/* JOrbis
* Copyright (C) 2000 ymnk, JCraft,Inc.
*
* Written by: 2000 ymnk<ymnk@jcraft.com>
*
* Many thanks to
* Monty <monty@xiph.org> and
* The XIPHOPHORUS Company http://www.xiph.org/ .
* JOrbis has been based on their awesome works, Vorbis codec.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public License
* as published by the Free Software Foundation; either version 2 of
* the License, or (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
package com.jcraft.jorbis;
class Mdct{
static private final float cPI3_8=0.38268343236508977175f;
static private final float cPI2_8=0.70710678118654752441f;
static private final float cPI1_8=0.92387953251128675613f;
int n;
int log2n;
float[] trig;
int[] bitrev;
float scale;
void init(int n){
bitrev=new int[n/4];
trig=new float[n+n/4];
int n2=n>>>1;
log2n=(int)Math.rint(Math.log(n)/Math.log(2));
this.n=n;
int AE=0;
int AO=1;
int BE=AE+n/2;
int BO=BE+1;
int CE=BE+n/2;
int CO=CE+1;
// trig lookups...
for(int i=0;i<n/4;i++){
trig[AE+i*2]=(float)Math.cos((Math.PI/n)*(4*i));
trig[AO+i*2]=(float)-Math.sin((Math.PI/n)*(4*i));
trig[BE+i*2]=(float)Math.cos((Math.PI/(2*n))*(2*i+1));
trig[BO+i*2]=(float)Math.sin((Math.PI/(2*n))*(2*i+1));
}
for(int i=0;i<n/8;i++){
trig[CE+i*2]=(float)Math.cos((Math.PI/n)*(4*i+2));
trig[CO+i*2]=(float)-Math.sin((Math.PI/n)*(4*i+2));
}
{
int mask=(1<<(log2n-1))-1;
int msb=1<<(log2n-2);
for(int i=0;i<n/8;i++){
int acc=0;
for(int j=0;msb>>>j!=0;j++)
if(((msb>>>j)&i)!=0)acc|=1<<j;
bitrev[i*2]=((~acc)&mask);
// bitrev[i*2]=((~acc)&mask)-1;
bitrev[i*2+1]=acc;
}
}
scale=4.f/n;
}
void clear(){
}
void forward(float[] in, float[] out){
}
float[] _x=new float[1024];
float[] _w=new float[1024];
synchronized void backward(float[] in, float[] out){
if(_x.length<n/2){_x=new float[n/2];}
if(_w.length<n/2){_w=new float[n/2];}
float[] x=_x;
float[] w=_w;
int n2=n>>>1;
int n4=n>>>2;
int n8=n>>>3;
// rotate + step 1
{
int inO=1;
int xO=0;
int A=n2;
int i;
for(i=0;i<n8;i++){
A-=2;
x[xO++]=-in[inO+2]*trig[A+1] - in[inO]*trig[A];
x[xO++]= in[inO]*trig[A+1] - in[inO+2]*trig[A];
inO+=4;
}
inO=n2-4;
for(i=0;i<n8;i++){
A-=2;
x[xO++]=in[inO]*trig[A+1] + in[inO+2]*trig[A];
x[xO++]=in[inO]*trig[A] - in[inO+2]*trig[A+1];
inO-=4;
}
}
float[] xxx=mdct_kernel(x,w,n,n2,n4,n8);
int xx=0;
// step 8
{
int B=n2;
int o1=n4,o2=o1-1;
int o3=n4+n2,o4=o3-1;
for(int i=0;i<n4;i++){
float temp1= (xxx[xx] * trig[B+1] - xxx[xx+1] * trig[B]);
float temp2=-(xxx[xx] * trig[B] + xxx[xx+1] * trig[B+1]);
out[o1]=-temp1;
out[o2]= temp1;
out[o3]= temp2;
out[o4]= temp2;
o1++;
o2--;
o3++;
o4--;
xx+=2;
B+=2;
}
}
}
private float[] mdct_kernel(float[] x, float[] w,
int n, int n2, int n4, int n8){
// step 2
int xA=n4;
int xB=0;
int w2=n4;
int A=n2;
for(int i=0;i<n4;){
float x0=x[xA] - x[xB];
float x1;
w[w2+i]=x[xA++]+x[xB++];
x1=x[xA]-x[xB];
A-=4;
w[i++]= x0 * trig[A] + x1 * trig[A+1];
w[i]= x1 * trig[A] - x0 * trig[A+1];
w[w2+i]=x[xA++]+x[xB++];
i++;
}
// step 3
{
for(int i=0;i<log2n-3;i++){
int k0=n>>>(i+2);
int k1=1<<(i+3);
int wbase=n2-2;
A=0;
float[] temp;
for(int r=0;r<(k0>>>2);r++){
int w1=wbase;
w2=w1-(k0>>1);
float AEv= trig[A],wA;
float AOv= trig[A+1],wB;
wbase-=2;
k0++;
for(int s=0;s<(2<<i);s++){
wB =w[w1] -w[w2];
x[w1] =w[w1] +w[w2];
wA =w[++w1] -w[++w2];
x[w1] =w[w1] +w[w2];
x[w2] =wA*AEv - wB*AOv;
x[w2-1]=wB*AEv + wA*AOv;
w1-=k0;
w2-=k0;
}
k0--;
A+=k1;
}
temp=w;
w=x;
x=temp;
}
}
// step 4, 5, 6, 7
{
int C=n;
int bit=0;
int x1=0;
int x2=n2-1;
for(int i=0;i<n8;i++){
int t1=bitrev[bit++];
int t2=bitrev[bit++];
float wA=w[t1]-w[t2+1];
float wB=w[t1-1]+w[t2];
float wC=w[t1]+w[t2+1];
float wD=w[t1-1]-w[t2];
float wACE=wA* trig[C];
float wBCE=wB* trig[C++];
float wACO=wA* trig[C];
float wBCO=wB* trig[C++];
x[x1++]=( wC+wACO+wBCE)*.5f;
x[x2--]=(-wD+wBCO-wACE)*.5f;
x[x1++]=( wD+wBCO-wACE)*.5f;
x[x2--]=( wC-wACO-wBCE)*.5f;
}
}
return(x);
}
}