.log.debug(
  218.             logPrefix,
  219.             'missed init segment at time, mapSize',
  220.             prefetchMap.size);
  221.       }
  222.       return null;
  223.     }
  224.   }
  226.   /**
  227.    * Clear All Helper
  228.    * @private
  229.    */
  230.   clearMap_(map) {
  231.     for (const reference of map.keys()) {
  232.       if (reference) {
  233.         this.abortPrefetchedSegment_(reference);
  234.       }
  235.     }
  236.   }
  238.   /** */
  239.   resetPosition() {
  240.     this.iterator_ = null;
  241.   }
  243.   /**
  244.    * Clear all segment data.
  245.    * @public
  246.    */
  247.   clearAll() {
  248.     this.clearMap_(this.segmentPrefetchMap_);
  249.     this.clearMap_(this.initSegmentPrefetchMap_);
  250.     this.resetPosition();
  251.     const logPrefix = shaka.media.SegmentPrefetch.logPrefix_(this.stream_);
  252.     shaka.log.debug(logPrefix, 'cleared all');
  253.   }
  255.   /**
  256.    * Remove a reference of prefetched segment if already exists.
  257.    * @param {!shaka.media.SegmentReference} reference
  258.    * @public
  259.    */
  260.   removeReference(reference) {
  261.     this.abortPrefetchedSegment_(reference);
  262.   }
  264.   /**
  265.    * @param {number} time
  266.    * @param {boolean=} clearInitSegments
  267.    */
  268.   evict(time, clearInitSegments = false) {
  269.     for (const ref of this.segmentPrefetchMap_.keys()) {
  270.       if (time > ref.endTime) {
  271.         this.abortPrefetchedSegment_(ref);
  272.       }
  273.     }
  274.     if (clearInitSegments) {
  275.       this.clearInitSegments_();
  276.     }
  277.   }
  279.   /**
  280.    * @param {boolean} reverse
  281.    */
  282.   setReverse(reverse) {
  283.     this.reverse_ = reverse;
  284.     if (this.iterator_) {
  285.       this.iterator_.setReverse(reverse);
  286.     }
  287.   }
  289.   /**
  290.    * Remove all init segments that don't have associated segments in
  291.    * the segment prefetch map.
  292.    * By default, with delete on get, the init segments should get removed as
  293.    * they are used. With deleteOnGet set to false, we need to clear them
  294.    * every so often once the segments that are associated with each init segment
  295.    * is no longer prefetched.
  296.    * @private
  297.    */
  298.   clearInitSegments_() {
  299.     const segmentReferences = Array.from(this.segmentPrefetchMap_.keys());
  300.     for (const initSegmentReference of this.initSegmentPrefetchMap_.keys()) {
  301.       // if no segment references this init segment, we should remove it.
  302.       const someReference = segmentReferences.some((segmentReference) => {
  303.         return shaka.media.InitSegmentReference.equal(
  304.             segmentReference.initSegmentReference, initSegmentReference);
  305.       });
  306.       if (!someReference) {
  307.         this.abortPrefetchedSegment_(initSegmentReference);
  308.       }
  309.     }
  310.   }
  312.   /**
  313.    * Reset the prefetchLimit and clear all internal states.
  314.    * Called by StreamingEngine when configure() was called.
  315.    * @param {number} newPrefetchLimit
  316.    * @public
  317.    */
  318.   resetLimit(newPrefetchLimit) {
  319.     goog.asserts.assert(newPrefetchLimit >= 0,
  320.         'The new prefetch limit must be >= 0.');
  322.     const logPrefix = shaka.media.SegmentPrefetch.logPrefix_(this.stream_);
  323.     shaka.log.debug(logPrefix, 'resetting prefetch limit to', newPrefetchLimit);
  324.     this.prefetchLimit_ = newPrefetchLimit;
  325.     const keyArr = Array.from(this.segmentPrefetchMap_.keys());
  326.     while (keyArr.length > newPrefetchLimit) {
  327.       const reference = keyArr.pop();
  328.       if (reference) {
  329.         this.abortPrefetchedSegment_(reference);
  330.       }
  331.     }
  332.     this.clearInitSegments_();
  333.   }
  335.   /**
  336.    * Called by Streaming Engine when switching variant.
  337.    * @param {shaka.extern.Stream} stream
  338.    * @public
  339.    */
  340.   switchStream(stream) {
  341.     if (stream && stream !== this.stream_) {
  342.       this.clearAll();
  343.       this.stream_ = stream;
  344.     }
  345.   }
  347.   /**
  348.    * Get the current stream.
  349.    * @public
  350.    * @return {shaka.extern.Stream}
  351.    */
  352.   getStream() {
  353.     return this.stream_;
  354.   }
  356.   /**
  357.    * Remove a segment from prefetch map and abort it.
  358.    * @param {!(shaka.media.SegmentReference|shaka.media.InitSegmentReference)}
  359.    *        reference
  360.    * @private
  361.    */
  362.   abortPrefetchedSegment_(reference) {
  363.     const logPrefix = shaka.media.SegmentPrefetch.logPrefix_(this.stream_);
  365.     let prefetchMap = this.segmentPrefetchMap_;
  366.     if (reference instanceof shaka.media.InitSegmentReference) {
  367.       prefetchMap = this.initSegmentPrefetchMap_;
  368.     }
  370.     const segmentPrefetchOperation = prefetchMap.get(reference);
  371.     prefetchMap.delete(reference);
  373.     if (segmentPrefetchOperation) {
  374.       segmentPrefetchOperation.abort();
  375.       if (reference instanceof shaka.media.SegmentReference) {
  376.         shaka.log.debug(
  377.             logPrefix,
  378.             'pop and abort prefetched segment at time:', reference.startTime);
  379.       } else {
  380.         shaka.log.debug(logPrefix, 'pop and abort prefetched init segment');
  381.       }
  382.     }
  383.   }
  385.   /**
  386.    * The prefix of the logs that are created in this class.
  387.    * @return {string}
  388.    * @private
  389.    */
  390.   static logPrefix_(stream) {
  391.     return 'SegmentPrefetch(' + stream.type + ':' + stream.id + ')';
  392.   }
  393. };
  395. /**
  396.  * @summary
  397.  * This class manages a segment prefetch operation.
  398.  */
  399. shaka.media.SegmentPrefetchOperation = class {
  400.   /**
  401.    * @param {shaka.media.SegmentPrefetch.FetchDispatcher} fetchDispatcher
  402.    */
  403.   constructor(fetchDispatcher) {
  404.     /** @private {shaka.media.SegmentPrefetch.FetchDispatcher} */
  405.     this.fetchDispatcher_ = fetchDispatcher;
  407.     /** @private {?function(BufferSource):!Promise} */
  408.     this.streamDataCallback_ = null;
  410.     /** @private {?shaka.net.NetworkingEngine.PendingRequest} */
  411.     this.operation_ = null;
  412.   }
  414.   /**
  415.    * @param {shaka.media.SegmentPrefetch.FetchDispatcher} fetchDispatcher
  416.    */
  417.   replaceFetchDispatcher(fetchDispatcher) {
  418.     this.fetchDispatcher_ = fetchDispatcher;
  419.   }
  421.   /**
  422.    * Fetch a segments
  423.    *
  424.    * @param {!(shaka.media.SegmentReference|shaka.media.InitSegmentReference)}
  425.    *        reference
  426.    * @param {!shaka.extern.Stream} stream
  427.    * @return {!Promise}
  428.    * @public
  429.    */
  430.   dispatchFetch(reference, stream) {
  431.     // We need to store the data, because streamDataCallback_ might not be
  432.     // available when you start getting the first data.
  433.     let buffered = new Uint8Array(0);
  434.     this.operation_ = this.fetchDispatcher_(
  435.         reference, stream, async (data) => {
  436.           if (buffered.byteLength > 0) {
  437.             buffered = shaka.util.Uint8ArrayUtils.concat(buffered, data);
  438.           } else {
  439.             buffered = data;
  440.           }
  441.           if (this.streamDataCallback_) {
  442.             await this.streamDataCallback_(buffered);
  443.             buffered = new Uint8Array(0);
  444.           }
  445.         });
  446.     return this.operation_.promise.catch((e) => {
  447.       // Ignore OPERATION_ABORTED errors.
  448.       if (e instanceof shaka.util.Error &&
  449.           e.code == shaka.util.Error.Code.OPERATION_ABORTED) {
  450.         return Promise.resolve();
  451.       }
  452.       // Continue to surface other errors.
  453.       return Promise.reject(e);
  454.     });
  455.   }
  457.   /**
  458.    * Get the operation of prefetched segment if already exists.
  459.    *
  460.    * @return {?shaka.net.NetworkingEngine.PendingRequest} op
  461.    * @public
  462.    */
  463.   getOperation() {
  464.     return this.operation_;
  465.   }
  467.   /**
  468.    * @param {?function(BufferSource):!Promise} streamDataCallback
  469.    * @public
  470.    */
  471.   setStreamDataCallback(streamDataCallback) {
  472.     this.streamDataCallback_ = streamDataCallback;
  473.   }
  475.   /**
  476.    * Abort the current operation if exists.
  477.    */
  478.   abort() {
  479.     if (this.operation_) {
  480.       this.operation_.abort();
  481.     }
  482.   }
  483. };
  485. /**
  486.  * @typedef {function(
  487.  *  !(shaka.media.InitSegmentReference|shaka.media.SegmentReference),
  488.  *  shaka.extern.Stream,
  489.  *  ?function(BufferSource):!Promise=
  490.  * ):!shaka.net.NetworkingEngine.PendingRequest}
  491.  *
  492.  * @description
  493.  * A callback function that fetches a segment.
  494.  * @export
  495.  */
  496. shaka.media.SegmentPrefetch.FetchDispatcher;