1 files changed, 89 insertions, 0 deletions
diff --git a/client/lib/spectrum.js b/client/lib/spectrum.js
new file mode 100644
index 0000000..2b30792
--- /dev/null
+++ b/client/lib/spectrum.js
@@ -0,0 +1,89 @@
+import Tone from 'tone'
+
+import output from './output'
+
+const signalWindows = require('signal-windows').windows
+const FFTJS = require('fft.js')
+
+const fft_size = 2 << 10
+const fft_overlap = fft_size / 4
+const half_fft_size = fft_size / 2
+
+const fft = new FFTJS(fft_size)
+
+function toSpectrum(pcm, sr){
+  sr = sr || 44100
+  const ham = signalWindows.construct('ham', fft_size)
+  const pcm_in = new Array(fft_size)
+  const pcm_length = pcm.length
+  const pcm_q_length = Math.ceil(pcm_length / fft_size) * fft_size
+  let i, j, fft_out, data = [];
+  for (i = -fft_size; i < pcm_q_length; i += fft_overlap) {
+    for (j = 0; j < fft_size; j++) {
+      pcm_in[j] = pcm[i+j] * ham[j] || 0
+    }
+    fft_out = fft.createComplexArray()
+    fft.realTransform(fft_out, pcm_in)
+    fft.completeSpectrum(fft_out)
+    data.push(fft_out)
+  }
+  return {
+    data,
+    sr,
+    fft_size,
+    fft_overlap,
+  }
+}
+
+function fromSpectrum(spec){
+  const data = spec.data
+  const sr = spec.sr
+  const fft_size = spec.fft_size
+  const fft_overlap = spec.fft_overlap
+  const spec_len = data.length
+
+  const ham = signalWindows.construct('ham', fft_size)
+  const out = fft.createComplexArray()
+  const pcm_length = fft_overlap * spec_len
+
+  const audioBuffer = Tone.context.createBuffer(1, pcm_length, sr)
+  const pcm = audioBuffer.getChannelData(0);
+
+  let i, j, u, v, _r, _i, col
+
+  for (i = 0; i < spec_len; i++) {
+    col = data[i]
+    fft.inverseTransform(out, col)
+    u = i * (fft_overlap)
+    // for (j = fft_size * 1/4; j < fft_size * 3/4; j++) {
+    //   pcm[u+j] = out[j*2] / ham[j] || 0
+    // }
+    for (j = 0; j < fft_size; j++) {
+      pcm[u+j] += out[j*2] * ham[j] || 0
+    }
+  }
+
+  fadeInOut(pcm, fft_size)
+
+  return audioBuffer
+}
+
+function fadeInOut(pcm, fade_size){
+  const pcm_length = pcm.length
+  let fade = 0, i
+  for (i = 0; i < fade_size; i++) {
+    fade = i / (fade_size)
+    fade *= fade
+    pcm[i] *= fade
+    pcm[pcm_length - i] *= fade
+  }
+}
+function fadeOut(pcm){
+  
+}
+
+export default {
+  toSpectrum,
+  fromSpectrum
+}
+