/* -*-mode:java; c-basic-offset:2; indent-tabs-mode:nil -*- */
/* 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 sound.jcraft.jorbis;
class Mdct{
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];
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);
}
}