Drop spatial audio tracks to fix encoding iPhone 16 videos

Fixes #1

Package.swift

@@ -23,6 +23,7 @@ let package = Package(
                 .process("Resources/test-720p-h264-24fps.mov"),
                 .process("Resources/test-no-audio.mp4"),
                 .process("Resources/test-no-video.m4a"),
+                .process("Resources/test-spatial-audio.mov"),
             ]
         ),
     ]

Sources/SJSAssetExportSession/Array+Extensions.swift

@@ -0,0 +1,18 @@
+//
+//  Array+Extensions.swift
+//  SJSAssetExportSession
+//
+//  Created by Sami Samhuri on 2024-10-04.
+//
+
+extension Array {
+    func filterAsync(_ isIncluded: (Element) async throws -> Bool) async rethrows -> [Element] {
+        var result: [Element] = []
+        for element in self {
+            if try await isIncluded(element) {
+                result.append(element)
+            }
+        }
+        return result
+    }
+}

Sources/SJSAssetExportSession/SampleWriter.swift

@@ -70,12 +70,16 @@ actor SampleWriter {
         writer.shouldOptimizeForNetworkUse = optimizeForNetworkUse
         writer.metadata = metadata
 
+        // Filter out disabled tracks to avoid problems encoding spatial audio. Ideally this would
+        // preserve track groups and make that all configurable.
         let audioTracks = try await asset.loadTracks(withMediaType: .audio)
+            .filterAsync { try await $0.load(.isEnabled) }
         // Audio is optional so only validate output settings when it's applicable.
         if !audioTracks.isEmpty {
             try Self.validateAudio(outputSettings: audioOutputSettings, writer: writer)
         }
         let videoTracks = try await asset.loadTracks(withMediaType: .video)
+            .filterAsync { try await $0.load(.isEnabled) }
         guard !videoTracks.isEmpty else { throw Error.setupFailure(.videoTracksEmpty) }
         try Self.validateVideo(outputSettings: videoOutputSettings, writer: writer)
         Self.warnAboutMismatchedVideoSize(

Tests/SJSAssetExportSessionTests/SJSAssetExportSessionTests.swift

@@ -357,4 +357,21 @@ final class ExportSessionTests {
         })?.load(.value) as? NSString
         #expect(commonMetadataValue == "+48.50176+123.34368/")
     }
+
+    @Test func test_works_with_spatial_audio_track() async throws {
+        let sourceURL = resourceURL(named: "test-spatial-audio.mov")
+        let destinationURL = makeTemporaryURL()
+
+        let subject = ExportSession()
+        try await subject.export(
+            asset: makeAsset(url: sourceURL),
+            video: .codec(.h264, size: CGSize(width: 720, height: 1280)),
+            to: destinationURL.url,
+            as: .mp4
+        )
+
+        let exportedAsset = AVURLAsset(url: destinationURL.url)
+        let audioTracks = try await exportedAsset.loadTracks(withMediaType: .audio)
+        #expect(audioTracks.count == 1)
+    }
 }