RecorderJS lib to produce wav single (mono) channel

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Expand view Topic review: RecorderJS lib to produce wav single (mono) channel

Re: RecorderJS lib to produce waw single (mono) channel

by pikalupapito » Wed Dec 11, 2019 7:44 am

Thanks a lot. Works like a charm!!

RecorderJS lib to produce wav single (mono) channel

by axew3 » Tue Nov 14, 2017 2:29 pm

I've come over a problem while writing the WP_w3all speech to WP plugin.
How to get a mono channel .wav from this library.
https://github.com/mattdiamond/Recorderjs
That is the question many are searching for as i can see around.
In short, this the answer.

to have a single mono channel .wav file, produced by this library, you have to open:
recorderWorker.js file
search for:

Code: Select all

function exportWAV(type){

  var bufferL = mergeBuffers(recBuffersL, recLength);
  var bufferR = mergeBuffers(recBuffersR, recLength);
  var interleaved = interleave(bufferL, bufferR);
  var dataview = encodeWAV(interleaved);
  var audioBlob = new Blob([dataview], { type: type });

  this.postMessage(audioBlob);
}
change into:

Code: Select all

function exportWAV(type){
  var bufferL = mergeBuffers(recBuffersL, recLength);
 // var bufferR = mergeBuffers(recBuffersR, recLength);
 // var interleaved = interleave(bufferL, bufferR);
 // var dataview = encodeWAV(interleaved);
 var dataview = encodeWAV(bufferL);
  var audioBlob = new Blob([dataview], { type: type });

  this.postMessage(audioBlob);
}
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Code: Select all

function encodeWAV(samples, mono){
  var buffer = new ArrayBuffer(44 + samples.length * 2);
  var view = new DataView(buffer);
  /* RIFF identifier */
  writeString(view, 0, 'RIFF');
  /* file length */
  view.setUint32(4, 32 + samples.length * 2, true);
  /* RIFF type */
  writeString(view, 8, 'WAVE');
  /* format chunk identifier */
  writeString(view, 12, 'fmt ');
  /* format chunk length */
  view.setUint32(16, 16, true);
  /* sample format (raw) */
  view.setUint16(20, 1, true);
  /* channel count */
  view.setUint16(22, mono?1:2, true);
  /* sample rate */
  view.setUint32(24, sampleRate, true);
  /* byte rate (sample rate * block align) */
  view.setUint32(28, sampleRate * 4, true);
  /* block align (channel count * bytes per sample) */
  view.setUint16(32, 4, true);
  /* bits per sample */
  view.setUint16(34, 16, true);
  /* data chunk identifier */
  writeString(view, 36, 'data');
  /* data chunk length */
  view.setUint32(40, samples.length * 2, true);

  floatTo16BitPCM(view, 44, samples);

  return view;
}
change into:

Code: Select all

function encodeWAV(samples){
  var buffer = new ArrayBuffer(44 + samples.length * 2);
  var view = new DataView(buffer);

  /* RIFF identifier */
  writeString(view, 0, 'RIFF');
  /* file length */
  view.setUint32(4, 32 + samples.length * 2, true);
  /* RIFF type */
  writeString(view, 8, 'WAVE');
  /* format chunk identifier */
  writeString(view, 12, 'fmt ');
  /* format chunk length */
  view.setUint32(16, 16, true);
  /* sample format (raw) */
  view.setUint16(20, 1, true);
  /* channel count */
  //view.setUint16(22, 2, true); /*STEREO*/
  view.setUint16(22, 1, true); /*MONO*/
  /* sample rate */
  view.setUint32(24, sampleRate, true);
  /* byte rate (sample rate * block align) */
  //view.setUint32(28, sampleRate * 4, true); /*STEREO*/
  view.setUint32(28, sampleRate * 2, true); /*MONO*/
  /* block align (channel count * bytes per sample) */
  //view.setUint16(32, 4, true); /*STEREO*/
  view.setUint16(32, 2, true); /*MONO*/
  /* bits per sample */
  view.setUint16(34, 16, true);
  /* data chunk identifier */
  writeString(view, 36, 'data');
  /* data chunk length */
  view.setUint32(40, samples.length * 2, true);

  floatTo16BitPCM(view, 44, samples);

  return view;
}
This is it.
I've also follow encoding the result to .flac, so i will github the entire thing, if i can find out the time.
But since the question about this seem not answered around (or i've not find out in any place), hope will may be a good help for someone searching for, and for me, to not loose time again if necessary.

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