Merge pull request #229 from videojs/live-start-time

Live start time tweaks

@@ -39,7 +39,7 @@
     "karma-sauce-launcher": "~0.1.8",
     "qunitjs": "^1.15.0",
     "sinon": "1.10.2",
-    "video.js": "^4.9.0"
+    "video.js": "^4.12.0"
   },
   "dependencies": {
     "pkcs7": "^0.2.2",

@@ -164,6 +164,16 @@ videojs.Hls.prototype.src = function(src) {
       });
     }
 
+    // Start live playlists 30 seconds before the current time
+    // This is done using the old playlist because of a race condition
+    // where the playlist selected below may not be loaded quickly
+    // enough to have its segments available for review. When we receive
+    // a loadedplaylist event, we will call translateMediaIndex and
+    // maintain our position at the live point.
+    if (this.duration() === Infinity && this.mediaIndex === 0) {
+      this.mediaIndex = videojs.Hls.getMediaIndexForLive_(oldMediaPlaylist);
+    }
+
     selectedPlaylist = this.selectPlaylist();
     oldBitrate = oldMediaPlaylist.attributes &&
                  oldMediaPlaylist.attributes.BANDWIDTH || 0;
@@ -179,11 +189,6 @@ videojs.Hls.prototype.src = function(src) {
       segmentDlTime = Infinity;
     }
 
-    // start live playlists 30 seconds before the current time
-    if (this.duration() === Infinity && this.mediaIndex === 0 && selectedPlaylist.segments) {
-      this.mediaIndex = videojs.Hls.setMediaIndexForLive(selectedPlaylist);
-    }
-
     // this threshold is to account for having a high latency on the manifest
     // request which is a somewhat small file.
     threshold = 10;
@@ -239,7 +244,14 @@ videojs.Hls.prototype.src = function(src) {
   });
 };
 
-videojs.Hls.setMediaIndexForLive = function(selectedPlaylist) {
+/* Returns the media index for the live point in the current playlist, and updates
+   the current time to go along with it.
+ */
+videojs.Hls.getMediaIndexForLive_ = function(selectedPlaylist) {
+  if (!selectedPlaylist.segments) {
+    return 0;
+  }
+
   var tailIterator = selectedPlaylist.segments.length,
       tailDuration = 0,
       targetTail = (selectedPlaylist.targetDuration || 10) * 3;
@@ -279,6 +291,11 @@ videojs.Hls.prototype.play = function() {
     this.mediaIndex = 0;
   }
 
+  if (this.duration() === Infinity && this.playlists.media() && !this.player().hasClass('vjs-has-started')) {
+    this.mediaIndex = videojs.Hls.getMediaIndexForLive_(this.playlists.media());
+    this.setCurrentTime(this.getCurrentTimeByMediaIndex_(this.playlists.media(), this.mediaIndex));
+  }
+
   // delegate back to the Flash implementation
   return videojs.Flash.prototype.play.apply(this, arguments);
 };
@@ -936,7 +953,7 @@ videojs.Hls.translateMediaIndex = function(mediaIndex, original, update) {
 
   if (translatedMediaIndex >= update.segments.length || translatedMediaIndex < 0) {
     // recalculate the live point if the streams are too far out of sync
-    return videojs.Hls.setMediaIndexForLive(update) + 1;
+    return videojs.Hls.getMediaIndexForLive_(update) + 1;
   }
 
   // sync on media sequence
@@ -974,6 +991,29 @@ videojs.Hls.getMediaIndexByTime = function(playlist, time) {
 };
 
 /**
+ * Determine the current time in seconds in one playlist by a media index. This
+ * function iterates through the segments of a playlist up to the specified index
+ * and then returns the time up to that point.
+ *
+ * @param playlist {object} The playlist of the segments being searched.
+ * @param mediaIndex {number} The index of the target segment in the playlist.
+ * @returns {number} The current time to that point, or 0 if none appropriate.
+ */
+videojs.Hls.prototype.getCurrentTimeByMediaIndex_ = function(playlist, mediaIndex) {
+  var index, time = 0;
+
+  if (!playlist.segments || mediaIndex === 0) {
+    return 0;
+  }
+
+  for (index = 0; index < mediaIndex; index++) {
+    time += playlist.segments[index].duration;
+  }
+
+  return time;
+};
+
+/**
  * A comparator function to sort two playlist object by bandwidth.
  * @param left {object} a media playlist object
  * @param right {object} a media playlist object

@@ -1249,6 +1249,22 @@ test('live playlist starts 30s before live', function() {
   strictEqual(player.hls.mediaIndex, 6, 'mediaIndex is updated after the reload');
 });
 
+test('live playlist starts with correct currentTime value', function() {
+  player.src({
+    src: 'http://example.com/manifest/liveStart30sBefore.m3u8',
+    type: 'application/vnd.apple.mpegurl'
+  });
+  openMediaSource(player);
+
+  standardXHRResponse(requests[0]);
+
+  player.hls.playlists.trigger('loadedmetadata');
+
+  player.hls.play();
+
+  strictEqual(player.currentTime(), 70, 'currentTime is updated at playback');
+});
+
 test('mediaIndex is zero before the first segment loads', function() {
   window.manifests['first-seg-load'] =
     '#EXTM3U\n' +
@@ -1720,6 +1736,7 @@ test('calling play() at the end of a video resets the media index', function() {
   player.hls.ended = function() {
     return true;
   };
+
   player.play();
   strictEqual(player.hls.mediaIndex, 0, 'index is 1 after the first segment');
 });