From b897d3c8c1cd4ac2eb6200724f538f412b913f0f Mon Sep 17 00:00:00 2001
From: Rob Walch <rwalch@apple.com>
Date: Mon, 8 May 2023 13:45:56 -0400
Subject: [PATCH] Fix AV desync regression in v1.4.0 when mp4 audio track
 timestamps start before video track timestamps Fixes #5452

---
 src/remux/passthrough-remuxer.ts | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/src/remux/passthrough-remuxer.ts b/src/remux/passthrough-remuxer.ts
index b9bf783334f..df1023e0901 100644
--- a/src/remux/passthrough-remuxer.ts
+++ b/src/remux/passthrough-remuxer.ts
@@ -167,20 +167,25 @@ class PassThroughRemuxer implements Remuxer {
       this.emitInitSegment = false;
     }
 
+    const duration = getDuration(data, initData);
     const startDTS = getStartDTS(initData, data);
     const decodeTime = startDTS === null ? timeOffset : startDTS;
     if (
-      isInvalidInitPts(initPTS, decodeTime, timeOffset) ||
+      isInvalidInitPts(initPTS, decodeTime, timeOffset, duration) ||
       (initSegment.timescale !== initPTS.timescale && accurateTimeOffset)
     ) {
       initSegment.initPTS = decodeTime - timeOffset;
+      if (initPTS && initPTS.timescale === 1) {
+        logger.warn(
+          `Adjusting initPTS by ${initSegment.initPTS - initPTS.baseTime}`
+        );
+      }
       this.initPTS = initPTS = {
         baseTime: initSegment.initPTS,
         timescale: 1,
       };
     }
 
-    const duration = getDuration(data, initData);
     const startTime = audioTrack
       ? decodeTime - initPTS.baseTime / initPTS.timescale
       : (lastEndTime as number);
@@ -244,14 +249,16 @@ class PassThroughRemuxer implements Remuxer {
 function isInvalidInitPts(
   initPTS: RationalTimestamp | null,
   startDTS: number,
-  timeOffset: number
+  timeOffset: number,
+  duration: number
 ): initPTS is null {
   if (initPTS === null) {
     return true;
   }
-  // InitPTS is invalid when it would cause start time to be negative, or distance from time offset to be more than 1 second
+  // InitPTS is invalid when distance from program would be more than segment duration or a minimum of one second
+  const minDuration = Math.max(duration, 1);
   const startTime = startDTS - initPTS.baseTime / initPTS.timescale;
-  return startTime < 0 && Math.abs(startTime - timeOffset) > 1;
+  return Math.abs(startTime - timeOffset) > minDuration;
 }
 
 function getParsedTrackCodec(