# AudioBuffer.copyFromChannel()

const audioCtx = wx.createWebAudioContext()
wx.request({
  url: 'xx.mp3', // 音频 url
  responseType: 'arraybuffer',
  success: res => {
    audioCtx.decodeAudioData(res.data, audioBuffer => {
      const channels = audioBuffer.numberOfChannels;
      const frameCount = audioCtx.sampleRate * 2.0;
      const anotherArray = new Float32Array(frameCount);
      const rate = audioBuffer.sampleRate
      const startOffset = 0
      const endOffset = rate * 3;
      const newAudioBuffer = audioCtx.createBuffer(channels,endOffset - startOffset,rate)
      const offset = 0

      for (let channel = 0; channel < channels; channel++) {
        audioBuffer.copyFromChannel(anotherArray, channel, startOffset);
        console.log('copyFromChannel 成功')
        newAudioBuffer.copyToChannel(anotherArray, channel, offset);
      }
    }, err => {
      console.error('decodeAudioData fail', err)
    })
  }
})