TimesliceVideo

A native macOS application for creating timeslice video effects, where each vertical column in the output represents a different moment in time from the original video.

Features

• Timeslice Effect: Transform videos by sampling vertical columns across time
• Real-time Preview: See exactly what your output will look like before processing
• Adjustable Parameters:
  • Start/End time selection
  • Speed factor (1x - 10x)
  • Custom time range selection
• Optimized Performance: Ultra-fast preview generation using AVAssetReader and direct pixel buffer access
• Native macOS Design: Clean SwiftUI interface with native controls

Requirements

• macOS 12.0+
• Xcode 13.4.1+
• Swift 5.0+

How It Works

The timeslice effect works by:

1. Extracting a single vertical column (default: middle column) from each frame in the selected time range
2. Applying the speed factor by sampling frames at intervals (e.g., 2x speed = every 2nd frame)
3. Assembling these columns horizontally into a single output image

This creates a unique visual effect where motion in the video appears "stretched" horizontally, with time represented spatially across the width of the image.

Architecture

The project follows a clean MVVM architecture:

• Models: VideoParameters.swift - Data models for video metadata and processing parameters
• ViewModels: VideoProcessorViewModel.swift - Business logic and state management
• Views: ContentView.swift - SwiftUI user interface
• Services:
  • VideoLoader.swift - Async video loading and metadata extraction
  • PreviewGenerator.swift - Optimized timeslice preview generation

Performance Optimizations

The preview generation is highly optimized using:

• AVAssetReader for sequential frame access
• Direct pixel buffer manipulation for column extraction
• Frame skipping based on speed factor
• Pre-allocated buffers for efficient memory usage
• BGRA pixel format with proper color channel handling

Typical performance:

• 2-3 second video: ~100-300ms
• 5 minute video at 1x speed: ~1-2 seconds

Usage

1. Launch the application
2. Click "Select Video File" and choose a video
3. Adjust the time range and speed factor using the sliders
4. Watch the preview update in real-time (with 500ms debouncing)
5. Click "Generate Output" to process the full video (coming soon)

License

MIT License - feel free to use and modify as needed.

Credits

Built with Swift, SwiftUI, and AVFoundation.