正儿八经学iOS系列 - AVPlayer实现流音频边播边存

边播边下有三套左右实现思路,本文使用AVPlayer + AVURLAsset实现。 概述 1 AVPlayer简介 AVPlayer存

边播边下有三套左右实现思路,本文使用AVPlayer + AVURLAsset实现。

概述

1. AVPlayer简介

  • AVPlayer存在于AVFoundation中,可以播放视频和音频,可以理解为一个随身听

  • AVPlayer的关联类:

(1)AVAsset:一个抽象类,不能直接使用,代表一个要播放的资源。可以理解为一个磁带子类AVURLAsset是根据URL生成的包含媒体信息的资源对象。我们就是要通过这个类的代理实现音频的边播边下的

(2)AVPlayerItem:可以理解为一个装在磁带盒子里的磁带

2. AVPlayer播放原理

  • 给播放器设置好想要它播放的URL

(1)播放器向URL所在的服务器发送请求,请求两个东西

(2)所需音频片段的起始offset

  • 所需的音频长度

  • 服务器根据请求的内容,返回数据

  • 播放器拿到数据拼装成文件

  • 播放器从拼装好的文件中,找出现在需要播放的片段,进行播放

3. 边播边下的原理

实现边下边播,其实就是手动实现AVPlayer的上列播放过程。

  • 当播放器需要预先缓存一些数据的时候,不让播放器直接向服务器发起请求,而是向我们自己写的某个类(暂且称之为播放器的秘书)发起缓存请求

  • 秘书根据播放器的缓存请求的请求内容,向服务器发起请求。

  • 服务器返回秘书所需的数据

  • 秘书把服务器返回的数据写进本地的缓存文件中

  • 当需要播放某段声音的时候,向秘书发出播放请求索要这段音频文件

  • 秘书从本地的缓存文件中找到播放器播放请求所需片段,返回给播放器

  • 播放器拿到数据开心滴播放

  • 当整首歌都缓存完成以后,秘书需要把缓存文件拷贝一份,改个名字,这个文件就是我们所需要的本地持久化文件

  • 下次播放器再播放歌曲的时候,先判断下本地有木有这个名字的文件,有则播放本地文件,木有则向秘书要数据

技术实现

OK,边播边下的原理知道了,我们可以正式写代码了~建议先从文末链接处把Demo下载下来,对着Demo咱们慢慢道来~

1. 类

共需要三个类:

  • MusicPlayerManager:CEO。单例,负责整个工程所有的播放、暂停、下一曲、结束、判断应该播放本地文件还是从服务器拉数据之类的事情

  • RequestLoader:就是上文所说的秘书,负责给播放器提供播放所需的音频片段,以及找人向服务器索要数据

  • RequestTask:秘书的小弟。负责和服务器连接、向服务器请求数据、把请求回来的数据写到本地缓存文件、把写完的缓存文件移到持久化目录去。所有脏活累活都是他做。

2. 方法

先从小弟说起

2.1.  RequestTask

2.1.0. 概说

如上文所说,小弟是负责做脏活累活的。 负责和服务器连接、向服务器请求数据、把请求回来的数据写到本地缓存文件、把写完的缓存文件移到持久化目录去

2.1.1. 初始化音频文件持久化文件夹 & 缓存文件

private func _initialTmpFile() { do { try NSFileManager.defaultManager().createDirectoryAtPath(StreamAudioConfig.audioDicPath, withIntermediateDirectories: true, attributes: nil) } catch { print("creat dic false -- error:/(error)") } if NSFileManager.defaultManager().fileExistsAtPath(StreamAudioConfig.tempPath) { try! NSFileManager.defaultManager().removeItemAtPath(StreamAudioConfig.tempPath) } NSFileManager.defaultManager().createFileAtPath(StreamAudioConfig.tempPath, contents: nil, attributes: nil) }

2.1.2. 与服务器建立连接请求数据

/** 连接服务器,请求数据(或拼range请求部分数据)(此方法中会将协议头修改为http) - parameter offset: 请求位置 */ public func set(URL url: NSURL, offset: Int) { func initialTmpFile() { try! NSFileManager.defaultManager().removeItemAtPath(StreamAudioConfig.tempPath) NSFileManager.defaultManager().createFileAtPath(StreamAudioConfig.tempPath, contents: nil, attributes: nil) } _updateFilePath(url) self.url = url self.offset = offset // 如果建立第二次请求,则需初始化缓冲文件 if taskArr.count >= 1 { initialTmpFile() } // 初始化已下载文件长度 downLoadingOffset = 0 // 把stream://xxx的头换成http://的头 let actualURLComponents = NSURLComponents(URL: url, resolvingAgainstBaseURL: false) actualURLComponents?.scheme = "http" guard let URL = actualURLComponents?.URL else {return} let request = NSMutableURLRequest(URL: URL, cachePolicy: NSURLRequestCachePolicy.ReloadIgnoringCacheData, timeoutInterval: 20.0) // 若非从头下载,且视频长度已知且大于零,则下载offset到videoLength的范围(拼request参数) if offset > 0 && videoLength > 0 { request.addValue("bytes=/(offset)-/(videoLength - 1)", forHTTPHeaderField: "Range") } connection?.cancel() connection = NSURLConnection(request: request, delegate: self, startImmediately: false) connection?.setDelegateQueue(NSOperationQueue.mainQueue()) connection?.start() }

2.1.3. 响应服务器的Response头

 public func connection(connection: NSURLConnection, didReceiveResponse response: NSURLResponse) { isFinishLoad = false guard response is NSHTTPURLResponse else {return} // 解析头部数据 let httpResponse = response as! NSHTTPURLResponse let dic = httpResponse.allHeaderFields let content = dic["Content-Range"] as? String let array = content?.componentsSeparatedByString("/") let length = array?.last // 拿到真实长度 var videoLength = 0 if Int(length ?? "0") == 0 { videoLength = Int(httpResponse.expectedContentLength) } else { videoLength = Int(length!)! } self.videoLength = videoLength //TODO: 此处需要修改为真实数据格式 - 从字典中取 self.mimeType = "video/mp4" // 回调 recieveVideoInfoHandler?(task: self, videoLength: videoLength, mimeType: mimeType!) // 连接加入到任务数组中 taskArr.append(connection) // 初始化文件传输句柄 fileHandle = NSFileHandle.init(forWritingAtPath: StreamAudioConfig.tempPath) }

2.1.4. 处理服务器返回的数据 - 写入缓存文件中

 public func connection(connection: NSURLConnection, didReceiveData data: NSData) { // 寻址到文件末尾 self.fileHandle?.seekToEndOfFile() self.fileHandle?.writeData(data) self.downLoadingOffset += data.length self.receiveVideoDataHandler?(task: self)// print("线程 - /(NSThread.currentThread())") // 注意,这里用子线程有问题 let queue = dispatch_queue_create("com.azen.taskConnect", DISPATCH_QUEUE_SERIAL) dispatch_async(queue) {// // 寻址到文件末尾// self.fileHandle?.seekToEndOfFile()// self.fileHandle?.writeData(data)// self.downLoadingOffset += data.length// self.receiveVideoDataHandler?(task: self)// let thread = NSThread.currentThread()// print("线程 - /(thread)") }

2.1.5. 服务器文件返回完毕,把缓存文件放入持久化文件夹

 public func connectionDidFinishLoading(connection: NSURLConnection) { func tmpPersistence() { isFinishLoad = true let fileName = url?.lastPathComponent// let movePath = audioDicPath.stringByAppendingPathComponent(fileName ?? "undefine.mp4") let movePath = StreamAudioConfig.audioDicPath + "//(fileName ?? "undefine.mp4")" _ = try? NSFileManager.defaultManager().removeItemAtPath(movePath) var isSuccessful = true do { try NSFileManager.defaultManager().copyItemAtPath(StreamAudioConfig.tempPath, toPath: movePath) } catch { isSuccessful = false print("tmp文件持久化失败") } if isSuccessful { print("持久化文件成功!路径 - /(movePath)") } } if taskArr.count < 2 { tmpPersistence() } receiveVideoFinishHanlder?(task: self) }

其他

其他方法包括断线重连以及公开一个cancel方法cancel掉和服务器的连接

2.2.  RequestTask

2.2.0. 概说

秘书要干的最主要的事情就是响应播放器老大的号令,所有方法都是围绕着播放器老大来的。秘书需要遵循AVAssetResourceLoaderDelegate协议才能被录用。

2.2.1. 代理方法,播放器需要缓存数据的时候,会调这个方法

这个方法其实是播放器在说:小秘呀,我想要这段音频文件。你能现在给我还是等等给我啊?

一定要返回:true,告诉播放器,我等等给你。

然后,立马找本地缓存文件里有木有这段数据,有把数据拿给播放器,如果木有,则派秘书的小弟向服务器要。

具体实现代码有点多,这里就不全部贴出来了。可以去看看文末的Demo记得赏颗星哟~

 /** 播放器问:是否应该等这requestResource加载完再说? 这里会出现很多个loadingRequest请求, 需要为每一次请求作出处理 - parameter resourceLoader: 资源管理器 - parameter loadingRequest: 每一小块数据的请求 - returns: */ public func resourceLoader(resourceLoader: AVAssetResourceLoader, shouldWaitForLoadingOfRequestedResource loadingRequest: AVAssetResourceLoadingRequest) -> Bool { // 添加请求到队列 pendingRequset.append(loadingRequest) // 处理请求 _dealWithLoadingRequest(loadingRequest) print("----/(loadingRequest)") return true }

2.2.2. 代理方法,播放器关闭了下载请求

 /** 播放器关闭了下载请求 播放器关闭一个旧请求,都会发起一到多个新请求,除非已经播放完毕了 - parameter resourceLoader: 资源管理器 - parameter loadingRequest: 待关请求 */ public func resourceLoader(resourceLoader: AVAssetResourceLoader, didCancelLoadingRequest loadingRequest: AVAssetResourceLoadingRequest) { guard let index = pendingRequset.indexOf(loadingRequest) else {return} pendingRequset.removeAtIndex(index) }

2.3.  MusicPlayerManager

2.3.0. 概说

负责调度所有播放器的,负责App中的一切涉及音频播放的事件

唔。。犯个小懒。。代码直接贴上来咯~要赶不上楼下的538路公交啦~~谢谢大家体谅哦~

public class MusicPlayerManager: NSObject { // public var status public var currentURL: NSURL? { get { guard let currentIndex = currentIndex, musicURLList = musicURLList where currentIndex < musicURLList.count else {return nil} return musicURLList[currentIndex] } } /**播放状态,用于需要获取播放器状态的地方KVO*/ public var status: ManagerStatus = .Non /**播放进度*/ public var progress: CGFloat { get { if playDuration > 0 { let progress = playTime / playDuration return progress } else { return 0 } } } /**已播放时长*/ public var playTime: CGFloat = 0 /**总时长*/ public var playDuration: CGFloat = CGFloat.max /**缓冲时长*/ public var tmpTime: CGFloat = 0 public var playEndConsul: (()->())? /**强引用控制器,防止被销毁*/ public var currentController: UIViewController? // private status private var currentIndex: Int? private var currentItem: AVPlayerItem? { get { if let currentURL = currentURL { let item = getPlayerItem(withURL: currentURL) return item } else { return nil } } } private var musicURLList: [NSURL]? // basic element public var player: AVPlayer? private var playerStatusObserver: NSObject? private var resourceLoader: RequestLoader = RequestLoader() private var currentAsset: AVURLAsset? private var progressCallBack: ((tmpProgress: Float?, playProgress: Float?)->())? public class var sharedInstance: MusicPlayerManager { struct Singleton { static let instance = MusicPlayerManager() } // 后台播放 let session = AVAudioSession.sharedInstance() do { try session.setActive(true) } catch { print(error) } do { try session.setCategory(AVAudioSessionCategoryPlayback) } catch { print(error) } return Singleton.instance } public enum ManagerStatus { case Non, LoadSongInfo, ReadyToPlay, Play, Pause, Stop }}// MARK: - basic public funcsextension MusicPlayerManager { /** 开始播放 */ public func play(musicURL: NSURL?) { guard let musicURL = musicURL else {return} if let index = getIndexOfMusic(music: musicURL) { // 歌曲在队列中,则按顺序播放 currentIndex = index } else { putMusicToArray(music: musicURL) currentIndex = 0 } playMusicWithCurrentIndex() } public func play(musicURL: NSURL?, callBack: ((tmpProgress: Float?, playProgress: Float?)->())?) { play(musicURL) progressCallBack = callBack } public func next() { currentIndex = getNextIndex() playMusicWithCurrentIndex() } public func previous() { currentIndex = getPreviousIndex() playMusicWithCurrentIndex() } /** 继续 */ public func goOn() { player?.rate = 1 } /** 暂停 - 可继续 */ public func pause() { player?.rate = 0 } /** 停止 - 无法继续 */ public func stop() { endPlay() }}// MARK: - private funcsextension MusicPlayerManager { private func putMusicToArray(music URL: NSURL) { if musicURLList == nil { musicURLList = [URL] } else { musicURLList!.insert(URL, atIndex: 0) } } private func getIndexOfMusic(music URL: NSURL) -> Int? { let index = musicURLList?.indexOf(URL) return index } private func getNextIndex() -> Int? { if let musicURLList = musicURLList where musicURLList.count > 0 { if let currentIndex = currentIndex where currentIndex + 1 < musicURLList.count { return currentIndex + 1 } else { return 0 } } else { return nil } } private func getPreviousIndex() -> Int? { if let currentIndex = currentIndex { if currentIndex - 1 >= 0 { return currentIndex - 1 } else { return musicURLList?.count ?? 1 - 1 } } else { return nil } } /** 从头播放音乐列表 */ private func replayMusicList() { guard let musicURLList = musicURLList where musicURLList.count > 0 else {return} currentIndex = 0 playMusicWithCurrentIndex() } /** 播放当前音乐 */ private func playMusicWithCurrentIndex() { guard let currentURL = currentURL else {return} // 结束上一首 endPlay() player = AVPlayer(playerItem: getPlayerItem(withURL: currentURL)) observePlayingItem() } /** 本地不存在,返回nil,否则返回本地URL */ private func getLocationFilePath(url: NSURL) -> NSURL? { let fileName = url.lastPathComponent let path = StreamAudioConfig.audioDicPath + "//(fileName ?? "tmp.mp4")" if NSFileManager.defaultManager().fileExistsAtPath(path) { let url = NSURL.init(fileURLWithPath: path) return url } else { return nil } } private func getPlayerItem(withURL musicURL: NSURL) -> AVPlayerItem { if let locationFile = getLocationFilePath(musicURL) { let item = AVPlayerItem(URL: locationFile) return item } else { let playURL = resourceLoader.getURL(url: musicURL)! // 转换协议头 let asset = AVURLAsset(URL: playURL) currentAsset = asset asset.resourceLoader.setDelegate(resourceLoader, queue: dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) let item = AVPlayerItem(asset: asset) return item } } private func setupPlayer(withURL musicURL: NSURL) { let songItem = getPlayerItem(withURL: musicURL) player = AVPlayer(playerItem: songItem) } private func playerPlay() { player?.play() } private func endPlay() { status = ManagerStatus.Stop player?.rate = 0 removeObserForPlayingItem() player?.replaceCurrentItemWithPlayerItem(nil) resourceLoader.cancel() currentAsset?.resourceLoader.setDelegate(nil, queue: nil) progressCallBack = nil resourceLoader = RequestLoader() playDuration = 0 playTime = 0 playEndConsul?() player = nil }}extension MusicPlayerManager { public override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer) { guard object is AVPlayerItem else {return} let item = object as! AVPlayerItem if keyPath == "status" { if item.status == AVPlayerItemStatus.ReadyToPlay { status = .ReadyToPlay print("ReadyToPlay") let duration = item.duration playerPlay() print(duration) } else if item.status == AVPlayerItemStatus.Failed { status = .Stop print("Failed") stop() } } else if keyPath == "loadedTimeRanges" { let array = item.loadedTimeRanges guard let timeRange = array.first?.CMTimeRangeValue else {return} // 缓冲时间范围 let totalBuffer = CMTimeGetSeconds(timeRange.start) + CMTimeGetSeconds(timeRange.duration) // 当前缓冲长度 tmpTime = CGFloat(tmpTime) print("共缓冲 - /(totalBuffer)") let tmpProgress = tmpTime / playDuration progressCallBack?(tmpProgress: Float(tmpProgress), playProgress: nil) } } private func observePlayingItem() { guard let currentItem = self.player?.currentItem else {return} // KVO监听正在播放的对象状态变化 currentItem.addObserver(self, forKeyPath: "status", options: NSKeyValueObservingOptions.New, context: nil) // 监听player播放情况 playerStatusObserver = player?.addPeriodicTimeObserverForInterval(CMTimeMake(1, 1), queue: dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), usingBlock: { [weak self] (time) in guard let `self` = self else {return} // 获取当前播放时间 self.status = .Play let currentTime = CMTimeGetSeconds(time) let totalTime = CMTimeGetSeconds(currentItem.duration) self.playDuration = CGFloat(totalTime) self.playTime = CGFloat(currentTime) print("current time ---- /(currentTime) ---- tutalTime ---- /(totalTime)") self.progressCallBack?(tmpProgress: nil, playProgress: Float(self.progress)) if totalTime - currentTime < 0.1 { self.endPlay() } }) as? NSObject // 监听缓存情况 currentItem.addObserver(self, forKeyPath: "loadedTimeRanges", options: NSKeyValueObservingOptions.New, context: nil) } private func removeObserForPlayingItem() { guard let currentItem = self.player?.currentItem else {return} currentItem.removeObserver(self, forKeyPath: "status") if playerStatusObserver != nil { player?.removeTimeObserver(playerStatusObserver!) playerStatusObserver = nil } currentItem.removeObserver(self, forKeyPath: "loadedTimeRanges") }}public struct StreamAudioConfig { static let audioDicPath: String = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.DocumentDirectory, NSSearchPathDomainMask.UserDomainMask, true).last! + "/streamAudio" // 缓冲文件夹 static let tempPath: String = audioDicPath + "/temp.mp4" // 缓冲文件路径 - 非持久化文件路径 - 当前逻辑下,有且只有一个缓冲文件}

iOS音频边播边下Demo,戳这里~

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