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package com.sun.media.sound;

Lanczos interpolation resampler.
Author:Karl Helgason
/** * Lanczos interpolation resampler. * * @author Karl Helgason */
public final class SoftLanczosResampler extends SoftAbstractResampler { float[][] sinc_table; int sinc_table_fsize = 2000; int sinc_table_size = 5; int sinc_table_center = sinc_table_size / 2; public SoftLanczosResampler() { super(); sinc_table = new float[sinc_table_fsize][]; for (int i = 0; i < sinc_table_fsize; i++) { sinc_table[i] = sincTable(sinc_table_size, -i / ((float) sinc_table_fsize)); } } // Normalized sinc function public static double sinc(double x) { return (x == 0.0) ? 1.0 : Math.sin(Math.PI * x) / (Math.PI * x); } // Generate sinc table public static float[] sincTable(int size, float offset) { int center = size / 2; float[] w = new float[size]; for (int k = 0; k < size; k++) { float x = (-center + k + offset); if (x < -2 || x > 2) w[k] = 0; else if (x == 0) w[k] = 1; else { w[k] = (float)(2.0 * Math.sin(Math.PI * x) * Math.sin(Math.PI * x / 2.0) / ((Math.PI * x) * (Math.PI * x))); } } return w; } @Override public int getPadding() // must be at least half of sinc_table_size { return sinc_table_size / 2 + 2; } @Override public void interpolate(float[] in, float[] in_offset, float in_end, float[] startpitch, float pitchstep, float[] out, int[] out_offset, int out_end) { float pitch = startpitch[0]; float ix = in_offset[0]; int ox = out_offset[0]; float ix_end = in_end; int ox_end = out_end; if (pitchstep == 0) { while (ix < ix_end && ox < ox_end) { int iix = (int) ix; float[] sinc_table = this.sinc_table[(int) ((ix - iix) * sinc_table_fsize)]; int xx = iix - sinc_table_center; float y = 0; for (int i = 0; i < sinc_table_size; i++, xx++) y += in[xx] * sinc_table[i]; out[ox++] = y; ix += pitch; } } else { while (ix < ix_end && ox < ox_end) { int iix = (int) ix; float[] sinc_table = this.sinc_table[(int) ((ix - iix) * sinc_table_fsize)]; int xx = iix - sinc_table_center; float y = 0; for (int i = 0; i < sinc_table_size; i++, xx++) y += in[xx] * sinc_table[i]; out[ox++] = y; ix += pitch; pitch += pitchstep; } } in_offset[0] = ix; out_offset[0] = ox; startpitch[0] = pitch; } }