iphone - 从视频文件中提取音频

Question

如何不使用 FFmpeg 从视频文件中提取音频？

我想使用 AVMutableComposition 和 AVURLAsset 来解决它。例如从 .mov 到 .m4a 文件的转换。

Answer 1

以下 Swift 5/iOS 12.3 代码显示了如何从电影文件 (.mov) 中提取音频并将其转换为音频文件 (.m4a)使用 AVURLAsset、AVMutableComposition 和 AVAssetExportSession:

import UIKit
import AVFoundation

class ViewController: UIViewController {

    @IBAction func extractAudioAndExport(_ sender: UIButton) {
        // Create a composition
        let composition = AVMutableComposition()
        do {
            let sourceUrl = Bundle.main.url(forResource: "Movie", withExtension: "mov")!
            let asset = AVURLAsset(url: sourceUrl)
            guard let audioAssetTrack = asset.tracks(withMediaType: AVMediaType.audio).first else { return }
            guard let audioCompositionTrack = composition.addMutableTrack(withMediaType: AVMediaType.audio, preferredTrackID: kCMPersistentTrackID_Invalid) else { return }
            try audioCompositionTrack.insertTimeRange(audioAssetTrack.timeRange, of: audioAssetTrack, at: CMTime.zero)
        } catch {
            print(error)
        }

        // Get url for output
        let outputUrl = URL(fileURLWithPath: NSTemporaryDirectory() + "out.m4a")
        if FileManager.default.fileExists(atPath: outputUrl.path) {
            try? FileManager.default.removeItem(atPath: outputUrl.path)
        }

        // Create an export session
        let exportSession = AVAssetExportSession(asset: composition, presetName: AVAssetExportPresetPassthrough)!
        exportSession.outputFileType = AVFileType.m4a
        exportSession.outputURL = outputUrl

        // Export file
        exportSession.exportAsynchronously {
            guard case exportSession.status = AVAssetExportSession.Status.completed else { return }

            DispatchQueue.main.async {
                // Present a UIActivityViewController to share audio file
                guard let outputURL = exportSession.outputURL else { return }
                let activityViewController = UIActivityViewController(activityItems: [outputURL], applicationActivities: [])
                self.present(activityViewController, animated: true, completion: nil)
            }
        }
    }

}