audio filters moved to its own files

src/net/torvald/terrarum/audio/dsp/Reverb.kt

@@ -0,0 +1,49 @@
+package net.torvald.terrarum.audio.dsp
+
+import com.jme3.math.FastMath
+import net.torvald.terrarum.audio.TerrarumAudioMixerTrack
+import kotlin.math.roundToInt
+
+class Reverb(val delayMS: Float = 36f, var feedback: Float = 0.92f, var lowpass: Float = 1200f): TerrarumAudioFilter() {
+
+    private val highpass = 80f
+
+    private var delay = (TerrarumAudioMixerTrack.SAMPLING_RATEF * delayMS / 1000f).roundToInt()
+    private val bufSize = delay + 2
+
+    private val buf = Array(2) { FloatArray(bufSize) }
+
+    private fun unshift(sample: Float, buf: FloatArray) {
+        for (i in bufSize - 1 downTo 1) {
+            buf[i] = buf[i - 1]
+        }
+        buf[0] = sample
+    }
+
+    private val out0 = FloatArray(2)
+
+    override fun thru(inbuf: List<FloatArray>, outbuf: List<FloatArray>) {
+        val RCLo: Float = 1f / (lowpass * FastMath.TWO_PI)
+        val RCHi: Float = 1f / (highpass * FastMath.TWO_PI)
+        val dt: Float = 1f / TerrarumAudioMixerTrack.SAMPLING_RATEF
+        val alphaLo = dt / (RCLo + dt)
+        val alphaHi = RCHi / (RCHi + dt)
+
+        for (ch in outbuf.indices) {
+            for (i in 0 until TerrarumAudioMixerTrack.BUFFER_SIZE / 4) {
+                val inn = inbuf[ch][i]
+
+                // reverb
+                val rev = buf[ch][delay - 1]
+                val out = inn - rev * feedback
+
+                // fill lpbuf
+                val lp0 = buf[ch][0]
+                val lp = lp0 + alphaLo * (out - lp0)
+                unshift(lp, buf[ch])
+
+                outbuf[ch][i] = out
+            }
+        }
+    }
+}