Playing custom audio with your own player

At a glance

Project structure

Source bundle/
├── SampleBufferPlayer/
│   ├── SampleBufferPlayerApp.swift
│   ├── ContentView.swift
│   ├── Player/
│   │   ├── SampleBufferPlayer.swift
│   │   ├── SampleBufferSerializer.swift
│   │   ├── SampleBufferItem.swift
│   │   └── SampleBufferSource.swift
│   └── General/
│       ├── RemoteCommandCenter.swift
│       ├── NowPlayingCenter.swift
│       └── PlaylistItem.swift
├── Configuration/
│   └── SampleCode.xcconfig
└── SampleBufferPlayer.xcodeproj/
    ├── .xcodesamplecode.plist
    └── project.pbxproj

Structure observations

• Architecturally prominent files are ranked from entry points and role-named declarations; resource-only paths are omitted.
• Primary languages: Swift.
• The verified tree contains 4 project/configuration file(s) and 14 source declaration(s).

Overall architecture

flowchart LR
    N1["SampleBufferPlayerApp"]
    N2["ContentView"]
    N3["RemoteCommandHandler"]
    N4["AVFoundation / MediaPlayer APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

SampleBufferPlayer/SampleBufferPlayerApp.swift:10 — architecture anchor

@main
struct SampleBufferPlayerApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

Interpretation

The arrows summarize the source-visible entry, role-named types or folders, and framework direction; when nodes come from structural folders, the sequence is a high-level interpretation rather than proof that every adjacent node calls the next. Ownership is claimed only where the next section cites a stored property or assignment. The diagram is intentionally limited to the dominant path into AVFAudio.

Ownership and state

classDiagram
    ContentView *-- SampleBufferPlayer : sampleBufferPlayer
    Playlist *-- Array : items
    Playlist *-- Int : currentIndex
    Playlist *-- DispatchSemaphore : atomicitySemaphore

Ownership evidence

SampleBufferPlayer/ContentView.swift:15 — stored dependency or nearest verified ownership anchor

struct ContentView: View {
    // ...
    @State private var sampleBufferPlayer = SampleBufferPlayer()
    // ...
}

Composition arrows indicate a source-visible construction expression or locally owned value state; aggregation means the owner stores or receives a dependency without proving exclusive lifetime ownership.

Concurrency, scheduling, and thread safety

Evidence limit: actor isolation, async/await, or Task creation does not by itself prove background-thread execution; Sendable conformance alone does not prove thread-safe mutation.

@MainActor/MainActor.run, DispatchQueue.main, and RunLoop.main are reported as distinct isolation, queue, and event-loop mechanisms. A plain Task is kept separate from Task.detached; neither is labeled as a background thread.

Reference code

SampleBufferPlayer/ContentView.swift:111 — representative execution boundary

struct ContentView: View {
    // ...
            await sampleBufferPlayer.loadPlaylist()
    // ...
}

State propagation, frameworks, and dependencies

Evidence limit: an import proves a source-level compilation dependency at the cited line; it does not prove runtime use, architectural adoption, or whether a Swift package is a direct application dependency.

receive(on:) describes downstream delivery scheduling, while subscribe(on:) describes upstream subscription/request/cancel scheduling. An import Combine alone establishes neither behavior nor a Store, reducer, Redux, or other application architecture.

Class and protocol design

SampleBufferPlayer/General/RemoteCommandCenter.swift:19 — representative type boundary

protocol RemoteCommandHandler: AnyObject {
    func performRemoteCommand(_: RemoteCommand)
}

The source explicitly defines local protocol relationships: SampleBufferPlayer → RemoteCommandHandler.

Access control

Reference code

SampleBufferPlayer/ContentView.swift:15 — representative boundary

struct ContentView: View {
    // ...
    @State private var sampleBufferPlayer = SampleBufferPlayer()
    // ...
}

Swift declarations without a modifier are internal; explicit private, fileprivate, private(set), public, or open entries above are interpreted by language semantics. Objective-C/C samples instead rely on header and implementation boundaries, which are not equivalent to Swift lexical privacy.

Logic ownership and placement

Design patterns

Naming conventions

• Types: App: SampleBufferPlayerApp; Command: RemoteCommand; Handler: RemoteCommandHandler; Player: SampleBufferPlayer; View: ContentView.
• Protocols: RemoteCommandHandler.
• Methods: transportButton, makeUIView, updateUIView, loadPlaylist, restorePlaylist, loadItem, setUpAudioSession, item.
• Files: SampleBufferPlayer/SampleBufferPlayerApp.swift, SampleBufferPlayer/ContentView.swift, SampleBufferPlayer/Player/SampleBufferPlayer.swift, SampleBufferPlayer/General/RemoteCommandCenter.swift, SampleBufferPlayer/Player/SampleBufferSerializer.swift, SampleBufferPlayer/General/NowPlayingCenter.swift.

Architecture takeaways

• SampleBufferPlayerApp is the main source-visible entry or composition anchor for this sample.
• Framework work reaches AVFoundation, MediaPlayer, SwiftUI, AVKit through a deliberately small high-level chain; the detailed API graph remains inside the cited implementation files.
• Stored-property evidence identifies lifecycle collaboration; it does not by itself prove exclusive object ownership.
• Access-control conclusions separate verified language visibility from the likely design rationale.
• Local protocol relationships provide an explicit substitution boundary.

Source map

• Official Apple documentation