Author fragmented MPEG-4 content with AVAssetWriter

5:36 - Instantiate AVAssetWriter and input

// Instantiate asset writer
let assetWriter = AVAssetWriter(contentType: UTType(AVFileType.mp4.rawValue)!)

// Add inputs
let videoInput = AVAssetWriterInput(mediaType: .video, outputSettings: compressionSettings)
			
assetWriter.add(videoInput)

6:28 - Configure AVAssetWriter

assetWriter.outputFileTypeProfile = .mpeg4AppleHLS

assetWriter.preferredOutputSegmentInterval = CMTime(seconds: 6.0, preferredTimescale: 1)

assetWriter.initialSegmentStartTime = myInitialSegmentStartTime

assetWriter.delegate = myDelegateObject

8:00 - Delegate methods

optional func assetWriter(_ writer: AVAssetWriter, didOutputSegmentData segmentData: Data, segmentType: AVAssetSegmentType)


optional func assetWriter(_ writer: AVAssetWriter, didOutputSegmentData segmentData: Data, segmentType: AVAssetSegmentType, segmentReport: AVAssetSegmentReport?)

8:37 - AVAssetSegmentType

public enum AVAssetSegmentType : Int {
    case initialization = 1 
    case separable = 2
}

13:45 - Custom segmentation

// Set properties
assetWriter.outputFileTypeProfile = .mpeg4AppleHLS

assetWriter.preferredOutputSegmentInterval = .indefinite

assetWriter.delegate = myDelegateObject

// Passthrough
let videoInput = AVAssetWriterInput(mediaType: .video, outputSettings: nil)

15:17 - Audio has dependencies

extension AVAssetTrack {
       /* indicates whether this audio track has dependencies (e.g. kAudioFormatMPEGD_USAC) */
    open var hasAudioSampleDependencies: Bool { get }
}