rx-player/src/transports/dash/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, getSegmentsFromSidx } from "../../parsers/containers/isobmff";
import { strToUtf8, utf8ToStr } from "../../utils/string_parsing";
import type {
  ISegmentContext,
  ISegmentParser,
  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.
 * @param {boolean} __priv_patchLastSegmentInSidx - Enable ugly Canal+-specific
 * fix for an issue people on the content-packaging side could not fix.
 * For more information on that, look at the code using it.
 * @returns {Object}
 */
function parseISOBMFFEmbeddedTextTrack(
  data: ArrayBuffer | Uint8Array | string,
  isChunked: boolean,
  context: ISegmentContext,
  initTimescale: number | undefined,
  __priv_patchLastSegmentInSidx?: boolean,
):
  | ISegmentParserParsedMediaChunk<ITextTrackSegmentData | null>
  | ISegmentParserParsedInitChunk<null> {
  const { segment } = context;
  const { isInit, indexRange } = segment;

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

  if (isInit) {
    const segmentList = getSegmentsFromSidx(
      chunkBytes,
      Array.isArray(indexRange) ? indexRange[0] : 0,
    );

    // This is a very specific handling for streams we know have a very
    // specific problem at Canal+: The last reference gives a truncated
    // segment.
    // Sadly, people on the packaging side could not fix all legacy contents.
    // This is an easy-but-ugly fix for those.
    // TODO Cleaner way? I tried to always check the obtained segment after
    // a byte-range request but it leads to a lot of code.
    if (
      __priv_patchLastSegmentInSidx === true &&
      segmentList !== null &&
      segmentList.length > 0
    ) {
      const lastSegment = segmentList[segmentList.length - 1];
      if (Array.isArray(lastSegment.range)) {
        lastSegment.range[1] = Infinity;
      }
    }

    const mdhdTimescale = getMDHDTimescale(chunkBytes);
    return {
      segmentType: "init",
      initializationData: null,
      initializationDataSize: 0,
      protectionData: [],
      initTimescale: mdhdTimescale,
      segmentList: segmentList ?? undefined,
    };
  }
  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: [context.periodStart, context.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: ArrayBuffer | Uint8Array | string,
  isChunked: boolean,
  context: ISegmentContext,
):
  | ISegmentParserParsedMediaChunk<ITextTrackSegmentData | null>
  | ISegmentParserParsedInitChunk<null> {
  const { periodStart, periodEnd, segment } = context;
  const { timestampOffset = 0 } = segment;
  if (segment.isInit) {
    return {
      segmentType: "init",
      initializationData: null,
      initializationDataSize: 0,
      protectionData: [],
      initTimescale: undefined,
    };
  }

  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);
  return {
    segmentType: "media",
    chunkData,
    chunkSize,
    chunkInfos: null,
    chunkOffset: timestampOffset,
    protectionData: [],
    appendWindow: [periodStart, periodEnd],
  };
}

/**
 * Generate a "segment parser" for DASH text tracks.
 *
 * @param {Object} config
 * @returns {Function}
 */
export default function generateTextTrackParser({
  __priv_patchLastSegmentInSidx,
}: {
  __priv_patchLastSegmentInSidx?: boolean | undefined;
}): ISegmentParser<
  ArrayBuffer | Uint8Array | string | null,
  ITextTrackSegmentData | null
> {
  /**
   * Parse TextTrack data.
   * @param {Object} loadedSegment
   * @param {Object} context
   * @param {number|undefined} initTimescale
   * @returns {Object}
   */
  return function textTrackParser(
    loadedSegment: {
      data: ArrayBuffer | Uint8Array | string | null;
      isChunked: boolean;
    },
    context: ISegmentContext,
    initTimescale: number | undefined,
  ):
    | ISegmentParserParsedMediaChunk<ITextTrackSegmentData | null>
    | ISegmentParserParsedInitChunk<null> {
    const { periodStart, periodEnd, segment } = context;
    const { data, isChunked } = loadedSegment;

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