pull apart segmentsDuration

Break segmentsDuration up into more manageable parts.

@@ -5,39 +5,17 @@
   'use strict';
 
   var DEFAULT_TARGET_DURATION = 10;
-  var duration, seekable, segmentsDuration;
+  var accumulateDuration, duration, seekable, segmentsDuration;
 
-  /**
-   * Calculate the media duration from the segments associated with a
-   * playlist. The duration of a subinterval of the available segments
-   * may be calculated by specifying a start and end index.
-   *
-   * @param playlist {object} a media playlist object
-   * @param startSequence {number} (optional) an inclusive lower
-   * boundary for the playlist.  Defaults to 0.
-   * @param endSequence {number} (optional) an exclusive upper boundary
-   * for the playlist.  Defaults to playlist length.
-   * @param strict {boolean} (optional) if true, the interval between
-   * the final segment and the subsequent segment will not be included
-   * in the result
-   * @return {number} the duration between the start index and end
-   * index.
-   */
-  segmentsDuration = function(playlist, startSequence, endSequence, strict) {
-    var targetDuration, i, j, segment, endSegment, expiredSegmentCount, result = 0;
-
-    startSequence = startSequence || 0;
-    i = startSequence;
-    endSequence = endSequence !== undefined ? endSequence : (playlist.segments || []).length;
-    targetDuration = playlist.targetDuration || DEFAULT_TARGET_DURATION;
-
-    // estimate expired segment duration using the target duration
-    expiredSegmentCount = Math.max(playlist.mediaSequence - startSequence, 0);
-    result += expiredSegmentCount * targetDuration;
-    i += expiredSegmentCount;
+  accumulateDuration = function(playlist, startSequence, endSequence, strict) {
+    var
+      result = 0,
+      targetDuration = playlist.targetDuration || DEFAULT_TARGET_DURATION,
+      segment, endSegment,
+      i, j;
 
     // accumulate the segment durations into the result
-    for (; i < endSequence; i++) {
+    for (i = startSequence; i < endSequence; i++) {
       segment = playlist.segments[i - playlist.mediaSequence];
 
       // when PTS values aren't available, use information from the playlist
@@ -49,7 +27,7 @@
 
       // find the last segment with PTS info and use that to calculate
       // the interval duration
-      for(j = i; j < endSequence - 1; j++) {
+      for (j = i; j < endSequence - 1; j++) {
         endSegment = playlist.segments[j - playlist.mediaSequence + 1];
         if (endSegment.maxVideoPts === undefined ||
             endSegment.discontinuity) {
@@ -81,6 +59,42 @@
   };
 
   /**
+   * Calculate the media duration from the segments associated with a
+   * playlist. The duration of a subinterval of the available segments
+   * may be calculated by specifying a start and end index.
+   *
+   * @param playlist {object} a media playlist object
+   * @param startSequence {number} (optional) an inclusive lower
+   * boundary for the playlist.  Defaults to 0.
+   * @param endSequence {number} (optional) an exclusive upper boundary
+   * for the playlist.  Defaults to playlist length.
+   * @param strict {boolean} (optional) if true, the interval between
+   * the final segment and the subsequent segment will not be included
+   * in the result
+   * @return {number} the duration between the start index and end
+   * index.
+   */
+  segmentsDuration = function(playlist, startSequence, endSequence, strict) {
+    var targetDuration, expiredSegmentCount, result = 0;
+
+    startSequence = startSequence || 0;
+    endSequence = endSequence !== undefined ? endSequence : (playlist.segments || []).length;
+    targetDuration = playlist.targetDuration || DEFAULT_TARGET_DURATION;
+
+    // estimate expired segment duration using the target duration
+    expiredSegmentCount = Math.max(playlist.mediaSequence - startSequence, 0);
+    result += expiredSegmentCount * targetDuration;
+
+    // accumulate the segment durations into the result
+    result += accumulateDuration(playlist,
+                                 startSequence + expiredSegmentCount,
+                                 endSequence,
+                                 strict);
+
+    return result;
+  };
+
+  /**
    * Calculates the duration of a playlist. If a start and end index
    * are specified, the duration will be for the subset of the media
    * timeline between those two indices. The total duration for live

@@ -3,7 +3,7 @@
   'use strict';
   var Playlist = videojs.Hls.Playlist;
 
-  module('Playlist Utilities');
+  module('Playlist Duration');
 
   test('total duration for live playlists is Infinity', function() {
     var duration = Playlist.duration({
@@ -16,7 +16,9 @@
     equal(duration, Infinity, 'duration is infinity');
   });
 
-  test('interval duration accounts for media sequences', function() {
+  module('Playlist Interval Duration');
+
+  test('accounts for media sequences', function() {
     var duration = Playlist.duration({
       mediaSequence: 10,
       endList: true,
@@ -38,7 +40,7 @@
     equal(duration, 14 * 10, 'duration includes dropped segments');
   });
 
-  test('interval duration uses PTS values when available', function() {
+  test('uses PTS values when available', function() {
     var duration = Playlist.duration({
       mediaSequence: 0,
       endList: true,
@@ -67,7 +69,7 @@
     equal(duration, ((4 * 10 * 1000 + 2) - 1) * 0.001, 'used PTS values');
   });
 
-  test('interval duration works when partial PTS information is available', function() {
+  test('works when partial PTS information is available', function() {
     var firstInterval, secondInterval, duration = Playlist.duration({
       mediaSequence: 0,
       endList: true,
@@ -111,7 +113,7 @@
           'calculated with mixed intervals');
   });
 
-  test('interval duration handles trailing segments without PTS information', function() {
+  test('handles trailing segments without PTS information', function() {
     var duration = Playlist.duration({
       mediaSequence: 0,
       endList: true,
@@ -139,7 +141,37 @@
     equal(duration, 10 + 9 + 10, 'calculated duration');
   });
 
-  test('interval duration counts the time between segments as part of the later segment duration', function() {
+  test('uses PTS intervals when the start and end segment have them', function() {
+    var playlist, duration;
+    playlist = {
+      mediaSequence: 0,
+      segments: [{
+        minVideoPts: 0,
+        minAudioPts: 0,
+        maxVideoPts: 10 * 1000,
+        maxAudioPts: 10 * 1000,
+        uri: '0.ts'
+      }, {
+        duration: 9,
+        uri: '1.ts'
+      },{
+        minVideoPts: 20 * 1000 + 100,
+        minAudioPts: 20 * 1000 + 100,
+        maxVideoPts: 30 * 1000 + 100,
+        maxAudioPts: 30 * 1000 + 100,
+        duration: 10,
+        uri: '2.ts'
+      }]
+    };
+    duration = Playlist.duration(playlist, 0, 2);
+
+    equal(duration, 20.1, 'used the PTS-based interval');
+
+    duration = Playlist.duration(playlist, 0, 3);
+    equal(duration, 30.1, 'used the PTS-based interval');
+  });
+
+  test('counts the time between segments as part of the later segment duration', function() {
     var duration = Playlist.duration({
       mediaSequence: 0,
       endList: true,
@@ -162,7 +194,7 @@
     equal(duration, (1 * 10 * 1000 + 100) * 0.001, 'included the segment gap');
   });
 
-  test('interval duration accounts for discontinuities', function() {
+  test('accounts for discontinuities', function() {
     var duration = Playlist.duration({
       mediaSequence: 0,
       endList: true,
@@ -186,7 +218,7 @@
     equal(duration, 10 + 10, 'handles discontinuities');
   });
 
-  test('interval duration does not count ending segment gaps across a discontinuity', function() {
+  test('does not count ending segment gaps across a discontinuity', function() {
     var duration = Playlist.duration({
       mediaSequence: 0,
       endList: true,
@@ -210,7 +242,7 @@
     equal(duration, (1 * 10 * 1000) * 0.001, 'did not include the segment gap');
   });
 
-  test('strict interval duration does not count ending segment gaps', function() {
+  test('strict duration does not count ending segment gaps', function() {
     var duration = Playlist.duration({
       mediaSequence: 0,
       endList: true,
@@ -233,6 +265,8 @@
     equal(duration, (1 * 10 * 1000) * 0.001, 'did not include the segment gap');
   });
 
+  module('Playlist Seekable');
+
   test('calculates seekable time ranges from the available segments', function() {
     var playlist = {
       mediaSequence: 0,