AVPlayer设置单个通道的音量

Question

我有两个AVPlayers，我的目标是在左声道中播放一个，在右声道中播放第二个。

我知道可以使用AVAudioPlayer轻松实现，但事实是我具有自定义的CachingPlayerItem类，可帮助播放缓存中的视频。

override func viewDidLoad() {
    super.viewDidLoad()

    titleLabel.text = vidTitle

    let playerItem = CachingPlayerItem.init(data: tmpData, mimeType: "video/mp4", fileExtension: ".mp4")
    self.player = AVPlayer(playerItem: playerItem)
    self.player.automaticallyWaitsToMinimizeStalling = false
    //self.player.pan = -1

    let voiceUrl = getDocumentsDirectory().appendingPathComponent(voicePath)
    let voiceItem = AVPlayerItem(url: voiceUrl)
    self.voicePlayer = AVPlayer(playerItem: voiceItem)
    self.voicePlayer.automaticallyWaitsToMinimizeStalling = false
    //self.voicePlayer.pan = 1
}