Add effects to already recorded sound with Web Audio API

Question

My task is to add some effect to the recorded file.

Here is a script in action I'm using Recorder.JS

and here is a code https://github.com/cwilso/AudioRecorder/blob/master/js/recorderjs/recorder.js

I want to add pitch.

I tried looking in other codes which add some effects to the audio. But it seems like recorder.js handles buffers differently.

edit

function playbackRecorderAudio() {
    audioRecorder.getBuffer(function(buffers) {
        var source = audioContext.createBufferSource();
        source.buffer = audioContext.createBuffer(1, buffers[0].length, 44100);
        source.buffer.getChannelData(0).set(buffers[0]);
        source.buffer.getChannelData(0).set(buffers[1]);
        source.connect(audioContext.destination);
        source.noteOn(0);
    });
}

here is how my code looks now, with this function, I request already recorded audio and play it back.

Can I simulate some effect to get close to this: http://www.youtube.com/watch?v=Lr80slqJ3zo This is in Georgian but I hope you get the idea. Its more like Helium Pitch. (note, I don't whant to change audio speed).

When I tried to research helium effect I found this: http://chemistry.about.com/b/2013/08/26/helium-voice-is-not-higher-in-pitch.htm it saies that sound should be 2.5 faster then air.

Can I get something close to this?

edit

from what @cwilso suggested, http://chromium.googlecode.com/svn/trunk/samples/audio/granular.html is the closest I have seen so far. But I could not manage to modify it, to work with my playbackRecorderAudio(). Thats why I'm starting a bounty with everything I have

edit

here is a jsFiddle of my code: http://jsfiddle.net/Lsvnp/1/

First let me describe what I'm trying to achieve: I want to record sound from users microphone, add this effect to it. When user press "stop recording" button (stopRecording function) , it will prepend HTML audio which will allow user to listen what he has recorded. If he likes it, he then will upload it to my server (uploadAudio function)

WHen page is loaded, recording is not initalized. to initialize recording, user has to press some button which will trigger recordAudio function.

Now the problem is that I don't know where to connect my playbackRecorderAudio function. to use it as coverter from buffer.

cwilso cwilso · Accepted Answer · 2014-01-06T18:32:48

You should probably look at using OfflineAudioContext rather than Recorder.JS - OAC can work in faster-than-realtime.

That said - "helium pitch" looks pretty hard to do, as it alters the harmonics of your voice. That sounds more like vocoding, with the voice sound being the modulator and the carrier, but shifting the harmonic bands (or something like that). The YouTube video you pointed to sounded like it was actually pitch-shifted, but with rate correction - like granular synthesis. Check out Chris Rogers' example http://chromium.googlecode.com/svn/trunk/samples/audio/granular.html - set the speed to 1.0, and the pitch to something greater than zero (several hundred cents, at least). Is this the effect you're looking for? If you, you can dig in to Chris' example to see how to do that, or use a live-effect version like the "pitch doubler" in my input effects (http://webaudiodemos.appspot.com/input/) (which can actually be set to be faster or slower, and controlled to be something other than octaves).

Add effects to already recorded sound with Web Audio API

3 Answers