Compare the old playlist to the update to determine the new media index

When refreshing a playlist, determine the new media index by comparing segment URIs. Consolidate playlist update logic. "Sliding window" live streams are now working.

Compare the old playlist to the update to determine the new media index
When refreshing a playlist, determine the new media index by comparing segment URIs. Consolidate playlist update logic. "Sliding window" live streams are now working.
David LaPalomento
Showing 4 changed files with 166 additions and 217 deletions
src/m3u8/m3u8-parser.js
src/videojs-hls.js
test/m3u8_test.js
test/videojs-hls_test.js
--- a/src/m3u8/m3u8-parser.js
View file @736b7c3
+++ b/src/m3u8/m3u8-parser.js
View file @736b7c3
@@ -35,8 +35,7 @@
    Stream = videojs.hls.Stream,
    LineStream,
    ParseStream,
-    Parser,
+    Parser;
-    merge;
  /**
   * A stream that buffers string input and generates a `data` event for each
@@ -456,52 +455,9 @@
    this.lineStream.push('\n');
  };
-  /**
-   * Merges two versions of a media playlist.
-   * @param base {object} the earlier version of the media playlist.
-   * @param update {object} the updates to apply to the base playlist.
-   * @return {object} a new media playlist object that combines the
-   * information in the two arguments.
-   */
-  merge = function(base, update) {
-    var
-      result = mergeOptions({}, base),
-      uri = update.segments[0].uri,
-      i = base.segments ? base.segments.length : 0,
-      byterange,
-      segment;
-    result = mergeOptions(result, update);
-    // align and apply the updated segments
-    while (i--) {
-      segment = base.segments[i];
-      if (uri === segment.uri) {
-        // if there is no byterange information, match by URI
-        if (!segment.byterange) {
-          result.segments = base.segments.slice(0, i).concat(update.segments);
-          break;
-        }
-        // if a byterange is specified, make sure the segments match exactly
-        byterange = update.segments[0].byterange || {};
-        if (segment.byterange.offset === byterange.offset &&
-            segment.byterange.length === byterange.length) {
-          result.segments = base.segments.slice(0, i).concat(update.segments);
-          break;
-        }
-      }
-    }
-    // concatenate the two arrays if there was no overlap
-    if (i < 0) {
-      result.segments = (base.segments || []).concat(update.segments);
-    }
-    return result;
-  };
  window.videojs.m3u8 = {
    LineStream: LineStream,
    ParseStream: ParseStream,
-    Parser: Parser,
+    Parser: Parser
-    merge: merge
  };
 })(window.videojs, window.parseInt, window.isFinite, window.videojs.util.mergeOptions);
--- a/src/videojs-hls.js
View file @736b7c3
+++ b/src/videojs-hls.js
View file @736b7c3
@@ -132,6 +132,12 @@ var
      duration = 0,
      i = playlist.segments.length,
      segment;
+    // if present, use the duration specified in the playlist
+    if (playlist.totalDuration) {
+      return playlist.totalDuration;
+    }
    // duration should be Infinity for live playlists
    if (!playlist.endList) {
      return window.Infinity;
@@ -205,7 +211,8 @@ var
      segmentXhr,
      downloadPlaylist,
-      fillBuffer;
+      fillBuffer,
+      updateCurrentPlaylist;
    // if the video element supports HLS natively, do nothing
    if (videojs.hls.supportsNativeHls) {
@@ -293,6 +300,28 @@ var
      fillBuffer(currentTime * 1000);
    });
+    /**
+     * Determine whether the current media playlist should be changed
+     * and trigger a switch if necessary. If a sufficiently fresh
+     * version of the target playlist is available, the switch will take
+     * effect immediately. Otherwise, the target playlist will be
+     * refreshed.
+     */
+    updateCurrentPlaylist = function() {
+      var playlist, mediaSequence;
+      playlist = player.hls.selectPlaylist();
+      mediaSequence = player.hls.mediaIndex + (player.hls.media.mediaSequence || 0);
+      if (!playlist.segments ||
+          mediaSequence < (playlist.mediaSequence || 0) ||
+          mediaSequence > (playlist.mediaSequence || 0) + playlist.segments.length) {
+        downloadPlaylist(resolveUrl(srcUrl, playlist.uri));
+      } else {
+        player.hls.media = playlist;
+        // update the duration
+        player.duration(totalDuration(player.hls.media));
+      }
+    };
    /**
     * Chooses the appropriate media playlist based on the current
@@ -382,7 +411,27 @@ var
      var xhr = new window.XMLHttpRequest();
      xhr.open('GET', url);
      xhr.onreadystatechange = function() {
-        var i, parser, playlist, playlistUri, refreshDelay;
+        var i, parser, playlist, playlistUri, refreshDelay,
+          updateMediaIndex = function(original, update) {
+            var
+              i = update.segments.length,
+              updatedIndex = 0,
+              originalSegment;
+            // no segments have been loaded from the original playlist
+            if (player.hls.mediaIndex === 0) {
+              return;
+            }
+            originalSegment = original.segments[player.hls.mediaIndex - 1];
+            while (i--) {
+              if (originalSegment.uri === update.segments[i].uri) {
+                updatedIndex = i + 1;
+                break;
+              }
+            }
+            player.hls.mediaIndex = updatedIndex;
+          };
        // wait until the request completes
        if (xhr.readyState !== 4) {
@@ -430,7 +479,15 @@ var
              }
              player.hls.master.playlists[i] =
-                videojs.m3u8.merge(playlist, parser.manifest);
+                videojs.util.mergeOptions(playlist, parser.manifest);
+              if (playlist !== player.hls.media) {
+                continue;
+              }
+              // determine the new mediaIndex if we're updating the
+              // current media playlist
+              updateMediaIndex(playlist, parser.manifest);
            }
          }
        } else {
@@ -453,11 +510,7 @@ var
          player.hls.media = player.hls.master.playlists[0];
          // update the duration
-          if (parser.manifest.totalDuration) {
-            player.duration(parser.manifest.totalDuration);
-          } else {
          player.duration(totalDuration(parser.manifest));
-          }
          // periodicaly check if the buffer needs to be refilled
          player.on('timeupdate', fillBuffer);
@@ -469,19 +522,7 @@ var
        }
        // select a playlist and download its metadata if necessary
-        playlist = player.hls.selectPlaylist();
+        updateCurrentPlaylist();
-        if (!playlist.segments) {
-          downloadPlaylist(resolveUrl(srcUrl, playlist.uri));
-        } else {
-          player.hls.media = playlist;
-          // update the duration
-          if (player.hls.media.totalDuration) {
-            player.duration(player.hls.media.totalDuration);
-          } else {
-            player.duration(totalDuration(player.hls.media));
-          }
-        }
        player.trigger('loadedmanifest');
      };
@@ -535,8 +576,6 @@ var
      segmentXhr.open('GET', segmentUri);
      segmentXhr.responseType = 'arraybuffer';
      segmentXhr.onreadystatechange = function() {
-        var playlist;
        // wait until the request completes
        if (this.readyState !== 4) {
          return;
@@ -591,12 +630,7 @@ var
        // figure out what stream the next segment should be downloaded from
        // with the updated bandwidth information
-        playlist = player.hls.selectPlaylist();
+        updateCurrentPlaylist();
-        if (!playlist.segments) {
-          downloadPlaylist(resolveUrl(srcUrl, playlist.uri));
-        } else {
-          player.hls.media = playlist;
-        }
      };
      startTime = +new Date();
      segmentXhr.send(null);
--- a/test/m3u8_test.js
View file @736b7c3
+++ b/test/m3u8_test.js
View file @736b7c3
@@ -513,131 +513,6 @@
    notStrictEqual(new Parser(), undefined, 'parser is defined');
  });
-  test('merges a manifest that strictly adds to an earlier one', function() {
-    var key, base, manifest, mid;
-    for (key in window.manifests) {
-      if (window.expected[key]) {
-        manifest = window.manifests[key];
-        // parse the first half of the manifest
-        mid = manifest.length / 2;
-        parser = new Parser();
-        parser.push(manifest.substring(0, mid));
-        base = parser.manifest;
-        if (!base.segments) {
-          // only test merges for media playlists
-          continue;
-        }
-        // attach the partial manifest to a new parser
-        parser = new Parser();
-        parser.push(manifest);
-        // merge the manifests together
-        deepEqual(m3u8.merge(base, parser.manifest),
-                  window.expected[key],
-                  key + '.m3u8 was parsed correctly');
-      }
-    }
-  });
-  test('merges overlapping segments without media sequences', function() {
-    var base;
-    parser = new Parser();
-    parser.push('#EXTM3U\n');
-    parser.push('#EXTINF:10,\n');
-    parser.push('0.ts\n');
-    parser.push('#EXTINF:10,\n');
-    parser.push('1.ts\n');
-    base = parser.manifest;
-    parser = new Parser();
-    parser.push('#EXTM3U\n');
-    parser.push('#EXTINF:10,\n');
-    parser.push('1.ts\n');
-    parser.push('#EXTINF:10,\n');
-    parser.push('2.ts\n');
-    deepEqual({
-      allowCache: true,
-      mediaSequence: 0,
-      segments: [{ duration: 10, uri: '0.ts'},
-                 { duration: 10, uri: '1.ts' },
-                 { duration: 10, uri: '2.ts' }]
-    }, m3u8.merge(base, parser.manifest), 'merges segment additions');
-  });
-  test('appends non-overlapping segments without media sequences', function() {
-    var base;
-    parser = new Parser();
-    parser.push('#EXTM3U\n');
-    parser.push('#EXTINF:10,\n');
-    parser.push('0.ts\n');
-    base = parser.manifest;
-    parser = new Parser();
-    parser.push('#EXTM3U\n');
-    parser.push('#EXTINF:10,\n');
-    parser.push('1.ts\n');
-    deepEqual({
-      allowCache: true,
-      mediaSequence: 0,
-      segments: [{ duration: 10, uri: '0.ts'},
-                 { duration: 10, uri: '1.ts' }]
-    }, m3u8.merge(base, parser.manifest), 'appends segment additions');
-  });
-  test('replaces segments when merging with a higher media sequence number', function() {
-    var base;
-    parser = new Parser();
-    parser.push('#EXTM3U\n');
-    parser.push('#EXT-X-MEDIA-SEQUENCE:3\n');
-    parser.push('#EXTINF:10,\n');
-    parser.push('3.ts\n');
-    base = parser.manifest;
-    parser = new Parser();
-    parser.push('#EXTM3U\n');
-    parser.push('#EXT-X-MEDIA-SEQUENCE:7\n');
-    parser.push('#EXTINF:10,\n');
-    parser.push('7.ts\n');
-    base = parser.manifest;
-    deepEqual({
-      allowCache: true,
-      mediaSequence:  7,
-      segments: [{ duration: 10, uri: '7.ts' }]
-    }, m3u8.merge(base, parser.manifest), 'replaces segments');
-  });
-  test('replaces overlapping segments when media sequence is present', function() {
-    var base;
-    parser = new Parser();
-    parser.push('#EXTM3U\n');
-    parser.push('#EXT-X-MEDIA-SEQUENCE:3\n');
-    parser.push('#EXTINF:10,\n');
-    parser.push('3.ts\n');
-    parser.push('#EXTINF:10,\n');
-    parser.push('4.ts\n');
-    base = parser.manifest;
-    parser = new Parser();
-    parser.push('#EXTM3U\n');
-    parser.push('#EXT-X-MEDIA-SEQUENCE:4\n');
-    parser.push('#EXTINF:10,\n');
-    parser.push('4.ts\n');
-    parser.push('#EXTINF:10,\n');
-    parser.push('5.ts\n');
-    base = parser.manifest;
-    deepEqual({
-      allowCache: true,
-      mediaSequence:  4,
-      segments: [{ duration: 10, uri: '4.ts' },
-                 { duration: 10, uri: '5.ts' }]
-    }, m3u8.merge(base, parser.manifest), 'replaces segments');
-  });
  module('m3u8s');
  test('parses static manifests as expected', function() {
--- a/test/videojs-hls_test.js
View file @736b7c3
+++ b/test/videojs-hls_test.js
View file @736b7c3
@@ -170,7 +170,7 @@ test('sets the duration if one is available on the playlist', function() {
    type: 'sourceopen'
  });
-  strictEqual(1, calls, 'duration is set');
+  strictEqual(calls, 2, 'duration is set');
 });
 test('calculates the duration if needed', function() {
@@ -186,7 +186,7 @@ test('calculates the duration if needed', function() {
    type: 'sourceopen'
  });
-  strictEqual(durations.length, 1, 'duration is set');
+  strictEqual(durations.length, 2, 'duration is set');
  strictEqual(durations[0],
              player.hls.media.segments.length * 10,
              'duration is calculated');
@@ -402,15 +402,12 @@ test('downloads additional playlists if required', function() {
      called = true;
      return playlist;
    }
-    playlist.segments = [];
+    playlist.segments = [1, 1, 1];
    return playlist;
  };
  xhrUrls = [];
  // the playlist selection is revisited after a new segment is downloaded
-  player.currentTime = function() {
-    return 1;
-  };
  player.trigger('timeupdate');
  strictEqual(2, xhrUrls.length, 'requests were made');
@@ -869,7 +866,7 @@ test('segment 500 should trigger MEDIA_ERR_ABORTED', function () {
 test('has no effect if native HLS is available', function() {
  videojs.hls.supportsNativeHls = true;
-  player.hls('manifest/master.m3u8');
+  player.hls('http://example.com/manifest/master.m3u8');
  ok(!(player.currentSrc() in videojs.mediaSources),
     'no media source was opened');
@@ -881,7 +878,7 @@ test('reloads live playlists', function() {
  window.setTimeout = function(callback, timeout) {
    callbacks.push({ callback: callback, timeout: timeout });
  };
-  player.hls('manifest/missingEndlist.m3u8');
+  player.hls('http://example.com/manifest/missingEndlist.m3u8');
  videojs.mediaSources[player.currentSrc()].trigger({
    type: 'sourceopen'
  });
@@ -893,7 +890,7 @@ test('reloads live playlists', function() {
 });
 test('duration is Infinity for live playlists', function() {
-  player.hls('manifest/missingEndlist.m3u8');
+  player.hls('http://example.com/manifest/missingEndlist.m3u8');
  videojs.mediaSources[player.currentSrc()].trigger({
    type: 'sourceopen'
  });
@@ -943,27 +940,114 @@ test('reloads a live playlist after half a target duration if it has not ' +
 test('merges playlist reloads', function() {
  var
-    realMerge = videojs.m3u8.merge,
+    oldPlaylist,
-    merges = 0,
    callback;
-  // capture timeouts and playlist merges
+  // capture timeouts
  window.setTimeout = function(cb) {
    callback = cb;
  };
-  videojs.m3u8.merge = function(base, update) {
-    merges++;
-    return update;
-  };
  player.hls('http://example.com/manifest/missingEndlist.m3u8');
  videojs.mediaSources[player.currentSrc()].trigger({
    type: 'sourceopen'
  });
+  oldPlaylist = player.hls.media;
  callback();
-  strictEqual(1, merges, 'reloaded playlist was merged');
+  ok(oldPlaylist !== player.hls.media, 'player.hls.media was updated');
+});
+test('updates the media index when a playlist reloads', function() {
+  var callback;
+  window.setTimeout = function(cb) {
+    callback = cb;
+  };
+  // the initial playlist
+  window.manifests['live-updating'] =
+    '#EXTM3U\n' +
+    '#EXTINF:10,\n' +
+    '0.ts\n' +
+    '#EXTINF:10,\n' +
+    '1.ts\n' +
+    '#EXTINF:10,\n' +
+    '2.ts\n';
+  player.hls('http://example.com/live-updating.m3u8');
+  videojs.mediaSources[player.currentSrc()].trigger({
+    type: 'sourceopen'
+  });
+  // play the stream until 2.ts is playing
+  player.hls.mediaIndex = 3;
+  // reload the updated playlist
+  window.manifests['live-updating'] =
+    '#EXTM3U\n' +
+    '#EXTINF:10,\n' +
+    '1.ts\n' +
+    '#EXTINF:10,\n' +
+    '2.ts\n' +
+    '#EXTINF:10,\n' +
+    '3.ts\n';
+  callback();
+  strictEqual(2, player.hls.mediaIndex, 'mediaIndex is updated after the reload');
+});
+test('mediaIndex is zero before the first segment loads', function() {
+  window.manifests['first-seg-load'] =
+    '#EXTM3U\n' +
+    '#EXTINF:10,\n' +
+    '0.ts\n';
+  window.XMLHttpRequest = function() {
+    this.open = function() {};
+    this.send = function() {};
+  };
+  player.hls('http://example.com/first-seg-load.m3u8');
+  videojs.mediaSources[player.currentSrc()].trigger({
+    type: 'sourceopen'
+  });
+  strictEqual(player.hls.mediaIndex, 0, 'mediaIndex is zero');
+});
+test('reloads out-of-date live playlists when switching variants', function() {
+  var callback;
+  // capture timeouts
+  window.setTimeout = function(cb) {
+    callback = cb;
+  };
+  player.hls('http://example.com/master.m3u8');
+  videojs.mediaSources[player.currentSrc()].trigger({
+    type: 'sourceopen'
+  });
+  // playing segment 15 on playlist 0
+  player.hls.master = {
+    playlists: [{
+      mediaSequence: 15,
+      segments: [{}, {}]
+    }, {
+      uri: 'http://example.com/variant-update.m3u8',
+      mediaSequence: 0,
+      segments: [{}, {}]
+    }]
+  };
+  player.hls.media = player.hls.master.playlists[0];
+  player.mediaIndex = 0;
+  window.manifests['variant-update'] = '#EXTM3U\n' +
+    '#EXT-X-MEDIA-SEQUENCE:16\n' +
+    '#EXTINF:10,\n' +
+    '16.ts\n';
+  // switch playlists
+  player.hls.selectPlaylist = function() {
+    return player.hls.master.playlists[1];
+  };
+  player.trigger('timeupdate');
-  videojs.m3u8.merge = realMerge;
+  ok(callback, 'reload is scheduled');
 });
 })(window, window.videojs);