ResampleLayerFFTFilter3.scala

def snd   = AudioFileIn("in")

val dur   =  60.0
//val pch = Seq(0.5, 1, 1.5, 2, 4)
val pch1  = Seq(0.6, 0.8, 1.0, 1.2, 1.4)
val pch2  = Seq(0.8, 0.9, 1.0, 1.1, 1.2)
val pch   = pch1 zip pch2
val freq0 =  200.0 // 100
val freq1 = 5000.0
val gain0 = 128.0
val gain1 =   1.0
val frag0 =   0.2 // 1.0
val frag1 =   4.0
val ovrlp =   4.0

val sr        = snd.sampleRate
val framesIn  = snd.numFrames
val framesOut = (dur * sr).toInt

def mkPosBs(phase: Double, 
            el: Double = 0.0, posSq: Seq[Double] = Nil, bsSq: Seq[Double] = Nil): (GE, GE) =
  if (el >= dur) {
    // println(s"# segments: ${posSq.size}")
    (ValueDoubleSeq(posSq: _*), ValueDoubleSeq(bsSq: _*))
  } else {
    val pos = el / dur
    val bs  = ((pos + phase) * 2 * math.Pi).sin.linLin(-1, 1, frag0, frag1)
    mkPosBs(phase, el + bs/ovrlp, posSq :+ pos, bsSq :+ bs)
  }
 
val mix = pch.zipWithIndex.foldLeft(0.0: GE) { case (in, ((speed1, speed2), si)) =>
  val (pos, bs) = mkPosBs(phase = si.linLin(0, pch.size, 0.0, 1.0))
  val f1      = speed1.reciprocal
  val f2      = speed2.reciprocal
  val f       = (f1 * f2).sqrt // approximate avg resampling factor
//  val f       = speed.reciprocal
  val frInR   = framesIn * f
  val fL      = Line(0.0, 1.0, frInR).linExp(0.0, 1.0, f1, f2)
  val r       = Resample(snd, fL)
//  if (si == 2) {
//    frInR.poll("frInR")
//    Length(r).poll("actual")
//  }
  val posInFr = (pos * frInR).toInt
  val posOutFr= (pos * framesOut).toInt
  val winSz   = (bs * sr).toInt
  val fftSz   = (winSz * 2).nextPowerOfTwo // toInt
  val step    = posOutFr.differentiate
  val spans   = posInFr zip (posInFr + winSz)
  val slic    = Slices(r, spans)
//  winSz.poll(1, "winSz")
//  posInFr.poll(1, s"posInFr ($speed)")
  val fft     = Real1FFT(slic, winSz, padding = fftSz - winSz, mode = 1)
  val magSz   = fftSz/2 + 1
  val mag     = fft.complex.mag
  val phase   = fft.complex.phase
  val freq    = pos.linLin(0, 1, freq0, freq1)
  val gain    = pos.linExp(0, 1, gain0, gain1)
  val gainH   = RepeatWindow(gain, 1, magSz)
  val freqN   = RepeatWindow(freq / sr, 1, magSz)
  val lpf     = LPF(mag, freqN) * gainH
  val rec     = (lpf zip phase).complex.polToCar
  val ifft    = Real1IFFT(rec, fftSz, mode = 1)
  val ifftR   = ResizeWindow(ifft, fftSz, stop = winSz - fftSz)
//  val layer   = ifftR * GenWindow.Hann(winSz)
  val layer   = ifftR
  val lap     = OverlapAdd(layer, winSz, step).take(framesOut)
  in + LeakDC(lap)
}

val amp   = mix.abs.maximum
val norm  = BufferDisk(mix) / amp
AudioFileOut("out", norm, sampleRate = sr)