Added support for the throughput of the whole system to the ABR algorithm (#918)

* Added support for the throughput of the whole system to the ABR algorithm to allow it to adjust better to poor performance especially with flash.

* Added tests for systemBandwidth and throughput

* Replaced instances of (new Date()).getTime() with Date.now()

* Removed redundant test and added a comment to explain bandwidith and throughput setters

* Renamed startOfLoad_ to startOfAppend which is a more accurate name

src/segment-loader.js

@@ -144,6 +144,7 @@ export default class SegmentLoader extends videojs.EventTarget {
     // public properties
     this.state = 'INIT';
     this.bandwidth = settings.bandwidth;
+    this.throughput = {rate: 0, count: 0};
     this.roundTrip = NaN;
     this.resetStats_();
 
@@ -754,6 +755,7 @@ export default class SegmentLoader extends videojs.EventTarget {
     if (request === this.xhr_.segmentXhr) {
       // the segment request is no longer outstanding
       this.xhr_.segmentXhr = null;
+      segmentInfo.startOfAppend = Date.now();
 
       // calculate the download bandwidth based on segment request
       this.roundTrip = request.roundTripTime;
@@ -903,6 +905,8 @@ export default class SegmentLoader extends videojs.EventTarget {
       }
     }
 
+    segmentInfo.byteLength = segmentInfo.bytes.byteLength;
+
     this.sourceUpdater_.appendBuffer(segmentInfo.bytes,
                                      this.handleUpdateEnd_.bind(this));
   }
@@ -919,6 +923,7 @@ export default class SegmentLoader extends videojs.EventTarget {
     let currentTime = this.currentTime_();
 
     this.pendingSegment_ = null;
+    this.recordThroughput_(segmentInfo);
 
     // add segment metadata if it we have gained information during the
     // last append
@@ -1017,6 +1022,31 @@ export default class SegmentLoader extends videojs.EventTarget {
     return timelineUpdated;
   }
 
+  /**
+   * Records the current throughput of the decrypt, transmux, and append
+   * portion of the semgment pipeline. `throughput.rate` is a the cumulative
+   * moving average of the throughput. `throughput.count` is the number of
+   * data points in the average.
+   *
+   * @private
+   * @param {Object} segmentInfo the object returned by loadSegment
+   */
+  recordThroughput_(segmentInfo) {
+    let rate = this.throughput.rate;
+    // Add one to the time to ensure that we don't accidentally attempt to divide
+    // by zero in the case where the throughput is ridiculously high
+    let segmentProcessingTime =
+      Date.now() - segmentInfo.startOfAppend + 1;
+    // Multiply by 8000 to convert from bytes/millisecond to bits/second
+    let segmentProcessingThroughput =
+      Math.floor((segmentInfo.byteLength / segmentProcessingTime) * 8 * 1000);
+
+    // This is just a cumulative moving average calculation:
+    //   newAvg = oldAvg + (sample - oldAvg) / (sampleCount + 1)
+    this.throughput.rate +=
+      (segmentProcessingThroughput - rate) / (++this.throughput.count);
+  }
+
   /**
    * add a number of seconds to the currentTime when determining which
    * segment to fetch in order to force the fetcher to advance in cases

src/videojs-contrib-hls.js

@@ -122,7 +122,7 @@ Hls.STANDARD_PLAYLIST_SELECTOR = function() {
 
     effectiveBitrate = variant.attributes.BANDWIDTH * BANDWIDTH_VARIANCE;
 
-    if (effectiveBitrate < this.bandwidth) {
+    if (effectiveBitrate < this.systemBandwidth) {
       bandwidthPlaylists.push(variant);
 
       // since the playlists are sorted in ascending order by
@@ -399,12 +399,55 @@ class HlsHandler extends Component {
           this.masterPlaylistController_.selectPlaylist = selectPlaylist.bind(this);
         }
       },
+      throughput: {
+        get() {
+          return this.masterPlaylistController_.mainSegmentLoader_.throughput.rate;
+        },
+        set(throughput) {
+          this.masterPlaylistController_.mainSegmentLoader_.throughput.rate = throughput;
+          // By setting `count` to 1 the throughput value becomes the starting value
+          // for the cumulative average
+          this.masterPlaylistController_.mainSegmentLoader_.throughput.count = 1;
+        }
+      },
       bandwidth: {
         get() {
           return this.masterPlaylistController_.mainSegmentLoader_.bandwidth;
         },
         set(bandwidth) {
           this.masterPlaylistController_.mainSegmentLoader_.bandwidth = bandwidth;
+          // setting the bandwidth manually resets the throughput counter
+          // `count` is set to zero that current value of `rate` isn't included
+          // in the cumulative average
+          this.masterPlaylistController_.mainSegmentLoader_.throughput = {rate: 0, count: 0};
+        }
+      },
+      /**
+       * `systemBandwidth` is a combination of two serial processes bit-rates. The first
+       * is the network bitrate provided by `bandwidth` and the second is the bitrate of
+       * the entire process after that - decryption, transmuxing, and appending - provided
+       * by `throughput`.
+       *
+       * Since the two process are serial, the overall system bandwidth is given by:
+       *   sysBandwidth = 1 / (1 / bandwidth + 1 / throughput)
+       */
+      systemBandwidth: {
+        get() {
+          let invBandwidth = 1 / (this.bandwidth || 1);
+          let invThroughput;
+
+          if (this.throughput > 0) {
+            invThroughput = 1 / this.throughput;
+          } else {
+            invThroughput = 0;
+          }
+
+          let systemBitrate = Math.floor(1 / (invBandwidth + invThroughput));
+
+          return systemBitrate;
+        },
+        set() {
+          videojs.log.error('The "systemBandwidth" property is read-only');
         }
       }
     });
@@ -451,7 +494,6 @@ class HlsHandler extends Component {
     // the bandwidth of the primary segment loader is our best
     // estimate of overall bandwidth
     this.on(this.masterPlaylistController_, 'progress', function() {
-      this.bandwidth = this.masterPlaylistController_.mainSegmentLoader_.bandwidth;
       this.tech_.trigger('progress');
     });
 

src/xhr.js

@@ -31,7 +31,7 @@ const xhrFactory = function() {
 
     let request = videojsXHR(options, function(error, response) {
       if (!error && request.response) {
-        request.responseTime = (new Date()).getTime();
+        request.responseTime = Date.now();
         request.roundTripTime = request.responseTime - request.requestTime;
         request.bytesReceived = request.response.byteLength || request.response.length;
         if (!request.bandwidth) {
@@ -63,7 +63,7 @@ const xhrFactory = function() {
       callback(error, request);
     });
 
-    request.requestTime = (new Date()).getTime();
+    request.requestTime = Date.now();
     return request;
   };
 

test/master-playlist-controller.test.js

@@ -175,7 +175,8 @@ QUnit.test('if buffered, will request second segment byte range', function() {
   this.masterPlaylistController.mainSegmentLoader_.sourceUpdater_.buffered = () => {
     return videojs.createTimeRanges([[0, 20]]);
   };
-
+  // 1ms have passed to upload 1kb that gives us a bandwidth of 1024 / 1 * 8 * 1000 = 8192000
+  this.clock.tick(1);
   // segment
   standardXHRResponse(this.requests[1]);
   this.masterPlaylistController.mediaSource.sourceBuffers[0].trigger('updateend');
@@ -183,11 +184,11 @@ QUnit.test('if buffered, will request second segment byte range', function() {
   QUnit.equal(this.requests[2].headers.Range, 'bytes=1823412-2299991');
 
   // verify stats
-  QUnit.equal(this.player.tech_.hls.stats.bandwidth, Infinity, 'Live stream');
+  QUnit.equal(this.player.tech_.hls.stats.bandwidth, 8192000, 'Live stream');
   QUnit.equal(this.player.tech_.hls.stats.mediaRequests, 1, '1 segment request');
   QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred,
-              16,
-              '16 bytes downloaded');
+              1024,
+              '1024 bytes downloaded');
 });
 
 QUnit.test('re-initializes the combined playlist loader when switching sources',
@@ -262,18 +263,19 @@ function() {
   this.player.tech_.on('progress', function() {
     progressCount++;
   });
-
+  // 1ms have passed to upload 1kb that gives us a bandwidth of 1024 / 1 * 8 * 1000 = 8192000
+  this.clock.tick(1);
   // segment
   standardXHRResponse(this.requests.shift());
   this.masterPlaylistController.mainSegmentLoader_.trigger('progress');
   QUnit.equal(progressCount, 1, 'fired a progress event');
 
   // verify stats
-  QUnit.equal(this.player.tech_.hls.stats.bandwidth, Infinity, 'Live stream');
+  QUnit.equal(this.player.tech_.hls.stats.bandwidth, 8192000, 'Live stream');
   QUnit.equal(this.player.tech_.hls.stats.mediaRequests, 1, '1 segment request');
   QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred,
-              16,
-              '16 bytes downloaded');
+              1024,
+              '1024 bytes downloaded');
 });
 
 QUnit.test('updates the enabled track when switching audio groups', function() {
@@ -470,6 +472,8 @@ QUnit.test('updates the combined segment loader on media changes', function() {
   this.masterPlaylistController.mainSegmentLoader_.playlist = function(update) {
     updates.push(update);
   };
+  // 1ms have passed to upload 1kb that gives us a bandwidth of 1024 / 1 * 8 * 1000 = 8192000
+  this.clock.tick(1);
 
   // downloading the new segment will update bandwidth and cause a
   // playlist change
@@ -481,12 +485,12 @@ QUnit.test('updates the combined segment loader on media changes', function() {
   QUnit.ok(updates.length > 0, 'updated the segment list');
 
   // verify stats
-  QUnit.equal(this.player.tech_.hls.stats.bandwidth, Infinity, 'Live stream');
+  QUnit.equal(this.player.tech_.hls.stats.bandwidth, 8192000, 'Live stream');
   QUnit.equal(this.player.tech_.hls.stats.mediaRequests, 1, '1 segment request');
   QUnit.equal(
     this.player.tech_.hls.stats.mediaBytesTransferred,
-    16,
-    '16 bytes downloaded');
+    1024,
+    '1024 bytes downloaded');
 });
 
 QUnit.test('selects a playlist after main/combined segment downloads', function() {
@@ -535,7 +539,8 @@ QUnit.test('updates the duration after switching playlists', function() {
 
     return this.masterPlaylistController.masterPlaylistLoader_.master.playlists[1];
   };
-
+  // 1ms have passed to upload 1kb that gives us a bandwidth of 1024 / 1 * 8 * 1000 = 8192000
+  this.clock.tick(1);
   // segment 0
   standardXHRResponse(this.requests[2]);
   this.masterPlaylistController.mediaSource.sourceBuffers[0].trigger('updateend');
@@ -546,11 +551,46 @@ QUnit.test('updates the duration after switching playlists', function() {
            'updates the duration');
 
   // verify stats
-  QUnit.equal(this.player.tech_.hls.stats.bandwidth, Infinity, 'Live stream');
+  QUnit.equal(this.player.tech_.hls.stats.bandwidth, 8192000, 'Live stream');
+  QUnit.equal(this.player.tech_.hls.stats.mediaRequests, 1, '1 segment request');
+  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred,
+              1024,
+              '1024 bytes downloaded');
+});
+
+QUnit.test('playlist selection uses systemBandwidth', function() {
+  this.masterPlaylistController.mediaSource.trigger('sourceopen');
+  this.player.width(1000);
+  this.player.height(900);
+
+  // master
+  standardXHRResponse(this.requests[0]);
+  // media
+  standardXHRResponse(this.requests[1]);
+  QUnit.ok(/media3\.m3u8/i.test(this.requests[1].url), 'Selected the highest rendition');
+
+  // 1ms have passed to upload 1kb that gives us a bandwidth of 1024 / 1 * 8 * 1000 = 8192000
+  this.clock.tick(1);
+  // segment 0
+  standardXHRResponse(this.requests[2]);
+  // 20ms have passed to upload 1kb that gives us a throughput of 1024 / 20 * 8 * 1000 = 409600
+  this.clock.tick(20);
+  this.masterPlaylistController.mediaSource.sourceBuffers[0].trigger('updateend');
+  // systemBandwidth is 1 / (1 / 8192000 + 1 / 409600) = ~390095
+
+  // media1
+  standardXHRResponse(this.requests[3]);
+  QUnit.ok(/media\.m3u8/i.test(this.requests[3].url), 'Selected the rendition < 390095');
+
+  QUnit.ok(this.masterPlaylistController.mediaSource.duration !== 0,
+           'updates the duration');
+
+  // verify stats
+  QUnit.equal(this.player.tech_.hls.stats.bandwidth, 8192000, 'Live stream');
   QUnit.equal(this.player.tech_.hls.stats.mediaRequests, 1, '1 segment request');
   QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred,
-              16,
-              '16 bytes downloaded');
+              1024,
+              '1024 bytes downloaded');
 });
 
 QUnit.test('removes request timeout when segment timesout on lowest rendition',

test/test-helpers.js

@@ -289,7 +289,7 @@ export const standardXHRResponse = function(request, data) {
     data = testDataManifests[manifestName];
   }
 
-  request.response = new Uint8Array(16).buffer;
+  request.response = new Uint8Array(1024).buffer;
   request.respond(200, {'Content-Type': contentType}, data);
 };
 

test/videojs-contrib-hls.test.js

@@ -157,7 +157,7 @@ QUnit.test('stats are reset on each new source', function() {
   standardXHRResponse(this.requests.shift());
   standardXHRResponse(this.requests.shift());
 
-  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 16, 'stat is set');
+  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 1024, 'stat is set');
   this.player.src({
     src: 'manifest/master.m3u8',
     type: 'application/vnd.apple.mpegurl'
@@ -387,7 +387,7 @@ QUnit.test('starts downloading a segment on loadedmetadata', function() {
                     'the first segment is requested');
 
   // verify stats
-  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 16, '16 bytes');
+  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 1024, '1024 bytes');
   QUnit.equal(this.player.tech_.hls.stats.mediaRequests, 1, '1 request');
 });
 
@@ -465,10 +465,52 @@ QUnit.test('downloads media playlists after loading the master', function() {
                     'first segment requested');
 
   // verify stats
-  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 16, '16 bytes');
+  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 1024, '1024 bytes');
   QUnit.equal(this.player.tech_.hls.stats.mediaRequests, 1, '1 request');
 });
 
+QUnit.test('setting bandwidth resets throughput', function() {
+  this.player.src({
+    src: 'manifest/master.m3u8',
+    type: 'application/vnd.apple.mpegurl'
+  });
+  this.player.tech_.hls.throughput = 1000;
+  QUnit.strictEqual(this.player.tech_.hls.throughput,
+                    1000,
+                    'throughput is set');
+  this.player.tech_.hls.bandwidth = 20e10;
+  QUnit.strictEqual(this.player.tech_.hls.throughput,
+                    0,
+                    'throughput is reset when bandwidth is specified');
+});
+
+QUnit.test('a thoughput of zero is ignored in systemBandwidth', function() {
+  this.player.src({
+    src: 'manifest/master.m3u8',
+    type: 'application/vnd.apple.mpegurl'
+  });
+  this.player.tech_.hls.bandwidth = 20e10;
+  QUnit.strictEqual(this.player.tech_.hls.throughput,
+                    0,
+                    'throughput is reset when bandwidth is specified');
+  QUnit.strictEqual(this.player.tech_.hls.systemBandwidth,
+                    20e10,
+                    'systemBandwidth is the same as bandwidth');
+});
+
+QUnit.test('systemBandwidth is a combination of thoughput and bandwidth', function() {
+  this.player.src({
+    src: 'manifest/master.m3u8',
+    type: 'application/vnd.apple.mpegurl'
+  });
+  this.player.tech_.hls.bandwidth = 20e10;
+  this.player.tech_.hls.throughput = 20e10;
+  // 1 / ( 1 / 20e10 + 1 / 20e10) = 10e10
+  QUnit.strictEqual(this.player.tech_.hls.systemBandwidth,
+                    10e10,
+                    'systemBandwidth is the combination of bandwidth and throughput');
+});
+
 QUnit.test('upshifts if the initial bandwidth hint is high', function() {
   this.player.src({
     src: 'manifest/master.m3u8',
@@ -498,7 +540,7 @@ QUnit.test('upshifts if the initial bandwidth hint is high', function() {
   );
 
   // verify stats
-  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 16, '16 bytes');
+  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 1024, '1024 bytes');
   QUnit.equal(this.player.tech_.hls.stats.mediaRequests, 1, '1 request');
 });
 
@@ -525,7 +567,7 @@ QUnit.test('downshifts if the initial bandwidth hint is low', function() {
                     'first segment requested');
 
   // verify stats
-  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 16, '16 bytes');
+  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 1024, '1024 bytes');
   QUnit.equal(this.player.tech_.hls.stats.mediaRequests, 1, '1 request');
 });
 
@@ -1543,7 +1585,7 @@ QUnit.test('calling play() at the end of a video replays', function() {
   QUnit.equal(seekTime, 0, 'seeked to the beginning');
 
   // verify stats
-  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 16, '16 bytes');
+  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 1024, '1024 bytes');
   QUnit.equal(this.player.tech_.hls.stats.mediaRequests, 1, '1 request');
 });
 
@@ -1626,7 +1668,7 @@ QUnit.test('seeking should abort an outstanding key request and create a new one
               'urls should match');
 
   // verify stats
-  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 16, '16 bytes');
+  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 1024, '1024 bytes');
   QUnit.equal(this.player.tech_.hls.stats.mediaRequests, 1, '1 request');
 });
 
@@ -1672,7 +1714,7 @@ QUnit.test('switching playlists with an outstanding key request aborts request a
               'http://media.example.com/fileSequence52-A.ts',
               'requested the segment');
   // verify stats
-  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 16, '16 bytes');
+  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 1024, '1024 bytes');
   QUnit.equal(this.player.tech_.hls.stats.mediaRequests, 1, '1 request');
 });
 
@@ -2000,7 +2042,7 @@ QUnit.test('cleans up the buffer when loading live segments', function() {
                   'remove called with the right range');
 
   // verify stats
-  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 16, '16 bytes');
+  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 1024, '1024 bytes');
   QUnit.equal(this.player.tech_.hls.stats.mediaRequests, 1, '1 request');
 });
 
@@ -2053,7 +2095,7 @@ QUnit.test('cleans up the buffer based on currentTime when loading a live segmen
   QUnit.deepEqual(removes[0], [0, 80 - 60], 'remove called with the right range');
 
   // verify stats
-  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 16, '16 bytes');
+  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 1024, '1024 bytes');
   QUnit.equal(this.player.tech_.hls.stats.mediaRequests, 1, '1 request');
 });
 
@@ -2092,7 +2134,7 @@ QUnit.test('cleans up the buffer when loading VOD segments', function() {
   QUnit.deepEqual(removes[0], [0, 120 - 60], 'remove called with the right range');
 
   // verify stats
-  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 16, '16 bytes');
+  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 1024, '1024 bytes');
   QUnit.equal(this.player.tech_.hls.stats.mediaRequests, 1, '1 request');
 });
 
@@ -2237,7 +2279,7 @@ QUnit.test('Allows overriding the global beforeRequest function', function() {
   delete videojs.Hls.xhr.beforeRequest;
 
   // verify stats
-  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 16, 'seen above');
+  QUnit.equal(this.player.tech_.hls.stats.mediaBytesTransferred, 1024, 'seen above');
   QUnit.equal(this.player.tech_.hls.stats.mediaRequests, 1, 'one segment request');
 });
 
@@ -2336,7 +2378,7 @@ QUnit.test('stats are reset on dispose', function() {
   // media
   standardXHRResponse(this.requests.shift());
 
-  QUnit.equal(hls.stats.mediaBytesTransferred, 16, 'stat is set');
+  QUnit.equal(hls.stats.mediaBytesTransferred, 1024, 'stat is set');
   hls.dispose();
   QUnit.equal(hls.stats.mediaBytesTransferred, 0, 'stat is reset');
 });
@@ -2408,7 +2450,7 @@ QUnit.test('downloads additional playlists if required', function() {
 
   // verify stats
   QUnit.equal(hls.stats.bandwidth, 3000000, 'default');
-  QUnit.equal(hls.stats.mediaBytesTransferred, 16, '16 bytes');
+  QUnit.equal(hls.stats.mediaBytesTransferred, 1024, '1024 bytes');
   QUnit.equal(hls.stats.mediaRequests, 1, '1 request');
 });
 
@@ -2449,7 +2491,7 @@ QUnit.test('waits to download new segments until the media playlist is stable',
 
   // verify stats
   QUnit.equal(hls.stats.bandwidth, Infinity, 'default');
-  QUnit.equal(hls.stats.mediaBytesTransferred, 16, '16 bytes');
+  QUnit.equal(hls.stats.mediaBytesTransferred, 1024, '1024 bytes');
   QUnit.equal(hls.stats.mediaRequests, 1, '1 request');
 });
 
@@ -2566,7 +2608,11 @@ QUnit.test('blacklists playlist if key requests fail', function() {
              '#EXT-X-ENDLIST\n');
 
   // segment 1
+  if (/key\.php/i.test(this.requests[0].url)) {
+    standardXHRResponse(this.requests.pop());
+  } else {
     standardXHRResponse(this.requests.shift());
+  }
   // fail key
   this.requests.shift().respond(404);
   QUnit.ok(hls.playlists.media().excludeUntil > 0,
@@ -2609,6 +2655,6 @@ QUnit.test('treats invalid keys as a key request failure and blacklists playlist
   QUnit.equal(this.env.log.warn.calls, 1, 'logged warning for blacklist');
 
   // verify stats
-  QUnit.equal(hls.stats.mediaBytesTransferred, 16, '16 bytes');
+  QUnit.equal(hls.stats.mediaBytesTransferred, 1024, '1024 bytes');
   QUnit.equal(hls.stats.mediaRequests, 1, '1 request');
 });