feat(MediaCap): Add polyfill for MediaCapabilities

If navigator.mediaCapabilties is not supported by the browser, use
MediaSource.isTypeSupported to check if the stream is supported.

Issue shaka-project#1391

Change-Id: Iee0c7e339add2a07028ed14a03df14e4d36a203e

build/types/polyfill

@@ -7,6 +7,7 @@
 +../../lib/polyfill/languages.js
 +../../lib/polyfill/mathround.js
 +../../lib/polyfill/mediasource.js
++../../lib/polyfill/media_capabilities.js
 +../../lib/polyfill/orientation.js
 +../../lib/polyfill/patchedmediakeys_apple.js
 +../../lib/polyfill/patchedmediakeys_ms.js

lib/polyfill/media_capabilities.js

@@ -0,0 +1,77 @@
+/*! @license
+ * Shaka Player
+ * Copyright 2016 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+goog.provide('shaka.polyfill.MediaCapabilities');
+
+goog.require('shaka.log');
+goog.require('shaka.polyfill');
+
+
+/**
+ * @summary A polyfill to provide navigator.mediaCapabilities on all browsers.
+ * This is necessary for Tizen 3, Xbox One and possibly others we have yet to
+ * discover.
+ */
+shaka.polyfill.MediaCapabilities = class {
+  /**
+   * Install the polyfill if needed.
+   */
+  static install() {
+    shaka.log.debug('MediaCapabilities: install');
+
+    if (navigator.mediaCapabilities) {
+      shaka.log.debug(
+          'MediaCapabilities: Native mediaCapabilities support found.');
+      return;
+    }
+
+    navigator.mediaCapabilities = /** @type {!MediaCapabilities} */ ({});
+    navigator.mediaCapabilities.decodingInfo =
+        shaka.polyfill.MediaCapabilities.decodingInfo_;
+  }
+
+  /**
+   * @param {!MediaDecodingConfiguration} mediaDecodingConfig
+   * @return {!Promise.<!MediaCapabilitiesDecodingInfo>}
+   * @private
+   */
+  static decodingInfo_(mediaDecodingConfig) {
+    const res = {
+      supported: false,
+      powerEfficient: true,
+      smooth: true,
+      keySystemAccess: null,
+      configuration: mediaDecodingConfig,
+    };
+
+    if (!mediaDecodingConfig) {
+      return Promise.resolve(res);
+    }
+
+    // Use 'MediaSource.isTypeSupported' to check if the stream is supported.
+    if (mediaDecodingConfig['video']) {
+      const contentType = mediaDecodingConfig['video'].contentType;
+      const isSupported = MediaSource.isTypeSupported(contentType);
+      if (!isSupported) {
+        return Promise.resolve(res);
+      }
+    }
+
+    if (mediaDecodingConfig['audio']) {
+      const contentType = mediaDecodingConfig['audio'].contentType;
+      const isSupported = MediaSource.isTypeSupported(contentType);
+      if (!isSupported) {
+        return Promise.resolve(res);
+      }
+    }
+
+    res.supported = true;
+    return Promise.resolve(res);
+  }
+};
+
+
+shaka.polyfill.register(shaka.polyfill.MediaCapabilities.install);

lib/util/stream_utils.js

@@ -9,7 +9,6 @@ goog.provide('shaka.util.StreamUtils');
 goog.require('goog.asserts');
 goog.require('shaka.log');
 goog.require('shaka.media.DrmEngine');
-goog.require('shaka.media.MediaSourceEngine');
 goog.require('shaka.text.TextEngine');
 goog.require('shaka.util.Functional');
 goog.require('shaka.util.LanguageUtils');
@@ -308,57 +307,37 @@ shaka.util.StreamUtils = class {
    * @private
    */
   static async filterManifestByMediaCapabilities_(manifest) {
-    if ('mediaCapabilities' in navigator) {
-      const MediaCapabilities = navigator.mediaCapabilities;
-      const getVariantDecodingInfo = (async (variant) => {
-        /** @type {!MediaDecodingConfiguration} */
-        const decodingConfig =
-            shaka.util.StreamUtils.prepareDecodingConfiguration_(variant);
-        const result = await MediaCapabilities.decodingInfo(decodingConfig);
-        variant.decodingInfos.push(result);
-      });
+    goog.asserts.assert(navigator.mediaCapabilities,
+        'MediaCapabilities should be valid.');
+
+    const MediaCapabilities = navigator.mediaCapabilities;
+    const getVariantDecodingInfo = (async (variant) => {
+      /** @type {!MediaDecodingConfiguration} */
+      const decodingConfig =
+          shaka.util.StreamUtils.prepareDecodingConfiguration_(variant);
+      const result = await MediaCapabilities.decodingInfo(decodingConfig);
+      variant.decodingInfos.push(result);
+    });
 
-      const operations = [];
-      for (const variant of manifest.variants) {
-        if (!variant.decodingInfos.length) {
-          operations.push(getVariantDecodingInfo(variant));
-        }
+    const operations = [];
+    for (const variant of manifest.variants) {
+      if (!variant.decodingInfos.length) {
+        operations.push(getVariantDecodingInfo(variant));
       }
-      await Promise.all(operations);
-
-      manifest.variants = manifest.variants.filter((variant) => {
-        const supported = variant.decodingInfos.some((decodingInfo) => {
-          return decodingInfo.supported;
-        });
-        // Filter out all unsupported variants.
-        if (!supported) {
-          shaka.log.debug('Dropping variant - not compatible with platform',
-              shaka.util.StreamUtils.getVariantSummaryString_(variant));
-        }
-        return supported;
-      });
-    } else {
-      // TODO: move to MediaCapabilities polyfill.
-      manifest.variants = manifest.variants.filter((variant) => {
-        const audio = variant.audio;
-        const video = variant.video;
-
-        if (audio && !shaka.media.MediaSourceEngine.isStreamSupported(audio)) {
-          shaka.log.debug(
-              'Dropping variant - audio not compatible with platform',
-              shaka.util.StreamUtils.getStreamSummaryString_(audio));
-          return false;
-        }
+    }
+    await Promise.all(operations);
 
-        if (video && !shaka.media.MediaSourceEngine.isStreamSupported(video)) {
-          shaka.log.debug(
-              'Dropping variant - video not compatible with platform',
-              shaka.util.StreamUtils.getStreamSummaryString_(video));
-          return false;
-        }
-        return true;
+    manifest.variants = manifest.variants.filter((variant) => {
+      const supported = variant.decodingInfos.some((decodingInfo) => {
+        return decodingInfo.supported;
       });
-    }
+      // Filter out all unsupported variants.
+      if (!supported) {
+        shaka.log.debug('Dropping variant - not compatible with platform',
+            shaka.util.StreamUtils.getVariantSummaryString_(variant));
+      }
+      return supported;
+    });
   }