我正在尝试使用 AVPlayer 淡入视频开头的音频轨道 . 播放视频时没有任何错误,似乎音量已经达到100%,并且我的 volumeRamp 音频淡入未执行 .

这是我的代码:

guard let url = (self.videoView.player?.currentItem?.asset as? AVURLAsset)?.url else { return }

    let asset = AVAsset(url: url) as AVAsset
    let duration = asset.duration
    let durationInSeconds = CMTimeGetSeconds(duration)
    let playerItem = AVPlayerItem(asset: asset)

    let firstSecond = CMTimeRangeMake(CMTimeMakeWithSeconds(0, 1), CMTimeMakeWithSeconds(1, 1))

    // Configure audio mix to fade in

    let audioParams = AVMutableAudioMixInputParameters(track: asset.tracks.first!)
    audioParams.setVolumeRamp(fromStartVolume: 0, toEndVolume: 1, timeRange: firstSecond)

    let mix = AVMutableAudioMix()
    mix.inputParameters = [audioParams]
    playerItem.audioMix = mix

    self.videoView.player?.replaceCurrentItem(with: playerItem)
    self.videoView.player?.play()

难道我做错了什么 ? (我正在用模拟器测试)