Javascript library for listening to a user's microphone and performing pitch/note detection, volume detection, recording, and general purpose data processing. Uses Web Audio API (only supported in Chrome at the moment) and DSP.js.
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README

// =============================================================================
// Who are we?
// =============================================================================
We are Max Deibel (deibel.max@gmail.com) and Patrick Yukman 
(contact@patrickyukman.com). We created this library as a stand-alone project, 
but it was motivated by our work on our senior project at Dartmouth College: 
VoxTrainer.

// =============================================================================
// About the library
// =============================================================================
This is a Javascript library which listens to microphone input and performs 
pitch/note detection, volume detection, recording, and general purpose data 
processing. It makes use of the Web Audio APi (which is only supported by Chrome
currently) and DSP.js.

To view a website with a simple demo of our project, please visit here:
http://deibelman.github.io/dart-mic/

// =============================================================================
// General usage
// =============================================================================
1. Create Microphone object ("mic").
2. Any function defined as "this.foo = function(param) { ... }" can then be 
	 called via the Microphone object.
	 Example: "mic.foo(param)"

// =============================================================================
// Function list (see "Function descriptions" for more details)
// =============================================================================
Microphone Setup:
	-Callable functions:
		-this.initialize
		-this.isInitialized
		-this.startListening
		-this.stopListening
		-this.startRecording
		-this.stopRecording
	-Helper functions:
		-gotStream
		-noStream
General Purpose:
	-Callable functions:
		-this.getMaxInputAmplitude
		-this.getFreq
		-this.getNote
		-this.getNoteCents
	-Helper functions:
		-matchNote
Autocorrelation:
	-Callable functions:
	-Helper functions:
		-autocorrelate
		-getPeakPeriodicity
		-computeFreqFromAutocorr
		-getNoteFromAutocorr
		-getNoteCentsFromAutocorr
FFT:
	-Callable Functions:
	-Helper Functions:
		-computeFreqFromFFT
		-jainsMethodInterpolate
		-getNoteFromFFT
		-getNoteCentsFromFFT
Recording:
	-Callable Functions:
	-Helper functions:
		-writeToWav
		-interleave
		-mergeBuffers
		-writeUTFBytes
Testing and Debugging:
	-Callable Functions:
		-this.logData
	-Helper Functions:
		-destroyClickedElement

// =============================================================================
// Function descriptions
// =============================================================================

--------------------------Microphone setup functions----------------------------
this.initialize
// initialize function. Properly initializes the parameters of a Microphone 
// object, defines the frequency-->note lookup table, and calls getUserMedia
// to request browser-level access to a user's microphone. In general, do not
// change any part of this initialize function without a compelling reason.
//
// Example: mic.initialize()

this.isInitialized
// isInitialized function. This function simply returns whether or not the 
// microphone object has been fully initialized (indicated by the var 
// 'initialized' being equal to true. Returns a boolean value.

this.startListening
// startListening function. Connects the microphone input to a processing node
// for future operations. Throws an error if the microphone hasn't been
// initialized before this function is called -- in other words, if a user
// tries to get mic data before allowing the browser permission to collect it.
//
// Example: mic.startListening()

this.stopListening
// stopListening function. Disconnects the microphone input. Can be called or
// tied to a button to save on processing.
//
// Example: mic.stopListening()

this.startRecording
// startRecording function. Begins gathering microphone input and storing it in
// a WAV file.
//
// Example: mic.startRecording()

this.stopRecording
// stopRecording function. Stops packaging incoming microphone data into WAV
// file.
//
// Example: mic.stopRecording()

gotStream
// gotStream function. This function is the success callback for getUserMedia
// and initializes the Web Audio API / DSP.JS structures that allow us to
// manipulate the data streaming in off the microphone.

noStream
// noStream function. This function is the failure callback for getUserMedia
// and alerts the user if their browser doesn't support getUserMedia.

--------------------------General purpose functions-----------------------------
this.getMaxInputAmplitude
// getMaxInputAmplitude function. Input: none. Output: the amplitude of the
// microphone signal, expressed in deciBels (scaled from -120). Gives an idea
// of the volume of the sound picked up by the microphone.
//
// Example: mic.getMaxInputAmplitude()

this.getFreq
// getFreq function. Input: the method number (default is 1 to use
// autocorrelation, 2 to use FFT). Output: the detected frequency calculated via
// the selected method.
//
// Example: mic.getFreq(1) //returns frequency calculated via autocorrelation

this.getNote
// getNote function. Input: the method number (default is 1 to use
// autocorrelation, 2 to use FFT). Output: the detected note calculated via
// the selected method.
//
// Example: mic.getNote(1) //returns note calculated via autocorrelation

this.getNoteCents
// getNoteCents function. Input: the method number (default is 1 to use
// autocorrelation, 2 to use FFT). Output: the detected note cents offset 
// calculated via the selected method.
//
// Example: mic.getNoteCents(2) //returns note cents offset calculated via FFT

matchNote
// matchNote function. Input: frequency, in Hertz. Output: closest note 
// value to that frequency. This function iterates over the JSON lookup table
// to find the nearest note to the input frequency and returns the note as a
// string.

--------------------------Autocorrelation functions-----------------------------
autocorrelate
// autocorrelate function. For each index in an array of length BUFFER_LEN,
// adds the data element at that index and the next index together, then stores
// it in a separate sums array.

getPeakPeriodicityIndex
// getPeakPeriodicityIndex function. After finding the second zero crossing
// in the passed sums array, finds the max peak that occcurs after that crossing

computeFreqFromAutocorr
// computeFreqFromAutocorr function. Gets the max peak index, and then 
// calculates the frequency by dividing the sample rate by that index.

getNoteFromAutocorr
// getNoteFromAutocorr function. Computes the current frequency with 
// computeFreqFromAutoCorr, then determines the current note by feeding the 
// current frequency to matchNote.

getNoteCentsFromAutocorr
// getNoteCentsFromAutocorr function. Computes the current frequency with 
// computeFreqFromAutocorr, then determines the current note by feeding the 
// current frequency to matchNote, and finally computes the cents offset from 
// the current note.

---------------------------------FFT functions----------------------------------
computeFreqFromFFT
// computeFreqFromFFT function. Input: none. Output: frequency of the sound 
// picked up by the microphone, computed via FFT. Automatically grabs the 
// current microphone data from the timeData global variable and uses the FFT
// defined in DSP.JS. Interpolates the FFT power spectrum to more accurately
// guess the actual value of the peak frequency of the signal.

jainsMethodInterpolate
// jainsMethodInterpolate function. Input: array of spectrum power values 
// returned from FFT; index of bin in spectrum array with max power value.
// Output: a fractional bin number indicating the interpolated location of
// the actual signal peak frequency. Uses neighbouring indices to the index of 
// greatest magnitude to create a more accurate estimate of the frequency. 
// Simply multiply the returned fractional bin index by the FFT spectrum 
// frequency resolution to get the estimate of the actual peak frequency.

getNoteFromFFT
// getNoteFromFFT function. Computes the current frequency with 
// computeFreqFromFFT, then determines the current note by feeding the current
// frequency to matchNote.

getNoteCentsFromFFT
// getNoteCentsFromFFT function. Computes the current frequency with 
// computeFreqFromFFT, then determines the current note by feeding the current
// frequency to matchNote, and finally computes the cents offset from the 
// current note.

------------------------------Recording functions-------------------------------
writeToWav
// writeToWav function. Writes our recording data to a .WAV file.

interleave
// interleave function. Takes the left and right channels and combines them
// into one array, alternating between the two channels to copy the values over.

mergeBuffers
// mergeBuffers function. Takes each of the individual channel buffers and
// combines them sequentially into one final result array, which has length
// equal to the given length of the recording.

writeUTFBytes
// writeUTFBytes function. Helper function for writeToWav.

--------------------------Test and debugging functions--------------------------
this.logData
// logData function. Logs time domain data, then frequency domain data for
// external analysis. Used as a debugging / quantitative analysis tool. If 
// needed, tie it to a button so problems can be logged in real time.
//
// Example: mic.logData() //will log time and frequency domain data in txt file


// =============================================================================
// License information
// =============================================================================
This code is released under the MIT Open Source License.

Copyright (c) 2013 Patrick Yukman and Max Deibel

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.