How to crop a video file given a start and end timestamp?

To crop a video file given a start and end timestamp, you can use the AVFoundation framework in iOS. Here’s a high-level overview of how you can achieve this:

1. Create an AVAsset: Load your video file into an AVAsset.

2. Create an AVAssetExportSession: Use this to export the cropped video.

3. Set the Time Range: Define the start and end times for the crop.

4. Export the Video: Perform the export operation.

Here’s a sample code snippet to illustrate these steps:

import AVFoundation

// Load the video file into an AVAsset
let videoURL = URL(fileURLWithPath: "path/to/your/video.mp4")
let asset = AVAsset(url: videoURL)

// Create an AVAssetExportSession
guard let exportSession = AVAssetExportSession(asset: asset, presetName: AVAssetExportPresetHighestQuality) else {
    fatalError("Failed to create export session")
}

// Set the output URL for the cropped video
let outputURL = URL(fileURLWithPath: "path/to/your/cropped_video.mp4")
exportSession.outputURL = outputURL
exportSession.outputFileType = .mp4

// Define the time range for cropping
let startTime = CMTime(seconds: 10, preferredTimescale: 600) // Start at 10 seconds
let endTime = CMTime(seconds: 20, preferredTimescale: 600) // End at 20 seconds
let timeRange = CMTimeRange(start: startTime, end: endTime)
exportSession.timeRange = timeRange

// Perform the export
exportSession.exportAsynchronously {
    switch exportSession.status {
    case .completed:
        print("Export completed successfully")
    case .failed:
        if let error = exportSession.error {
            print("Export failed with error: \(error.localizedDescription)")
        }
    case .cancelled:
        print("Export cancelled")
    default:
        break
    }
}

This code will crop the video between the specified start and end times and save it to the specified output URL.

For more detailed information on working with AVFoundation, you can refer to the session Build compelling spatial photo and video experiences from WWDC 2024.