Audio wave normalization has unexpected behaviour when using the normalize Wavesurfer option while also using the ZoomPlugin

[filipkoukal]

Bug description

Audio wave normalization doesn't work as expected when using the normalize Wavesurfer option while also using the ZoomPlugin.
How to reproduce:

1. Zoom in on an area
2. Move right or left along the audio wave to view a before unseen part of audio wave

Environment

• Browser: Chrome

Minimal code snippet

import WaveSurfer from 'wavesurfer.js'
import ZoomPlugin from 'wavesurfer.js/dist/plugins/zoom';


const wavesurfer = WaveSurfer.create({
    container: document.body,
    waveColor: 'rgb(200, 0, 200)',
    progressColor: 'rgb(100, 0, 100)',
    url: '/examples/audio/demo.wav',
    normalize: true,
})

wavesurfer.registerPlugin(ZoomPlugin.create())

wavesurfer.on('interaction', () => {
  wavesurfer.play()
})

Expected result

The audio wave is stable even when moving left or right along the wave when using the normalize option.

Obtained result

When moving left or right along the zoomed audio wave, previously unseen parts aren't normalized correctly.

Screenshots

[katspaugh]

Good catch. The reason is the normalization is performed on render, for each visible chunk individually. It should instead normalize by max value across the entire array of peaks.