AVAudioEngine寻找这首歌的时间 [英] AVAudioEngine seek the time of the song

问题描述

我正在使用 AVAudioPlayerNode 播放一首歌，我正在尝试使用 UISlider 控制时间，但我可以弄清楚如何使用 AVAUdioEngine 来寻找时间。

I am playing a song using AVAudioPlayerNode and I am trying to control its time using a UISlider but I can't figure it out how to seek the time using AVAUdioEngine.

推荐答案

经过多次尝试和错误后，我想我终于弄明白了。

After MUCH trial and error I think I have finally figured this out.

首先，您需要计算文件的采样率。为此，请获取AudioNode的最后渲染时间：

First you need to calculate the sample rate of your file. To do this get the last render time of your AudioNode:

var nodetime: AVAudioTime  = self.playerNode.lastRenderTime
var playerTime: AVAudioTime = self.playerNode.playerTimeForNodeTime(nodetime)
var sampleRate = playerTime.sampleRate

然后，将采样率乘以新的时间（以秒为单位）。这将为您提供想要启动播放器的歌曲的确切帧：

Then, multiply your sample rate by the new time in seconds. This will give you the exact frame of the song at which you want to start the player:

var newsampletime = AVAudioFramePosition(sampleRate * Double(Slider.value))

接下来，您将要计算那里的帧数保留在音频文件中：

Next, you are going to want to calculate the amount of frames there are left in the audio file:

var length = Float(songDuration!) - Slider.value
var framestoplay = AVAudioFrameCount(Float(playerTime.sampleRate) * length)

最后，停止节点，安排新段音频，并再次启动你的节点！

Finally, stop your node, schedule the new segment of audio, and start your node again!

playerNode.stop()

if framestoplay > 1000 {
   playerNode.scheduleSegment(audioFile, startingFrame: newsampletime, frameCount: framestoplay, atTime: nil,completionHandler: nil)
}

playerNode.play()

如果您需要进一步解释，我在这里写了一个简短的教程： http://swiftexplained.com/?p=9

If you need further explanation I wrote a short tutorial here: http://swiftexplained.com/?p=9

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