buffer at the current time range end instead of incrementing a variable. closes #423

@@ -2,7 +2,7 @@ CHANGELOG
 =========
 
 ## HEAD (Unreleased)
-_(none)_
+* buffer at the current time range end instead of incrementing a variable. ([view](https://github.com/videojs/videojs-contrib-hls/pull/423))
 
 --------------------
 

@@ -44,7 +44,7 @@
     "karma-sauce-launcher": "~0.1.8",
     "qunitjs": "^1.18.0",
     "sinon": "1.10.2",
-    "video.js": "^5.0.0-rc.96"
+    "video.js": "^5.1.0"
   },
   "dependencies": {
     "pkcs7": "^0.2.2",

@@ -367,7 +367,17 @@
    * closest playback position that is currently available.
    */
   PlaylistLoader.prototype.getMediaIndexForTime_ = function(time) {
-    var i, j, segment, targetDuration;
+    var
+      i,
+      segment,
+      originalTime = time,
+      targetDuration = this.media_.targetDuration || 10,
+      numSegments = this.media_.segments.length,
+      lastSegment = numSegments - 1,
+      startIndex,
+      endIndex,
+      knownStart,
+      knownEnd;
 
     if (!this.media_) {
       return 0;
@@ -379,57 +389,105 @@
       return 0;
     }
 
-    // 1) Walk backward until we find the latest segment with timeline
+    // 1) Walk backward until we find the first segment with timeline
     // information that is earlier than `time`
-    targetDuration = this.media_.targetDuration || 10;
-    i = this.media_.segments.length;
-    while (i--) {
+    for (i = lastSegment; i >= 0; i--) {
       segment = this.media_.segments[i];
       if (segment.end !== undefined && segment.end <= time) {
-        time -= segment.end;
+        startIndex = i + 1;
+        knownStart = segment.end;
+        if (startIndex >= numSegments) {
+          // The last segment claims to end *before* the time we are
+          // searching for so just return it
+          return numSegments;
+        }
         break;
       }
-      if (segment.start !== undefined && segment.start < time) {
-
+      if (segment.start !== undefined && segment.start <= time) {
         if (segment.end !== undefined && segment.end > time) {
           // we've found the target segment exactly
           return i;
         }
+        startIndex = i;
+        knownStart = segment.start;
+        break;
+      }
+    }
 
-        time -= segment.start;
-        time -= segment.duration || targetDuration;
-        if (time < 0) {
-          // the segment with start information is also our best guess
-          // for the momment
-          return i;
+    // 2) Walk forward until we find the first segment with timeline
+    // information that is greater than `time`
+    for (i = 0; i < numSegments; i++) {
+      segment = this.media_.segments[i];
+      if (segment.start !== undefined && segment.start > time) {
+        endIndex = i - 1;
+        knownEnd = segment.start;
+        if (endIndex < 0) {
+          // The first segment claims to start *after* the time we are
+          // searching for so just return it
+          return -1;
         }
         break;
       }
+      if (segment.end !== undefined && segment.end > time) {
+        endIndex = i;
+        knownEnd = segment.end;
+        break;
+      }
     }
-    i++;
 
-    // 2) Walk forward, testing each segment to see if `time` falls within it
-    for (j = i; j < this.media_.segments.length; j++) {
-      segment = this.media_.segments[j];
-      time -= segment.duration || targetDuration;
+    if (startIndex !== undefined) {
+      // We have a known-start point that is before our desired time so
+      // walk from that point forwards
+      time = time - knownStart;
+      for (i = startIndex; i < (endIndex || numSegments); i++) {
+        segment = this.media_.segments[i];
+        time -= segment.duration || targetDuration;
+        if (time < 0) {
+          return i;
+        }
+      }
 
-      if (time < 0) {
-        return j;
+      if (i === endIndex) {
+        // We haven't found a segment but we did hit a known end point
+        // so fallback to "Algorithm Jon" - try to interpolate the segment
+        // index based on the known span of the timeline we are dealing with
+        // and the number of segments inside that span
+        return startIndex + Math.floor(
+          ((originalTime - knownStart) / (knownEnd - knownStart)) *
+          (endIndex - startIndex));
       }
 
-      // 2a) If we discover a segment that has timeline information
-      // before finding the result segment, the playlist information
-      // must have been inaccurate. Start a binary search for the
-      // segment which contains `time`. If the guess turns out to be
-      // incorrect, we'll have more info to work with next time.
-      if (segment.start !== undefined || segment.end !== undefined) {
-        return Math.floor((j - i) * 0.5);
+      // We _still_ haven't found a segment so load the last one
+      return lastSegment;
+    } else if (endIndex !== undefined) {
+      // We _only_ have a known-end point that is after our desired time so
+      // walk from that point backwards
+      time = knownEnd - time;
+      for (i = endIndex; i >= 0; i--) {
+        segment = this.media_.segments[i];
+        time -= segment.duration || targetDuration;
+        if (time < 0) {
+          return i;
+        }
       }
+      // We haven't found a segment so load the first one
+      return 0;
+    } else {
+      // We known nothing so use "Algorithm A" - walk from the front
+      // of the playlist naively subtracking durations until we find
+      // a segment that contains time and return it
+      for (i = 0; i < numSegments; i++) {
+        segment = this.media_.segments[i];
+        time -= segment.duration || targetDuration;
+        if (time < 0) {
+          return i;
+        }
+      }
+      // We are out of possible candidates so load the last one...
+      // The last one is the least likely to overlap a buffer and therefore
+      // the one most likely to tell us something about the timeline
+      return lastSegment;
     }
-
-    // the playback position is outside the range of available
-    // segments so return the length
-    return this.media_.segments.length;
   };
 
   videojs.Hls.PlaylistLoader = PlaylistLoader;

@@ -653,8 +653,8 @@
     equal(loader.getMediaIndexForTime_(3), 0, 'time three is index zero');
     equal(loader.getMediaIndexForTime_(10), 2, 'time 10 is index 2');
     equal(loader.getMediaIndexForTime_(22),
-          3,
-          'time greater than the length is index 3');
+          2,
+          'time greater than the length is index 2');
   });
 
   test('returns the lower index when calculating for a segment boundary', function() {
@@ -683,9 +683,9 @@
                              '1002.ts\n');
     loader.media().segments[0].start = 150;
 
-    equal(loader.getMediaIndexForTime_(0), 0, 'the lowest returned value is zero');
-    equal(loader.getMediaIndexForTime_(45), 0, 'expired content returns zero');
-    equal(loader.getMediaIndexForTime_(75), 0, 'expired content returns zero');
+    equal(loader.getMediaIndexForTime_(0), -1, 'the lowest returned value is  negative one');
+    equal(loader.getMediaIndexForTime_(45), -1, 'expired content returns negative one');
+    equal(loader.getMediaIndexForTime_(75), -1, 'expired content returns  negative one');
     equal(loader.getMediaIndexForTime_(50 + 100), 0, 'calculates the earliest available position');
     equal(loader.getMediaIndexForTime_(50 + 100 + 2), 0, 'calculates within the first segment');
     equal(loader.getMediaIndexForTime_(50 + 100 + 2), 0, 'calculates within the first segment');

@@ -218,6 +218,7 @@ module('HLS', {
       var el = document.createElement('div');
       el.id = 'vjs_mock_flash_' + nextId++;
       el.className = 'vjs-tech vjs-mock-flash';
+      el.duration = Infinity;
       el.vjs_load = function() {};
       el.vjs_getProperty = function(attr) {
         if (attr === 'buffered') {
@@ -1131,7 +1132,7 @@ test('buffers based on the correct TimeRange if multiple ranges exist', function
     return videojs.createTimeRange(buffered);
   };
   currentTime = 8;
-  buffered = [[0, 10], [20, 40]];
+  buffered = [[0, 10], [20, 30]];
 
   standardXHRResponse(requests[0]);
   standardXHRResponse(requests[1]);
@@ -1144,14 +1145,9 @@ test('buffers based on the correct TimeRange if multiple ranges exist', function
   currentTime = 22;
   player.tech_.hls.sourceBuffer.trigger('updateend');
   player.tech_.hls.checkBuffer_();
-  strictEqual(requests.length, 2, 'made no additional requests');
-
-  buffered = [[0, 10], [20, 30]];
-  player.tech_.hls.checkBuffer_();
-  standardXHRResponse(requests[2]);
   strictEqual(requests.length, 3, 'made three requests');
   strictEqual(requests[2].url,
-              absoluteUrl('manifest/media-00004.ts'),
+              absoluteUrl('manifest/media-00003.ts'),
               'made segment request');
 });
 
@@ -1381,7 +1377,7 @@ test('seeking in an empty playlist is a non-erroring noop', function() {
   equal(requests.length, requestsLength, 'made no additional requests');
 });
 
-test('duration is Infinity for live playlists', function() {
+test('tech\'s duration reports Infinity for live playlists', function() {
   player.src({
     src: 'http://example.com/manifest/missingEndlist.m3u8',
     type: 'application/vnd.apple.mpegurl'
@@ -1390,9 +1386,13 @@ test('duration is Infinity for live playlists', function() {
 
   standardXHRResponse(requests[0]);
 
-  strictEqual(player.tech_.hls.mediaSource.duration,
+  strictEqual(player.tech_.duration(),
+              Infinity,
+              'duration on the tech is infinity');
+
+  notEqual(player.tech_.hls.mediaSource.duration,
               Infinity,
-              'duration is infinity');
+              'duration on the mediaSource is not infinity');
 });
 
 test('live playlist starts three target durations before live', function() {
@@ -1644,7 +1644,7 @@ test('calls mediaSource\'s timestampOffset on discontinuity', function() {
 });
 
 test('sets timestampOffset when seeking with discontinuities', function() {
-  var removes = [], timeRange = videojs.createTimeRange(0, 10);
+  var timeRange = videojs.createTimeRange(0, 10);
 
   player.src({
     src: 'discontinuity.m3u8',
@@ -1670,18 +1670,12 @@ test('sets timestampOffset when seeking with discontinuities', function() {
                          '3.ts\n' +
                          '#EXT-X-ENDLIST\n');
   player.tech_.hls.sourceBuffer.timestampOffset = 0;
-  player.tech_.hls.sourceBuffer.remove = function(start, end) {
-    timeRange = videojs.createTimeRange();
-    removes.push([start, end]);
-  };
-
   player.currentTime(21);
   clock.tick(1);
   equal(requests.shift().aborted, true, 'aborted first request');
   standardXHRResponse(requests.pop()); // 3.ts
   clock.tick(1000);
   equal(player.tech_.hls.sourceBuffer.timestampOffset, 20, 'timestampOffset starts at zero');
-  equal(removes.length, 1, 'remove was called');
 });
 
 test('can seek before the source buffer opens', function() {