Merge pull request #198 from videojs/hotfix/early-bw-estimation

Scale the initial bandwidth estimate

@@ -138,7 +138,14 @@ videojs.Hls.prototype.handleSourceOpen = function() {
     };
 
     oldMediaPlaylist = this.playlists.media();
-    this.setBandwidth(this.playlists);
+    // the bandwidth estimate for the first segment is based on round trip
+    // time for the master playlist. the master playlist is almost always
+    // tiny so the round trip time is dominated by latency and so the
+    // computed bandwidth is much lower than steady-state. to account for
+    // this, we scale the bandwidth estimate from the master playlist.
+    this.setBandwidth({
+      bandwidth: this.playlists.bandwidth * 5
+    });
 
     selectedPlaylist = this.selectPlaylist();
     oldBitrate = oldMediaPlaylist.attributes &&

@@ -94,11 +94,11 @@
             </p>
             The video is available at
             <ul>
-              <li><input class=bitrate type=number min=1 value=65536> bits per second</li>
-              <li><input class=bitrate type=number min=1 value=153600> bits per second</li>
-              <li><input class=bitrate type=number min=1 value=450560> bits per second</li>
-              <li><input class=bitrate type=number min=1 value=921600> bits per second</li>
-              <li><input class=bitrate type=number min=1 value=1536000> bits per second</li>
+              <li><input class=bitrate type=number min=1 value=312000> bits per second</li>
+              <li><input class=bitrate type=number min=1 value=524000> bits per second</li>
+              <li><input class=bitrate type=number min=1 value=1296000> bits per second</li>
+              <li><input class=bitrate type=number min=1 value=2125000> bits per second</li>
+              <li><input class=bitrate type=number min=1 value=3125000> bits per second</li>
             </ul>
           </form>
         </section>

 (function(window, document) {
   'use strict';
   var segmentDuration = 9, // seconds
-      segmentCount = 100,
+      segmentCount = 10,
       duration = segmentDuration * segmentCount,
       propagationDelay = 0.5,
 
@@ -171,13 +171,21 @@
           return currentTime;
         };
 
+        bandwidths.sort(function(left, right) {
+          return left.time - right.time;
+        });
+
         // respond to the playlist requests
+        requests[0].bandwidth = bandwidths[0].bandwidth;
         requests.shift().respond(200, null, master);
+        requests[0].bandwidth = bandwidths[0].bandwidth;
         requests[0].respond(200, null, playlistResponse(+requests[0].url.match(/\d+$/)));
         requests.shift();
 
-        bandwidths.sort(function(left, right) {
-          return left.time - right.time;
+        // record the measured bandwidth for the playlist requests
+        results.effectiveBandwidth.push({
+          time: 0,
+          bandwidth: player.hls.bandwidth
         });
 
         // pre-calculate the bandwidth at each second

@@ -618,6 +618,21 @@ test('selects a playlist below the current bandwidth', function() {
               'the low bitrate stream is selected');
 });
 
+test('scales the bandwidth estimate for the first segment', function() {
+  player.src({
+    src: 'manifest/master.m3u8',
+    type: 'application/vnd.apple.mpegurl'
+  });
+  openMediaSource(player);
+
+  requests[0].bandwidth = 500;
+  requests.shift().respond(200, null,
+                           '#EXTM3U\n' +
+                           '#EXT-X-PLAYLIST-TYPE:VOD\n' +
+                           '#EXT-X-TARGETDURATION:10\n');
+  equal(player.hls.bandwidth, 500 * 5, 'scaled the bandwidth estimate by 5');
+});
+
 test('raises the minimum bitrate for a stream proportionially', function() {
   var playlist;
   player.src({