Web Audio API - get Buffer from MediaElementAudioSourceNode

[Max Gherkins]

Hey,

is there a way to use the AudioBuffer from a
MediaElementAudioSourceNode as a BufferSourceNode?

I'd really love to use methods like noteOn and noteGrain on a audio
source retrieved from a <audio/> element.


So that you could have something like:

​var context = new webkitAudioContext();
var mediaSource = context.createMediaElementSource( myAudioElement );
var bufferSource = context.createBufferSource();

bufferSource.buffer = mediaSource.getBuffer() // <- fantasy code...

bufferSource.connect(context.destination);
bufferSource.noteOn(0);
​
Is that possible by any chance ?

Of course there's the possibilty of loading the AudioData directly
into the buffer via XHR request, but the request underlies some
restrictions (hello CORS) which the audio element does not.


Thank you in advance!


Cheers

Max

[PhistucK]

I am not familiar with the Web Audio API enough, but if you add the "crossorigin" attribute to the audio element, does that give you more capabilities?

☆PhistucK

Max




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[Max Gherkins]

Hello,

thanks for your reply.

The audio element actually loads cross-domain content without problems. 

I don't even need to add the attribute.

The question is if it's possible the get the audio buffer from an audio element to use it in a buffersourcenode, which would bring the benefit 

of using methods like noteOn(), noteGrain() etc.

(I don't even know if there's a way to do this)

Of course i could load the audiodata directly via XHR request, but this again wouldn't work with cross domain requests...

Cheers

Max

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[PhistucK]

I know it is possible, but I thought it enables more features.

Just like adding it to <video> allows you to add screenshots of the video to <canvas>.

☆PhistucK

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[Peter Beverloo]

On Thu, Jul 12, 2012 at 8:51 AM, Max Gherkins <m...@web-development.cc> wrote:

Of course i could load the audiodata directly via XHR request, but this again wouldn't work with cross domain requests...

You can use XMLHttpRequest to load audio fragments to be used with the Web Audio API. See this article for more information:

http://www.html5rocks.com/en/tutorials/webaudio/intro/

For cross-domain requests using XMLHttpRequest, you can utilize CORS:

http://www.html5rocks.com/en/tutorials/cors/

This does mean that you have to be in control of the server, as you'll have to send a Access-Control-Allow-Origin header as part of your response. The article goes into more detail on that.

Peter

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[Max Gherkins]

Hey,

thanks for your reply!

i'm aware of the possibility to load audio data via XHR and there's nothing wrong with that. 

I was just wondering if you could extract the audio buffer from an <audio>-element using the web audio api.

cheers

Max

[Max Gherkins]

ah, ok. I didn't get that :)

I'll give it try - thank you ! 

[Chris Wilson]

No, I don't think you can extract the buffer directly from an <audio> element in the way you're suggesting.  You may not have a full buffer (e.g. when the <audio> is being streamed).

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[Max Gherkins]

Thanks, you might be right that there's no way to extract the buffer.

But events like "loadeddata" would help to detect when the data is fully buffered, wouldn't they?

[camwest]

I would also like to be able to get a buffer from a MediaElementAudioSourceNode. I'd like to create a visualization waveform of the audio file loaded into player.

☆PhistucK

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[Chris Wilson]

If you want a visualization of the entire file (i.e. you're loading an entire file, not streaming), can you not just load it via XHR and CreateBuffer?  I doubt the actual buffer bits could be shared with <audio> players in many implementations anyway, and the confusion resulting in this call not always working (when it's streaming) would be hard to explain.  You can, of course, do live visualizations with RealtimeAnalyserNodes.

I guess what I'm saying is - it makes sense, if you really want this low-level access, to just use web audio end-to-end; you need to directly access the buffer anyway, so playing it yourself doesn't seem like a hard thing to take on.  Or am I missing something about the scenario?

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[Benjamin Rumble]

looks like you CAN now do this 

http://isflashdeadyet.com/tests/web-audio-visualization/

[Jari Pennanen]

No it's not possible even now.

That example you linked uses the "MediaElementAudioSourceNode" which doesn't have start() and stop() methods etc. like in buffer. Reason we need the buffer is that it's programmatically better.

[Yuan Yuan]

Hi Max,

I know it has been a long time since 2012. :)

I'm facing the same problem and just wondering whether you have got any solution or not.

Thanks,

Yuan

[Y Simon]

Sure,

It is now 2020, still....