Dreamio turn document · May 25, 2026

Native player audio track selection

Dreamio's VLC-backed native player now exposes embedded audio tracks, adds a far-left audio menu to the control bar, and refreshes the player chrome with a more iOS-native glass treatment.

Summary

Added audio track discovery and selection to native playback so multi-language MKV and similar files can be switched without leaving the player.

Changes Made

Extended NativePlaybackBackend with audio track state, a selection API, and an audio-track-change callback.
Read MobileVLCKit audio track names, indexes, and current selection from VLCMediaPlayer.
Added an audio menu button on the far left side of the native controls using the waveform.circle symbol.
Grouped skip/play/skip into a centered playback cluster so the play button stays visually centered.
Updated the control surface and buttons with translucent material, softer radius, subtle borders, and lighter glass-like control wells.

Context

The player already exposed embedded subtitle tracks through MobileVLCKit. The same streams often include multiple audio tracks, such as alternate languages or commentary, but the native player had no way to inspect or switch them.

The user-provided diagnostics showed VLC discovering embedded subtitle tracks while the UI still lacked track filtering for audio. This change follows the existing subtitle menu pattern instead of creating a separate player path.

Important Implementation Details

AudioTrack currently aliases the existing SubtitleTrack value shape because both VLC APIs expose an integer id and display name.
The audio button is enabled only when VLC reports more than one selectable audio track, keeping single-track files quiet.
The backend fires onAudioTracksChange when VLC enters playback/buffering and when elementary streams are added.
Selection is applied with mediaPlayer.currentAudioTrackIndex, matching the existing subtitle selection style.

Relevant Diff Snippets

Rendered with @pierre/diffs/ssr from the current git diff.

Dreamio/NativePlaybackBackend.swift

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    var onFailure: ((Error) -> Void)? { get set }
    var onStateChange: (() -> Void)? { get set }
    var onSubtitleTracksChange: (() -> Void)? { get set }
    var isPlaying: Bool { get }
    var isSeekable: Bool { get }
    var duration: TimeInterval { get }
    var currentTime: TimeInterval { get }
    var remainingTime: TimeInterval { get }
    var position: Float { get }
    var subtitleTracks: [SubtitleTrack] { get }
    var selectedSubtitleTrackID: Int32 { get }
    var subtitleDelay: TimeInterval { get }
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    func togglePlayPause()
    func seek(to position: Float)
    func jump(by seconds: TimeInterval)
    func selectSubtitleTrack(id: Int32)
    func adjustSubtitleDelay(by seconds: TimeInterval)
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    var onFailure: ((Error) -> Void)? { get set }
    var onStateChange: (() -> Void)? { get set }
    var onSubtitleTracksChange: (() -> Void)? { get set }
    var onAudioTracksChange: (() -> Void)? { get set }
    var isPlaying: Bool { get }
    var isSeekable: Bool { get }
    var duration: TimeInterval { get }
    var currentTime: TimeInterval { get }
    var remainingTime: TimeInterval { get }
    var position: Float { get }
    var audioTracks: [AudioTrack] { get }
    var selectedAudioTrackID: Int32 { get }
    var subtitleTracks: [SubtitleTrack] { get }
    var selectedSubtitleTrackID: Int32 { get }
    var subtitleDelay: TimeInterval { get }
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    func togglePlayPause()
    func seek(to position: Float)
    func jump(by seconds: TimeInterval)
    func selectAudioTrack(id: Int32)
    func selectSubtitleTrack(id: Int32)
    func adjustSubtitleDelay(by seconds: TimeInterval)
    @discardableResult

Dreamio/StreamCandidate.swift

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    let name: String
}

#if DEBUG
enum SubtitleDebugFormatter {
    static func candidateSummary(_ candidates: [SubtitleCandidate]) -> String {
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    }
}

struct StreamClassification {
    let sourceKind: StreamSourceKind
    let containerGuess: StreamContainerGuess39 unmodified lines
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    let name: String
}

typealias AudioTrack = SubtitleTrack

#if DEBUG
enum SubtitleDebugFormatter {
    static func candidateSummary(_ candidates: [SubtitleCandidate]) -> String {
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    }
}

enum AudioOptionMapper {
    static func options(from tracks: [AudioTrack]) -> [AudioTrack] {
        tracks.filter { $0.id >= 0 }
    }
}

struct StreamClassification {
    let sourceKind: StreamSourceKind
    let containerGuess: StreamContainerGuess

Dreamio/VLCNativePlaybackBackend.swift

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    var onFailure: ((Error) -> Void)?
    var onStateChange: (() -> Void)?
    var onSubtitleTracksChange: (() -> Void)?

#if canImport(MobileVLCKit)
    private let mediaPlayer = VLCMediaPlayer()
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#endif
    }

    func selectSubtitleTrack(id: Int32) {
#if canImport(MobileVLCKit)
        didUserSelectSubtitleTrack = true
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#endif
    }

    var subtitleTracks: [SubtitleTrack] {
#if canImport(MobileVLCKit)
        let names = mediaPlayer.videoSubTitlesNames as? [String] ?? []
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    }

#if DEBUG
    private func logSubtitleTracks(reason: String) {
        let names = mediaPlayer.videoSubTitlesNames as? [String] ?? []
        let indexes = mediaPlayer.videoSubTitlesIndexes as? [NSNumber] ?? []
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            reapplyAutoSelectedSubtitleTrackIfNeeded(reason: stateName(mediaPlayer.state))
            onReady?()
            onStateChange?()
        case .error:
            onFailure?(NativePlaybackError.playbackFailed)
        case .paused, .stopped, .ended:
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        case .esAdded:
            selectInitialSubtitleTrackIfNeeded(reason: "esAdded")
#if DEBUG
            logSubtitleTracks(reason: "esAdded")
#endif
            onSubtitleTracksChange?()
        default:
            break17 unmodified lines
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    var onFailure: ((Error) -> Void)?
    var onStateChange: (() -> Void)?
    var onSubtitleTracksChange: (() -> Void)?
    var onAudioTracksChange: (() -> Void)?

#if canImport(MobileVLCKit)
    private let mediaPlayer = VLCMediaPlayer()
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#endif
    }

    func selectAudioTrack(id: Int32) {
#if canImport(MobileVLCKit)
#if DEBUG
        logAudioTracks(reason: "before-select-\(id)")
#endif
        mediaPlayer.currentAudioTrackIndex = id
#if DEBUG
        logAudioTracks(reason: "after-select-\(id)")
#endif
        onAudioTracksChange?()
#endif
    }

    func selectSubtitleTrack(id: Int32) {
#if canImport(MobileVLCKit)
        didUserSelectSubtitleTrack = true
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#endif
    }

    var audioTracks: [AudioTrack] {
#if canImport(MobileVLCKit)
        let names = mediaPlayer.audioTrackNames as? [String] ?? []
        let indexes = mediaPlayer.audioTrackIndexes as? [NSNumber] ?? []
        return zip(indexes, names).map { index, name in
            AudioTrack(id: index.int32Value, name: name)
        }
#else
        []
#endif
    }

    var selectedAudioTrackID: Int32 {
#if canImport(MobileVLCKit)
        mediaPlayer.currentAudioTrackIndex
#else
        -1
#endif
    }

    var subtitleTracks: [SubtitleTrack] {
#if canImport(MobileVLCKit)
        let names = mediaPlayer.videoSubTitlesNames as? [String] ?? []
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    }

#if DEBUG
    private func logAudioTracks(reason: String) {
        let names = mediaPlayer.audioTrackNames as? [String] ?? []
        let indexes = mediaPlayer.audioTrackIndexes as? [NSNumber] ?? []
        print("[DreamioVLC] audio tracks reason=\(reason) names=\(names) indexes=\(indexes.map { $0.int32Value }) selected=\(mediaPlayer.currentAudioTrackIndex)")
    }

    private func logSubtitleTracks(reason: String) {
        let names = mediaPlayer.videoSubTitlesNames as? [String] ?? []
        let indexes = mediaPlayer.videoSubTitlesIndexes as? [NSNumber] ?? []
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            reapplyAutoSelectedSubtitleTrackIfNeeded(reason: stateName(mediaPlayer.state))
            onReady?()
            onStateChange?()
            onAudioTracksChange?()
        case .error:
            onFailure?(NativePlaybackError.playbackFailed)
        case .paused, .stopped, .ended:
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        case .esAdded:
            selectInitialSubtitleTrackIfNeeded(reason: "esAdded")
#if DEBUG
            logAudioTracks(reason: "esAdded")
            logSubtitleTracks(reason: "esAdded")
#endif
            onAudioTracksChange?()
            onSubtitleTracksChange?()
        default:
            break

Dreamio/NativePlayerViewController.swift

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    private var progressTimer: Timer?
    private var isScrubbing = false
    private var attachedSubtitleURLs: Set<URL>
    private var captionsMenuSignature: String?
    var onDismiss: (() -> Void)?

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    private let controlsContainer: UIVisualEffectView = {
        let view = UIVisualEffectView(effect: UIBlurEffect(style: .systemUltraThinMaterialDark))
        view.translatesAutoresizingMaskIntoConstraints = false
        view.layer.cornerRadius = 16
        view.clipsToBounds = true
        return view
    }()

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    private let playPauseButton = NativePlayerViewController.iconButton(systemName: "pause.fill", label: "Play or Pause")
    private let jumpBackButton = NativePlayerViewController.iconButton(systemName: "gobackward.15", label: "Jump Back 15 Seconds")
    private let jumpForwardButton = NativePlayerViewController.iconButton(systemName: "goforward.15", label: "Jump Forward 15 Seconds")
    private let captionsButton = NativePlayerViewController.iconButton(systemName: "captions.bubble", label: "Captions")

    private let elapsedLabel: UILabel = {
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                self?.refreshControls()
            }
        }
    }

    private func startStartupTimer() {
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        playPauseButton.addTarget(self, action: #selector(togglePlayPause), for: .touchUpInside)
        jumpBackButton.addTarget(self, action: #selector(jumpBack), for: .touchUpInside)
        jumpForwardButton.addTarget(self, action: #selector(jumpForward), for: .touchUpInside)
        captionsButton.showsMenuAsPrimaryAction = true
        playPauseButton.layer.cornerRadius = 21
        scrubber.addTarget(self, action: #selector(scrubbingStarted), for: .touchDown)
        scrubber.addTarget(self, action: #selector(scrubberChanged), for: .valueChanged)
        scrubber.addTarget(self, action: #selector(scrubbingEnded), for: [.touchUpInside, .touchUpOutside, .touchCancel])
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        timeAndScrubRow.alignment = .center
        timeAndScrubRow.spacing = 8

        let controlRow = UIStackView(arrangedSubviews: [jumpBackButton, playPauseButton, jumpForwardButton, captionsButton])
        controlRow.translatesAutoresizingMaskIntoConstraints = false
        controlRow.axis = .horizontal
        controlRow.alignment = .center
        controlRow.distribution = .equalSpacing
        controlRow.spacing = 14

        let stack = UIStackView(arrangedSubviews: [timeAndScrubRow, controlRow])
        stack.translatesAutoresizingMaskIntoConstraints = false
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            playPauseButton.heightAnchor.constraint(equalToConstant: 42),
            jumpForwardButton.widthAnchor.constraint(equalToConstant: 36),
            jumpForwardButton.heightAnchor.constraint(equalToConstant: 36),
            captionsButton.widthAnchor.constraint(equalToConstant: 36),
            captionsButton.heightAnchor.constraint(equalToConstant: 36)
        ])
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        return UIMenu(title: "Captions", children: trackActions + [delayActions])
    }

    private func startProgressUpdates() {
        progressTimer?.invalidate()
        progressTimer = Timer.scheduledTimer(withTimeInterval: 0.5, repeats: true) { [weak self] _ in
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    }

    private func refreshControls() {
        let subtitleTracks = backend.subtitleTracks
        playPauseButton.setImage(UIImage(systemName: backend.isPlaying ? "pause.fill" : "play.fill"), for: .normal)
        scrubber.isEnabled = backend.isSeekable
        jumpBackButton.isEnabled = backend.isSeekable
        jumpForwardButton.isEnabled = backend.isSeekable
        updateCaptionsMenuIfNeeded(subtitleTracks: subtitleTracks)
        elapsedLabel.text = PlaybackTimeFormatter.label(for: backend.currentTime)
        remainingLabel.text = "-\(PlaybackTimeFormatter.label(for: backend.remainingTime))"
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        [scrubber, jumpBackButton, jumpForwardButton].forEach { $0.alpha = backend.isSeekable ? 1 : 0.45 }
    }

    private func updateCaptionsMenuIfNeeded(subtitleTracks: [SubtitleTrack]) {
        let selectedTrackID = backend.selectedSubtitleTrackID
        let signature = captionsMenuSignatureValue(
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        tracks: [SubtitleTrack],
        selectedTrackID: Int32,
        delay: TimeInterval
    ) -> String {
        let trackSignature = tracks
            .map { "\($0.id):\($0.name)" }
            .joined(separator: "|")
        return "\(trackSignature)#selected=\(selectedTrackID)#delay=\(String(format: "%.1f", delay))"
    }

    private func revealControls() {
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        button.translatesAutoresizingMaskIntoConstraints = false
        button.setImage(UIImage(systemName: systemName), for: .normal)
        button.tintColor = .white
        button.backgroundColor = UIColor.black.withAlphaComponent(0.35)
        button.layer.cornerRadius = 18
        button.accessibilityLabel = label
        return button
    }8 unmodified lines
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    private var progressTimer: Timer?
    private var isScrubbing = false
    private var attachedSubtitleURLs: Set<URL>
    private var audioMenuSignature: String?
    private var captionsMenuSignature: String?
    var onDismiss: (() -> Void)?

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    private let controlsContainer: UIVisualEffectView = {
        let view = UIVisualEffectView(effect: UIBlurEffect(style: .systemUltraThinMaterialDark))
        view.translatesAutoresizingMaskIntoConstraints = false
        view.layer.cornerRadius = 22
        view.clipsToBounds = true
        view.backgroundColor = UIColor.white.withAlphaComponent(0.08)
        view.layer.borderColor = UIColor.white.withAlphaComponent(0.18).cgColor
        view.layer.borderWidth = 1
        return view
    }()

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    private let playPauseButton = NativePlayerViewController.iconButton(systemName: "pause.fill", label: "Play or Pause")
    private let jumpBackButton = NativePlayerViewController.iconButton(systemName: "gobackward.15", label: "Jump Back 15 Seconds")
    private let jumpForwardButton = NativePlayerViewController.iconButton(systemName: "goforward.15", label: "Jump Forward 15 Seconds")
    private let audioButton = NativePlayerViewController.iconButton(systemName: "waveform.circle", label: "Audio Tracks")
    private let captionsButton = NativePlayerViewController.iconButton(systemName: "captions.bubble", label: "Captions")

    private let elapsedLabel: UILabel = {
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                self?.refreshControls()
            }
        }
        backend.onAudioTracksChange = { [weak self] in
            DispatchQueue.main.async {
                self?.refreshControls()
            }
        }
    }

    private func startStartupTimer() {
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        playPauseButton.addTarget(self, action: #selector(togglePlayPause), for: .touchUpInside)
        jumpBackButton.addTarget(self, action: #selector(jumpBack), for: .touchUpInside)
        jumpForwardButton.addTarget(self, action: #selector(jumpForward), for: .touchUpInside)
        audioButton.showsMenuAsPrimaryAction = true
        captionsButton.showsMenuAsPrimaryAction = true
        playPauseButton.layer.cornerRadius = 24
        scrubber.addTarget(self, action: #selector(scrubbingStarted), for: .touchDown)
        scrubber.addTarget(self, action: #selector(scrubberChanged), for: .valueChanged)
        scrubber.addTarget(self, action: #selector(scrubbingEnded), for: [.touchUpInside, .touchUpOutside, .touchCancel])
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        timeAndScrubRow.alignment = .center
        timeAndScrubRow.spacing = 8

        let playbackCluster = UIStackView(arrangedSubviews: [jumpBackButton, playPauseButton, jumpForwardButton])
        playbackCluster.translatesAutoresizingMaskIntoConstraints = false
        playbackCluster.axis = .horizontal
        playbackCluster.alignment = .center
        playbackCluster.distribution = .equalCentering
        playbackCluster.spacing = 14

        let controlRow = UIStackView(arrangedSubviews: [audioButton, playbackCluster, captionsButton])
        controlRow.translatesAutoresizingMaskIntoConstraints = false
        controlRow.axis = .horizontal
        controlRow.alignment = .center
        controlRow.distribution = .equalCentering
        controlRow.spacing = 18

        let stack = UIStackView(arrangedSubviews: [timeAndScrubRow, controlRow])
        stack.translatesAutoresizingMaskIntoConstraints = false
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            playPauseButton.heightAnchor.constraint(equalToConstant: 42),
            jumpForwardButton.widthAnchor.constraint(equalToConstant: 36),
            jumpForwardButton.heightAnchor.constraint(equalToConstant: 36),
            audioButton.widthAnchor.constraint(equalToConstant: 36),
            audioButton.heightAnchor.constraint(equalToConstant: 36),
            playbackCluster.centerXAnchor.constraint(equalTo: controlRow.centerXAnchor),
            captionsButton.widthAnchor.constraint(equalToConstant: 36),
            captionsButton.heightAnchor.constraint(equalToConstant: 36)
        ])
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        return UIMenu(title: "Captions", children: trackActions + [delayActions])
    }

    private func audioMenu() -> UIMenu {
        let selectedTrackID = backend.selectedAudioTrackID
        let tracks = backend.audioTracks
        let options = AudioOptionMapper.options(from: tracks)
#if DEBUG
        print("[DreamioAudio] build-menu tracks=\(SubtitleDebugFormatter.trackSummary(tracks)) selected=\(selectedTrackID)")
#endif
        let trackActions = options.map { track in
            UIAction(
                title: track.name,
                state: track.id == selectedTrackID ? .on : .off
            ) { [weak self] _ in
                guard let self else {
                    return
                }
#if DEBUG
                print("[DreamioAudio] select-request id=\(track.id) name=\(track.name) before=\(self.backend.selectedAudioTrackID)")
#endif
                self.backend.selectAudioTrack(id: track.id)
#if DEBUG
                print("[DreamioAudio] select-result id=\(track.id) after=\(self.backend.selectedAudioTrackID) tracks=\(SubtitleDebugFormatter.trackSummary(self.backend.audioTracks))")
#endif
                self.audioMenuSignature = nil
                self.refreshControls()
            }
        }

        return UIMenu(title: "Audio", children: trackActions)
    }

    private func startProgressUpdates() {
        progressTimer?.invalidate()
        progressTimer = Timer.scheduledTimer(withTimeInterval: 0.5, repeats: true) { [weak self] _ in
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    }

    private func refreshControls() {
        let audioTracks = backend.audioTracks
        let subtitleTracks = backend.subtitleTracks
        playPauseButton.setImage(UIImage(systemName: backend.isPlaying ? "pause.fill" : "play.fill"), for: .normal)
        scrubber.isEnabled = backend.isSeekable
        jumpBackButton.isEnabled = backend.isSeekable
        jumpForwardButton.isEnabled = backend.isSeekable
        updateAudioMenuIfNeeded(audioTracks: audioTracks)
        updateCaptionsMenuIfNeeded(subtitleTracks: subtitleTracks)
        elapsedLabel.text = PlaybackTimeFormatter.label(for: backend.currentTime)
        remainingLabel.text = "-\(PlaybackTimeFormatter.label(for: backend.remainingTime))"
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        [scrubber, jumpBackButton, jumpForwardButton].forEach { $0.alpha = backend.isSeekable ? 1 : 0.45 }
    }

    private func updateAudioMenuIfNeeded(audioTracks: [AudioTrack]) {
        let selectedTrackID = backend.selectedAudioTrackID
        let signature = trackMenuSignatureValue(
            tracks: audioTracks,
            selectedTrackID: selectedTrackID
        )
        let hasSelectableTrack = AudioOptionMapper.options(from: audioTracks).count > 1
        audioButton.isEnabled = hasSelectableTrack
        audioButton.alpha = hasSelectableTrack ? 1 : 0.45
        guard signature != audioMenuSignature else {
            return
        }

        audioMenuSignature = signature
        audioButton.menu = audioMenu()
#if DEBUG
        print("[DreamioAudio] refresh-menu enabled=\(audioButton.isEnabled) tracks=\(SubtitleDebugFormatter.trackSummary(audioTracks)) selected=\(selectedTrackID)")
#endif
    }

    private func updateCaptionsMenuIfNeeded(subtitleTracks: [SubtitleTrack]) {
        let selectedTrackID = backend.selectedSubtitleTrackID
        let signature = captionsMenuSignatureValue(
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        tracks: [SubtitleTrack],
        selectedTrackID: Int32,
        delay: TimeInterval
    ) -> String {
        let trackSignature = trackMenuSignatureValue(tracks: tracks, selectedTrackID: selectedTrackID)
        return "\(trackSignature)#delay=\(String(format: "%.1f", delay))"
    }

    private func trackMenuSignatureValue(
        tracks: [SubtitleTrack],
        selectedTrackID: Int32
    ) -> String {
        let trackSignature = tracks
            .map { "\($0.id):\($0.name)" }
            .joined(separator: "|")
        return "\(trackSignature)#selected=\(selectedTrackID)"
    }

    private func revealControls() {
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        button.translatesAutoresizingMaskIntoConstraints = false
        button.setImage(UIImage(systemName: systemName), for: .normal)
        button.tintColor = .white
        button.backgroundColor = UIColor.white.withAlphaComponent(0.12)
        button.layer.cornerRadius = 18
        button.layer.borderColor = UIColor.white.withAlphaComponent(0.16).cgColor
        button.layer.borderWidth = 1
        button.accessibilityLabel = label
        return button
    }

Expected Impact for End-Users

When a native-played file has multiple embedded audio tracks, users can open the new audio menu and choose the language or alternate mix they want. The play button remains centered, and the controls should feel more at home on iOS.

Validation

Ran xcodebuild -workspace Dreamio.xcworkspace -scheme Dreamio -destination 'platform=iOS Simulator,name=iPhone 17' build: passed.
Attempted iPhone 16 simulator validation first, but that simulator was not installed on this machine.
No real-device playback stream was available in this turn, so actual multi-audio switching still needs a device check with an MKV that contains multiple audio languages.

Issues, Limitations, and Mitigations

MobileVLCKit track discovery is event-driven, so the menu appears after VLC reports the stream tracks. The UI refreshes on playback, buffering, and elementary-stream-added events to mitigate delayed discovery.
The visual update uses UIKit blur/material styling rather than directly adopting iOS 26-only UIGlassEffect, keeping the project buildable for its current iOS 16 deployment target while following Liquid Glass principles.
Manual validation is still needed on a device with a known multi-audio stream.

Follow-up Work

Use a known multi-language MKV on device and confirm the menu lists all audio tracks and switches without playback restart.
Consider parsing VLC track names into cleaner language labels if raw names are noisy.
Promote the track model from a typealias to distinct audio/subtitle structs if audio-specific metadata is added later.