stack-chan

/****************************************************************************
 *
 * NAME: PitchShift
 * VERSION: 1.2
 * HOME URL: http://www.dspdimension.com
 * KNOWN BUGS: none
 *
 * SYNOPSIS: Routine for doing pitch shifting while maintaining
 * duration using the Short Time Fourier Transform.
 *
 * DESCRIPTION: The routine takes a pitchShift factor value which is between 0.5
 * (one octave down) and 2. (one octave up). A value of exactly 1 does not change
 * the pitch. numSampsToProcess tells the routine how many samples in indata[0...
 * numSampsToProcess-1] should be pitch shifted and moved to outdata[0 ...
 * numSampsToProcess-1]. The two buffers can be identical (ie. it can process the
 * data in-place). fftFrameSize defines the FFT frame size used for the
 * processing. Typical values are 1024, 2048 and 4096. It may be any value <=
 * MAX_FRAME_LENGTH but it MUST be a power of 2. osamp is the STFT
 * oversampling factor which also determines the overlap between adjacent STFT
 * frames. It should at least be 4 for moderate scaling ratios. A value of 32 is
 * recommended for best quality. sampleRate takes the sample rate for the signal
 * in unit Hz, ie. 44100 for 44.1 kHz audio. The data passed to the routine in
 * indata[] should be in the range [-1.0, 1.0), which is also the output range
 * for the data, make sure you scale the data accordingly (for 16bit signed integers
 * you would have to divide (and multiply) by 32768).
 *
 * COPYRIGHT 1999-2006 Stephan M. Bernsee <smb [AT] dspdimension [DOT] com>
 *
 *                       The Wide Open License (WOL)
 *
 * Permission to use, copy, modify, distribute and sell this software and its
 * documentation for any purpose is hereby granted without fee, provided that
 * the above copyright notice and this license appear in all source copies.
 * THIS SOFTWARE IS PROVIDED "AS IS" WITHOUT EXPRESS OR IMPLIED WARRANTY OF
 * ANY KIND. See http://www.dspguru.com/wol.htm for more information.
 *
 *****************************************************************************/
import wae from 'web-audio-engine'

const AudioContext = wae.RenderingAudioContext
const audioCtx = new AudioContext()

export default function shiftPitch(audioBuffer, shiftAmount) {
  /* monoral */
  let in_data_l = audioBuffer.getChannelData(0)
  in_data_l = PitchShift(shiftAmount, in_data_l.length, 1024, 10, audioCtx.sampleRate, in_data_l)
  audioBuffer.copyToChannel(in_data_l, 0)
}

/*
function loadTheTrack() {
  var input = document.createElement('input')
  input.type = 'file'
  input.style = 'display:none'
  input.onchange = function (e) {
    var file = e.target.files[0]
    console.log(file)
    var reader = new FileReader()
    reader.onload = function () {
      console.log('decoding audio data with' + this.result)
      document.getElementById('status').innerText = 'Pitch Shifting (yeah it takes a min)....'
      audioCtx.decodeAudioData(
        this.result,
        (decodedData) => {
          var source = audioCtx.createBufferSource() // creates a sound source
          source.buffer = decodedData // tell the source which sound to play
          source.connect(audioCtx.destination) // connect the source to the context's destination (the speakers)
          console.log('starting')
          document.getElementById('status').innerText = 'Playing...'
          source.start(0) // play the source now
        },
        (e) => {
          alert('Sorry this browser unable to download this file... try Chrome')
        }
      )
    }
    reader.readAsArrayBuffer(file)
  }
  document.getElementById('wrapper').appendChild(input)
  input.click()
}
*/

function PitchShift(
  /* float[*/ pitchShift,
  /* long */ numSampsToProcess,
  /* long */ fftFrameSize,
  /* long */ osamp,
  /* float[*/ sampleRate,
  /* float[] */ indata,
) {
  /* double */ let magn
  /* double */ let phase
  /* double */ let tmp
  /* double */ let window
  /* double */ let real
  /* double */ let imag
  /* double */ let freqPerBin
  /* double */ let expct
  /* long */ let i
  /* long */ let k
  /* long */ let qpd
  /* long */ let index
  /* long */ let inFifoLatency
  /* long */ let stepSize
  /* long */ let fftFrameSize2

  const MAX_FRAME_LENGTH = 16000
  const gInFIFO = new Array(MAX_FRAME_LENGTH).fill(0.0)
  const gOutFIFO = new Array(MAX_FRAME_LENGTH).fill(0.0)
  const gFFTworksp = new Array(2 * MAX_FRAME_LENGTH).fill(0.0)
  const gLastPhase = new Array(MAX_FRAME_LENGTH / 2 + 1).fill(0.0)
  const gSumPhase = new Array(MAX_FRAME_LENGTH / 2 + 1).fill(0.0)
  const gOutputAccum = new Array(2 * MAX_FRAME_LENGTH).fill(0.0)
  const gAnaFreq = new Array(MAX_FRAME_LENGTH).fill(0.0)
  const gAnaMagn = new Array(MAX_FRAME_LENGTH).fill(0.0)
  const gSynFreq = new Array(MAX_FRAME_LENGTH).fill(0.0)
  const gSynMagn = new Array(MAX_FRAME_LENGTH).fill(0.0)
  let gRover = 0

  /* float[] */ const outdata = indata
  /* set up some handy variables */
  fftFrameSize2 = Math.trunc(fftFrameSize / 2)
  stepSize = Math.trunc(fftFrameSize / osamp)
  freqPerBin = sampleRate / /* (double) */ fftFrameSize
  expct = (2.0 * Math.PI * /* (double) */ stepSize) / /* (double) */ fftFrameSize
  inFifoLatency = Math.trunc(fftFrameSize - stepSize)
  if (gRover === 0) gRover = inFifoLatency

  /* main processing loop */
  for (i = 0; i < numSampsToProcess; i++) {
    /* As long as we have not yet collected enough data just read in */
    gInFIFO[gRover] = indata[i]
    outdata[i] = gOutFIFO[gRover - inFifoLatency]
    gRover++

    /* now we have enough data for processing */
    if (gRover >= fftFrameSize) {
      gRover = inFifoLatency

      /* do windowing and re,im interleave */
      for (k = 0; k < fftFrameSize; k++) {
        window = -0.5 * Math.cos((2.0 * Math.PI * /* (double) */ k) / /* (double) */ fftFrameSize) + 0.5
        gFFTworksp[2 * k] = /* (float) */ gInFIFO[k] * window
        gFFTworksp[2 * k + 1] = 0.0
      }

      /* ***************** ANALYSIS ******************* */
      /* do transform */
      ShortTimeFourierTransform(gFFTworksp, fftFrameSize, -1)

      /* this is the analysis step */
      for (k = 0; k <= fftFrameSize2; k++) {
        /* de-interlace FFT buffer */
        real = gFFTworksp[2 * k]
        imag = gFFTworksp[2 * k + 1]

        /* compute magnitude and phase */
        magn = 2.0 * Math.sqrt(real * real + imag * imag)
        phase = Math.atan2(imag, real)

        /* compute phase difference */
        tmp = phase - gLastPhase[k]
        gLastPhase[k] = /* (float) */ phase

        /* subtract expected phase difference */
        tmp -= /* (double) */ k * expct

        /* map delta phase into +/- Pi interval */
        qpd = /* (long) */ Math.trunc(tmp / Math.PI)
        if (qpd >= 0) qpd += qpd & 1
        else qpd -= qpd & 1
        tmp -= Math.PI * /* (double) */ qpd

        /* get deviation from bin frequency from the +/- Pi interval */
        tmp = (osamp * tmp) / (2.0 * Math.PI)

        /* compute the k-th partials' true frequency */
        tmp = /* (double) */ k * freqPerBin + tmp * freqPerBin

        /* store magnitude and true frequency in analysis arrays */
        gAnaMagn[k] = /* (float) */ magn
        gAnaFreq[k] = /* (float) */ tmp
      }

      /* ***************** PROCESSING ******************* */
      /* this does the actual pitch shifting */
      for (let zero = 0; zero < fftFrameSize; zero++) {
        gSynMagn[zero] = 0
        gSynFreq[zero] = 0
      }

      for (k = 0; k <= fftFrameSize2; k++) {
        index = /* (long) */ Math.trunc(k * pitchShift)
        if (index <= fftFrameSize2) {
          gSynMagn[index] += gAnaMagn[k]
          gSynFreq[index] = gAnaFreq[k] * pitchShift
        }
      }

      /* ***************** SYNTHESIS ******************* */
      /* this is the synthesis step */
      for (k = 0; k <= fftFrameSize2; k++) {
        /* get magnitude and true frequency from synthesis arrays */
        magn = gSynMagn[k]
        tmp = gSynFreq[k]

        /* subtract bin mid frequency */
        tmp -= /* (double) */ k * freqPerBin

        /* get bin deviation from freq deviation */
        tmp /= freqPerBin

        /* take osamp into account */
        tmp = (2.0 * Math.PI * tmp) / osamp

        /* add the overlap phase advance back in */
        tmp += /* (double) */ k * expct

        /* accumulate delta phase to get bin phase */
        gSumPhase[k] += /* (float) */ tmp
        phase = gSumPhase[k]

        /* get real and imag part and re-interleave */
        gFFTworksp[2 * k] = /* (float) */ magn * Math.cos(phase)
        gFFTworksp[2 * k + 1] = /* (float) */ magn * Math.sin(phase)
      }

      /* zero negative frequencies */
      for (k = fftFrameSize + 2; k < 2 * fftFrameSize; k++) gFFTworksp[k] = 0.0

      /* do inverse transform */
      ShortTimeFourierTransform(gFFTworksp, fftFrameSize, 1)

      /* do windowing and add to output accumulator */
      for (k = 0; k < fftFrameSize; k++) {
        window = -0.5 * Math.cos((2.0 * Math.PI * /* (double) */ k) / /* (double) */ fftFrameSize) + 0.5
        gOutputAccum[k] += /* (float) */ (2.0 * window * gFFTworksp[2 * k]) / (fftFrameSize2 * osamp)
      }
      for (k = 0; k < stepSize; k++) gOutFIFO[k] = gOutputAccum[k]

      /* shift accumulator */
      //memmove(gOutputAccum, gOutputAccum + stepSize, fftFrameSize * sizeof(float));
      for (k = 0; k < fftFrameSize; k++) {
        gOutputAccum[k] = gOutputAccum[k + stepSize]
      }

      /* move input FIFO */
      for (k = 0; k < inFifoLatency; k++) gInFIFO[k] = gInFIFO[k + stepSize]
    }
  }
  return outdata
}

function ShortTimeFourierTransform(/* float[] */ fftBuffer, /* long */ fftFrameSize, /* long */ sign) {
  /* float */ let wr
  /* float */ let wi
  /* float */ let arg
  /* float */ let temp
  /* float */ let tr
  /* float */ let ti
  /* float */ let ur
  /* float */ let ui
  /* long */ let i
  /* long */ let bitm
  /* long */ let j
  /* long */ let le
  /* long */ let le2
  /* long */ let k

  for (i = 2; i < 2 * fftFrameSize - 2; i += 2) {
    for (bitm = 2, j = 0; bitm < 2 * fftFrameSize; bitm <<= 1) {
      if ((i & bitm) !== 0) j++
      j <<= 1
    }
    if (i < j) {
      temp = fftBuffer[i]
      fftBuffer[i] = fftBuffer[j]
      fftBuffer[j] = temp
      temp = fftBuffer[i + 1]
      fftBuffer[i + 1] = fftBuffer[j + 1]
      fftBuffer[j + 1] = temp
    }
  }
  /* long */ const max = /* (long) */ Math.trunc(Math.log(fftFrameSize) / Math.log(2.0) + 0.5)
  for (k = 0, le = 2; k < max; k++) {
    le <<= 1
    le2 = le >> 1
    ur = 1.0
    ui = 0.0
    arg = /* (float) */ Math.PI / (le2 >> 1)
    wr = /* (float) */ Math.cos(arg)
    wi = /* (float) */ sign * Math.sin(arg)
    for (j = 0; j < le2; j += 2) {
      for (i = j; i < 2 * fftFrameSize; i += le) {
        tr = fftBuffer[i + le2] * ur - fftBuffer[i + le2 + 1] * ui
        ti = fftBuffer[i + le2] * ui + fftBuffer[i + le2 + 1] * ur
        fftBuffer[i + le2] = fftBuffer[i] - tr
        fftBuffer[i + le2 + 1] = fftBuffer[i + 1] - ti
        fftBuffer[i] += tr
        fftBuffer[i + 1] += ti
      }
      tr = ur * wr - ui * wi
      ui = ur * wi + ui * wr
      ur = tr
    }
  }
}