exportPeaks is failing with 'Invalid array length'

[doctor30309]

Bug description

Once the wave file is loaded and the redrawcomplete event is triggered, I call exportPeaks and receive and error generated inside wavesurfer.js. The wav file duration is 82 seconds. It plays as expected.

Environment

• Browser: Chrome

Minimal code snippet

import WaveSurfer from 'https://cdn.jsdelivr.net/npm/wavesurfer.js@7/dist/wavesurfer.esm.js'

var wavesurfer = WaveSurfer.create({
        container: $(div)[0],
        waveColor: '#FFF',
        progressColor: '#443e3c',
        height: 60,
        /** Stretch the waveform to the full height */
        normalize: true,
        /** The cursor width */
        cursorWidth: 1,
        barWidth: 1,
        barRadius: 3,
        fillParent: true,
        interact: true,
        dragToSeek: true,
        url: compUrl,
    });

wavesurfer.on('redrawcomplete', processWaveReadyEvent);

const peaks = wavesurfer.exportPeaks({
        channels: 2, // how many audio channels to export, defaults to 1
        maxLength: 30000, // how many peaks per channel
        precision: 1e3, // round to 3 digits after comma
    });

Expected result

I would receive a valid array of peaks.

Obtained result

Uncaught (in promise) RangeError: Invalid array length
at u (wavesurfer.esm.js:1:13712)
at h.renderMultiCanvas (wavesurfer.esm.js:1:13967)
at h.renderChannel (wavesurfer.esm.js:1:14957)
at h. (wavesurfer.esm.js:1:16209)
at Generator.next ()
at wavesurfer.esm.js:1:283
at new Promise ()
at t (wavesurfer.esm.js:1:28)
at h.render (wavesurfer.esm.js:1:15005)
at u. (wavesurfer.esm.js:1:26674)

Screenshots

[doctor30309]

Reopening. Problem occurs on larger wav files. I upped the maxLength to 30000. Had no affect.

The wave file I am trying to load is 14:52 in length. Large wav file.

[doctor30309]

I jacked up the maxLength to 60000 and got the large file through the process. So the question: if maxLength is supposed to limit how much data is generated in the peak array returned, why does it throw an error if the number of peaks exceeds the maxLength?

[katspaugh]

Probably just a bug somewhere here:

https://github.com/katspaugh/wavesurfer.js/blob/main/src/wavesurfer.ts#L528

Likely an off-by-one index going over the channel data size. Perhaps Math.ceil should be Math.floor.