[iOS] Fix External Subtitle Selection (#1445)

* | Type          | Internal Subtitles | Internal Audio | External Subtitles | External Audio |
|---------------|-----------------|--------------------|----------------|----------------|
| Transcode     | ✅              | ❌                 | ✅             | ❌             |
| DirectPlay     | ✅              | ✅                 | ✅             | ✅*             |

* WIP - GetMasterHlsVideoPlaylistParameters

* WIP

* Cleanup unused code.

* Cleanup comments.

* Remove changes to GetMasterHlsVideoPlaylistParameters

* Change to use Max instead of a magic number.

* Update MediaStream.swift

Co-authored-by: Ethan Pippin <ethanpippin2343@gmail.com>

* Update MediaStream.swift

Co-authored-by: Ethan Pippin <ethanpippin2343@gmail.com>

* Update MediaStream.swift

Co-authored-by: Ethan Pippin <ethanpippin2343@gmail.com>

* Update MediaStream.swift

Co-authored-by: Ethan Pippin <ethanpippin2343@gmail.com>

* New and Improved.

* Ensure we are using the right audio track.

---------

Co-authored-by: Ethan Pippin <ethanpippin2343@gmail.com>

Shared/Extensions/JellyfinAPI/BaseItemDto/BaseItemDto+VideoPlayerViewModel.swift

@@ -125,11 +125,12 @@ extension BaseItemDto {
         let userSession = Container.shared.currentUserSession()!
 
         let testStartTime = Date()
-        try await userSession.client.send(Paths.getBitrateTestBytes(size: testSize))
+        _ = try await userSession.client.send(Paths.getBitrateTestBytes(size: testSize))
         let testDuration = Date().timeIntervalSince(testStartTime)
         let testSizeBits = Double(testSize * 8)
         let testBitrate = testSizeBits / testDuration
 
-        return Int(testBitrate)
+        /// Exceeding 500 mbps will produce an invalid URL
+        return min(Int(testBitrate), PlaybackBitrate.max.rawValue)
     }
 }

Shared/Extensions/JellyfinAPI/MediaStream.swift

@@ -216,37 +216,59 @@ extension MediaStream {
 
 extension [MediaStream] {
 
-    // TODO: explain why adjustment is necessary
+    /// Adjusts track indexes for a full set of media streams.
-    func adjustExternalSubtitleIndexes(audioStreamCount: Int) -> [MediaStream] {
+    /// For non-transcode stream types:
-        guard allSatisfy({ $0.type == .subtitle }) else { return self }
+    ///   Internal tracks (non-external) are ordered as: Video, Audio, Subtitles, then any others.
-        let embeddedSubtitleCount = filter { !($0.isExternal ?? false) }.count
+    ///   Their relative order within each group is preserved and indexes start at 0.
+    /// For transcode stream type:
+    ///   Only the first internal video track and the first internal audio track are included, in that order.
+    /// In both cases, external tracks are appended in their original order with indexes continuing after internal tracks.
+    func adjustedTrackIndexes(for streamType: StreamType, selectedAudioStreamIndex: Int) -> [MediaStream] {
+        let internalTracks = self.filter { !($0.isExternal ?? false) }
+        let externalTracks = self.filter { $0.isExternal ?? false }
 
-        var mediaStreams = self
+        var orderedInternal: [MediaStream] = []
 
-        for (i, mediaStream) in mediaStreams.enumerated() {
+        let subtitleInternal = internalTracks.filter { $0.type == .subtitle }
-            guard mediaStream.isExternal ?? false else { continue }
-            var copy = mediaStream
-            copy.index = (copy.index ?? 0) + 1 + embeddedSubtitleCount + audioStreamCount
 
-            mediaStreams[i] = copy
+        // TODO: Do we need this for other media types? I think movies/shows we only care about video, audio, and subtitles.
+        let otherInternal = internalTracks.filter { $0.type != .video && $0.type != .audio && $0.type != .subtitle }
+
+        if streamType == .transcode {
+            // Only include the first video and first audio track for transcode.
+            let videoInternal = internalTracks.filter { $0.type == .video }
+            let audioInternal = internalTracks.filter { $0.type == .audio }
+
+            if let firstVideo = videoInternal.first {
+                orderedInternal.append(firstVideo)
+            }
+            if let selectedAudio = audioInternal.first(where: { $0.index == selectedAudioStreamIndex }) {
+                orderedInternal.append(selectedAudio)
+            }
+
+            orderedInternal += subtitleInternal
+            orderedInternal += otherInternal
+        } else {
+            let videoInternal = internalTracks.filter { $0.type == .video }
+            let audioInternal = internalTracks.filter { $0.type == .audio }
+
+            orderedInternal = videoInternal + audioInternal + subtitleInternal + otherInternal
         }
 
-        return mediaStreams
+        var newInternalTracks: [MediaStream] = []
-    }
+        for (index, var track) in orderedInternal.enumerated() {
-
+            track.index = index
-    // TODO: explain why adjustment is necessary
+            newInternalTracks.append(track)
-    func adjustAudioForExternalSubtitles(externalMediaStreamCount: Int) -> [MediaStream] {
-        guard allSatisfy({ $0.type == .audio }) else { return self }
-
-        var mediaStreams = self
-
-        for (i, mediaStream) in mediaStreams.enumerated() {
-            var copy = mediaStream
-            copy.index = (copy.index ?? 0) - externalMediaStreamCount
-            mediaStreams[i] = copy
         }
 
-        return mediaStreams
+        var newExternalTracks: [MediaStream] = []
+        let startingIndexForExternal = newInternalTracks.count
+        for (offset, var track) in externalTracks.enumerated() {
+            track.index = startingIndexForExternal + offset
+            newExternalTracks.append(track)
+        }
+
+        return newInternalTracks + newExternalTracks
     }
 
     var has4KVideo: Bool {

Shared/Extensions/JellyfinAPI/SubtitleProfile.swift

@@ -34,7 +34,7 @@ extension SubtitleProfile {
         @ArrayBuilder<SubtitleFormat> containers: () -> [SubtitleFormat]
     ) -> [SubtitleProfile] {
         containers().map {
-            SubtitleProfile(container: $0.rawValue, method: method)
+            SubtitleProfile(container: nil, format: $0.rawValue, method: method)
         }
     }
 }

Shared/ViewModels/VideoPlayerViewModel.swift

@@ -29,7 +29,6 @@ class VideoPlayerViewModel: ViewModel {
     let streamType: StreamType
 
     var hlsPlaybackURL: URL {
-
         let parameters = Paths.GetMasterHlsVideoPlaylistParameters(
             isStatic: true,
             tag: mediaSource.eTag,
@@ -90,9 +89,11 @@ class VideoPlayerViewModel: ViewModel {
         item: BaseItemDto,
         mediaSource: MediaSourceInfo,
         playSessionID: String,
+        // TODO: Remove?
         videoStreams: [MediaStream],
         audioStreams: [MediaStream],
         subtitleStreams: [MediaStream],
+        // <- End of Potential Remove?
         selectedAudioStreamIndex: Int,
         selectedSubtitleStreamIndex: Int,
         chapters: [ChapterInfo.FullInfo],
@@ -102,11 +103,17 @@ class VideoPlayerViewModel: ViewModel {
         self.mediaSource = mediaSource
         self.playSessionID = playSessionID
         self.playbackURL = playbackURL
-        self.videoStreams = videoStreams
+
-        self.audioStreams = audioStreams
+        guard let mediaStreams = mediaSource.mediaStreams else {
-            .adjustAudioForExternalSubtitles(externalMediaStreamCount: subtitleStreams.filter { $0.isExternal ?? false }.count)
+            fatalError("Media source does not have any streams")
-        self.subtitleStreams = subtitleStreams
+        }
-            .adjustExternalSubtitleIndexes(audioStreamCount: audioStreams.count)
+
+        let adjustedStreams = mediaStreams.adjustedTrackIndexes(for: streamType, selectedAudioStreamIndex: selectedAudioStreamIndex)
+
+        self.videoStreams = adjustedStreams.filter { $0.type == .video }
+        self.audioStreams = adjustedStreams.filter { $0.type == .audio }
+        self.subtitleStreams = adjustedStreams.filter { $0.type == .subtitle }
+
         self.selectedAudioStreamIndex = selectedAudioStreamIndex
         self.selectedSubtitleStreamIndex = selectedSubtitleStreamIndex
         self.chapters = chapters