如何在使用AVComposition时避免Airplay冻结？

Question

我的代码如下：

//init mix composition
let mixComposition = AVMutableComposition()

//video asset
let videoAsset = AVURLAsset(url: VIDEO_URL)
let videoTrack = mixComposition.addMutableTrack(withMediaType: AVMediaTypeVideo, preferredTrackID: kCMPersistentTrackID_Invalid)
try? videoTrack.insertTimeRange(CMTimeRangeMake(kCMTimeZero, videoAsset.duration), of: videoAsset.tracks(withMediaType: AVMediaTypeVideo).first!, at: kCMTimeZero)

//audio track
let audioTrack = mixComposition.addMutableTrack(withMediaType: AVMediaTypeAudio, preferredTrackID: kCMPersistentTrackID_Invalid)
try? audioTrack.insertTimeRange(CMTimeRangeMake(kCMTimeZero, videoAsset.duration), of: videoAsset.tracks(withMediaType: AVMediaTypeAudio).first!, at: kCMTimeZero)

//subtitles
let path = Bundle.main.path(forResource: "subtitle", ofType: "vtt")!
let subtitleAsset = AVAsset(url: URL(fileURLWithPath: path))
let subtitleTrack = mixComposition.addMutableTrack(withMediaType: AVMediaTypeText, preferredTrackID: kCMPersistentTrackID_Invalid)
try? subtitleTrack.insertTimeRange(CMTimeRangeMake(kCMTimeZero, videoAsset.duration), of: subtitleAsset.tracks(withMediaType: AVMediaTypeText)[0], at: kCMTimeZero)

 //setup player and play
 let item = AVPlayerItem(asset: videoAsset)
 let player = AVPlayer(playerItem: item)
 self.player = player
 self.player?.allowsExternalPlayback = true
 self.player?.usesExternalPlaybackWhileExternalScreenIsActive = true
 self.player?.play()

当询问videoAsset.isCompatibleWithAirPlayVideo是否为true时，它会返回true。当你加载应用程序时，一切都很顺利，直到你进入Airplay模式，屏幕就会冻结，直到你再次退出Airplay模式。

如果您将mixComposition更改为videoAsset，这将是完全不同的行为。现在它都可以工作了，但是你不会有外部字幕。

有没有其他人遇到过这个问题?解决方法是什么。我的最终目标是在mp4视频中加入外部字幕。

Answer 1

我在我的应用程序中的代码几乎与你的完全相同，它在Airplay模式下工作，所以我认为你几乎就在那里。

我从webserver上加载了视频、音频和vtt字幕，遇到了两个主要挑战：

无论plist设置如何，除非来自https-host，否则

1. 音频无法播放(从https播放的视频只持续10-12分钟的电影。解决方案是使用FileManager

从.documentDirectory下载字幕并加载

与您的代码唯一不同的是，我初始化了一个AVPlayerViewController并将播放器设置为AVPlayer：

var moviePlayer = AVPlayerViewController()
moviePlayer.player = player

然后呈现moviePlayer

self.view.window?.rootViewController?.present(self.moviePlayer, animated: true, completion : { self.moviePlayerFinishedLoading() } 
self.moviePlayer.player?.play()

希望这能有所帮助