Generating spatial audio from a multichannel audio stream

At a glance

Project structure

Source bundle/
└── SpatialAudioRenderer/
    ├── SpatialAudioRendererApp.swift
    └── Shared/
        ├── UI/
        │   ├── Models/
        │   │   └── ChainViewModel.swift
        │   ├── ChainView.swift
        │   └── ContentView.swift
        ├── Audio Engine/
        │   ├── AudioEngine.h
        │   ├── AudioEngine.mm
        │   ├── Nodes/
        │   │   ├── AUSMRenderer.h
        │   │   ├── AUSMRenderer.mm
        │   │   ├── AudioFileReader.mm
        │   │   └── AudioFileReader.h
        │   └── AudioKernel.h
        └── Helpers/
            └── AllocatedAudioBufferList.h

Structure observations

• Architecturally prominent files are ranked from entry points and role-named declarations; resource-only paths are omitted.
• Primary languages: C/Objective-C header, Objective-C++, Swift.
• The verified tree contains 4 project/configuration file(s) and 12 source declaration(s).

Overall architecture

flowchart LR
    N1["SpatialAudioRendererApp"]
    N2["ContentView"]
    N3["ChainViewModel"]
    N4["AudioEngine"]
    N5["AudioToolbox APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4
    N4 --> N5

Reference code

SpatialAudioRenderer/SpatialAudioRendererApp.swift:9 — architecture anchor

@main
struct SpatialAudioRendererApp: App {
    let model = ChainViewModel()

    var body: some Scene {
        WindowGroup {
            ContentView()
                .environmentObject(model)
        }
    }
}

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 Audio Toolbox.

Ownership and state

classDiagram
    SpatialAudioRendererApp *-- ChainViewModel : model
    NodeModel *-- Int : id
    NodeModel *-- String : name
    NodeModel *-- String : subTitle

Ownership evidence

SpatialAudioRenderer/SpatialAudioRendererApp.swift:11 — stored dependency or nearest verified ownership anchor

@main
struct SpatialAudioRendererApp: App {
    let model = ChainViewModel()
    // ...
}

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.

No source-visible execution, scheduling, or synchronization boundary was found in the indexed source.

@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.

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

SpatialAudioRenderer/SpatialAudioRendererApp.swift:10 — representative type boundary

@main
struct SpatialAudioRendererApp: App {
    let model = ChainViewModel()
    // ...
}

No local protocol conformance is claimed as protocol-oriented design; external framework conformances are listed only as dependencies.

Access control

Reference code

SpatialAudioRenderer/Shared/Audio Engine/AudioEngine.h:13 — representative boundary

@interface AudioEngine : NSObject
// ...
@property (readonly) AudioFileReader * __nullable fileReader;
// ...
@end

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: SpatialAudioRendererApp; Engine: AudioEngine; Model: NodeModel; Renderer: AUSMRenderer; View: ChainView, ContentView; ViewModel: ChainViewModel.
• Protocols: no local protocol declaration in the scanned source.
• Methods: audioSamples, loadAudio, handleRouteChange, init.
• Files: SpatialAudioRenderer/SpatialAudioRendererApp.swift, SpatialAudioRenderer/Shared/UI/Models/ChainViewModel.swift, SpatialAudioRenderer/Shared/Audio Engine/AudioEngine.h, SpatialAudioRenderer/Shared/Audio Engine/AudioEngine.mm, SpatialAudioRenderer/Shared/Audio Engine/Nodes/AUSMRenderer.h, SpatialAudioRenderer/Shared/UI/ChainView.swift.

Architecture takeaways

• SpatialAudioRendererApp is the main source-visible entry or composition anchor for this sample.
• Framework work reaches SwiftUI, AudioToolbox, AVFoundation, AudioUnit 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.
• The source does not justify labeling the design protocol-oriented.

Source map

• Official Apple documentation