shaka-player/lib/util/pssh.js

DASH/EME video player library

/**
 * @license
 * Copyright 2016 Google Inc.
 *
 * 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.
 */

goog.provide('shaka.util.Pssh');

goog.require('goog.asserts');
goog.require('shaka.log');
goog.require('shaka.util.Mp4Parser');
goog.require('shaka.util.Uint8ArrayUtils');


/**
 * Parse a PSSH box and extract the system IDs.
 *
 * @param {!Uint8Array} psshBox
 * @constructor
 * @struct
 * @throws {shaka.util.Error} if a PSSH box is truncated or contains a size
 *   field over 53 bits.
 */
shaka.util.Pssh = function(psshBox) {
  /**
   * In hex.
   * @type {!Array.<string>}
   */
  this.systemIds = [];

  /**
   * In hex.
   * @type {!Array.<string>}
   */
  this.cencKeyIds = [];

    /**
     * Array with the pssh boxes found.
     * @type {!Array.<!Uint8Array>}
     */
    this.data = [];

  new shaka.util.Mp4Parser()
      .box('moov', shaka.util.Mp4Parser.children)
      .fullBox('pssh', (box) => this.parsePsshBox_(box))
      .parse(psshBox);

    if (this.data.length == 0) {
    shaka.log.warning('No pssh box found!');
  }
};


/**
 * @param {!shaka.extern.ParsedBox} box
 * @private
 */
shaka.util.Pssh.prototype.parsePsshBox_ = function(box) {
  goog.asserts.assert(
      box.version != null,
      'PSSH boxes are full boxes and must have a valid version');

  goog.asserts.assert(
      box.flags != null,
      'PSSH boxes are full boxes and must have a valid flag');

  if (box.version > 1) {
    shaka.log.warning('Unrecognized PSSH version found!');
    return;
  }

    // The "reader" gives us a view on the payload of the box.  Create a new
    // view that contains the whole box.
    const dataView = box.reader.getDataView();
    goog.asserts.assert(
        dataView.byteOffset >= 12, 'DataView at incorrect position');
    const pssh =
        new Uint8Array(dataView.buffer, dataView.byteOffset - 12, box.size);
    this.data.push(pssh);

    this.systemIds.push(
        shaka.util.Uint8ArrayUtils.toHex(box.reader.readBytes(16)));
  if (box.version > 0) {
    let numKeyIds = box.reader.readUint32();
    for (let i = 0; i < numKeyIds; ++i) {
      let keyId = shaka.util.Uint8ArrayUtils.toHex(box.reader.readBytes(16));
      this.cencKeyIds.push(keyId);
    }
  }
};


/**
 * Creates a pssh blob from the given system ID and data.
 *
 * @param {!Uint8Array} data
 * @param {!Uint8Array} systemId
 * @return {!Uint8Array}
 */
shaka.util.Pssh.createPssh = function(data, systemId) {
  const dataLength = data.length;
  const psshSize = 0x4 + 0x4 + 0x4 + systemId.length + 0x4 + dataLength;

  /** @type {!ArrayBuffer} */
  const psshBoxBuffer = new ArrayBuffer(psshSize);

  /** @type {!Uint8Array} */
  const psshBox = new Uint8Array(psshBoxBuffer);

  /** @type {!DataView} */
  const psshData = new DataView(psshBoxBuffer);

  let byteCursor = 0;
  psshData.setUint32(byteCursor, psshSize);
  byteCursor += 0x4;
  psshData.setUint32(byteCursor, 0x70737368);  // 'pssh'
  byteCursor += 0x4;
  psshData.setUint32(byteCursor, 0);  // flags
  byteCursor += 0x4;
  psshBox.set(systemId, byteCursor);
  byteCursor += systemId.length;
  psshData.setUint32(byteCursor, dataLength);
  byteCursor += 0x4;
  psshBox.set(data, byteCursor);
  byteCursor += dataLength;

  goog.asserts.assert(byteCursor === psshSize,
      'PSSH invalid length.');

  return psshBox;
};

/**
 * Normalise the initData array. This is to apply browser specific
 * work-arounds, e.g. removing duplicates which appears to occur
 * intermittently when the native msneedkey event fires (i.e. event.initData
 * contains dupes).
 *
 * @param {!Uint8Array} initData
 * @return {!Uint8Array}
 */
shaka.util.Pssh.normaliseInitData = function(initData) {
  if (!initData) {
    return initData;
  }

  const pssh = new shaka.util.Pssh(initData);

  // If there is only a single pssh, return the original array.
    if (pssh.data.length <= 1) {
    return initData;
  }

  // Dedupe psshData.
  /** @type {!Array.<!Uint8Array>} */
  const dedupedInitDatas = [];
    for (const initData of pssh.data) {
    const found = dedupedInitDatas.some((x) => {
      return shaka.util.Uint8ArrayUtils.equal(x, initData);
    });

    if (!found) {
      dedupedInitDatas.push(initData);
    }
  }

  return shaka.util.Uint8ArrayUtils.concat(...dedupedInitDatas);
};