CODEWITHSUNDEEP
webrtcaudio-streamingweb-audio-apiopenwebrtc
praveen.kd
praveen.kd

Reputation: 48

Noise Cancellation using WebAudioApi and WebAssembly

I am trying to create a noise cancellation filter in WebRtc using my C library compiled into wasm and called from Javascript.

I am able to capture the pcm audio using WebAudioApi and process the frame with wasm.

Here is my code :

navigator.mediaDevices.getUserMedia(constraints).then(function success(stream) {
var audiocontext;
var audiosource;
var audiopreprocessnode;

 audiocontext = new (window.AudioContext || window.webkitAudioContext)();
 audiosource = audiocontext.createMediaStreamSource(stream);
 audioPreprocessNode = audioCtx.createScriptProcessor(2048,1,1);

 audiosource.connect(audioPreprocessNode);
 audioPreprocessNode.connect(audioCtx.destination);
 
 audioPreprocessNode.onaudioprocess = function(e) {
 
console.log(e.inputBuffer.getChannelData(0));

 // audio captured from mic is denoised using wasm
 var denoised_array = Module["_denoise"](e.inputBuffer.getChannelData(0));
 e.inputBuffer.getChannelData(0).set(denoised_array);
 
 console.log(e.inputBuffer.getChannelData(0)); 
 
 }
   
}

I used onaudioprocess to capture the input frame and set the processed(denoised) frame in the inputbuffer. I used two logs to check whether the values are altered after processing and it is changing , However the processed values are not sent to the webrtc stream , unaltered original frame only sent to the stream.

After studying WebaudioApi docs , i found "Any script modifications to this AudioBuffer outside of this scope will not produce any audible effects."

https://www.w3.org/2014/annotation/experiment/webaudio.html#AudioProcessingEvent-section

Is there anyway to send this processed(denoised) frame in the webrtc stream. Any help would be appreciatable.

Upvotes: 0

Views: 2279

Answers (1)

chrisguttandin
chrisguttandin

Reputation: 9076

If you want the ScriptProcessorNode to output the modified signal you need to set the outputbuffer on the AudioProcessingEvent.

// ...

var denoised_array = Module["_denoise"](e.inputBuffer.getChannelData(0));

e.outputbuffer.getChannelData(0).set(denoised_array);

// ...

Upvotes: 2

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