Class

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.

Declaration

class AVAssetExportSession : NSObject

Overview

Prior to initializing an instance of AVAssetExportSession, you can use allExportPresets() to get the complete list of presets available. Use exportPresets(compatibleWith:) to get a list of presets that are compatible with a specific asset.

After you have initialized an export session with the asset that contains the source media, the export preset name (presetName), and the output file type (outputFileType), you can start the export running by invoking exportAsynchronously(completionHandler:). Because the export is performed asynchronously, this method returns immediately—you can use progress to check on the progress. Depending on the capabilities of the device, some exports may be queued when multiple exports are attempted. When this happens, the status of a queued export will indicate that it's waiting (AVAssetExportSession.Status.waiting).

The completion handler you supply to exportAsynchronously(completionHandler:) is called whether the export fails, completes, or is cancelled. Upon completion, the status property indicates whether the export has completed successfully. If it has failed, the value of the error property supplies additional information about the reason for the failure.

Topics

Initializing a Session

init?(asset: AVAsset, presetName: String)

Creates an asset export session with a specified asset and preset.

Configuring Output

var outputURL: URL?

The URL of the export session’s output.

var supportedFileTypes: [AVFileType]

An array containing the types of files the session can write.

var outputFileType: AVFileType?

The type of file written by the session.

var fileLengthLimit: Int64

The file length that the output of the session should not exceed.

var timeRange: CMTimeRange

The time range exported from the source.

var metadata: [AVMetadataItem]?

The metadata written to the output file by the export session.

var metadataItemFilter: AVMetadataItemFilter?

Specifies a filter object used during export to determine which metadata items to transfer from the source asset.

var audioMix: AVAudioMix?

The parameters for audio mixing and an indication whether to enable nondefault audio mixing for export.

var audioTimePitchAlgorithm: AVAudioTimePitchAlgorithm

A processing algorithm used to manage audio pitch for scaled audio edits.

var shouldOptimizeForNetworkUse: Bool

A Boolean value that indicates whether to optimize the movie should for network use.

var videoComposition: AVVideoComposition?

The instructions for video composition, and indicates whether video composition is enabled for export.

var customVideoCompositor: AVVideoCompositing?

The custom video compositor instance used, if any.

var canPerformMultiplePassesOverSourceMediaData: Bool

A Boolean value that indicates whether the export session can perform multiple passes over the source media to achieve better results.

var directoryForTemporaryFiles: URL?

A directory that is suitable for containing temporary files generated during the export process.

Configuring Export Presets

var presetName: String

The name of the preset used to initialize the session.

class func allExportPresets() -> [String]

Returns all available export preset names.

class func exportPresets(compatibleWith: AVAsset) -> [String]

Returns the identifiers compatible with a given asset.

class func determineCompatibility(ofExportPreset: String, with: AVAsset, outputFileType: AVFileType?, completionHandler: (Bool) -> Void)

Reports the compatibility of an export present, asset, and output file type to the specified block.

Export Preset Names for Device-Appropriate QuickTime Files

You use these export options to produce QuickTime movie files with video size appropriate to the current device.

Export Preset Names for QuickTime Files of a Given Size

You use these export options to produce QuickTime movie files with a specified video size.

Export Preset Name for iTunes Audio

You use this export option to produce an audio-only MPEG 4 Audio file with appropriate iTunes gapless playback data.

Export Preset Names for Apple Devices

You use these export options to produce playable files for use on specific Apple devices.

Export Preset Name for Pass Through

You use this export option to let all tracks pass through as formatted unless otherwise prohibited.

func determineCompatibleFileTypes(completionHandler: ([AVFileType]) -> Void)

Reports the compatible file types for the current export session to the specified block.

Exporting Media

func exportAsynchronously(completionHandler: () -> Void)

Starts the asynchronous execution of an export session.

func cancelExport()

Cancels the execution of an export session.

var error: Error?

Describes the error that occurred.

enum AVAssetExportSession.Status

A set of statuses used for relaying the state of an export session.

var estimatedOutputFileLength: Int64

The estimated size, in bytes, of the exported file.

var maxDuration: CMTime

Provides an estimate of the maximum duration of the exported media.

Getting Export Status

var progress: Float

The progress of the export on a scale from 0 to 1.

var status: AVAssetExportSession.Status

The status of the export session.

Accessing the Asset

var asset: AVAsset

The asset used to initialize the export session.

Relationships

Inherits From

NSObject