Use JavascriptSubtitlesOctopus if canvas and web workers are available.

package.json

@@ -24,7 +24,8 @@
     "libjass": "^0.11.0",
     "shaka-player": "^2.5.5",
     "sortablejs": "^1.9.0",
-    "swiper": "^3.4.2"
+    "swiper": "^3.4.2",
+    "libass-wasm": "^2.1.1"
   },
   "scripts": {
     "serve": "webpack-dev-server --config webpack.dev.js --open",

src/bundle.js

@@ -42,3 +42,7 @@ _define("sortable", function() { return sortable; });
 var libjass = require("libjass");
 require("libjass/libjass.css");
 _define("libjass", function() { return libjass; });
+
+// libass-wasm
+var libass_wasm = require("libass-wasm");
+_define("JavascriptSubtitlesOctopus", function() { return libass_wasm; });

src/components/htmlvideoplayer/plugin.js

@@ -27,6 +27,14 @@ define(['browser', 'require', 'events', 'apphost', 'loading', 'dom', 'playbackMa
         return _supportsTextTracks;
     }
 
+    function supportsCanvas() {
+        return !!document.createElement('canvas').getContext;
+    }
+
+    function supportsWebWorkers() {
+        return !!window.Worker;
+    }
+
     function enableNativeTrackSupport(currentSrc, track) {
 
         if (track) {
@@ -185,6 +193,7 @@ define(['browser', 'require', 'events', 'apphost', 'loading', 'dom', 'playbackMa
 
         var lastCustomTrackMs = 0;
         var currentClock;
+        var currentSubtitlesOctopus;
         var currentAssRenderer;
         var customTrackIndex = -1;
 
@@ -960,6 +969,12 @@ define(['browser', 'require', 'events', 'apphost', 'loading', 'dom', 'playbackMa
             currentClock = null;
             self._currentAspectRatio = null;
 
+            var octopus = currentSubtitlesOctopus;
+            if (octopus) {
+                octopus.dispose();
+            }
+            currentSubtitlesOctopus = null;
+
             var renderer = currentAssRenderer;
             if (renderer) {
                 renderer.setEnabled(false);
@@ -1024,6 +1039,21 @@ define(['browser', 'require', 'events', 'apphost', 'loading', 'dom', 'playbackMa
             lastCustomTrackMs = 0;
         }
 
+        function renderWithSubtitlesOctopus(videoElement, track, item) {
+            var options = {
+                video: videoElement,
+                subUrl: getTextTrackUrl(track, item),
+                fonts: [],
+                workerUrl: appRouter.baseUrl() + "/JavascriptSubtitlesOctopus/subtitles-octopus-worker.js",
+                onError: function() {
+                    htmlMediaHelper.onErrorInternal(self, 'mediadecodeerror')
+                }
+            };
+            require(['JavascriptSubtitlesOctopus'], function(SubtitlesOctopus) {
+                currentSubtitlesOctopus = new SubtitlesOctopus(options);
+            });
+        }
+
         function renderWithLibjass(videoElement, track, item) {
 
             var rendererSettings = {};
@@ -1071,6 +1101,14 @@ define(['browser', 'require', 'events', 'apphost', 'loading', 'dom', 'playbackMa
             });
         }
 
+        function renderSsaAss(videoElement, track, item) {
+            if (supportsCanvas() && supportsWebWorkers()) {
+                renderWithSubtitlesOctopus(videoElement, track, item);
+            } else {
+                renderWithLibjass(videoElement, track, item);
+            }
+        }
+
         function onVideoResize() {
             if (browser.iOS) {
                 // the new sizes will be delayed for about 500ms with wkwebview
@@ -1181,7 +1219,7 @@ define(['browser', 'require', 'events', 'apphost', 'loading', 'dom', 'playbackMa
                 var format = (track.Codec || '').toLowerCase();
                 if (format === 'ssa' || format === 'ass') {
                     // libjass is needed here
-                    renderWithLibjass(videoElement, track, item);
+                    renderSsaAss(videoElement, track, item);
                     return;
                 }
 

src/components/htmlvideoplayer/style.css

@@ -24,6 +24,10 @@
     z-index: 1000;
 }
 
+.videoPlayerContainer .libassjs-canvas-parent {
+    order: -1;
+}
+
 video::-webkit-media-controls {
     display: none !important;
 }

webpack.common.js

@@ -10,9 +10,18 @@ module.exports = {
         ]
     },
     plugins: [
-        new CopyPlugin([{
+        new CopyPlugin([
+            {
                 from: "**/*",
                 to: "."
-        }])
+            },
+            {
+                from: "../node_modules/libass-wasm/dist/subtitles-octopus-worker.*",
+                to: "JavascriptSubtitlesOctopus",
+                transformPath(targetPath, absolutePath) {
+                    return Promise.resolve(path.join("JavascriptSubtitlesOctopus", path.basename(targetPath)));
+                }
+            }
+        ])
     ]
 };