Merge pull request #184 from bc-bbay/master

Setting start position on a live stream

@@ -89,6 +89,18 @@ videojs.Hls.prototype.src = function(src) {
   });
 };
 
+videojs.Hls.setMediaIndexForLive = function(selectedPlaylist) {
+  var tailIterator = selectedPlaylist.segments.length,
+      tailDuration = 0;
+
+  while (tailDuration < 30 && tailIterator > 0) {
+    tailDuration += selectedPlaylist.segments[tailIterator - 1].duration;
+    tailIterator--;
+  }
+
+  return tailIterator;
+};
+
 videojs.Hls.prototype.handleSourceOpen = function() {
   // construct the video data buffer and set the appropriate MIME type
   var
@@ -142,6 +154,11 @@ videojs.Hls.prototype.handleSourceOpen = function() {
       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;
@@ -781,14 +798,15 @@ videojs.Hls.getPlaylistTotalDuration = function(playlist) {
  * playlist
  */
 videojs.Hls.translateMediaIndex = function(mediaIndex, original, update) {
-  var
-    i,
-    originalSegment;
+  var i,
+      originalSegment,
+      translatedMediaIndex;
 
   // no segments have been loaded from the original playlist
   if (mediaIndex === 0) {
     return 0;
   }
+
   if (!(update && update.segments)) {
     // let the media index be zero when there are no segments defined
     return 0;
@@ -803,8 +821,15 @@ videojs.Hls.translateMediaIndex = function(mediaIndex, original, update) {
     }
   }
 
+  translatedMediaIndex = (mediaIndex + (original.mediaSequence - update.mediaSequence));
+
+  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;
+  }
+
   // sync on media sequence
-  return (original.mediaSequence + mediaIndex) - update.mediaSequence;
+  return translatedMediaIndex;
 };
 
 /**

+{
+  "allowCache": true,
+  "mediaSequence": 0,
+  "segments": [
+    {
+      "duration": 10,
+      "uri": "001.ts"
+    },
+    {
+      "duration": 19,
+      "uri": "002.ts"
+    },
+    {
+      "duration": 10,
+      "uri": "003.ts"
+    },
+    {
+      "duration": 11,
+      "uri": "004.ts"
+    },
+    {
+      "duration": 10,
+      "uri": "005.ts"
+    },
+    {
+      "duration": 10,
+      "uri": "006.ts"
+    },
+    {
+      "duration": 10,
+      "uri": "007.ts"
+    },
+    {
+      "duration": 10,
+      "uri": "008.ts"
+    },
+    {
+      "duration": 16,
+      "uri": "009.ts"
+    }
+  ],
+  "targetDuration": 19
+}
\ No newline at end of file

+#EXTM3U
+#EXT-X-MEDIA-SEQUENCE:0
+#EXT-X-ALLOW-CACHE:YES
+#EXT-X-TARGETDURATION:19
+#EXTINF:10,0
+001.ts
+#EXTINF:19,0
+002.ts
+#EXTINF:10,0
+003.ts
+#EXTINF:11,0
+004.ts
+#EXTINF:10,0
+005.ts
+#EXTINF:10,0
+006.ts
+#EXTINF:10,0
+007.ts
+#EXTINF:10,0
+008.ts
+#EXTINF:16,0
+009.ts
\ No newline at end of file

@@ -1054,6 +1054,20 @@ test('updates the media index when a playlist reloads', function() {
   strictEqual(player.hls.mediaIndex, 2, 'mediaIndex is updated after the reload');
 });
 
+test('live playlist starts 30s before live', 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');
+
+  strictEqual(player.hls.mediaIndex, 6, 'mediaIndex is updated after the reload');
+});
+
 test('mediaIndex is zero before the first segment loads', function() {
   window.manifests['first-seg-load'] =
     '#EXTM3U\n' +