fix(HLS): Fix presentation delay for small live playlists (eg: 3-4 se…

…gments) (#5687)
shaka-project · Oct 4, 2023 · 10b03e7 · 10b03e7
1 parent ac8bb85
commit 10b03e7
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Showing 2 changed files with 43 additions and 5 deletions.
diff --git a/lib/hls/hls_parser.js b/lib/hls/hls_parser.js
@@ -787,7 +787,7 @@ shaka.hls.HlsParser = class {
     // enough info here to determine the presentation type and duration.
     if (playlist.type == shaka.hls.PlaylistType.MEDIA) {
       if (this.isLive_()) {
-        this.changePresentationTimelineToLive_();
+        this.changePresentationTimelineToLive_(playlist);
         const delay = this.getUpdatePlaylistDelay_();
         this.updatePlaylistTimer_.tickAfter(/* seconds= */ delay);
       }
@@ -2054,7 +2054,7 @@ shaka.hls.HlsParser = class {
       if (this.isLive_() && !wasLive) {
         // Now that we know that the presentation is live, convert the timeline
         // to live.
-        this.changePresentationTimelineToLive_();
+        this.changePresentationTimelineToLive_(playlist);
       }
 
       // Copy values from the real stream info to our initial one.
@@ -2770,9 +2770,10 @@ shaka.hls.HlsParser = class {
 
 
   /**
+   * @param {!shaka.hls.Playlist} playlist
    * @private
    */
-  changePresentationTimelineToLive_() {
+  changePresentationTimelineToLive_(playlist) {
     // The live edge will be calculated from segments, so we don't need to
     // set a presentation start time.  We will assert later that this is
     // working as expected.
@@ -2795,8 +2796,12 @@ shaka.hls.HlsParser = class {
     } else if (this.presentationDelay_) {
       presentationDelay = this.presentationDelay_;
     } else {
-      const numberOfSegments = this.config_.hls.liveSegmentsDelay;
-      presentationDelay = this.maxTargetDuration_ * numberOfSegments;
+      const playlistSegments = playlist.segments.length;
+      let delaySegments = this.config_.hls.liveSegmentsDelay;
+      if (delaySegments > (playlistSegments - 2)) {
+        delaySegments = Math.max(1, playlistSegments - 2);
+      }
+      presentationDelay = this.maxTargetDuration_ * delaySegments;
     }
 
     this.presentationTimeline_.setPresentationStartTime(0);

diff --git a/test/hls/hls_live_unit.js b/test/hls/hls_live_unit.js
@@ -540,10 +540,43 @@ describe('HlsParser live', () => {
 
     it('sets 3 times target duration as presentation delay if not configured',
         async () => {
+          const media = [
+            '#EXTM3U\n',
+            '#EXT-X-TARGETDURATION:5\n',
+            '#EXT-X-MAP:URI="init.mp4",BYTERANGE="616@0"\n',
+            '#EXT-X-MEDIA-SEQUENCE:0\n',
+            '#EXTINF:2,\n',
+            'main.mp4\n',
+            '#EXTINF:2,\n',
+            'main.mp4\n',
+            '#EXTINF:2,\n',
+            'main.mp4\n',
+            '#EXTINF:2,\n',
+            'main.mp4\n',
+            '#EXTINF:2,\n',
+            'main.mp4\n',
+            '#EXTINF:2,\n',
+            'main.mp4\n',
+          ].join('');
           const manifest = await testInitialManifest(master, media);
           expect(manifest.presentationTimeline.getDelay()).toBe(15);
         });
 
+    it('sets 1 times target duration as presentation delay if there are not enough segments', async () => { // eslint-disable-line max-len
+      const media = [
+        '#EXTM3U\n',
+        '#EXT-X-TARGETDURATION:5\n',
+        '#EXT-X-MAP:URI="init.mp4",BYTERANGE="616@0"\n',
+        '#EXT-X-MEDIA-SEQUENCE:0\n',
+        '#EXTINF:2,\n',
+        'main.mp4\n',
+        '#EXTINF:2,\n',
+        'main.mp4\n',
+      ].join('');
+      const manifest = await testInitialManifest(master, media);
+      expect(manifest.presentationTimeline.getDelay()).toBe(5);
+    });
+
     it('sets presentation delay if defined', async () => {
       const media = [
         '#EXTM3U\n',