Feature request, or: add fade-in before the audio / fade-out affter the audio

[sangtv123]

Hey, thank you for testing and contributing to wavesurfer.js!

Please make sure you can check all of these points below before opening an issue:

(You don't have to post this section)

• I have checked the FAQ and it doesn't solve my problem.
• I have checked the documentation and it doesn't solve my problem
• I have searched for already open issues which desribe my problem.
• The issue I'm having is related to and caused by wavesurfer.js, not by other software (which maybe packages and uses wavesurfer incorrectly) – In that case you should open the issue on the respective project pages.

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Wavesurfer.js version(s):

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Code needed to reproduce the issue:

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Use behaviour needed to reproduce the issue:

[daslicht]

I solved it manually but just setting teh volume 2 0 before playback and then just fade it in via js

[entonbiba]

@quynhanhsang you can do this two ways, one using requestAnimationFrame. I'll see if I can add this as a option to the library soon for fade in and fade out effects.

var start = 0;

function fadeIn(time) {
    if (!start){
        start = time;
    }
    var progress = time - start;
    wavesurfer.setVolume(progress / 5000);
    if (progress < 5000) {
        window.requestAnimationFrame(fadeIn);
    }        
}
 
wavesurfer.on('waveform-ready', function () {
    wavesurfer.setVolume(0);
});

wavesurfer.on('play', function () {
    window.requestAnimationFrame(fadeIn);
});

wavesurfer.on('finish', function () {
    start = 0;
});

[lucastheis]

Are there any downsides to fading-in using AudioContext() as follows (assuming backend is set to 'MediaElement')?

const audioContext = new AudioContext()
const mediaNode = audioContext.createMediaElementSource(wavesurfer.media);
const gainNode = audioContext.createGain();
mediaNode.connect(gainNode).connect(audioContext.destination);

gainNode.gain.setValueAtTime(0, start);
gainNode.gain.linearRampToValueAtTime(1, start + duration);

Using requestAnimationFrame has the limitation that it only updates the volume every 16ms or so, which may be too slow for fast fade-ins.