Encoding video for offline transcoding

At a glance

Project structure

Source bundle/
├── Swift/
│   ├── VTEncoderForTranscoding/
│   │   ├── CommandOptions.swift
│   │   └── VTEncoderForTranscoding.swift
│   └── VTEncoderUtils/
│       ├── VideoSource.swift
│       ├── RealTimeVideoSource.swift
│       ├── VTEncoderUtil.swift
│       └── VideoSink.swift
└── Objective-C/
    ├── VTEncoderForTranscoding/
    │   ├── main.m
    │   └── VTEncoderForTranscoding.h
    └── VTEncoderUtils/
        ├── VideoSource.h
        ├── VideoSource.m
        ├── VideoSink.h
        └── VideoSink.m

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 6 project/configuration file(s) and 24 source declaration(s).

Overall architecture

flowchart LR
    Bundle["Sample bundle"]
    V1["Objective-C"]
    V2["Swift"]
    Boundary["VideoToolbox APIs"]
    Bundle --> V1
    V1 --> Boundary
    Bundle --> V2
    V2 --> Boundary

Reference code

Swift/VTEncoderForTranscoding/CommandOptions.swift:13 — architecture anchor

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

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
    CommandOptions *-- CommandConfiguration : configuration
    CommandOptions *-- String : sourceMovie
    CommandOptions *-- Int : bitrate
    CommandOptions o-- CodecType : codecType

Ownership evidence

Swift/VTEncoderForTranscoding/CommandOptions.swift:16 — stored dependency or nearest verified ownership anchor

    static var configuration = CommandConfiguration(
        usage: """
            VTEncoderForTranscoding <source-movie> [<options>]
            """)

    /// The source movie file from which to read video frames.
    @Argument(help: "The source movie file from which to read video frames.")

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.

Class and protocol design

Swift/VTEncoderForTranscoding/CommandOptions.swift:14 — representative type boundary

struct CommandOptions: AsyncParsableCommand {
    // ...
}

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

Access control

Reference code

Objective-C/VTEncoderUtils/VideoSource.h:23 — representative boundary

@interface VideoSource : NSObject
// ...
@property(nonatomic, readonly) float frameRate;
// ...
@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: feature-specific names rather than reusable layer suffixes.
• Protocols: no local protocol declaration in the scanned source.
• Methods: validate, run, frames, enqueue, dequeue, wait, signal, next.
• Files: Swift/VTEncoderForTranscoding/CommandOptions.swift, Swift/VTEncoderUtils/VideoSource.swift, Swift/VTEncoderUtils/RealTimeVideoSource.swift, Objective-C/VTEncoderUtils/VideoSource.h, Objective-C/VTEncoderUtils/VideoSource.m, Objective-C/VTEncoderUtils/VideoSink.h.

Architecture takeaways

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