From 14e61a7368ddbd66c4b10f3b0475840cc50512bd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=81lvaro=20Velad=20Galv=C3=A1n?= <alvaro.velad@mirada.tv>
Date: Tue, 10 May 2022 22:19:46 +0200
Subject: [PATCH] feat(hls): Add support for EXT-X-GAP (#4208)

Related to 42eecc84
Closes #1308
---
 lib/hls/hls_parser.js         | 12 +++++++++++-
 lib/media/streaming_engine.js |  7 +++++++
 lib/player.js                 | 23 ++++++++++++++++++-----
 lib/util/error.js             |  6 ++++++
 4 files changed, 42 insertions(+), 6 deletions(-)

diff --git a/lib/hls/hls_parser.js b/lib/hls/hls_parser.js
index 9f667f73cd..82d62e4fd7 100644
--- a/lib/hls/hls_parser.js
+++ b/lib/hls/hls_parser.js
@@ -1902,6 +1902,11 @@ shaka.hls.HlsParser = class {
         const pAbsoluteUri = shaka.hls.Utils.constructAbsoluteUri(
             absoluteMediaPlaylistUri, pUri);
 
+        let partialStatus = shaka.media.SegmentReference.Status.AVAILABLE;
+        if (item.getAttributeValue('GAP') == 'YES') {
+          partialStatus = shaka.media.SegmentReference.Status.MISSING;
+        }
+
         const partial = new shaka.media.SegmentReference(
             pStartTime,
             pEndTime,
@@ -1911,7 +1916,12 @@ shaka.hls.HlsParser = class {
             initSegmentReference,
             /* timestampOffset= */ 0, // This value is ignored in sequence mode.
             /* appendWindowStart= */ 0,
-            /* appendWindowEnd= */ Infinity);
+            /* appendWindowEnd= */ Infinity,
+            /* partialReferences= */ [],
+            /* tilesLayout= */ '',
+            /* tileDuration= */ null,
+            /* syncTime= */ null,
+            partialStatus);
         partialSegmentRefs.push(partial);
       } // for-loop of hlsSegment.partialSegments
     } else {
diff --git a/lib/media/streaming_engine.js b/lib/media/streaming_engine.js
index 3d79bdc645..ef55a7fdad 100644
--- a/lib/media/streaming_engine.js
+++ b/lib/media/streaming_engine.js
@@ -1215,6 +1215,13 @@ shaka.media.StreamingEngine = class {
     mediaState.performingUpdate = true;
 
     try {
+      if (reference.getStatus() ==
+          shaka.media.SegmentReference.Status.MISSING) {
+        throw new shaka.util.Error(
+            shaka.util.Error.Severity.RECOVERABLE,
+            shaka.util.Error.Category.NETWORK,
+            shaka.util.Error.Code.SEGMENT_MISSING);
+      }
       await this.initSourceBuffer_(mediaState, reference);
       this.destroyer_.ensureNotDestroyed();
       if (this.fatalError_) {
diff --git a/lib/player.js b/lib/player.js
index 45a4e8f61f..4e42b7f563 100644
--- a/lib/player.js
+++ b/lib/player.js
@@ -5521,17 +5521,30 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
    * @private
    */
   tryToRecoverFromError_(error) {
-    if (error.code !== shaka.util.Error.Code.HTTP_ERROR ||
-      error.category !== shaka.util.Error.Category.NETWORK) {
+    if ((error.code != shaka.util.Error.Code.HTTP_ERROR &&
+      error.code != shaka.util.Error.Code.SEGMENT_MISSING) ||
+      error.category != shaka.util.Error.Category.NETWORK) {
       return false;
     }
 
-    const maxDisabledTime = this.config_.streaming.maxDisabledTime;
+    let maxDisabledTime = this.config_.streaming.maxDisabledTime;
     if (maxDisabledTime == 0) {
-      return false;
+      if (error.code == shaka.util.Error.Code.SEGMENT_MISSING) {
+        // Spec: https://datatracker.ietf.org/doc/html/draft-pantos-hls-rfc8216bis#section-6.3.3
+        // The client SHOULD NOT attempt to load Media Segments that have been
+        // marked with an EXT-X-GAP tag, or to load Partial Segments with a
+        // GAP=YES attribute. Instead, clients are encouraged to look for
+        // another Variant Stream of the same Rendition which does not have the
+        // same gap, and play that instead.
+        maxDisabledTime = 1;
+      } else {
+        return false;
+      }
     }
 
-    shaka.log.debug('Recoverable NETWORK HTTP_ERROR, trying to recover...');
+    if (error.code == shaka.util.Error.Code.HTTP_ERROR) {
+      shaka.log.debug('Recoverable NETWORK HTTP_ERROR, trying to recover...');
+    }
 
     // Obtain the active variant and disable it from manifest variants
     const activeVariantTrack = this.getVariantTracks().find((t) => t.active);
diff --git a/lib/util/error.js b/lib/util/error.js
index 8185ced008..f15eddce1c 100644
--- a/lib/util/error.js
+++ b/lib/util/error.js
@@ -267,6 +267,12 @@ shaka.util.Error.Code = {
    */
   'ATTEMPTS_EXHAUSTED': 1010,
 
+  /**
+   * The segment is missing.
+   * <br> error.data[0] is the URI.
+   */
+  'SEGMENT_MISSING': 1011,
+
 
   /** The text parser failed to parse a text stream due to an invalid header. */
   'INVALID_TEXT_HEADER': 2000,