Apply TypeScript to Fragment & LevelKey

src/controller/audio-stream-controller.js

@@ -12,7 +12,7 @@ import { ErrorTypes, ErrorDetails } from '../errors';
 import { logger } from '../utils/logger';
 import { findFragWithCC } from '../utils/discontinuities';
 import { FragmentState } from './fragment-tracker';
-import Fragment from '../loader/fragment';
+import Fragment, { ElementaryStreamTypes } from '../loader/fragment';
 import BaseStreamController, { State } from './base-stream-controller';
 const { performance } = window;
 
@@ -615,7 +615,7 @@ class AudioStreamController extends BaseStreamController {
         data.endDTS = data.startDTS + fragCurrent.duration;
       }
 
-      fragCurrent.addElementaryStream(Fragment.ElementaryStreamTypes.AUDIO);
+      fragCurrent.addElementaryStream(ElementaryStreamTypes.AUDIO);
 
       logger.log(`parsed ${data.type},PTS:[${data.startPTS.toFixed(3)},${data.endPTS.toFixed(3)}],DTS:[${data.startDTS.toFixed(3)}/${data.endDTS.toFixed(3)}],nb:${data.nb}`);
       LevelHelper.updateFragPTSDTS(track.details, fragCurrent, data.startPTS, data.endPTS);

src/controller/stream-controller.js

@@ -7,7 +7,7 @@ import { BufferHelper } from '../utils/buffer-helper';
 import Demuxer from '../demux/demuxer';
 import Event from '../events';
 import { FragmentState } from './fragment-tracker';
-import Fragment from '../loader/fragment';
+import Fragment, { ElementaryStreamTypes } from '../loader/fragment';
 import PlaylistLoader from '../loader/playlist-loader';
 import * as LevelHelper from './level-helper';
 import TimeRanges from '../utils/time-ranges';
@@ -1000,11 +1000,11 @@ class StreamController extends BaseStreamController {
       }
 
       if (data.hasAudio === true) {
-        frag.addElementaryStream(Fragment.ElementaryStreamTypes.AUDIO);
+        frag.addElementaryStream(ElementaryStreamTypes.AUDIO);
       }
 
       if (data.hasVideo === true) {
-        frag.addElementaryStream(Fragment.ElementaryStreamTypes.VIDEO);
+        frag.addElementaryStream(ElementaryStreamTypes.VIDEO);
       }
 
       logger.log(`Parsed ${data.type},PTS:[${data.startPTS.toFixed(3)},${data.endPTS.toFixed(3)}],DTS:[${data.startDTS.toFixed(3)}/${data.endDTS.toFixed(3)}],nb:${data.nb},dropped:${data.dropped || 0}`);
@@ -1305,7 +1305,7 @@ class StreamController extends BaseStreamController {
     const media = this.mediaBuffer ? this.mediaBuffer : this.media;
     if (media) {
       // filter fragments potentially evicted from buffer. this is to avoid memleak on live streams
-      this.fragmentTracker.detectEvictedFragments(Fragment.ElementaryStreamTypes.VIDEO, media.buffered);
+      this.fragmentTracker.detectEvictedFragments(ElementaryStreamTypes.VIDEO, media.buffered);
     }
     // move to IDLE once flush complete. this should trigger new fragment loading
     this.state = State.IDLE;

src/loader/fragment.ts

@@ -0,0 +1,168 @@
+
+import { buildAbsoluteURL } from 'url-toolkit';
+import { logger } from '../utils/logger';
+import LevelKey from './level-key';
+
+export enum ElementaryStreamTypes {
+  AUDIO = 'audio',
+  VIDEO = 'video',
+}
+
+export default class Fragment {
+  private _url: string | null = null;
+  private _byteRange: number[] | null = null;
+  private _decryptdata: LevelKey | null = null;
+
+  // Holds the types of data this fragment supports
+  private _elementaryStreams: Record<ElementaryStreamTypes, boolean> = {
+    [ElementaryStreamTypes.AUDIO]: false,
+    [ElementaryStreamTypes.VIDEO]: false
+  };
+
+  public rawProgramDateTime: string | null = null;
+  public programDateTime: number | null = null;
+  public tagList: Array<string[]> = [];
+
+  // TODO: Move at least baseurl to constructor.
+  // Currently we do a two-pass construction as use the Fragment class almost like a object for holding parsing state.
+  // It may make more sense to just use a POJO to keep state during the parsing phase.
+  // Have Fragment be the representation once we have a known state?
+  // Something to think on.
+
+  // relurl is the portion of the URL that comes from inside the playlist.
+  public relurl!: string;
+  // baseurl is the URL to the playlist
+  public baseurl!: string;
+  // EXTINF has to be present for a m3u8 to be considered valid
+  public duration!: number;
+  // sn notates the sequence number for a segment, and if set to a string can be 'initSegment'
+  public sn: number | 'initSegment' = 0;
+  // levelkey is the EXT-X-KEY that applies to this segment for decryption
+  // core difference from the private field _decryptdata is the lack of the initialized IV
+  // _decryptdata will set the IV for this segment based on the segment number in the fragment
+  public levelkey?: LevelKey;
+
+  // setByteRange converts a EXT-X-BYTERANGE attribute into a two element array
+  setByteRange (value: string, previousFrag?: Fragment) {
+    const params = value.split('@', 2);
+    const byteRange: number[] = [];
+    if (params.length === 1) {
+      byteRange[0] = previousFrag ? previousFrag.byteRangeEndOffset : 0;
+    } else {
+      byteRange[0] = parseInt(params[1]);
+    }
+    byteRange[1] = parseInt(params[0]) + byteRange[0];
+    this._byteRange = byteRange;
+  }
+
+  get url () {
+    if (!this._url && this.relurl) {
+      this._url = buildAbsoluteURL(this.baseurl, this.relurl, { alwaysNormalize: true });
+    }
+
+    return this._url;
+  }
+
+  set url (value) {
+    this._url = value;
+  }
+
+  get byteRange (): number[] {
+    if (!this._byteRange) {
+      return [];
+    }
+
+    return this._byteRange;
+  }
+
+  /**
+   * @type {number}
+   */
+  get byteRangeStartOffset () {
+    return this.byteRange[0];
+  }
+
+  get byteRangeEndOffset () {
+    return this.byteRange[1];
+  }
+
+  get decryptdata (): LevelKey | null {
+    if (!this.levelkey && !this._decryptdata) {
+      return null;
+    }
+
+    if (!this._decryptdata && this.levelkey) {
+      // TODO look for this warning for 'initSegment' sn getting used in decryption IV
+      if (typeof this.sn !== 'number') {
+        logger.warn(`undefined behaviour for sn="${this.sn}" in IV generation`);
+      }
+      this._decryptdata = this.fragmentDecryptdataFromLevelkey(this.levelkey, this.sn as number);
+    }
+
+    return this._decryptdata;
+  }
+
+  get endProgramDateTime () {
+    if (this.programDateTime === null) {
+      return null;
+    }
+
+    if (!Number.isFinite(this.programDateTime)) {
+      return null;
+    }
+
+    let duration = !Number.isFinite(this.duration) ? 0 : this.duration;
+
+    return this.programDateTime + (duration * 1000);
+  }
+
+  get encrypted () {
+    return !!((this.decryptdata && this.decryptdata.uri !== null) && (this.decryptdata.key === null));
+  }
+
+  /**
+   * @param {ElementaryStreamTypes} type
+   */
+  addElementaryStream (type: ElementaryStreamTypes) {
+    this._elementaryStreams[type] = true;
+  }
+
+  /**
+   * @param {ElementaryStreamTypes} type
+   */
+  hasElementaryStream (type: ElementaryStreamTypes) {
+    return this._elementaryStreams[type] === true;
+  }
+
+  /**
+   * Utility method for parseLevelPlaylist to create an initialization vector for a given segment
+   * @returns {Uint8Array}
+   */
+  createInitializationVector (segmentNumber: number): Uint8Array {
+    let uint8View = new Uint8Array(16);
+
+    for (let i = 12; i < 16; i++) {
+      uint8View[i] = (segmentNumber >> 8 * (15 - i)) & 0xff;
+    }
+
+    return uint8View;
+  }
+
+  /**
+   * Utility method for parseLevelPlaylist to get a fragment's decryption data from the currently parsed encryption key data
+   * @param levelkey - a playlist's encryption info
+   * @param segmentNumber - the fragment's segment number
+   * @returns {*} - an object to be applied as a fragment's decryptdata
+   */
+  fragmentDecryptdataFromLevelkey (levelkey: LevelKey, segmentNumber: number): LevelKey {
+    let decryptdata = levelkey;
+
+    if (levelkey && levelkey.method && levelkey.uri && !levelkey.iv) {
+      decryptdata = new LevelKey(levelkey.baseuri, levelkey.reluri);
+      decryptdata.method = levelkey.method;
+      decryptdata.iv = this.createInitializationVector(segmentNumber);
+    }
+
+    return decryptdata;
+  }
+}