partitioned fft wip

src/net/torvald/terrarum/audio/FFT.kt

@@ -5,10 +5,10 @@ import org.apache.commons.math3.transform.DftNormalization
 import org.apache.commons.math3.transform.TransformType
 import org.apache.commons.math3.util.FastMath
 
-data class FComplex(var real: Float = 0f, var imaginary: Float = 0f) {
+data class FComplex(var re: Float = 0f, var im: Float = 0f) {
     operator fun times(other: FComplex) = FComplex(
-        this.real * other.real - this.imaginary * other.imaginary,
-        this.real * other.imaginary + this.imaginary * other.real
+        this.re * other.re - this.im * other.im,
+        this.re * other.im + this.im * other.re
     )
 }
 
@@ -34,8 +34,8 @@ object FFT {
     fun ifftAndGetReal(y: Array<FComplex>): FloatArray {
         val dataRI = Array<FloatArray>(2) { FloatArray(y.size) }
         for (i in y.indices) {
-            dataRI[0][i] = y[i].real
-            dataRI[1][i] = y[i].imaginary
+            dataRI[0][i] = y[i].re
+            dataRI[1][i] = y[i].im
         }
 
         transformInPlace(dataRI, DftNormalization.STANDARD, TransformType.INVERSE)
@@ -112,8 +112,6 @@ object FFT {
 
         bitReversalShuffle2(dataR, dataI)
 
-        // Do 4-term DFT.
-
         // Do 4-term DFT.
         if (type == TransformType.INVERSE) {
             var i0 = 0

src/net/torvald/terrarum/audio/TerrarumAudioFilter.kt

@@ -315,12 +315,16 @@ class Convolv(ir: File, val gain: Float = 1f / 256f): TerrarumAudioFilter() {
 
     private val fftLen: Int
     private val convFFT: Array<Array<FComplex>>
+    private val convFFTpartd: Array<Array<Array<FComplex>>> // index: Channel, partition, frequencies
     private val inbuf: Array<FloatArray>
 
     private val BLOCKSIZE = BUFFER_SIZE / 4
 
     var processingSpeed = 1f; private set
 
+    private val partSizes: IntArray
+    private val partOffsets: IntArray
+
     init {
         if (!ir.exists()) {
             throw IllegalArgumentException("Impulse Response file '${ir.path}' does not exist.")
@@ -358,6 +362,30 @@ class Convolv(ir: File, val gain: Float = 1f / 256f): TerrarumAudioFilter() {
         }
 
 //        println("convFFT Length = ${convFFT[0].size}")
+
+        if (fftLen < BUFFER_SIZE) // buffer size is always 4x the samples in the buffer
+            throw Error("FIR size is too small (minimum: $BUFFER_SIZE samples)")
+
+
+        val partitions = ArrayList<Int>()
+        var cnt = fftLen
+        while (cnt > BUFFER_SIZE / 4) {
+            cnt /= 2
+            partitions.add(cnt)
+        }
+        partitions.add(cnt)
+
+        partSizes = partitions.reversed().toIntArray()
+        partOffsets = partSizes.clone().also { it[0] = 0 }
+
+        // allocate arrays
+        convFFTpartd = Array(2) { ch ->
+            Array(partSizes.size) { partNo ->
+                Array(partSizes[partNo]) {
+                    convFFT[ch][partOffsets[partNo] + it]
+                }
+            }
+        }
     }
 
     /**