AVAsset (video) から音声削除

AVAsset+Extensions.swift

extension AVAsset {

    // Modified from: https://stackoverflow.com/questions/42383260/swift-remove-audio-from-video
    var silentVideoAsset: AVAsset? {
        let composition = AVMutableComposition()

        guard
            let videoTrack = self.tracks(withMediaType: .video).first,
            let compositionVideoTrack = composition.addMutableTrack(withMediaType: .video, preferredTrackID: kCMPersistentTrackID_Invalid)
            else { return nil }

        do {
            try compositionVideoTrack.insertTimeRange(CMTimeRange(start: kCMTimeZero, duration: videoTrack.timeRange.duration),
                                                      of: videoTrack,
                                                      at: kCMTimeZero)
            return composition
        } catch {
            return nil
        }
    }
}

guard let silentVideoAsset = asset.silentVideoAsset else { return }