ios - AV播放器 : Fade in audio of a video

Question

我正在尝试使用 AVPlayer 在视频开头淡入音轨。我在播放视频时没有任何错误，似乎音量已经是 100%，而且我的 volumeRamp 音频淡入没有执行。

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()

我做错了什么吗？ (我正在用模拟器测试)

Answer 1

如此处所述:Apple Library

AVAudioMix 仅支持基于文件的 Assets 。