From 30fd63abf2d40b4fd9975515008f07b37508fb5a Mon Sep 17 00:00:00 2001
From: Sacha Elkaim <37674225+sachaelkaim@users.noreply.github.com>
Date: Tue, 4 Apr 2023 05:12:21 -0400
Subject: [PATCH] fix: Handle empty media segments for Mp4VttParser (#5131)

Fixes #4429
---
 lib/text/mp4_vtt_parser.js       | 4 ++++
 test/text/mp4_vtt_parser_unit.js | 8 ++++++++
 2 files changed, 12 insertions(+)

diff --git a/lib/text/mp4_vtt_parser.js b/lib/text/mp4_vtt_parser.js
index 570e74f6e6..90f34eba08 100644
--- a/lib/text/mp4_vtt_parser.js
+++ b/lib/text/mp4_vtt_parser.js
@@ -97,6 +97,10 @@ shaka.text.Mp4VttParser = class {
    * @export
    */
   parseMedia(data, time) {
+    if (!data.length) {
+      return [];
+    }
+
     if (!this.timescale_) {
       // Missing timescale for VTT content. We should have seen the init
       // segment.
diff --git a/test/text/mp4_vtt_parser_unit.js b/test/text/mp4_vtt_parser_unit.js
index a6e945646e..46e49d0660 100644
--- a/test/text/mp4_vtt_parser_unit.js
+++ b/test/text/mp4_vtt_parser_unit.js
@@ -171,6 +171,14 @@ describe('Mp4VttParser', () => {
     verifyHelper(cues, result);
   });
 
+  it('handles empty media segments', () => {
+    const parser = new shaka.text.Mp4VttParser();
+    parser.parseInit(vttInitSegment);
+    const time = {periodStart: 0, segmentStart: 0, segmentEnd: 0, vttOffset: 0};
+    const result = parser.parseMedia(new Uint8Array(0), time);
+    verifyHelper([], result);
+  });
+
   it('rejects init segment with no vtt', () => {
     const error = shaka.test.Util.jasmineError(new shaka.util.Error(
         shaka.util.Error.Severity.CRITICAL,