Merge pull request video-dev#1131 from flavioribeiro/master

avoid showing repeated webvtt cues

src/controller/timeline-controller.js

@@ -275,9 +275,15 @@ class TimelineController extends EventHandler {
 
         // Parse the WebVTT file contents.
         WebVTTParser.parse(payload, this.initPTS, vttCCs, frag.cc, function (cues) {
+            const currentTrack = textTracks[frag.trackId];
             // Add cues and trigger event with success true.
             cues.forEach(cue => {
-              textTracks[frag.trackId].addCue(cue);
+              // Sometimes there are cue overlaps on segmented vtts so the same
+              // cue can appear more than once in different vtt files.
+              // This avoid showing duplicated cues with same timecode and text.
+              if (!currentTrack.cues.getCueById(cue.id)) {
+                currentTrack.addCue(cue);
+              }
             });
             hls.trigger(Event.SUBTITLE_FRAG_PROCESSED, {success: true, frag: frag});
           },

src/utils/webvtt-parser.js

@@ -17,6 +17,16 @@ const cueString2millis = function(timeString) {
     return ts;
 };
 
+// From https://github.com/darkskyapp/string-hash
+const hash = function(text) {
+    let hash = 5381;
+    let i = text.length;
+    while (i) {
+        hash = (hash * 33) ^ text.charCodeAt(--i);
+    }
+    return (hash >>> 0).toString();
+};
+
 const calculateOffset = function(vttCCs, cc, presentationTime) {
     let currCC = vttCCs[cc];
     let prevCC = vttCCs[currCC.prevCC];
@@ -81,6 +91,10 @@ const WebVTTParser = {
             cue.startTime += cueOffset - localTime;
             cue.endTime += cueOffset - localTime;
 
+            // Create a unique hash id for a cue based on start/end times and text.
+            // This helps timeline-controller to avoid showing repeated captions.
+            cue.id = hash(cue.startTime) + hash(cue.endTime) + hash(cue.text);
+
             // Fix encoding of special characters. TODO: Test with all sorts of weird characters.
             cue.text = decodeURIComponent(escape(cue.text));
             if (cue.endTime > 0) {