Editing Spatial Audio with an audio mix

At a glance

Project structure

Source bundle/
├── SpatialAudioCLI/
│   ├── SpatialAudioCLI.swift
│   ├── SpatialUtility.swift
│   ├── Actions.swift
│   └── AudioUnitHost.swift
├── Configuration/
│   └── SampleCode.xcconfig
└── SpatialAudioCLI.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 3 project/configuration file(s) and 9 source declaration(s).

Overall architecture

flowchart LR
    N1["SpatialAudioCLI"]
    N2["Cinematic APIs"]
    N1 --> N2

Reference code

SpatialAudioCLI/SpatialAudioCLI.swift:12 — architecture anchor

@main
struct SpatialAudioCLI: AsyncParsableCommand {
    // ...
    static let configuration = CommandConfiguration(
            abstract: """
            Use Audio Mix with spatial audio assets.
            """,
            usage: """
                preview <input-file> [--duration <duration>] [--intensity <intensity>] [--style <style>]
                bake <input-file> [--intensity <intensity>] [--style <style>] [--output <file>] [--delete] [--include-video]
                process <input-file> "" + [--audio-output-format <audio-output-format>]
                """
            )
    // ...
}

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 Cinematic.

Ownership and state

classDiagram
    SpatialAudioCLI *-- CommandConfiguration : configuration
    SpatialAudioCLI *-- String : action
    SpatialAudioCLI *-- URL : inputFile
    SpatialAudioCLI *-- Float : duration

Ownership evidence

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

@main
struct SpatialAudioCLI: AsyncParsableCommand {
    // ...
}

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

SpatialAudioCLI/Actions.swift:11 — representative execution boundary

    @MainActor
    /*
     Use `AVPlayer` with an `AVAudioMix` to preview the audio mix parameters for
     a number of seconds that the 'duration' option specifies.
     */
    static func preview(_ previewInput: SpatialUtility.PreviewInput) async throws {
        // ...
        print("Preview: effectIntensity=\(previewInput.intensity), renderingStyle=\(previewInput.style)")
        // ...
    }

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

SpatialAudioCLI/SpatialAudioCLI.swift:13 — representative type boundary

@main
struct SpatialAudioCLI: AsyncParsableCommand {
    // ...
    var action: String
    // ...
}

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

Access control

Reference code

SpatialAudioCLI/AudioUnitHost.swift:13 — representative boundary

class AudioUnitHost {
    // ...
    public var auAudioMix = AVAudioUnitEffect()
    // ...
}

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

Main application flow

sequenceDiagram
    participant Actions
    participant processedAudioAsset
    participant asset
    participant exportSession
    Actions->>processedAudioAsset: loadTracks()
    Actions->>Actions: processedAudioTrack()
    Actions->>asset: loadTracks()
    Actions->>Actions: videoTrack()
    Actions->>Actions: videoTrack()
    Actions->>exportSession: export()
    Actions->>exportSession: export()

Reference code

SpatialAudioCLI/Actions.swift:277 — saveProcessedFile()

struct Actions {
    // ...
            let videoTimeRange = try await videoTrack!.load(.timeRange)
    // ...
}

Naming conventions

• Types: feature-specific names rather than reusable layer suffixes.
• Protocols: no local protocol declaration in the scanned source.
• Methods: validate, run, verifyCNSpatialAudioRenderingStyle, verifyAudioOutput, deleteFiles, preview, bake, bakeReadWrite.
• Files: SpatialAudioCLI/SpatialAudioCLI.swift, SpatialAudioCLI/SpatialUtility.swift, SpatialAudioCLI/Actions.swift, SpatialAudioCLI/AudioUnitHost.swift.

Architecture takeaways

• SpatialAudioCLI is the main source-visible entry or composition anchor for this sample.
• Framework work reaches Cinematic, AVFoundation, ArgumentParser 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