fix: bad timeline changes (#1526)

src/segment-loader.js

@@ -406,6 +406,33 @@ export const shouldWaitForTimelineChange = ({
   return false;
 };
 
+export const shouldFixBadTimelineChanges = (timelineChangeController) => {
+  if (!timelineChangeController) {
+    return false;
+  }
+  const pendingAudioTimelineChange = timelineChangeController.pendingTimelineChange({ type: 'audio' });
+  const pendingMainTimelineChange = timelineChangeController.pendingTimelineChange({ type: 'main' });
+  const hasPendingTimelineChanges = pendingAudioTimelineChange && pendingMainTimelineChange;
+  const differentPendingChanges = hasPendingTimelineChanges && pendingAudioTimelineChange.to !== pendingMainTimelineChange.to;
+  const isNotInitialPendingTimelineChange = hasPendingTimelineChanges && pendingAudioTimelineChange.from !== -1 && pendingMainTimelineChange.from !== -1;
+
+  if (isNotInitialPendingTimelineChange && differentPendingChanges) {
+    return true;
+  }
+
+  return false;
+};
+
+export const fixBadTimelineChange = (segmentLoader) => {
+  if (!segmentLoader) {
+    return;
+  }
+  segmentLoader.pause();
+  segmentLoader.abort_();
+  segmentLoader.resetEverything();
+  segmentLoader.load();
+};
+
 export const mediaDuration = (timingInfos) => {
   let maxDuration = 0;
 
@@ -2130,6 +2157,9 @@ Fetch At Buffer: ${this.fetchAtBuffer_}
         audioDisabled: this.audioDisabled_
       })
     ) {
+      if (shouldFixBadTimelineChanges(this.timelineChangeController_)) {
+        fixBadTimelineChange(this);
+      }
       return false;
     }
 
@@ -2180,6 +2210,7 @@ Fetch At Buffer: ${this.fetchAtBuffer_}
       return false;
     }
 
+    // we need to allow an append here even if we're moving to different timelines.
     if (
       shouldWaitForTimelineChange({
         timelineChangeController: this.timelineChangeController_,
@@ -2189,6 +2220,9 @@ Fetch At Buffer: ${this.fetchAtBuffer_}
         audioDisabled: this.audioDisabled_
       })
     ) {
+      if (shouldFixBadTimelineChanges(this.timelineChangeController_)) {
+        fixBadTimelineChange(this);
+      }
       return false;
     }
 

test/segment-loader.test.js

@@ -9,7 +9,9 @@ import {
   mediaDuration,
   getTroublesomeSegmentDurationMessage,
   getSyncSegmentCandidate,
-  segmentInfoString
+  segmentInfoString,
+  shouldFixBadTimelineChanges,
+  fixBadTimelineChange
 } from '../src/segment-loader';
 import mp4probe from 'mux.js/lib/mp4/probe';
 import {
@@ -465,6 +467,90 @@ QUnit.test('main loader does not wait if pending audio timeline change matches s
   );
 });
 
+QUnit.module('shouldFixBadTimelineChange');
+
+QUnit.test('shouldFixBadTimelineChange returns true when timelines are both changing to different timelines', function(assert) {
+  const timelineChangeController = {
+    pendingTimelineChange({ type }) {
+      if (type === 'audio') {
+        return { from: 1, to: 2 };
+      } else if (type === 'main') {
+        return { from: 2, to: 1 };
+      }
+    }
+  };
+
+  assert.ok(shouldFixBadTimelineChanges(timelineChangeController), 'should fix a bad timeline change');
+});
+
+QUnit.test('shouldFixBadTimelineChange returns false when only one timeline has a pending change', function(assert) {
+  const timelineChangeController = {
+    pendingTimelineChange({ type }) {
+      if (type === 'audio') {
+        return { from: 1, to: 2 };
+      }
+    }
+  };
+
+  assert.notOk(shouldFixBadTimelineChanges(timelineChangeController), 'should not fix a timeline change');
+});
+
+QUnit.test('shouldFixBadTimelineChange returns false when both timelines are changing to the same value', function(assert) {
+  const timelineChangeController = {
+    pendingTimelineChange({ type }) {
+      if (type === 'audio') {
+        return { from: 1, to: 2 };
+      } else if (type === 'main') {
+        return { from: 1, to: 2 };
+      }
+    }
+  };
+
+  assert.notOk(shouldFixBadTimelineChanges(timelineChangeController), 'should not fix a good timeline change');
+});
+
+QUnit.test('shouldFixBadTimelineChange returns false when timelineChangeController is undefined', function(assert) {
+  const timelineChangeController = undefined;
+
+  assert.notOk(shouldFixBadTimelineChanges(timelineChangeController), 'should not fix a timeline change with no timelineChangeController');
+});
+
+QUnit.module('fixBadTimelineChange');
+
+QUnit.test('fixBadTimelineChange calls pause, resetEverything and load on a segmentLoader', function(assert) {
+  let pauseCalls = 0;
+  let resetEverythingCalls = 0;
+  let loadCalls = 0;
+  let abortCalls = 0;
+  let mockSegmentLoader = {
+    pause() {
+      pauseCalls++;
+    },
+    abort_() {
+      abortCalls++;
+    },
+    resetEverything() {
+      resetEverythingCalls++;
+    },
+    load() {
+      loadCalls++;
+    }
+  };
+
+  fixBadTimelineChange(mockSegmentLoader);
+  assert.equal(pauseCalls, 1, 'calls pause once');
+  assert.equal(resetEverythingCalls, 1, 'calls resetEverything once');
+  assert.equal(loadCalls, 1, 'calls load once');
+
+  // early return if undefined. call counts remain the same.
+  mockSegmentLoader = undefined;
+  fixBadTimelineChange(mockSegmentLoader);
+  assert.equal(pauseCalls, 1, 'calls pause once');
+  assert.equal(resetEverythingCalls, 1, 'calls resetEverything once');
+  assert.equal(loadCalls, 1, 'calls load once');
+  assert.equal(abortCalls, 1, 'calls abort once');
+});
+
 QUnit.module('safeBackBufferTrimTime');
 
 QUnit.test('uses 30s before playhead when seekable start is 0', function(assert) {
@@ -1582,6 +1668,132 @@ QUnit.module('SegmentLoader', function(hooks) {
       });
     });
 
+    QUnit.test('hasEnoughInfoToLoad_ calls fixBadTimelineChange', function(assert) {
+      loader.dispose();
+      loader = new SegmentLoader(LoaderCommonSettings.call(this, {
+        loaderType: 'audio'
+      }), {});
+      const origPause = loader.pause;
+      const origLoad = loader.load;
+      const origResetEverything = loader.resetEverything;
+      let pauseCalls = 0;
+      let loadCalls = 0;
+      let resetEverythingCalls = 0;
+
+      loader.pause = () => {
+        pauseCalls++;
+        origPause.call(loader);
+      };
+      loader.load = () => {
+        loadCalls++;
+        origLoad.call(loader);
+      };
+      loader.resetEverything = () => {
+        resetEverythingCalls++;
+        origResetEverything.call(loader);
+      };
+      loader.timelineChangeController_.pendingTimelineChange = ({ type }) => {
+        if (type === 'audio') {
+          return {
+            from: 3,
+            to: 2
+          };
+        } else if (type === 'main') {
+          return {
+            from: 0,
+            to: 1
+          };
+        }
+      };
+
+      const playlist = playlistWithDuration(20);
+
+      playlist.discontinuityStarts = [1];
+      loader.getCurrentMediaInfo_ = () => {
+        return {
+          hasVideo: true,
+          hasAudio: false,
+          isMuxed: false
+        };
+      };
+
+      return this.setupMediaSource(loader.mediaSource_, loader.sourceUpdater_).then(() => {
+        loader.playlist(playlist);
+        loader.load();
+        this.clock.tick(1);
+        assert.equal(pauseCalls, 1, '1 pause call expected');
+        assert.equal(loadCalls, 2, '2 load calls expected');
+        assert.equal(resetEverythingCalls, 2, '1 load calls expected');
+      });
+    });
+
+    QUnit.test('hasEnoughInfoToAppend_ calls fixBadTimelineChange', function(assert) {
+      loader.dispose();
+      loader = new SegmentLoader(LoaderCommonSettings.call(this, {
+        loaderType: 'main'
+      }), {});
+      const origPause = loader.pause;
+      const origLoad = loader.load;
+      const origResetEverything = loader.resetEverything;
+      let pauseCalls = 0;
+      let loadCalls = 0;
+      let resetEverythingCalls = 0;
+
+      loader.pause = () => {
+        pauseCalls++;
+        origPause.call(loader);
+      };
+      loader.load = () => {
+        loadCalls++;
+        origLoad.call(loader);
+      };
+      loader.resetEverything = () => {
+        resetEverythingCalls++;
+        origResetEverything.call(loader);
+      };
+      loader.timelineChangeController_.pendingTimelineChange = ({ type }) => {
+        if (type === 'audio') {
+          return {
+            from: 3,
+            to: 2
+          };
+        } else if (type === 'main') {
+          return {
+            from: 0,
+            to: 1
+          };
+        }
+      };
+      this.sourceUpdater_.ready = () => {
+        return true;
+      };
+
+      const playlist = playlistWithDuration(20);
+
+      playlist.discontinuityStarts = [1];
+      loader.getCurrentMediaInfo_ = () => {
+        return {
+          hasVideo: true,
+          hasAudio: false,
+          isMuxed: false
+        };
+      };
+      loader.pendingSegment_ = {
+        foo: 'bar',
+        videoTimingInfo: 1
+      };
+      loader.audioDisabled_ = true;
+
+      return this.setupMediaSource(loader.mediaSource_, loader.sourceUpdater_).then(() => {
+        loader.playlist(playlist);
+        loader.load();
+        this.clock.tick(1);
+        assert.equal(pauseCalls, 1, '1 pause call expected');
+        assert.equal(loadCalls, 2, '2 load calls expected');
+        assert.equal(resetEverythingCalls, 2, '1 load calls expected');
+      });
+    });
+
     QUnit.test('audio loader does not wait to request segment even if timestamp offset is nonzero', function(assert) {
       loader.dispose();
       loader = new SegmentLoader(LoaderCommonSettings.call(this, {