Using voice processing

At a glance

Project structure

Source bundle/
├── AVEchoTouch/
│   ├── LevelMeterView.swift
│   ├── AppDelegate.swift
│   ├── AudioEngine.swift
│   ├── ViewController.swift
│   ├── PowerMeter.swift
│   ├── MeterTable.swift
│   ├── Base.lproj/
│   │   ├── LaunchScreen.storyboard
│   │   └── Main.storyboard
│   └── Info.plist
├── AVEchoTouch.xcodeproj/
│   ├── .xcodesamplecode.plist
│   └── project.pbxproj
└── Configuration/
    └── SampleCode.xcconfig

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 6 project/configuration file(s) and 12 source declaration(s).

Overall architecture

flowchart LR
    N1["AppDelegate"]
    N2["ViewController"]
    N3["AudioLevelProvider"]
    N4["AVFoundation / UIKit APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

AVEchoTouch/AppDelegate.swift:10 — architecture anchor

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        return true
    }
}

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
    AudioLevels *-- Float : level
    AudioLevels *-- Float : peakLevel
    ColorThreshold o-- UIColor : color
    ColorThreshold *-- CGFloat : maxValue

Ownership evidence

AVEchoTouch/LevelMeterView.swift:11 — stored dependency or nearest verified ownership anchor

struct AudioLevels {
    let level: Float
    let peakLevel: Float
}

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

AVEchoTouch/LevelMeterView.swift:16 — representative type boundary

protocol AudioLevelProvider {
    var levels: AudioLevels { get }
}

The source explicitly defines local protocol relationships: PowerMeter → AudioLevelProvider.

Access control

Reference code

AVEchoTouch/AudioEngine.swift:13 — representative boundary

class AudioEngine {
    // ...
    private var recordedFileURL = URL(fileURLWithPath: "input.caf", isDirectory: false, relativeTo: URL(fileURLWithPath: NSTemporaryDirectory()))
    // ...
}

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: Controller: ViewController; Delegate: AppDelegate; Engine: AudioEngine; Provider: AudioLevelProvider; View: LevelMeterView.
• Protocols: AudioLevelProvider.
• Methods: setupView, updateLEDs, installDisplayLink, uninstallDisplayLink, updateMeter, clamp, reset, application.
• Files: AVEchoTouch/LevelMeterView.swift, AVEchoTouch/AppDelegate.swift, AVEchoTouch/AudioEngine.swift, AVEchoTouch/ViewController.swift, AVEchoTouch/PowerMeter.swift, AVEchoTouch/MeterTable.swift.

Architecture takeaways

• AppDelegate is the main source-visible entry or composition anchor for this sample.
• Framework work reaches AVFoundation, UIKit, Accelerate 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