diff --git a/src/demux/mp4demuxer.ts b/src/demux/mp4demuxer.ts
index 5886b942713..bdfe5d8c5b9 100644
--- a/src/demux/mp4demuxer.ts
+++ b/src/demux/mp4demuxer.ts
@@ -20,6 +20,7 @@ import {
   parseInitSegment,
   RemuxerTrackIdConfig,
   hasMoofData,
+  IEmsgParsingData,
 } from '../utils/mp4-tools';
 import { dummyTrack } from './dummy-demuxed-track';
 import type { HlsEventEmitter } from '../events';
@@ -155,10 +156,7 @@ class MP4Demuxer implements Demuxer {
         emsgs.forEach((data: Uint8Array) => {
           const emsgInfo = parseEmsg(data);
           if (emsgSchemePattern.test(emsgInfo.schemeIdUri)) {
-            const pts = Number.isFinite(emsgInfo.presentationTime)
-              ? emsgInfo.presentationTime! / emsgInfo.timeScale
-              : timeOffset +
-                emsgInfo.presentationTimeDelta! / emsgInfo.timeScale;
+            const pts = getEmsgStartTime(emsgInfo, timeOffset);
             let duration =
               emsgInfo.eventDuration === 0xffffffff
                 ? Number.POSITIVE_INFINITY
@@ -180,11 +178,7 @@ class MP4Demuxer implements Demuxer {
             this.config.enableEmsgKLVMetadata &&
             emsgInfo.schemeIdUri.startsWith('urn:misb:KLV:bin:1910.1')
           ) {
-            const pts = Number.isFinite(emsgInfo.presentationTime)
-              ? emsgInfo.presentationTime! / emsgInfo.timeScale
-              : timeOffset +
-                emsgInfo.presentationTimeDelta! / emsgInfo.timeScale;
-
+            const pts = getEmsgStartTime(emsgInfo, timeOffset);
             id3Track.samples.push({
               data: emsgInfo.payload,
               len: emsgInfo.payload.byteLength,
@@ -222,4 +216,14 @@ class MP4Demuxer implements Demuxer {
   }
 }
 
+function getEmsgStartTime(
+  emsgInfo: IEmsgParsingData,
+  timeOffset: number,
+): number {
+  return Number.isFinite(emsgInfo.presentationTime)
+    ? (emsgInfo.presentationTime as number) / emsgInfo.timeScale
+    : timeOffset +
+        (emsgInfo.presentationTimeDelta as number) / emsgInfo.timeScale;
+}
+
 export default MP4Demuxer;