rx-player/src/transports/local/text_parser.ts

Canal+ HTML5 Video Player

/**
 * Copyright 2015 CANAL+ Group
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import { getMDHDTimescale } from "../../parsers/containers/isobmff";
import { strToUtf8, utf8ToStr } from "../../utils/string_parsing";
import type {
  ILoadedTextSegmentFormat,
  ISegmentContext,
  ISegmentParserParsedInitChunk,
  ISegmentParserParsedMediaChunk,
  ITextTrackSegmentData,
} from "../types";
import getISOBMFFTimingInfos from "../utils/get_isobmff_timing_infos";
import inferSegmentContainer from "../utils/infer_segment_container";
import {
  getISOBMFFEmbeddedTextTrackData,
  getPlainTextTrackData,
} from "../utils/parse_text_track";

/**
 * Parse TextTrack data when it is embedded in an ISOBMFF file.
 * @param {ArrayBuffer|Uint8Array|string} data - The segment data.
 * @param {boolean} isChunked - If `true`, the `data` may contain only a
 * decodable subpart of the full data in the linked segment.
 * @param {Object} context - Object describing the context of the given
 * segment's data: of which segment, `Representation`, `Adaptation`, `Period`,
 * `Manifest` it is a part of etc.
 * @param {number|undefined} initTimescale - `timescale` value - encountered
 * in this linked initialization segment (if it exists) - that may also apply
 * to that segment if no new timescale is defined in it.
 * Can be `undefined` if no timescale was defined, if it is not known, or if
 * no linked initialization segment was yet parsed.
 * @returns {Object}
 */
function parseISOBMFFEmbeddedTextTrack(
  data: string | Uint8Array | ArrayBuffer,
  isChunked: boolean,
  context: ISegmentContext,
  initTimescale: number | undefined,
):
  | ISegmentParserParsedInitChunk<null>
  | ISegmentParserParsedMediaChunk<ITextTrackSegmentData | null> {
  const { periodStart, periodEnd, segment } = context;

  let chunkBytes;
  if (typeof data === "string") {
    chunkBytes = strToUtf8(data);
  } else if (data instanceof Uint8Array) {
    chunkBytes = data;
  } else {
    chunkBytes = new Uint8Array(data);
  }

  if (segment.isInit) {
    const mdhdTimescale = getMDHDTimescale(chunkBytes);
    return {
      segmentType: "init",
      initializationData: null,
      initializationDataSize: 0,
      initTimescale: mdhdTimescale,
      protectionData: [],
    };
  }
  const chunkInfos = getISOBMFFTimingInfos(chunkBytes, isChunked, segment, initTimescale);
  const chunkData = getISOBMFFEmbeddedTextTrackData(
    context,
    chunkBytes,
    chunkInfos,
    isChunked,
  );
  const chunkOffset = segment.timestampOffset ?? 0;
  return {
    segmentType: "media",
    chunkData,
    chunkSize: chunkBytes.length,
    chunkInfos,
    chunkOffset,
    protectionData: [],
    appendWindow: [periodStart, periodEnd],
  };
}

/**
 * Parse TextTrack data when it is in plain text form.
 * @param {ArrayBuffer|Uint8Array|string} data - The segment data.
 * @param {boolean} isChunked - If `true`, the `data` may contain only a
 * decodable subpart of the full data in the linked segment.
 * @param {Object} context - Object describing the context of the given
 * segment's data: of which segment, `Representation`, `Adaptation`, `Period`,
 * `Manifest` it is a part of etc.
 * @returns {Object}
 */
function parsePlainTextTrack(
  data: string | Uint8Array | ArrayBuffer,
  isChunked: boolean,
  context: ISegmentContext,
):
  | ISegmentParserParsedInitChunk<null>
  | ISegmentParserParsedMediaChunk<ITextTrackSegmentData | null> {
  const { segment, periodStart, periodEnd } = context;
  if (segment.isInit) {
    return {
      segmentType: "init",
      initializationData: null,
      initializationDataSize: 0,
      initTimescale: undefined,
      protectionData: [],
    };
  }

  let textTrackData: string;
  let chunkSize: number | undefined;
  if (typeof data !== "string") {
    const bytesData = data instanceof Uint8Array ? data : new Uint8Array(data);
    textTrackData = utf8ToStr(bytesData);
    chunkSize = bytesData.length;
  } else {
    textTrackData = data;
  }
  const chunkData = getPlainTextTrackData(context, textTrackData, isChunked);
  const chunkOffset = segment.timestampOffset ?? 0;
  return {
    segmentType: "media",
    chunkData,
    chunkSize,
    chunkInfos: null,
    chunkOffset,
    protectionData: [],
    appendWindow: [periodStart, periodEnd],
  };
}

/**
 * Parse TextTrack data.
 * @param {Object} loadedSegment
 * @param {Object} context
 * @param {number | undefined} initTimescale
 * @returns {Object}
 */
export default function textTrackParser(
  loadedSegment: { data: ILoadedTextSegmentFormat; isChunked: boolean },
  context: ISegmentContext,
  initTimescale: number | undefined,
):
  | ISegmentParserParsedInitChunk<null>
  | ISegmentParserParsedMediaChunk<ITextTrackSegmentData | null> {
  const { segment, periodStart, periodEnd } = context;
  const { data, isChunked } = loadedSegment;

  if (data === null) {
    // No data, just return an empty placeholder object
    if (segment.isInit) {
      return {
        segmentType: "init",
        initializationData: null,
        initializationDataSize: 0,
        protectionData: [],
        initTimescale: undefined,
      };
    }
    const chunkOffset = segment.timestampOffset ?? 0;
    return {
      segmentType: "media",
      chunkData: null,
      chunkSize: 0,
      chunkInfos: null,
      chunkOffset,
      protectionData: [],
      appendWindow: [periodStart, periodEnd],
    };
  }

  const containerType = inferSegmentContainer(context.type, context.mimeType);

  // TODO take a look to check if this is an ISOBMFF/webm when undefined?
  if (containerType === "webm") {
    // TODO Handle webm containers
    throw new Error("Text tracks with a WEBM container are not yet handled.");
  } else if (containerType === "mp4") {
    return parseISOBMFFEmbeddedTextTrack(data, isChunked, context, initTimescale);
  } else {
    return parsePlainTextTrack(data, isChunked, context);
  }
}