html5 record input buffer using recorder.js

Question

I am using html5 web audio api in my application. Application is simple, I have

BufferSourceNode -> GainNode -> lowpass filter -> context.destination

Now I want to save the output after applying the filters. So I decided to add recorder before context.destination. But this doesn't work, it gives some noise sound while playing the audio, though my recorder records filter effects successfully.

Am I doing it in right way or is there any better way to do this?

cwilso · Accepted Answer · 2013-09-18 12:46:50Z

1

Two things:

1) if you are going to use the buffer anyway - even if you're not() - you might want to consider using an OfflineAudioContext (https://dvcs.w3.org/hg/audio/raw-file/tip/webaudio/specification.html#OfflineAudioContext-section). OACs can run faster than real-time, so you don't need to "record" it in real-time; you set up your nodes, call startRendering(), and the oncomplete event hands you an audiobuffer. () If you still want a .WAV file, you can pull the WAV encoding function out of Recordjs and use it to encode an arbitrary buffer.

2) That sounds like an error in your code - it should work either way, without causing extra noise. Do you have a code sample you can send me?

answered Sep 18, 2013 at 12:46

cwilso

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3 Comments

pramodtech Over a year ago

hi cwilso, here is how I implemented OAC gist.github.com/pramodtech/8347621 , I'm not sure if I did it right.. can u guide me on this? thanks.

cwilso Over a year ago

You shouldn't need to use all of record.js to do the recording - OfflineAudioContext will do it for you. Call startRendering() first, after setting an oncomplete handler - THEN call all your start(0)s, etc. You'll receive an oncomplete event when it's finished, with a renderedBuffer - this is the results of your rendering. Take THAT and use the encoding from record.js to generate your .WAV file.

cwilso Over a year ago

Should have mentioned - you CAN'T currently use record.js in offline contexts in Chrome, because we have a bug that prevents script processor nodes from working properly.

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