最近在做一個東西的時候，需要把一張或者多張圖片合成為一個視訊檔案，並加入到視訊軌道中進行播放或者匯出，而不單單是把圖片當做水印加到現有的視訊上，做的時候首先考慮到的當然是AVAssetWriter，但是在做的時候還是遇到了很多問題，首先我用的是swift 3，翻遍了StackOverFlow也沒有找到合適的，當然也有點偷懶的意思，想直接搜來完事兒。

第一次做的時候，因為裡面的很多介面及操作都是非同步的方式，但是當在測試的時候，發現我現有流程的程式碼中用需要和其他流程的程式碼同步，所以又改成了同步的方式。下面就直接貼程式碼了：

非同步的方式：

//
//  DOVImagesToVideoAsync.swift
//  ImagesToVideo
//
//  Created by Wulei on 2016/12/24.
//  Copyright © 2016年 wulei. All rights reserved.
//

import Foundation
import AVFoundation
import UIKit

typealias DOVMovieMakerCompletion = (URL) -> Void
fileprivate typealias DOVMovieMakerUIImageExtractor = (AnyObject) -> UIImage?

class DOVImageToVideoAsync: NSObject{
    
    //MARK: Private Properties
    
    private var assetWriter:AVAssetWriter!
    private var writeInput:AVAssetWriterInput!
    private var bufferAdapter:AVAssetWriterInputPixelBufferAdaptor!
    private var videoSettings:[String : Any]!
    private var frameTime:CMTime!
    private var fileURL:URL!
    private var completionBlock: DOVMovieMakerCompletion?
    
    //MARK: Class Method
    
    class func videoSettings(codec:String, width:Int, height:Int) -> [String: Any]{
        if(Int(width) % 16 != 0){
            print("warning: video settings width must be divisible by 16")
        }
        
        let videoSettings:[String: Any] = [AVVideoCodecKey: AVVideoCodecH264,
                                           AVVideoWidthKey: width,
                                           AVVideoHeightKey: height]
        
        return videoSettings
    }
    
    //MARK: Public methods
    
    init(videoSettings: [String: Any]) {
        super.init()
        
        let paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
        var tempPath:String
        repeat{
            let random = arc4random()
            tempPath = paths[0] + "/\(random).mp4"
        }while(FileManager.default.fileExists(atPath: tempPath))
        //        let tempPath = paths[0] + "/exprotvideo.mp4"
        //        if(FileManager.default.fileExists(atPath: tempPath)){
        //            guard (try? FileManager.default.removeItem(atPath: tempPath)) != nil else {
        //                print("remove path failed")
        //                return
        //            }
        //        }
        
        self.fileURL = URL(fileURLWithPath: tempPath)
        self.assetWriter = try! AVAssetWriter(url: self.fileURL, fileType: AVFileTypeQuickTimeMovie)
        
        self.videoSettings = videoSettings
        self.writeInput = AVAssetWriterInput(mediaType: AVMediaTypeVideo, outputSettings: videoSettings)
        assert(self.assetWriter.canAdd(self.writeInput), "add failed")
        
        self.assetWriter.add(self.writeInput)
        let bufferAttributes:[String: Any] = [kCVPixelBufferPixelFormatTypeKey as String: Int(kCVPixelFormatType_32ARGB)]
        self.bufferAdapter = AVAssetWriterInputPixelBufferAdaptor(assetWriterInput: self.writeInput, sourcePixelBufferAttributes: bufferAttributes)
        self.frameTime = CMTimeMake(1, 1)
    }
    
    func createMovieFrom(urls: [URL], withCompletion: @escaping DOVMovieMakerCompletion){
        self.createMovieFromSource(images: urls as [AnyObject], extractor:{(inputObject:AnyObject) ->UIImage? in
            return UIImage(data: try! Data(contentsOf: inputObject as! URL))}, withCompletion: withCompletion)
    }
    
    func createMovieFrom(images: [UIImage], withCompletion: @escaping DOVMovieMakerCompletion){
        self.createMovieFromSource(images: images, extractor: {(inputObject:AnyObject) -> UIImage? in
            return inputObject as? UIImage}, withCompletion: withCompletion)
    }
    
    //MARK: Private methods
    
    private func createMovieFromSource(images: [AnyObject], extractor: @escaping DOVMovieMakerUIImageExtractor, withCompletion: @escaping CXEMovieMakerCompletion){
        self.completionBlock = withCompletion
        
        self.assetWriter.startWriting()
        self.assetWriter.startSession(atSourceTime: kCMTimeZero)
        
        let mediaInputQueue = DispatchQueue(label: "mediaInputQueue")
        var i = 0
        let frameNumber = images.count
        self.writeInput.requestMediaDataWhenReady(on: mediaInputQueue){
            while(true){
                if(i >= frameNumber){
                    break
                }
                
                if (self.writeInput.isReadyForMoreMediaData){
                    var sampleBuffer:CVPixelBuffer?
                    autoreleasepool{
                        let img = extractor(images[i])
                        if img == nil{
                            i += 1
                            print("Warning: counld not extract one of the frames")
                            //                            continue
                        }
                        sampleBuffer = self.newPixelBufferFrom(cgImage: img!.cgImage!)
                    }
                    if (sampleBuffer != nil){
                        if(i == 0){
                            self.bufferAdapter.append(sampleBuffer!, withPresentationTime: kCMTimeZero)
                        }else{
                            let value = i - 1
                            let lastTime = CMTimeMake(Int64(value), self.frameTime.timescale)
                            let presentTime = CMTimeAdd(lastTime, self.frameTime)
                            self.bufferAdapter.append(sampleBuffer!, withPresentationTime: presentTime)
                        }
                        i = i + 1
                    }
                }
            }
            self.writeInput.markAsFinished()
            self.assetWriter.finishWriting {
                DispatchQueue.main.sync {
                    self.completionBlock!(self.fileURL)
                }
            }
        }
    }
    
    private func newPixelBufferFrom(cgImage:CGImage) -> CVPixelBuffer?{
        let options:[String: Any] = [kCVPixelBufferCGImageCompatibilityKey as String: true, kCVPixelBufferCGBitmapContextCompatibilityKey as String: true]
        var pxbuffer:CVPixelBuffer?
        let frameWidth = self.videoSettings[AVVideoWidthKey] as! Int
        let frameHeight = self.videoSettings[AVVideoHeightKey] as! Int
        
        let status = CVPixelBufferCreate(kCFAllocatorDefault, frameWidth, frameHeight, kCVPixelFormatType_32ARGB, options as CFDictionary?, &pxbuffer)
        assert(status == kCVReturnSuccess && pxbuffer != nil, "newPixelBuffer failed")
        
        CVPixelBufferLockBaseAddress(pxbuffer!, CVPixelBufferLockFlags(rawValue: 0))
        let pxdata = CVPixelBufferGetBaseAddress(pxbuffer!)
        let rgbColorSpace = CGColorSpaceCreateDeviceRGB()
        let context = CGContext(data: pxdata, width: frameWidth, height: frameHeight, bitsPerComponent: 8, bytesPerRow: CVPixelBufferGetBytesPerRow(pxbuffer!), space: rgbColorSpace, bitmapInfo: CGImageAlphaInfo.noneSkipFirst.rawValue)
        assert(context != nil, "context is nil")
        
        context!.concatenate(CGAffineTransform.identity)
        context!.draw(cgImage, in: CGRect(x: 0, y: 0, width: cgImage.width, height: cgImage.height))
        CVPixelBufferUnlockBaseAddress(pxbuffer!, CVPixelBufferLockFlags(rawValue: 0))
        return pxbuffer
    }
}
 

//
//  DOVImagesToVideoSync.swift
//  ImagesToVideo
//
//  Created by Wulei on 2016/12/24.
//  Copyright © 2016年 wulei. All rights reserved.
//

import Foundation
import AVFoundation
import UIKit

fileprivate typealias DOVMovieMakerUIImageExtractor = (AnyObject) -> UIImage?


class DOVImageToVideoSync: NSObject{
    
    //MARK: Private Properties
    
    private var assetWriter:AVAssetWriter!
    private var writeInput:AVAssetWriterInput!
    private var bufferAdapter:AVAssetWriterInputPixelBufferAdaptor!
    private var videoSettings:[String : Any]!
    private var frameTime:CMTime!
    private var fileURL:URL!
    
    //MARK: Class Method
    
    class func videoSettings(codec:String, width:Int, height:Int) -> [String: Any]{
        if(Int(width) % 16 != 0){
            print("warning: video settings width must be divisible by 16")
        }
        
        let videoSettings:[String: Any] = [AVVideoCodecKey: AVVideoCodecH264,
                                           AVVideoWidthKey: width,
                                           AVVideoHeightKey: height]
        
        return videoSettings
    }
    
    //MARK: Public methods
    
    init(videoSettings: [String: Any]) {
        super.init()
        
        let paths = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)
        var tempPath:String
        repeat{
            let random = arc4random()
            tempPath = paths[0] + "/\(random).mp4"
        }while(FileManager.default.fileExists(atPath: tempPath))
        
        self.fileURL = URL(fileURLWithPath: tempPath)
        self.assetWriter = try! AVAssetWriter(url: self.fileURL, fileType: AVFileTypeQuickTimeMovie)
        
        self.videoSettings = videoSettings
        self.writeInput = AVAssetWriterInput(mediaType: AVMediaTypeVideo, outputSettings: videoSettings)
        assert(self.assetWriter.canAdd(self.writeInput), "add failed")
        
        self.assetWriter.add(self.writeInput)
        let bufferAttributes:[String: Any] = [kCVPixelBufferPixelFormatTypeKey as String: Int(kCVPixelFormatType_32ARGB)]
        self.bufferAdapter = AVAssetWriterInputPixelBufferAdaptor(assetWriterInput: self.writeInput, sourcePixelBufferAttributes: bufferAttributes)
        self.frameTime = CMTimeMake(600, 600)
    }
    
    func createMovieFrom(url: URL, duration:Int) -> URL{
        var urls = [URL]()
        var index = duration
        while(index > 0){
            urls.append(url)
            index -= 1
        }
        return self.createMovieFromSource(images: urls as [AnyObject], extractor:{(inputObject:AnyObject) ->UIImage? in
            return UIImage(data: try! Data(contentsOf: inputObject as! URL))})
    }
    
    func createMovieFrom(image: UIImage, duration:Int) -> URL{
        var images = [UIImage]()
        var index = duration
        while(index > 0){
            images.append(image)
            index -= 1
        }
        return self.createMovieFromSource(images: images, extractor: {(inputObject:AnyObject) -> UIImage? in
            return inputObject as? UIImage})
    }
    
    //MARK: Private methods
    
    private func createMovieFromSource(images: [AnyObject], extractor: @escaping DOVMovieMakerUIImageExtractor) -> URL{
        
        self.assetWriter.startWriting()
        //        self.assetWriter.startSession(atSourceTime: kCMTimeZero)
        let zeroTime = CMTimeMake(Int64(0),self.frameTime.timescale)
        self.assetWriter.startSession(atSourceTime: zeroTime)
        
        var i = 0
        let frameNumber = images.count
        
        while !self.writeInput.isReadyForMoreMediaData {}
        
        while(true){
            if(i >= frameNumber){
                break
            }
            
            if (self.writeInput.isReadyForMoreMediaData){
                var sampleBuffer:CVPixelBuffer?
                autoreleasepool{
                    let img = extractor(images[i])
                    if img == nil{
                        i += 1
                        print("Warning: counld not extract one of the frames")
                        //                            continue
                    }
                    sampleBuffer = self.newPixelBufferFrom(cgImage: img!.cgImage!)
                }
                if (sampleBuffer != nil){
                    if(i == 0){
                        self.bufferAdapter.append(sampleBuffer!, withPresentationTime: kCMTimeZero)
                    }else{
                        let value = i - 1
                        let lastTime = CMTimeMake(Int64(value), self.frameTime.timescale)
                        let presentTime = CMTimeAdd(lastTime, self.frameTime)
                        self.bufferAdapter.append(sampleBuffer!, withPresentationTime: presentTime)
                    }
                    i = i + 1
                }
            }
        }
        self.writeInput.markAsFinished()
        self.assetWriter.finishWriting {}
        
        var isSuccess:Bool = false
        while(!isSuccess){
            switch self.assetWriter.status {
            case .completed:
                isSuccess = true
                print("completed")
            case .writing:
                sleep(1)
                print("writing")
            case .failed:
                isSuccess = true
                print("failed")
            case .cancelled:
                isSuccess = true
                print("cancelled")
            default:
                isSuccess = true
                print("unknown")
            }
        }
        return self.fileURL
    }
    
    private func newPixelBufferFrom(cgImage:CGImage) -> CVPixelBuffer?{
        let options:[String: Any] = [kCVPixelBufferCGImageCompatibilityKey as String: true, kCVPixelBufferCGBitmapContextCompatibilityKey as String: true]
        var pxbuffer:CVPixelBuffer?
        let frameWidth = self.videoSettings[AVVideoWidthKey] as! Int
        let frameHeight = self.videoSettings[AVVideoHeightKey] as! Int
        
        let status = CVPixelBufferCreate(kCFAllocatorDefault, frameWidth, frameHeight, kCVPixelFormatType_32ARGB, options as CFDictionary?, &pxbuffer)
        assert(status == kCVReturnSuccess && pxbuffer != nil, "newPixelBuffer failed")
        
        CVPixelBufferLockBaseAddress(pxbuffer!, CVPixelBufferLockFlags(rawValue: 0))
        let pxdata = CVPixelBufferGetBaseAddress(pxbuffer!)
        let rgbColorSpace = CGColorSpaceCreateDeviceRGB()
        let context = CGContext(data: pxdata, width: frameWidth, height: frameHeight, bitsPerComponent: 8, bytesPerRow: CVPixelBufferGetBytesPerRow(pxbuffer!), space: rgbColorSpace, bitmapInfo: CGImageAlphaInfo.noneSkipFirst.rawValue)
        assert(context != nil, "context is nil")
        
        context!.concatenate(CGAffineTransform.identity)
        context!.draw(cgImage, in: CGRect(x: 0, y: 0, width: cgImage.width, height: cgImage.height))
        CVPixelBufferUnlockBaseAddress(pxbuffer!, CVPixelBufferLockFlags(rawValue: 0))
        return pxbuffer
    }
}