Using HEVC video with alpha

At a glance

Project structure

Source bundle/
├── HEVC-Videos-With-Alpha-AssetWriting/
│   ├── HEVC-Videos-With-Alpha-AssetWriting/
│   │   ├── AppDelegate.swift
│   │   ├── Base.lproj/
│   │   │   └── MainMenu.xib
│   │   └── Info.plist
│   └── HEVC-Videos-With-Alpha-AssetWriting.xcodeproj/
│       ├── .xcodesamplecode.plist
│       └── project.pbxproj
├── HEVC-Videos-With-Alpha-Exports/
│   ├── HEVC-Videos-With-Alpha-Exports/
│   │   └── main.swift
│   └── HEVC-Videos-With-Alpha-Exports.xcodeproj/
│       ├── .xcodesamplecode.plist
│       └── project.pbxproj
├── HEVC-Videos-With-Alpha-Playback/
│   ├── HEVC-Videos-With-Alpha-Playback/
│   │   ├── AppDelegate.swift
│   │   └── ViewController.swift
│   └── HEVC-Videos-With-Alpha-Playback.xcodeproj/
│       └── .xcodesamplecode.plist
└── 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 14 project/configuration file(s) and 4 source declaration(s).

Overall architecture

flowchart LR
    Bundle["Sample bundle"]
    V1["HEVC-Videos-With-Alpha-AssetWriting"]
    V2["HEVC-Videos-With-Alpha-Playback"]
    Boundary["AVFoundation APIs"]
    Bundle --> V1
    V1 --> Boundary
    Bundle --> V2
    V2 --> Boundary

Reference code

HEVC-Videos-With-Alpha-AssetWriting/HEVC-Videos-With-Alpha-AssetWriting/AppDelegate.swift:21 — architecture anchor

@NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate, SCNSceneRendererDelegate {
    @IBOutlet weak var sceneKitView: SCNView!
    // ...
}

Interpretation

The branches represent separate entry-bearing project variants in the downloaded bundle, not runtime calls between those variants. Each branch is intentionally collapsed at the documented framework boundary; the detailed target-local flow remains in the cited files. Ownership is claimed only where the next section cites a stored property or assignment.

Ownership and state

classDiagram
    ExportSettings *-- CMTime : duration
    ExportSettings *-- CMTimeScale : frameRate
    ExportSettings *-- CGRect : viewport
    AppDelegate o-- SCNView : sceneKitView

Ownership evidence

HEVC-Videos-With-Alpha-AssetWriting/HEVC-Videos-With-Alpha-AssetWriting/AppDelegate.swift:14 — stored dependency or nearest verified ownership anchor

struct ExportSettings {
    static let duration = CMTime(value: 5, timescale: 1)
    static let frameRate = CMTimeScale(60)
    static let height = 720
    static let width = 1280
    static let viewport = CGRect(x: 0, y: 0, width: width, height: height)
}

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

HEVC-Videos-With-Alpha-AssetWriting/HEVC-Videos-With-Alpha-AssetWriting/AppDelegate.swift:177 — representative execution boundary

@NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate, SCNSceneRendererDelegate {
    // ...
        let mediaDataRequestQueue = DispatchQueue(label: "com.apple.apple-samplecode.HEVC-Videos-With-Alpha-AssetWriting.mediaDataRequestQueue")
    // ...
}

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

HEVC-Videos-With-Alpha-AssetWriting/HEVC-Videos-With-Alpha-AssetWriting/AppDelegate.swift:22 — representative type boundary

@NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate, SCNSceneRendererDelegate {
    @IBOutlet weak var sceneKitView: SCNView!
    // ...
}

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

Access control

Reference code

HEVC-Videos-With-Alpha-Exports/HEVC-Videos-With-Alpha-Exports/main.swift:16 — representative boundary

    public var description: String {
        // ...
        case .unknown: return "unknown"
        // ...
    }

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.
• Protocols: no local protocol declaration in the scanned source.
• Methods: applicationDidFinishLaunching, renderNextFrameAsynchronously, renderer, makeAssetWriter, exportToHEVCMovieWithAlphaAsynchronously, pressedRecord, applicationWillTerminate, exportToHEVCWithAlphaAsynchronously.
• Files: HEVC-Videos-With-Alpha-AssetWriting/HEVC-Videos-With-Alpha-AssetWriting/AppDelegate.swift, HEVC-Videos-With-Alpha-Playback/HEVC-Videos-With-Alpha-Playback/AppDelegate.swift, HEVC-Videos-With-Alpha-Playback/HEVC-Videos-With-Alpha-Playback/ViewController.swift.

Architecture takeaways

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