Merge pull request video-dev#3540 from video-dev/bugfix/live-fragment…

…-finder

Fix live fragment finder logic

src/controller/base-stream-controller.ts

@@ -808,7 +808,7 @@ export default class BaseStreamController
     levelDetails: LevelDetails,
     fragments: Array<Fragment>
   ): Fragment | null {
-    const { config, fragPrevious } = this;
+    const fragPrevious = this.fragPrevious;
     let frag: Fragment | null = null;
     if (fragPrevious) {
       if (levelDetails.hasProgramDateTime) {
@@ -819,7 +819,7 @@ export default class BaseStreamController
         frag = findFragmentByPDT(
           fragments,
           fragPrevious.endProgramDateTime,
-          config.maxFragLookUpTolerance
+          this.config.maxFragLookUpTolerance
         );
       }
       if (!frag) {
@@ -853,14 +853,14 @@ export default class BaseStreamController
       }
     } else {
       // Find a new start fragment when fragPrevious is null
-      const liveStart =
-        this.hls.liveSyncPosition ||
-        levelDetails.edge - levelDetails.totalduration / 2;
-      frag = this.getFragmentAtPosition(
-        liveStart,
-        levelDetails.edge,
-        levelDetails
-      );
+      const liveStart = this.hls.liveSyncPosition;
+      if (liveStart !== null) {
+        frag = this.getFragmentAtPosition(
+          liveStart,
+          levelDetails.edge,
+          levelDetails
+        );
+      }
     }
 
     return frag;

src/controller/fragment-finders.ts

@@ -157,11 +157,14 @@ export function pdtWithinToleranceTest(
   return endProgramDateTime - candidateLookupTolerance > pdtBufferEnd;
 }
 
-export function findFragWithCC(fragments, CC): Fragment | null {
+export function findFragWithCC(
+  fragments: Fragment[],
+  cc: number
+): Fragment | null {
   return BinarySearch.search(fragments, (candidate) => {
-    if (candidate.cc < CC) {
+    if (candidate.cc < cc) {
       return 1;
-    } else if (candidate.cc > CC) {
+    } else if (candidate.cc > cc) {
       return -1;
     } else {
       return 0;

src/controller/latency-controller.ts

@@ -83,15 +83,13 @@ export default class LatencyController implements ComponentAPI {
       return null;
     }
     const edge = levelDetails.edge;
-    return Math.min(
-      Math.max(
-        edge - levelDetails.totalduration,
-        liveEdge - targetLatency - this.edgeStalled
-      ),
+    const syncPosition = liveEdge - targetLatency - this.edgeStalled;
+    const min = edge - levelDetails.totalduration;
+    const max =
       edge -
-        ((this.config.lowLatencyMode && levelDetails.partTarget) ||
-          levelDetails.targetduration)
-    );
+      ((this.config.lowLatencyMode && levelDetails.partTarget) ||
+        levelDetails.targetduration);
+    return Math.min(Math.max(min, syncPosition), max);
   }
 
   get edgeStalled(): number {

tests/unit/controller/stream-controller.ts

@@ -106,9 +106,6 @@ describe('StreamController', function () {
     fragPrevious.cc = 0;
 
     const levelDetails = new LevelDetails('');
-    levelDetails.startSN = mockFragments[0].sn;
-    levelDetails.endSN = mockFragments[mockFragments.length - 1].sn;
-    levelDetails.fragments = mockFragments;
 
     const bufferEnd = fragPrevious.start + fragPrevious.duration;
     const end =
@@ -117,6 +114,14 @@ describe('StreamController', function () {
 
     beforeEach(function () {
       streamController['fragPrevious'] = fragPrevious;
+      levelDetails.startSN = mockFragments[0].sn;
+      levelDetails.endSN = mockFragments[mockFragments.length - 1].sn;
+      levelDetails.fragments = mockFragments;
+      levelDetails.targetduration = mockFragments[0].duration;
+      levelDetails.totalduration = mockFragments.reduce(
+        (sum, frag) => sum + frag.duration,
+        0
+      );
     });
 
     it('PTS search choosing wrong fragment (3 instead of 2) after level loaded', function () {
@@ -149,21 +154,127 @@ describe('StreamController', function () {
       expect(actual).to.equal(mockFragments[mockFragments.length - 1]);
     });
 
-    describe('PDT Searching during a live stream', function () {
-      it('PDT search choosing fragment after level loaded', function () {
+    describe('getInitialLiveFragment', function () {
+      let fragPrevious;
+
+      beforeEach(function () {
+        // onLevelUpdated updates  latencyController.levelDetails used to get live sync position
+        hls['latencyController']['levelDetails'] = levelDetails;
+
+        fragPrevious = new Fragment(PlaylistLevelType.MAIN, '');
+        // Fragment with PDT 1505502681523 in level 1 does not have the same sn as in level 2 where cc is 1
+        fragPrevious.cc = 0;
+        fragPrevious.programDateTime = 1505502681523;
+        fragPrevious.duration = 5.0;
+        fragPrevious.level = 1;
+        fragPrevious.start = 15.0;
+        fragPrevious.sn = 3;
+        streamController['fragPrevious'] = fragPrevious;
+
         levelDetails.PTSKnown = false;
         levelDetails.alignedSliding = false;
         levelDetails.live = true;
+      });
+
+      describe('with program-date-time', function () {
+        it('does PDT search, choosing fragment after level loaded', function () {
+          const foundFragment = streamController['getInitialLiveFragment'](
+            levelDetails,
+            mockFragments
+          );
+          expect(foundFragment).to.equal(
+            mockFragments[4],
+            `Expected sn 4, found sn segment ${
+              foundFragment ? foundFragment.sn : -1
+            }`
+          );
+        });
+      });
 
-        const foundFragment = streamController['getInitialLiveFragment'](
-          levelDetails,
-          mockFragments
-        );
-        const resultSN = foundFragment ? foundFragment.sn : -1;
-        expect(foundFragment).to.equal(
-          mockFragments[2],
-          'Expected sn 2, found sn segment ' + resultSN
-        );
+      describe('without program-date-time', function () {
+        const fragmentsWithoutPdt = mockFragments.map((frag) => {
+          const newFragment = new Fragment(PlaylistLevelType.MAIN, '');
+          return Object.assign(newFragment, frag, {
+            programDateTime: null,
+          });
+        });
+
+        beforeEach(function () {
+          // For sn lookup, cc much match
+          fragPrevious.cc = 1;
+
+          levelDetails.PTSKnown = false;
+          levelDetails.alignedSliding = false;
+          levelDetails.live = true;
+          levelDetails.startSN = fragmentsWithoutPdt[0].sn;
+          levelDetails.endSN =
+            fragmentsWithoutPdt[fragmentsWithoutPdt.length - 1].sn;
+          levelDetails.fragments = fragmentsWithoutPdt;
+        });
+
+        it('finds the next fragment to load based on the last fragment buffered', function () {
+          fragPrevious.sn = 0;
+          let foundFragment = streamController['getInitialLiveFragment'](
+            levelDetails,
+            fragmentsWithoutPdt
+          );
+          expect(foundFragment).to.equal(
+            fragmentsWithoutPdt[1],
+            `Expected sn 1, found sn segment ${
+              foundFragment ? foundFragment.sn : -1
+            }`
+          );
+
+          fragPrevious.sn = 3;
+          foundFragment = streamController['getInitialLiveFragment'](
+            levelDetails,
+            fragmentsWithoutPdt
+          );
+          expect(foundFragment).to.equal(
+            fragmentsWithoutPdt[4],
+            `Expected sn 4, found sn segment ${
+              foundFragment ? foundFragment.sn : -1
+            }`
+          );
+        });
+
+        it('finds the first fragment to load when starting or re-syncing with a live stream', function () {
+          streamController['fragPrevious'] = null;
+
+          const foundFragment = streamController['getInitialLiveFragment'](
+            levelDetails,
+            fragmentsWithoutPdt
+          );
+          expect(foundFragment).to.equal(
+            fragmentsWithoutPdt[2],
+            `Expected sn 2, found sn segment ${
+              foundFragment ? foundFragment.sn : -1
+            }`
+          );
+        });
+
+        it('finds the fragment with the same cc when there is no sn match', function () {
+          fragPrevious.cc = 0;
+          const foundFragment = streamController['getInitialLiveFragment'](
+            levelDetails,
+            fragmentsWithoutPdt
+          );
+          expect(foundFragment).to.equal(
+            fragmentsWithoutPdt[0],
+            `Expected sn 0, found sn segment ${
+              foundFragment ? foundFragment.sn : -1
+            }`
+          );
+        });
+
+        it('returns null when there is no cc match with the previous segment', function () {
+          fragPrevious.cc = 2;
+          const foundFragment = streamController['getInitialLiveFragment'](
+            levelDetails,
+            fragmentsWithoutPdt
+          );
+          expect(foundFragment).to.equal(null);
+        });
       });
     });
   });