1.AVFoundation

1. NSString

• A static, plain-text Unicode string object that bridges to String

• use NSString when you need reference semantics or other Foundation-specific behavior

2. NSObject

The root class of most Objective-C class hierarchies, from which subclasses inherit a basic interface to the runtime system and the ability to behave as Objective-C objects.

3. AVFoundation

AVFoundation - 시각 청각 미디어 자료를 플레이하고 생성하는 프레임워크.

3.1 AVURLAsset

AVURLAsset is a concrete subclass of AVAsset. When you create an asset as shown below, you’re actually creating an AVURLAsset instance.

3.2 AVAssetExportSession

An object that transcodes the contents of an asset source object to create an output of the form described by a specified export preset.

  open func cropVideoWithUrl(videoUrl url: URL, startTime: CGFloat, duration: CGFloat, completion: ((_ videoPath: URL?, _ error: NSError?) -> Void)?) {
    
    DispatchQueue.global().async {
      let asset = AVURLAsset(url: url, options: nil)
      let exportSession = AVAssetExportSession(asset: asset, presetName: "AVAssetExportPresetHighestQuality")
      let paths: NSArray = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true) as NSArray
      var outputURL = paths.object(at: 0) as! String
      let manager = FileManager.default
        
        
      do {
        try manager.createDirectory(atPath: outputURL, withIntermediateDirectories: true, attributes: nil)
      } catch _ {
      }
        
      outputURL = outputURL.convert.appendingPathComponent("output.mp4")
      
      do {
        try manager.removeItem(atPath: outputURL)
      } catch _ {
      }
        
        
      if let exportSession = exportSession as AVAssetExportSession? {
        exportSession.outputURL = URL(fileURLWithPath: outputURL)
        exportSession.shouldOptimizeForNetworkUse = true
        exportSession.outputFileType = AVFileType.mp4
        let start = CMTimeMakeWithSeconds(Float64(startTime), preferredTimescale: 600)
        let duration = CMTimeMakeWithSeconds(Float64(duration), preferredTimescale: 600)
        let range = CMTimeRangeMake(start: start, duration: duration)
        
        exportSession.timeRange = range
        
        exportSession.exportAsynchronously { () -> Void in
          
          switch exportSession.status {
          case AVAssetExportSessionStatus.completed:
            completion?(exportSession.outputURL, nil)
          case AVAssetExportSessionStatus.failed:
            print("Failed: \(String(describing: exportSession.error))")
          case AVAssetExportSessionStatus.cancelled:
            print("Failed: \(String(describing: exportSession.error))")
          default:
            print("default case")
          }
            
        }
      }
        
        
      DispatchQueue.main.async {
      }
    }
  }
}