From 3d51b7588b94432fc622290cc3ac3ae7e573787d Mon Sep 17 00:00:00 2001
From: Mads Odgaard <mads.odgaard@frameo.com>
Date: Fri, 3 Jul 2026 09:53:44 +0200
Subject: [PATCH] fix bug with empty audio track

---
 Sources/NextLevelSessionExporter.swift | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Sources/NextLevelSessionExporter.swift b/Sources/NextLevelSessionExporter.swift
index 91c664b..4cbc707 100644
--- a/Sources/NextLevelSessionExporter.swift
+++ b/Sources/NextLevelSessionExporter.swift
@@ -675,6 +675,13 @@ extension NextLevelSessionExporter {
             }
         }
 
+        // If every audio track was filtered out above (e.g. asset only has APAC/spatial audio),
+        // there's nothing left for AVAssetReaderAudioMixOutput, which requires at least one track.
+        guard audioTracksToUse.count > 0 else {
+            self._audioOutput = nil
+            return
+        }
+
         self._audioOutput = AVAssetReaderAudioMixOutput(audioTracks: audioTracksToUse, audioSettings: nil)
         self._audioOutput?.alwaysCopiesSampleData = false
         self._audioOutput?.audioMix = self.audioMix