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AVFoundation素材的获取与编辑：点亮视频创作灵感的工具集

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AVFoundation框架中的素材获取

AVFoundation框架为我们提供了多种获取素材的途径，无论是从照片库中导入，还是通过相机进行拍摄，AVFoundation都能轻松满足您的需求。

从照片库获取素材

PhotosKit：管理相册资源的利器

PhotosKit是一个强大的框架，它提供了管理照片和视频的接口，您可以轻松地从照片库中获取所需的素材。只需几行代码，您就可以访问照片库中的所有相册和资源，并轻松地将它们添加到您的视频项目中。

// 获取所有相册
let albums = PHPhotoLibrary.shared().albums

// 遍历相册
for album in albums {
    // 获取相册中的所有资源
    let assets = PHAsset.fetchAssets(in: album, options: nil)

    // 遍历资源
    for asset in assets {
        // 获取资源的URL
        let url = asset.url

        // 将资源添加到视频项目中
        // ...
    }
}

通过相机拍摄素材

AVCapture：让相机成为您的创作工具

AVCapture模块负责处理相机拍摄的部分，它提供了丰富的接口，让您可以控制相机的各个方面，如分辨率、帧率、对焦、曝光等。您可以使用AVCaptureSession来创建捕捉会话，并通过AVCaptureDeviceInput来添加相机设备。

// 创建捕捉会话
let captureSession = AVCaptureSession()

// 添加相机设备输入
let device = AVCaptureDevice.default(for: .video)!
let input = try AVCaptureDeviceInput(device: device)
captureSession.addInput(input)

// 添加输出
let output = AVCaptureMovieFileOutput()
captureSession.addOutput(output)

// 开始捕捉
captureSession.startRunning()

// 停止捕捉
captureSession.stopRunning()

AVFoundation框架中的素材处理

获取了素材之后，您就可以对它们进行各种处理，如剪辑、拼接、添加转场和特效等。AVFoundation框架提供了丰富的API，让您可以轻松地实现这些操作。

剪辑素材

AVMutableComposition：剪辑素材的利器

AVMutableComposition是一个强大的类，它可以帮助您将多个素材剪辑成一个完整的视频。您可以使用AVMutableCompositionTrack来创建视频和音频轨道，并使用AVMutableVideoCompositionInstruction来指定素材的剪辑方式。

// 创建可变合成
let composition = AVMutableComposition()

// 创建视频轨道
let videoTrack = composition.addMutableTrack(withMediaType: .video, preferredTrackID: kCMPersistentTrackID_Invalid)!

// 创建音频轨道
let audioTrack = composition.addMutableTrack(withMediaType: .audio, preferredTrackID: kCMPersistentTrackID_Invalid)!

// 将素材添加到视频轨道
let videoAsset = AVAsset(url: videoURL)
let videoTimeRange = CMTimeRange(start: CMTime.zero, duration: videoAsset.duration)
try! videoTrack.insertTimeRange(videoTimeRange, of: videoAsset, at: CMTime.zero)

// 将素材添加到音频轨道
let audioAsset = AVAsset(url: audioURL)
let audioTimeRange = CMTimeRange(start: CMTime.zero, duration: audioAsset.duration)
try! audioTrack.insertTimeRange(audioTimeRange, of: audioAsset, at: CMTime.zero)

// 创建合成指令
let instruction = AVMutableVideoCompositionInstruction()
instruction.timeRange = CMTimeRange(start: CMTime.zero, duration: composition.duration)

// 添加视频轨道指令
let videoLayerInstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: videoTrack)
videoLayerInstruction.setTransform(CGAffineTransform.identity, at: CMTime.zero)
instruction.layerInstructions = [videoLayerInstruction]

// 添加音频轨道指令
let audioLayerInstruction = AVMutableAudioMixInputParameters(track: audioTrack)
audioLayerInstruction.setVolume(1.0, at: CMTime.zero)
instruction.audioMix.inputParameters = [audioLayerInstruction]

// 创建合成器
let exporter = AVAssetExportSession(asset: composition, presetName: AVAssetExportPresetHighestQuality)!
exporter.outputURL = outputURL
exporter.outputFileType = .mp4

// 导出合成视频
exporter.exportAsynchronously(completionHandler: {
    // ...
})

拼接素材

AVMutableVideoComposition：拼接素材的神器

AVMutableVideoComposition可以帮助您将多个素材拼接成一个完整的视频。您可以使用AVMutableCompositionTrack来创建视频和音频轨道，并使用AVMutableVideoCompositionInstruction来指定素材的拼接方式。

// 创建可变合成
let composition = AVMutableComposition()

// 创建视频轨道
let videoTrack = composition.addMutableTrack(withMediaType: .video, preferredTrackID: kCMPersistentTrackID_Invalid)!

// 创建音频轨道
let audioTrack = composition.addMutableTrack(withMediaType: .audio, preferredTrackID: kCMPersistentTrackID_Invalid)!

// 将素材添加到视频轨道
for i in 0..<素材数量 {
    let videoAsset = AVAsset(url: videoURLs[i])
    let videoTimeRange = CMTimeRange(start: CMTime.zero, duration: videoAsset.duration)
    try! videoTrack.insertTimeRange(videoTimeRange, of: videoAsset, at: CMTime(seconds: Double(i) * videoAsset.duration.seconds, preferredTimescale: videoAsset.duration.timescale))
}

// 将素材添加到音频轨道
for i in 0..<素材数量 {
    let audioAsset = AVAsset(url: audioURLs[i])
    let audioTimeRange = CMTimeRange(start: CMTime.zero, duration: audioAsset.duration)
    try! audioTrack.insertTimeRange(audioTimeRange, of: audioAsset, at: CMTime(seconds: Double(i) * audioAsset.duration.seconds, preferredTimescale: audioAsset.duration.timescale))
}

// 创建合成指令
let instruction = AVMutableVideoCompositionInstruction()
instruction.timeRange = CMTimeRange(start: CMTime.zero, duration: composition.duration)

// 添加视频轨道指令
let videoLayerInstruction = AVMutableVideoCompositionLayerInstruction(assetTrack: videoTrack)
videoLayerInstruction.setTransform(CGAffineTransform.identity, at: CMTime.zero)
instruction.layerInstructions = [videoLayerInstruction]

// 添加音频轨道指令
let audioLayerInstruction = AVMutableAudioMixInputParameters(track: audioTrack)
audioLayerInstruction.setVolume(1.0, at: CMTime.zero)
instruction.audioMix.inputParameters = [audioLayerInstruction]

// 创建合成器
let exporter = AVAssetExportSession(asset: composition, presetName: AVAssetExportPresetHighestQuality)!
exporter.outputURL = outputURL
exporter.outputFileType = .mp4

// 导出合成视频
exporter.exportAsynchronously(completionHandler: {
    // ...
})

添加转场

AVVideoTransition：转场的艺术

AVVideoTransition可以帮助您在两个素材之间添加转场效果。您可以使用AVMutableVideoComposition来创建合成视频，并使用AVMutableVideoCompositionInstruction来指定素材的转场方式。

// 创建可变合成
let composition = AVMutableComposition()

// 创建视频轨道
let videoTrack = composition.addMutableTrack(withMediaType: .video, preferredTrackID: kCMPersistentTrackID_Invalid)!

// 创建音频轨道
let audioTrack = composition.addMutableTrack(withMediaType: .audio, preferredTrackID: kCMPersistentTrackID_Invalid)!

// 将素材添加到视频轨道
let videoAsset1 = AVAsset(url: videoURL1)
let videoTimeRange1 = CMTimeRange(start: CMTime.zero, duration: videoAsset1.duration)
try! videoTrack.insertTimeRange(videoTimeRange1, of: videoAsset1, at: CMTime.zero)

let videoAsset2 = AVAsset(url: videoURL2)
let videoTimeRange2 = CMTimeRange(start: CMTime.zero, duration: videoAsset2.duration)
try! videoTrack.insertTimeRange(videoTimeRange2, of: videoAsset2, at: videoTimeRange1.duration)

// 将素材添加到音频轨道
let audioAsset1 = AVAsset(url: audioURL1)
let audioTimeRange1 =