fix(DASH): Ignore early segments in a period (#7910)

Now we always are fitting the timeline

Backported to v4.9.x

Author: avelad

lib/dash/segment_template.js

@@ -121,24 +121,6 @@ shaka.dash.SegmentTemplate = class {
 
       shaka.log.debug(`New manifest ${periodStart} - ${periodEnd}`);
 
-      /* When to fit segments.  All refactors should honor/update this table:
-       *
-       * | dynamic | infinite | last   | should | notes                     |
-       * |         | period   | period | fit    |                           |
-       * | ------- | -------- | ------ | ------ | ------------------------- |
-       * |     F   |     F    |    X   |    T   | typical VOD               |
-       * |     F   |     T    |    X   |    X   | impossible: infinite VOD  |
-       * |     T   |     F    |    F   |    T   | typical live, old period  |
-       * |     T   |     F    |    T   |    F   | typical IPR               |
-       * |     T   |     T    |    F   |    X   | impossible: old, infinite |
-       * |     T   |     T    |    T   |    F   | typical live, new period  |
-       */
-
-      // We never fit the final period of dynamic content, which could be
-      // infinite live (with no limit to fit to) or IPR (which would expand the
-      // most recent segment to the end of the presentation).
-      const shouldFit = !(context.dynamic && context.periodInfo.isLastPeriod);
-
       if (!segmentIndex) {
         shaka.log.debug(`Creating TSI with end ${periodEnd}`);
         segmentIndex = new TimelineSegmentIndex(
@@ -149,14 +131,13 @@ shaka.dash.SegmentTemplate = class {
             periodStart,
             periodEnd,
             initSegmentReference,
-            shouldFit,
             aesKey,
             context.representation.segmentSequenceCadence,
         );
       } else {
         const tsi = /** @type {!TimelineSegmentIndex} */(segmentIndex);
         tsi.appendTemplateInfo(
-            info, periodStart, periodEnd, shouldFit, initSegmentReference);
+            info, periodStart, periodEnd, initSegmentReference);
 
         const availabilityStart =
           context.presentationTimeline.getSegmentAvailabilityStart();
@@ -184,7 +165,7 @@ shaka.dash.SegmentTemplate = class {
           if (segmentIndex instanceof shaka.dash.TimelineSegmentIndex &&
               segmentIndex.isEmpty()) {
             segmentIndex.appendTemplateInfo(info, periodStart,
-                periodEnd, shouldFit, initSegmentReference);
+                periodEnd, initSegmentReference);
           }
           return Promise.resolve(segmentIndex);
         },
@@ -668,38 +649,42 @@ shaka.dash.TimelineSegmentIndex = class extends shaka.media.SegmentIndex {
    * @param {number} periodStart
    * @param {number} periodEnd
    * @param {shaka.media.InitSegmentReference} initSegmentReference
-   * @param {boolean} shouldFit
    * @param {shaka.extern.aesKey|undefined} aesKey
    * @param {number} segmentSequenceCadence
   */
   constructor(templateInfo, representationId, bandwidth, getBaseUris,
-      periodStart, periodEnd, initSegmentReference, shouldFit,
+      periodStart, periodEnd, initSegmentReference,
       aesKey, segmentSequenceCadence) {
     super([]);
 
     /** @private {?shaka.dash.SegmentTemplate.SegmentTemplateInfo} */
     this.templateInfo_ = templateInfo;
+
     /** @private {?string} */
     this.representationId_ = representationId;
+
     /** @private {number} */
     this.bandwidth_ = bandwidth;
-    /** @private {function():Array.<string>} */
+
+    /** @private {function(): Array<string>} */
     this.getBaseUris_ = getBaseUris;
+
     /** @private {number} */
     this.periodStart_ = periodStart;
+
     /** @private {number} */
     this.periodEnd_ = periodEnd;
+
     /** @private {shaka.media.InitSegmentReference} */
     this.initSegmentReference_ = initSegmentReference;
+
     /** @private {shaka.extern.aesKey|undefined} */
     this.aesKey_ = aesKey;
+
     /** @private {number} */
     this.segmentSequenceCadence_ = segmentSequenceCadence;
 
-
-    if (shouldFit) {
-      this.fitTimeline();
-    }
+    this.fitTimeline();
   }
 
   /**
@@ -767,11 +752,9 @@ shaka.dash.TimelineSegmentIndex = class extends shaka.media.SegmentIndex {
    * @param {shaka.dash.SegmentTemplate.SegmentTemplateInfo} info
    * @param {number} periodStart
    * @param {number} periodEnd
-   * @param {boolean} shouldFit
    * @param {shaka.media.InitSegmentReference} initSegmentReference
    */
-  appendTemplateInfo(info, periodStart, periodEnd, shouldFit,
-      initSegmentReference) {
+  appendTemplateInfo(info, periodStart, periodEnd, initSegmentReference) {
     this.updateInitSegmentReference(initSegmentReference);
     if (!this.templateInfo_) {
       this.templateInfo_ = info;
@@ -805,9 +788,7 @@ shaka.dash.TimelineSegmentIndex = class extends shaka.media.SegmentIndex {
       }
     }
 
-    if (shouldFit) {
-      this.fitTimeline();
-    }
+    this.fitTimeline();
   }
 
   /**
@@ -852,14 +833,19 @@ shaka.dash.TimelineSegmentIndex = class extends shaka.media.SegmentIndex {
       return;
     }
     const timeline = this.templateInfo_.timeline;
-    while (timeline.length) {
-      const lastTimePeriod = timeline[timeline.length - 1];
-      if (lastTimePeriod.start >= this.periodEnd_) {
-        timeline.pop();
+    goog.asserts.assert(timeline, 'Timeline should be non-null!');
+    const newTimeline = [];
+    for (const range of timeline) {
+      if (range.start >= this.periodEnd_) {
+        // Starts after end of period.
+      } else if (range.end <= 0) {
+        // Ends before start of period.
       } else {
-        break;
+        // Usable.
+        newTimeline.push(range);
       }
     }
+    this.templateInfo_.timeline = newTimeline;
 
     this.evict(this.periodStart_);