dubbing_lib/ios/Classes/DubbingComposer.swift

//
//  DubbingComposer.swift
//  dubit
//
//  Created by zack on 16/12/20.
//  Copyright © 2016年 Chengdu Aitu Education Technology Ltd. All rights reserved.
//

import Foundation
import AVFoundation

class DubbingComposer {
    var timeline: [Double]
    var videoUrl: URL
    var musicUrl: URL
    var recordsUrl: [String]
    var preTime: Double = 0
    
    init(timeline: [Double], videoUrl: URL, musicUrl: URL, recordsUrl: [String]){
        self.timeline = timeline
        self.videoUrl = videoUrl
        self.musicUrl = musicUrl
        self.recordsUrl = recordsUrl
    }
    
    func compose(_ output: URL, onSuccess successBlock: (()->())?, onFail failBlock:((_ message: String)->())? ) {
        
        //初始化合成器
        let composition = AVMutableComposition()
        
        //为合成器添加视频轨道
        let videoTrack = composition.addMutableTrack(withMediaType: AVMediaType.video, preferredTrackID: kCMPersistentTrackID_Invalid)
        let videoAsset = AVURLAsset(url: videoUrl, options: nil)
        let videoTimeRange = CMTimeRangeMake(start: CMTime.zero, duration: videoAsset.duration)
        do {
            try videoTrack?.insertTimeRange(videoTimeRange, of: videoAsset.tracks(withMediaType: AVMediaType.video).first!, at: CMTime.zero)
        }
        catch {
            DispatchQueue.main.async(execute: { 
                failBlock?("Fail on load video")
            })
            return
        }
        
        //添加音乐轨道
        let musicTrack = composition.addMutableTrack(withMediaType: AVMediaType.audio, preferredTrackID: kCMPersistentTrackID_Invalid)
        let musicAsset = AVURLAsset(url: musicUrl, options: nil)
        let musicTimeRange = videoTimeRange
        do {
            try musicTrack?.insertTimeRange(musicTimeRange, of: musicAsset.tracks(withMediaType: AVMediaType.audio).first!, at: CMTime.zero)
            print("创建音乐音轨成功")
        }
        catch {
            print("创建音乐音轨失败")
        }
        
        //添加两条配音轨道
        let recordTrackA = composition.addMutableTrack(withMediaType: AVMediaType.audio, preferredTrackID: kCMPersistentTrackID_Invalid)
        let recordTrackB = composition.addMutableTrack(withMediaType: AVMediaType.audio, preferredTrackID: kCMPersistentTrackID_Invalid)
        
        //将配音交替放入两条配音轨道
        for (i, url) in recordsUrl.enumerated() {
            let recordUrl = URL(fileURLWithPath: url)
            let recordAsset = AVURLAsset(url: recordUrl, options: nil)
            let recordRange = CMTimeRangeMake(start: CMTime.zero, duration: recordAsset.duration)
            let currentSec = timeline[i]
            let beginSec = currentSec > preTime ? currentSec - preTime : currentSec
            let beginTime = CMTimeMakeWithSeconds(beginSec, preferredTimescale: 100)
            let recordAssetTrack = recordAsset.tracks(withMediaType: AVMediaType.audio).first!
            let recordTrack = i % 2 == 0 ? recordTrackA : recordTrackB
            do {
                try recordTrack?.insertTimeRange(recordRange, of: recordAssetTrack, at: beginTime)
            }
            catch{
                print("Composer error on record: \(i)")
            }
        }
        
        let manager = FileManager.default
        do {
            try manager.removeItem(at: output)
            print("删除旧输出成功")
        }
        catch {
            print("删除旧输出失败")
        }
        
        //输出到文件
        if let assetExport = AVAssetExportSession(asset: composition, presetName: AVAssetExportPresetMediumQuality) {
            assetExport.outputFileType = AVFileType.mp4
            assetExport.outputURL = output
            assetExport.shouldOptimizeForNetworkUse = true
            assetExport.exportAsynchronously(completionHandler: { 
                successBlock?()
                return
            })

        }
        else {
            DispatchQueue.main.async(execute: { 
                failBlock?("Something wrong on composition")
            })
        }
    }
}