iOS 17使用AVMutableMovie/AVPlayer直播流出现黑屏问题求助

问题概述 #

在iOS 17系统中，通过WSS抓取5秒分片视频数据，使用AVMutableMovie初始化AVPlayerItem，并通过replaceCurrentItem(with:)切换分片实现直播播放时，出现持续黑屏现象，该功能在iOS 16上运行正常。尝试调整播放逻辑后虽能播放，但切换分片时会出现画面闪烁。

可能原因 #

iOS 17对AVMutableMovie的内存数据初始化逻辑做了调整，直接通过Data初始化的AVMutableMovie可能未正确解析或加载媒体轨道，导致AVPlayerItem无法渲染画面。此外，频繁调用replaceCurrentItem(with:)会触发播放器的资源重置，引发闪烁。

解决方案 #

1. 验证AVMutableMovie轨道有效性 #

在创建AVPlayerItem前，先检查AVMutableMovie是否包含有效轨道，避免加载无效资源：

private func playNext() {
    let nextSet = self.dataCollector.getNextItem(length: self.configuration.frameDelay)
    guard nextSet.count == self.configuration.frameDelay else { return }
    
    var playerTime = self.player.currentItem != nil ? Int(CMTimeGetSeconds(player.currentTime())) : 0
    var allData = Data()
    allData.appendAll(dataSet: dataCollector.getFileType())
    
    nextSet.forEach { data in
        playerTime += 1
        allData.append(data.getFragmentData())
        self.currentFragmentTimes.updateValue(data.getFragmentTime(), forKey: playerTime)
    }
    
    guard allData.count > 0 else { return }
    
    // 初始化AVMutableMovie并检查轨道
    guard let movie = AVMutableMovie(data: allData, options: nil),
          movie.tracks.count > 0 else {
        // 处理无效媒体数据情况
        return
    }
    
    let playerItem = AVPlayerItem(asset: movie)
    // 监听item状态，确保准备就绪后播放
    let statusObserver = playerItem.observe(\.status, options: [.new]) { [weak self] item, change in
        guard let self = self else { return }
        if item.status == .readyToPlay {
            self.player.replaceCurrentItem(with: item)
            self.player.play()
        } else if item.status == .failed {
            // 处理加载失败
            print("Player item failed: \(item.error?.localizedDescription ?? "Unknown error")")
        }
    }
    // 保存观察者引用避免被释放
    self.itemObservers.append(statusObserver)
    self.playerInitializedTime = nil
}

2. 改用AVURLAsset加载临时文件 #

iOS 17对内存媒体数据的兼容性下降，建议将分片数据写入临时文件，通过AVURLAsset加载，提升兼容性：

private func playNext() {
    let nextSet = self.dataCollector.getNextItem(length: self.configuration.frameDelay)
    guard nextSet.count == self.configuration.frameDelay else { return }
    
    var playerTime = self.player.currentItem != nil ? Int(CMTimeGetSeconds(player.currentTime())) : 0
    var allData = Data()
    allData.appendAll(dataSet: dataCollector.getFileType())
    
    nextSet.forEach { data in
        playerTime += 1
        allData.append(data.getFragmentData())
        self.currentFragmentTimes.updateValue(data.getFragmentTime(), forKey: playerTime)
    }
    
    guard allData.count > 0 else { return }
    
    // 创建临时文件URL
    let tempDir = NSTemporaryDirectory()
    let tempFileName = UUID().uuidString + ".mp4" // 根据实际媒体格式调整后缀
    let tempFileURL = URL(fileURLWithPath: tempDir).appendingPathComponent(tempFileName)
    
    do {
        try allData.write(to: tempFileURL)
        let asset = AVURLAsset(url: tempFileURL)
        let playerItem = AVPlayerItem(asset: asset)
        
        // 监听状态并播放
        let statusObserver = playerItem.observe(\.status, options: [.new]) { [weak self] item, change in
            guard let self = self else { return }
            if item.status == .readyToPlay {
                self.player.replaceCurrentItem(with: item)
                self.player.play()
                // 播放完成后删除临时文件
                DispatchQueue.global().async {
                    try? FileManager.default.removeItem(at: tempFileURL)
                }
            }
        }
        self.itemObservers.append(statusObserver)
        self.playerInitializedTime = nil
    } catch {
        print("Failed to write temp file: \(error)")
    }
}

3. 使用AVQueuePlayer实现无缝切换 #

频繁调用replaceCurrentItem(with:)是导致闪烁的主要原因，改用AVQueuePlayer预加载下一个分片，实现无缝播放：

// 初始化时替换为AVQueuePlayer
private let player = AVQueuePlayer()

private func playNext() {
    let nextSet = self.dataCollector.getNextItem(length: self.configuration.frameDelay)
    guard nextSet.count == self.configuration.frameDelay else { return }
    
    var playerTime = self.player.currentItem != nil ? Int(CMTimeGetSeconds(player.currentTime())) : 0
    var allData = Data()
    allData.appendAll(dataSet: dataCollector.getFileType())
    
    nextSet.forEach { data in
        playerTime += 1
        allData.append(data.getFragmentData())
        self.currentFragmentTimes.updateValue(data.getFragmentTime(), forKey: playerTime)
    }
    
    guard allData.count > 0 else { return }
    
    // 写入临时文件并创建AVPlayerItem
    let tempDir = NSTemporaryDirectory()
    let tempFileName = UUID().uuidString + ".mp4"
    let tempFileURL = URL(fileURLWithPath: tempDir).appendingPathComponent(tempFileName)
    
    do {
        try allData.write(to: tempFileURL)
        let asset = AVURLAsset(url: tempFileURL)
        let playerItem = AVPlayerItem(asset: asset)
        
        // 监听当前播放项结束事件，自动添加下一个项
        let endObserver = playerItem.observe(\.status, options: [.new]) { [weak self] item, change in
            guard let self = self else { return }
            if item.status == .readyToPlay {
                // 如果队列中没有正在播放的项，直接插入并播放
                if self.player.items().isEmpty {
                    self.player.insert(item, after: nil)
                    self.player.play()
                } else {
                    // 否则添加到队列末尾
                    self.player.insert(item, after: self.player.currentItem)
                }
                // 播放完成后删除临时文件
                NotificationCenter.default.addObserver(forName: .AVPlayerItemDidPlayToEndTime, object: item, queue: .main) { _ in
                    DispatchQueue.global().async {
                        try? FileManager.default.removeItem(at: tempFileURL)
                    }
                }
            }
        }
        self.itemObservers.append(endObserver)
        self.playerInitializedTime = nil
    } catch {
        print("Failed to write temp file: \(error)")
    }
}

注意事项 #

• 确保分片媒体数据格式一致，避免因格式切换导致播放异常。
• 及时清理临时文件和观察者引用，避免内存泄漏。
• 针对iOS 17，优先使用AVURLAsset而非内存数据初始化的AVMutableMovie，提升兼容性。

内容的提问来源于stack exchange，提问作者Rajeev Ghantasala