Source: lib/util/mime_utils.js

  1. /**
  2.  * @license
  3.  * Copyright 2016 Google Inc.
  4.  *
  5.  * Licensed under the Apache License, Version 2.0 (the "License");
  6.  * you may not use this file except in compliance with the License.
  7.  * You may obtain a copy of the License at
  8.  *
  9.  *     http://www.apache.org/licenses/LICENSE-2.0
  10.  *
  11.  * Unless required by applicable law or agreed to in writing, software
  12.  * distributed under the License is distributed on an "AS IS" BASIS,
  13.  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14.  * See the License for the specific language governing permissions and
  15.  * limitations under the License.
  16.  */
  18. goog.provide('shaka.util.MimeUtils');
  21. /**
  22.  * @summary A set of utility functions for dealing with MIME types.
  23.  */
  24. shaka.util.MimeUtils = class {
  25.   /**
  26.    * Takes a MIME type and optional codecs string and produces the full MIME
  27.    * type.
  28.    *
  29.    * @param {string} mimeType
  30.    * @param {string=} codecs
  31.    * @return {string}
  32.    */
  33.   static getFullType(mimeType, codecs) {
  34.     let fullMimeType = mimeType;
  35.     if (codecs) {
  36.       fullMimeType += '; codecs="' + codecs + '"';
  37.     }
  38.     return fullMimeType;
  39.   }
  41.   /**
  42.    * Takes a Stream object and produces an extended MIME type with information
  43.    * beyond the container and codec type, when available.
  44.    *
  45.    * @param {shakaExtern.Stream} stream
  46.    * @return {string}
  47.    */
  48.   static getExtendedType(stream) {
  49.     const components = [stream.mimeType];
  51.     const extendedMimeParams = shaka.util.MimeUtils.EXTENDED_MIME_PARAMETERS_;
  52.     extendedMimeParams.forEach((mimeKey, streamKey) => {
  53.       const value = stream[streamKey];
  54.       if (value) {
  55.         components.push(mimeKey + '="' + value + '"');
  56.       }
  57.     });
  59.     return components.join(';');
  60.   }
  62.   /**
  63.    * Split a list of codecs encoded in a string into a list of codecs.
  64.    * @param {string} codecs
  65.    * @return {!Array.<string>}
  66.    */
  67.   static splitCodecs(codecs) {
  68.     return codecs.split(',');
  69.   }
  71.   /**
  72.    * Get the base codec from a codec string.
  73.    *
  74.    * @param {string} codecString
  75.    * @return {string}
  76.    */
  77.   static getCodecBase(codecString) {
  78.     const parts = shaka.util.MimeUtils.getCodecParts_(codecString);
  79.     return parts[0];
  80.   }
  82.   /**
  83.    * Get the base and profile of a codec string. Where [0] will be the codec
  84.    * base and [1] will be the profile.
  85.    * @param {string} codecString
  86.    * @return {!Array.<string>}
  87.    * @private
  88.    */
  89.   static getCodecParts_(codecString) {
  90.     const parts = codecString.split('.');
  92.     const base = parts[0];
  94.     parts.pop();
  95.     const profile = parts.join('.');
  97.     // Make sure that we always return a "base" and "profile".
  98.     return [base, profile];
  99.   }
  100. };
  103. /**
  104.  * A map from Stream object keys to MIME type parameters.  These should be
  105.  * ignored by platforms that do not recognize them.
  106.  *
  107.  * This initial set of parameters are all recognized by Chromecast.
  108.  *
  109.  * @const {!Map.<string, string>}
  110.  * @private
  111.  */
  112. shaka.util.MimeUtils.EXTENDED_MIME_PARAMETERS_ = new Map()
  113.   .set('codecs', 'codecs')
  114.   .set('frameRate', 'framerate')  // Ours is camelCase, theirs is lowercase.
  115.   .set('bandwidth', 'bitrate')  // They are in the same units: bits/sec.
  116.   .set('width', 'width')
  117.   .set('height', 'height')
  118.   .set('channelsCount', 'channels');
  121. /**
  122.  * A mimetype created for CEA closed captions.
  123.  * @const {string}
  124.  */
  125. shaka.util.MimeUtils.CLOSED_CAPTION_MIMETYPE = 'application/cea-608';