AI core code examples

import AVFoundation
import Vision

func processVideo(videoURL: URL) {
    let asset = AVAsset(url: videoURL)
    let generator = AVAssetImageGenerator(asset: asset)
    generator.appliesPreferredTrackTransform = true
    
    // Configure frame sampling (1 frame/second)
    let duration = CMTimeGetSeconds(asset.duration)
    for timestamp in stride(from: 0, to: duration, by: 1) {
        let time = CMTimeMakeWithSeconds(timestamp, preferredTimescale: 600)
        
        do {
            let cgImage = try generator.copyCGImage(at: time, actualTime: nil)
            let requestHandler = VNImageRequestHandler(cgImage: cgImage)
            let textRequest = VNRecognizeTextRequest { request, error in
                processTextResults(request: request, timestamp: timestamp)
            }
            
            // Set OCR parameters
            textRequest.recognitionLevel = .accurate
            textRequest.usesLanguageCorrection = true
            textRequest.recognitionLanguages = ["zh-Hans", "en"] // Chinese & English
            
            try requestHandler.perform([textRequest])
        } catch {
            print("OCR Error: \(error.localizedDescription)")
        }
    }
}

private func processTextResults(request: VNRequest, timestamp: Double) {
    guard let observations = request.results as? [VNRecognizedTextObservation] else { return }
    
    for observation in observations {
        guard let topCandidate = observation.topCandidates(1).first else { continue }
        let text = topCandidate.string
        let confidence = topCandidate.confidence
        
        // Store text with timestamp (e.g., CoreData/SQLite)
        saveToIndex(text: text, timestamp: timestamp, confidence: confidence)
    }
}

func saveToIndex(text: String, timestamp: Double, confidence: Float) {
    // CoreData Entity: VideoIndexEntry
    let context = persistentContainer.viewContext
    let newEntry = VideoIndexEntry(context: context)
    
    newEntry.id = UUID()
    newEntry.text = text
    newEntry.timestamp = timestamp
    newEntry.confidence = confidence
    
    // Hybrid indexing: CoreData + SQLite FTS5 for full-text search
    if confidence > 0.85 { // High-confidence entries only
        executeFTSIndexing(text: text, timestamp: timestamp)
    }
    
    try? context.save()
}

private func executeFTSIndexing(text: String, timestamp: Double) {
    let db = try! Connection("video_fts.sqlite")
    try! db.run(videoFTS.create(.ifNotExists) { table in
        table.column(text)
        table.column(timestamp)
    }
    try! db.run(videoFTS.insert(text <- text, timestamp <- timestamp))
}

func searchVideo(keyword: String) -> [SearchResult] {
    // Use SQLite FTS5 for prefix/wildcard matching
    let query = """
    SELECT timestamp, snippet(videoFTS, 0, '<b>', '</b>', '...', 16) 
    FROM videoFTS 
    WHERE text MATCH '\(keyword)*' 
    ORDER BY rank
    """
    
    var results = [SearchResult]()
    let db = try! Connection("video_fts.sqlite")
    try! db.prepare(query).forEach { row in
        let timestamp = row[0] as! Double
        let snippet = row[1] as! String
        results.append(SearchResult(timestamp: timestamp, preview: snippet))
    }
    
    // Fallback to CoreData for low-confidence matches
    if results.isEmpty {
        results = fetchFromCoreData(keyword: keyword)
    }
    
    return results
}