GitHub - samsonjs/SJSAssetExportSession: An alternative to AVAssetExportSession with customizable audio and video settings

Overview

SJSAssetExportSession is an alternative to AVAssetExportSession that lets you provide custom audio and video settings, without dropping down into the world of AVAssetReader and AVAssetWriter. It has similar capabilites to SDAVAssetExportSession but the API is completely different, the code is written in Swift, and it's ready for the world of strict concurrency.

You shouldn't have to read through audio settings and video settings just to set the bitrate, and setting the frame rate can be tricky, so there's a nicer API that builds these settings dictionaries with some commonly used settings.

Installation

The only way to install this package is with Swift Package Manager (SPM). Please file a new issue or submit a pull-request if you want to use something else.

Supported Platforms

This package is supported on iOS 17.0+, macOS Sonoma 14.0+, and visionOS 1.3+.

Xcode

When you're integrating this into an app with Xcode then go to your project's Package Dependencies and enter the URL https://github.com/samsonjs/SJSAssetExportSession and then go through the usual flow for adding packages.

Swift Package Manager (SPM)

When you're integrating this using SPM on its own then add this to the list of dependencies your Package.swift file:

.package(url: "https://github.com/samsonjs/SJSAssetExportSession.git", .upToNextMajor(from: "0.4.0"))

and then add "SJSAssetExportSession" to the list of dependencies in your target as well.

Usage

There are two ways of exporting assets: one using dictionaries for audio and video settings just like with SDAVAssetExportSession, and the other using a builder-like API with data structures for commonly used settings.

The Nice Way

This should be fairly self-explanatory:

let sourceURL = URL.documentsDirectory.appending(component: "some-video.mov")
let sourceAsset = AVURLAsset(url: sourceURL, options: [
    AVURLAssetPreferPreciseDurationAndTimingKey: true,
])
let destinationURL = URL.temporaryDirectory.appending(component: "shiny-new-video.mp4")
let exporter = ExportSession()
Task {
    for await progress in exporter.progressStream {
        print("Export progress: \(progress)")
    }
}

try await exporter.export(
    asset: sourceAsset,
    video: .codec(.h264, width: 1280, height: 720),
    to: destinationURL,
    as: .mp4
)

Most of the audio and video configuration is optional which is why there are no audio settings specified here. By default you get AAC with 2 channels at a 44.1 KHz sample rate.

All Nice Parameters

Here are all of the parameters you can pass into the nice export method:

let sourceURL = URL.documentsDirectory.appending(component: "some-video.mov")
let sourceAsset = AVURLAsset(url: sourceURL, options: [
    AVURLAssetPreferPreciseDurationAndTimingKey: true,
])
let destinationURL = URL.temporaryDirectory.appending(component: "shiny-new-video.mp4")
let exporter = ExportSession()
Task {
    for await progress in exporter.progressStream {
        print("Export progress: \(progress)")
    }
}

let locationMetadata = AVMutableMetadataItem()
locationMetadata.key = AVMetadataKey.commonKeyLocation.rawValue as NSString
locationMetadata.keySpace = .common
locationMetadata.value = "+48.50176+123.34368/" as NSString
try await exporter.export(
    asset: sourceAsset,
    optimizeForNetworkUse: true,
    metadata: [locationMetadata],
    timeRange: CMTimeRange(start: .zero, duration: .seconds(1)),
    audio: .format(.mp3).channels(1).sampleRate(22_050),
    video: .codec(.h264, width: 1280, height: 720)
        .fps(24)
        .bitrate(1_000_000)
        .color(.sdr),
    to: destinationURL,
    as: .mp4
    )

The Most Flexible Way

When you need all the control you can get down to the nitty gritty details. This code does the exact same thing as the code above:

let sourceURL = URL.documentsDirectory.appending(component: "some-video.mov")
let sourceAsset = AVURLAsset(url: sourceURL, options: [
    AVURLAssetPreferPreciseDurationAndTimingKey: true,
])
let destinationURL = URL.temporaryDirectory.appending(component: "shiny-new-video.mp4")
let exporter = ExportSession()
Task {
    for await progress in exporter.progressStream {
        print("Export progress: \(progress)")
    }
}

let locationMetadata = AVMutableMetadataItem()
locationMetadata.key = AVMetadataKey.commonKeyLocation.rawValue as NSString
locationMetadata.keySpace = .common
locationMetadata.value = "+48.50176+123.34368/" as NSString

let videoComposition = try await AVMutableVideoComposition.videoComposition(withPropertiesOf: sourceAsset)
videoComposition.renderSize = CGSize(width: 1280, height: 720)
videoComposition.sourceTrackIDForFrameTiming = kCMPersistentTrackID_Invalid
videoComposition.frameDuration = CMTime(value: 600 / 24, timescale: 600) // 24 fps
videoComposition.colorPrimaries = AVVideoColorPrimaries_ITU_R_709_2
videoComposition.colorTransferFunction = AVVideoTransferFunction_ITU_R_709_2
videoComposition.colorYCbCrMatrix = AVVideoYCbCrMatrix_ITU_R_709_2
try await exporter.export(
    asset: sourceAsset,
    optimizeForNetworkUse: true,
    metadata: [locationMetadata],
    timeRange: CMTimeRange(start: .zero, duration: .seconds(1)),
    audioOutputSettings: [
        AVFormatIDKey: kAudioFormatMPEGLayer3,
        AVNumberOfChannelsKey: NSNumber(value: 1),
        AVSampleRateKey: NSNumber(value: 22_050),
    ],
    videoOutputSettings: [
        AVVideoCodecKey: AVVideoCodecType.h264.rawValue,
        AVVideoCompressionPropertiesKey: [
            AVVideoProfileLevelKey: AVVideoProfileLevelH264HighAutoLevel,
            AVVideoAverageBitRateKey: NSNumber(value: 1_000_000),
        ] as [String: any Sendable],
        AVVideoColorPropertiesKey: [
            AVVideoColorPrimariesKey: AVVideoColorPrimaries_ITU_R_709_2,
            AVVideoTransferFunctionKey: AVVideoTransferFunction_ITU_R_709_2,
            AVVideoYCbCrMatrixKey: AVVideoYCbCrMatrix_ITU_R_709_2,
        ],
    ],
    composition: videoComposition,
    to: destinationURL,
    as: .mp4
)

It's an effective illustration of why the nicer API exists right? But when you need this flexibility then it's available for you.

Mix and Match

AudioOutputSettings and VideoOutputSettings have a property named settingsDictionary and you can use that to bootstrap your own custom settings.

let sourceURL = URL.documentsDirectory.appending(component: "some-video.mov")
let sourceAsset = AVURLAsset(url: sourceURL, options: [
    AVURLAssetPreferPreciseDurationAndTimingKey: true,
])
let destinationURL = URL.temporaryDirectory.appending(component: "shiny-new-video.mp4")
let exporter = ExportSession()
Task {
    for await progress in exporter.progressStream {
        print("Export progress: \(progress)")
    }
}

var audioSettings = AudioOutputSettings.default.settingsDictionary
audioSettings[AVVideoAverageBitRateKey] = 65_536
let videoSettings = VideoOutputSettings
    .codec(.hevc, width: 1280, height: 720)
    .settingsDictionary
try await exporter.export(
    asset: sourceAsset,
    audioOutputSettings: audioSettings,
    videoOutputSettings: videoSettings,
    to: destinationURL,
    as: .mp4
)