feat: default lang and mpv audio track switching

Model/Applications/InvidiousAPI.swift

@@ -685,50 +685,93 @@ final class InvidiousAPI: Service, ObservableObject, VideosAPI {
         }
     }
 
+    func extractXTags(from urlString: String) -> [String: String] {
+        guard let urlComponents = URLComponents(string: urlString),
+              let queryItems = urlComponents.queryItems,
+              let xtagsValue = queryItems.first(where: { $0.name == "xtags" })?.value else {
+            return [:]
+        }
+
+        guard let decoded = xtagsValue.removingPercentEncoding else { return [:] }
+
+        // Parse key-value pairs (format: key1=value1:key2=value2)
+        // Example: "acont=dubbed-auto:lang=en-US"
+        let pairs = decoded.split(separator: ":")
+        var result: [String: String] = [:]
+        for pair in pairs {
+            let parts = pair.split(separator: "=", maxSplits: 1)
+            if parts.count == 2 {
+                result[String(parts[0])] = String(parts[1])
+            }
+        }
+        return result
+    }
+
     private func extractAdaptiveFormats(from streams: [JSON], videoId: String?) -> [Stream] {
-        let audioStreams = streams
+        let audioTracks = streams
             .filter { $0["type"].stringValue.starts(with: "audio/mp4") }
             .sorted {
                 $0.dictionaryValue["bitrate"]?.int ?? 0 >
                     $1.dictionaryValue["bitrate"]?.int ?? 0
             }
-        guard let audioStream = audioStreams.first else {
+            .compactMap { audioStream -> Stream.AudioTrack? in
+                guard let url = audioStream["url"].url,
+                      let audioItag = audioStream["itag"].string
+                else { return nil }
+
+                let finalURL: URL
+                if let videoId, account.instance.invidiousCompanion {
+                    let audioCompanionURLString = "\(account.instance.apiURLString)/latest_version?id=\(videoId)&itag=\(audioItag)"
+                    finalURL = URL(string: audioCompanionURLString) ?? url
+                } else {
+                    finalURL = url
+                }
+
+                let xTags = extractXTags(from: url.absoluteString)
+
+                return Stream.AudioTrack(
+                    url: finalURL,
+                    content: xTags["acont"],
+                    language: xTags["lang"]
+                )
+            }
+            .sorted {
+                /// Always prefer original audio streams over dubbed ones
+                !$0.isDubbed && $1.isDubbed
+            }
+
+        guard !audioTracks.isEmpty else {
             return .init()
         }
 
         let videoStreams = streams.filter { $0["type"].stringValue.starts(with: "video/") }
 
         return videoStreams.compactMap { videoStream in
-            guard let audioAssetURL = audioStream["url"].url,
-                  let videoAssetURL = videoStream["url"].url,
-                  let audioItag = audioStream["itag"].string,
+            guard let videoAssetURL = videoStream["url"].url,
                   let videoItag = videoStream["itag"].string
             else {
                 return nil
             }
-            let finalAudioURL: URL
             let finalVideoURL: URL
 
             if let videoId, account.instance.invidiousCompanion {
-                let audioCompanionURLString = "\(account.instance.apiURLString)/latest_version?id=\(videoId)&itag=\(audioItag)"
                 let videoCompanionURLString = "\(account.instance.apiURLString)/latest_version?id=\(videoId)&itag=\(videoItag)"
-                finalAudioURL = URL(string: audioCompanionURLString) ?? audioAssetURL
                 finalVideoURL = URL(string: videoCompanionURLString) ?? videoAssetURL
             } else {
-                finalAudioURL = audioAssetURL
                 finalVideoURL = videoAssetURL
             }
 
             return Stream(
                 instance: account.instance,
-                audioAsset: AVURLAsset(url: finalAudioURL),
+                audioAsset: AVURLAsset(url: audioTracks[0].url),
                 videoAsset: AVURLAsset(url: finalVideoURL),
                 resolution: Stream.Resolution.from(resolution: videoStream["resolution"].stringValue),
                 kind: .adaptive,
                 encoding: videoStream["encoding"].string,
                 videoFormat: videoStream["type"].string,
                 bitrate: videoStream["bitrate"].int,
-                requestRange: videoStream["init"].string ?? videoStream["index"].string
+                requestRange: videoStream["init"].string ?? videoStream["index"].string,
+                audioTracks: audioTracks
             )
         }
     }

Model/Player/Backends/MPVBackend.swift

@@ -185,6 +185,10 @@ final class MPVBackend: PlayerBackend {
     var audioSampleRate: String {
         client?.audioSampleRate ?? "unknown"
     }
+    
+    var availableAudioTracks: [Stream.AudioTrack] {
+        stream?.audioTracks ?? []
+    }
 
     init() {
         clientTimer = .init(interval: .seconds(Self.timeUpdateInterval), mode: .infinite) { [weak self] _ in
@@ -243,6 +247,9 @@ final class MPVBackend: PlayerBackend {
 
         let updateCurrentStream = {
             DispatchQueue.main.async { [weak self] in
+                if self?.video?.id != video.id {
+                    self?.model.selectedAudioTrackIndex = 0
+                }
                 self?.stream = stream
                 self?.video = video
                 self?.model.stream = stream
@@ -319,6 +326,7 @@ final class MPVBackend: PlayerBackend {
                         startPlaying()
                     }
 
+                    stream.audioAsset = AVURLAsset(url: stream.audioTracks[stream.selectedAudioTrackIndex].url)
                     let fileToLoad = self.model.musicMode ? stream.audioAsset.url : stream.videoAsset.url
                     let audioTrack = self.model.musicMode ? nil : stream.audioAsset.url
 
@@ -728,4 +736,13 @@ final class MPVBackend: PlayerBackend {
             logger.info("MPV backend received unhandled property: \(name)")
         }
     }
+
+    func switchAudioTrack(to index: Int) {
+        guard let stream, let video else { return }
+
+        stream.selectedAudioTrackIndex = index
+        model.saveTime { [weak self] in
+            self?.playStream(stream, of: video, preservingTime: true, upgrading: false)
+        }
+    }
 }

Model/Player/PlayerModel.swift

@@ -210,6 +210,14 @@ final class PlayerModel: ObservableObject {
         var keyPressMonitor: Any?
     #endif
 
+    @Published var selectedAudioTrackIndex = 0 {
+        didSet {
+            if oldValue != selectedAudioTrackIndex {
+                handleAudioTrackChange()
+            }
+        }
+    }
+
     init() {
         #if os(iOS)
             isOrientationLocked = Defaults[.isOrientationLocked]
@@ -1467,4 +1475,12 @@ final class PlayerModel: ObservableObject {
             }
         }
     #endif
+
+    private func handleAudioTrackChange() {
+        (backend as? MPVBackend)?.switchAudioTrack(to: selectedAudioTrackIndex)
+    }
+
+    var availableAudioTracks: [Stream.AudioTrack] {
+        (backend as? MPVBackend)?.availableAudioTracks ?? []
+    }
 }

Model/Stream.swift

@@ -191,6 +191,25 @@ class Stream: Equatable, Hashable, Identifiable {
             return .unknown
         }
     }
+    
+    struct AudioTrack: Hashable, Identifiable {
+        let id = UUID().uuidString
+        let url: URL
+        let content: String?
+        let language: String?
+        
+        var displayLanguage: String {
+            LanguageCodes(rawValue: language ?? "")?.description.capitalized ?? language ?? "Unknown"
+        }
+        
+        var description: String {
+            "\(displayLanguage) (\(content ?? "Unknown"))"
+        }
+        
+        var isDubbed: Bool {
+            content?.lowercased().starts(with: "dubbed") ?? false
+        }
+    }
 
     let id = UUID()
 
@@ -208,6 +227,8 @@ class Stream: Equatable, Hashable, Identifiable {
     var videoFormat: String?
     var bitrate: Int?
     var requestRange: String?
+    var audioTracks: [AudioTrack] = []
+    var selectedAudioTrackIndex = 0
 
     init(
         instance: Instance? = nil,
@@ -220,7 +241,8 @@ class Stream: Equatable, Hashable, Identifiable {
         encoding: String? = nil,
         videoFormat: String? = nil,
         bitrate: Int? = nil,
-        requestRange: String? = nil
+        requestRange: String? = nil,
+        audioTracks: [AudioTrack] = []
     ) {
         self.instance = instance
         self.audioAsset = audioAsset
@@ -233,6 +255,7 @@ class Stream: Equatable, Hashable, Identifiable {
         format = .from(videoFormat ?? "")
         self.bitrate = bitrate
         self.requestRange = requestRange
+        self.audioTracks = audioTracks
     }
 
     var isLocal: Bool {