misc/libtremor/tremor/mdct.c
changeset 7849 a12155461b34
parent 7697 767d3c4153a1
--- a/misc/libtremor/tremor/mdct.c	Sun Oct 28 03:48:37 2012 +0100
+++ b/misc/libtremor/tremor/mdct.c	Sun Oct 28 04:00:07 2012 +0100
@@ -6,14 +6,14 @@
  * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
  * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING.       *
  *                                                                  *
- * THE OggVorbis 'TREMOR' SOURCE CODE IS (C) COPYRIGHT 1994-2003    *
+ * THE OggVorbis 'TREMOR' SOURCE CODE IS (C) COPYRIGHT 1994-2002    *
  * BY THE Xiph.Org FOUNDATION http://www.xiph.org/                  *
  *                                                                  *
  ********************************************************************
 
  function: normalized modified discrete cosine transform
            power of two length transform only [64 <= n ]
- last mod: $Id: mdct.c,v 1.9.6.5 2003/04/29 04:03:27 xiphmont Exp $
+ last mod: $Id: mdct.c,v 1.9 2002/10/16 09:17:39 xiphmont Exp $
 
  Original algorithm adapted long ago from _The use of multirate filter
  banks for coding of high quality digital audio_, by T. Sporer,
@@ -33,62 +33,23 @@
  ********************************************************************/
 
 #include "ivorbiscodec.h"
-#include "os.h"
+#include "codebook.h"
 #include "misc.h"
 #include "mdct.h"
 #include "mdct_lookup.h"
 
-STIN void presymmetry(DATA_TYPE *in,int n2,int step){
-  DATA_TYPE *aX;
-  DATA_TYPE *bX;
-  LOOKUP_T *T;
-  int n4=n2>>1;
-  
-  aX            = in+n2-3;
-  T             = sincos_lookup0;
-
-  do{
-    REG_TYPE  r0= aX[0];
-    REG_TYPE  r2= aX[2];
-    XPROD31( r0, r2, T[0], T[1], &aX[0], &aX[2] ); T+=step;
-    aX-=4;
-  }while(aX>=in+n4);
-  do{
-    REG_TYPE  r0= aX[0];
-    REG_TYPE  r2= aX[2];
-    XPROD31( r0, r2, T[1], T[0], &aX[0], &aX[2] ); T-=step;
-    aX-=4;
-  }while(aX>=in);
-
-  aX            = in+n2-4;
-  bX            = in;
-  T             = sincos_lookup0;
-  do{
-    REG_TYPE  ri0= aX[0];
-    REG_TYPE  ri2= aX[2];
-    REG_TYPE  ro0= bX[0];
-    REG_TYPE  ro2= bX[2];
-    
-    XNPROD31( ro2, ro0, T[1], T[0], &aX[0], &aX[2] ); T+=step;
-    XNPROD31( ri2, ri0, T[0], T[1], &bX[0], &bX[2] );
-    
-    aX-=4;
-    bX+=4;
-  }while(aX>=in+n4);
-
-}
 
 /* 8 point butterfly (in place) */
 STIN void mdct_butterfly_8(DATA_TYPE *x){
 
-  REG_TYPE r0   = x[0] + x[1];
-  REG_TYPE r1   = x[0] - x[1];
-  REG_TYPE r2   = x[2] + x[3];
-  REG_TYPE r3   = x[2] - x[3];
-  REG_TYPE r4   = x[4] + x[5];
-  REG_TYPE r5   = x[4] - x[5];
-  REG_TYPE r6   = x[6] + x[7];
-  REG_TYPE r7   = x[6] - x[7];
+  REG_TYPE r0   = x[4] + x[0];
+  REG_TYPE r1   = x[4] - x[0];
+  REG_TYPE r2   = x[5] + x[1];
+  REG_TYPE r3   = x[5] - x[1];
+  REG_TYPE r4   = x[6] + x[2];
+  REG_TYPE r5   = x[6] - x[2];
+  REG_TYPE r6   = x[7] + x[3];
+  REG_TYPE r7   = x[7] - x[3];
 
 	   x[0] = r5   + r3;
 	   x[1] = r7   - r1;
@@ -103,25 +64,29 @@
 
 /* 16 point butterfly (in place, 4 register) */
 STIN void mdct_butterfly_16(DATA_TYPE *x){
-  
-  REG_TYPE r0, r1, r2, r3;
-  
-	   r0 = x[ 8] - x[ 9]; x[ 8] += x[ 9];
-	   r1 = x[10] - x[11]; x[10] += x[11];
-	   r2 = x[ 1] - x[ 0]; x[ 9]  = x[ 1] + x[0];
-	   r3 = x[ 3] - x[ 2]; x[11]  = x[ 3] + x[2];
-	   x[ 0] = MULT31((r0 - r1) , cPI2_8);
-	   x[ 1] = MULT31((r2 + r3) , cPI2_8);
-	   x[ 2] = MULT31((r0 + r1) , cPI2_8);
-	   x[ 3] = MULT31((r3 - r2) , cPI2_8);
+
+  REG_TYPE r0, r1;
+
+	   r0 = x[ 0] - x[ 8]; x[ 8] += x[ 0];
+	   r1 = x[ 1] - x[ 9]; x[ 9] += x[ 1];
+	   x[ 0] = MULT31((r0 + r1) , cPI2_8);
+	   x[ 1] = MULT31((r1 - r0) , cPI2_8);
 	   MB();
 
-	   r2 = x[12] - x[13]; x[12] += x[13];
-	   r3 = x[14] - x[15]; x[14] += x[15];
-	   r0 = x[ 4] - x[ 5]; x[13]  = x[ 5] + x[ 4];
-	   r1 = x[ 7] - x[ 6]; x[15]  = x[ 7] + x[ 6];
-	   x[ 4] = r2; x[ 5] = r1; 
-	   x[ 6] = r3; x[ 7] = r0;
+	   r0 = x[10] - x[ 2]; x[10] += x[ 2];
+	   r1 = x[ 3] - x[11]; x[11] += x[ 3];
+	   x[ 2] = r1; x[ 3] = r0;
+	   MB();
+
+	   r0 = x[12] - x[ 4]; x[12] += x[ 4];
+	   r1 = x[13] - x[ 5]; x[13] += x[ 5];
+	   x[ 4] = MULT31((r0 - r1) , cPI2_8);
+	   x[ 5] = MULT31((r0 + r1) , cPI2_8);
+	   MB();
+
+	   r0 = x[14] - x[ 6]; x[14] += x[ 6];
+	   r1 = x[15] - x[ 7]; x[15] += x[ 7];
+	   x[ 6] = r0; x[ 7] = r1;
 	   MB();
 
 	   mdct_butterfly_8(x);
@@ -131,40 +96,48 @@
 /* 32 point butterfly (in place, 4 register) */
 STIN void mdct_butterfly_32(DATA_TYPE *x){
 
-  REG_TYPE r0, r1, r2, r3;
+  REG_TYPE r0, r1;
+
+	   r0 = x[30] - x[14]; x[30] += x[14];           
+	   r1 = x[31] - x[15]; x[31] += x[15];
+	   x[14] = r0; x[15] = r1;
+	   MB();
 
-	   r0 = x[16] - x[17]; x[16] += x[17];
-	   r1 = x[18] - x[19]; x[18] += x[19];
-	   r2 = x[ 1] - x[ 0]; x[17]  = x[ 1] + x[ 0];
-	   r3 = x[ 3] - x[ 2]; x[19]  = x[ 3] + x[ 2];
-	   XNPROD31( r0, r1, cPI3_8, cPI1_8, &x[ 0], &x[ 2] );
-	   XPROD31 ( r2, r3, cPI1_8, cPI3_8, &x[ 1], &x[ 3] );
+	   r0 = x[28] - x[12]; x[28] += x[12];           
+	   r1 = x[29] - x[13]; x[29] += x[13];
+	   XNPROD31( r0, r1, cPI1_8, cPI3_8, &x[12], &x[13] );
+	   MB();
+
+	   r0 = x[26] - x[10]; x[26] += x[10];
+	   r1 = x[27] - x[11]; x[27] += x[11];
+	   x[10] = MULT31((r0 - r1) , cPI2_8);
+	   x[11] = MULT31((r0 + r1) , cPI2_8);
 	   MB();
 
-	   r0 = x[20] - x[21]; x[20] += x[21];
-	   r1 = x[22] - x[23]; x[22] += x[23];
-	   r2 = x[ 5] - x[ 4]; x[21]  = x[ 5] + x[ 4];
-	   r3 = x[ 7] - x[ 6]; x[23]  = x[ 7] + x[ 6];
-	   x[ 4] = MULT31((r0 - r1) , cPI2_8);
-	   x[ 5] = MULT31((r3 + r2) , cPI2_8);
-	   x[ 6] = MULT31((r0 + r1) , cPI2_8);
-	   x[ 7] = MULT31((r3 - r2) , cPI2_8);
+	   r0 = x[24] - x[ 8]; x[24] += x[ 8];
+	   r1 = x[25] - x[ 9]; x[25] += x[ 9];
+	   XNPROD31( r0, r1, cPI3_8, cPI1_8, &x[ 8], &x[ 9] );
+	   MB();
+
+	   r0 = x[22] - x[ 6]; x[22] += x[ 6];
+	   r1 = x[ 7] - x[23]; x[23] += x[ 7];
+	   x[ 6] = r1; x[ 7] = r0;
 	   MB();
 
-	   r0 = x[24] - x[25]; x[24] += x[25];           
-	   r1 = x[26] - x[27]; x[26] += x[27];
-	   r2 = x[ 9] - x[ 8]; x[25]  = x[ 9] + x[ 8];
-	   r3 = x[11] - x[10]; x[27]  = x[11] + x[10];
-	   XNPROD31( r0, r1, cPI1_8, cPI3_8, &x[ 8], &x[10] );
-	   XPROD31 ( r2, r3, cPI3_8, cPI1_8, &x[ 9], &x[11] );
+	   r0 = x[ 4] - x[20]; x[20] += x[ 4];
+	   r1 = x[ 5] - x[21]; x[21] += x[ 5];
+	   XPROD31 ( r0, r1, cPI3_8, cPI1_8, &x[ 4], &x[ 5] );
 	   MB();
 
-	   r0 = x[28] - x[29]; x[28] += x[29];           
-	   r1 = x[30] - x[31]; x[30] += x[31];
-	   r2 = x[12] - x[13]; x[29]  = x[13] + x[12];
-	   r3 = x[15] - x[14]; x[31]  = x[15] + x[14];
-	   x[12] = r0; x[13] = r3; 
-	   x[14] = r1; x[15] = r2;
+	   r0 = x[ 2] - x[18]; x[18] += x[ 2];
+	   r1 = x[ 3] - x[19]; x[19] += x[ 3];
+	   x[ 2] = MULT31((r1 + r0) , cPI2_8);
+	   x[ 3] = MULT31((r1 - r0) , cPI2_8);
+	   MB();
+
+	   r0 = x[ 0] - x[16]; x[16] += x[ 0];
+	   r1 = x[ 1] - x[17]; x[17] += x[ 1];
+	   XPROD31 ( r0, r1, cPI1_8, cPI3_8, &x[ 0], &x[ 1] );
 	   MB();
 
 	   mdct_butterfly_16(x);
@@ -174,30 +147,87 @@
 /* N/stage point generic N stage butterfly (in place, 2 register) */
 STIN void mdct_butterfly_generic(DATA_TYPE *x,int points,int step){
 
-  LOOKUP_T   *T  = sincos_lookup0;
-  DATA_TYPE *x1  = x + points - 4;
-  DATA_TYPE *x2  = x + (points>>1) - 4;
-  REG_TYPE   r0, r1, r2, r3;
+  LOOKUP_T *T   = sincos_lookup0;
+  DATA_TYPE *x1        = x + points      - 8;
+  DATA_TYPE *x2        = x + (points>>1) - 8;
+  REG_TYPE   r0;
+  REG_TYPE   r1;
 
   do{
-    r0 = x1[0] - x1[1]; x1[0] += x1[1];
-    r1 = x1[3] - x1[2]; x1[2] += x1[3];
-    r2 = x2[1] - x2[0]; x1[1]  = x2[1] + x2[0];
-    r3 = x2[3] - x2[2]; x1[3]  = x2[3] + x2[2];
-    XPROD31( r1, r0, T[0], T[1], &x2[0], &x2[2] );
-    XPROD31( r2, r3, T[0], T[1], &x2[1], &x2[3] ); T+=step;
-    x1-=4; 
-    x2-=4;
+    r0 = x1[6] - x2[6]; x1[6] += x2[6];
+    r1 = x2[7] - x1[7]; x1[7] += x2[7];
+    XPROD31( r1, r0, T[0], T[1], &x2[6], &x2[7] ); T+=step;
+
+    r0 = x1[4] - x2[4]; x1[4] += x2[4];
+    r1 = x2[5] - x1[5]; x1[5] += x2[5];
+    XPROD31( r1, r0, T[0], T[1], &x2[4], &x2[5] ); T+=step;
+
+    r0 = x1[2] - x2[2]; x1[2] += x2[2];
+    r1 = x2[3] - x1[3]; x1[3] += x2[3];
+    XPROD31( r1, r0, T[0], T[1], &x2[2], &x2[3] ); T+=step;
+
+    r0 = x1[0] - x2[0]; x1[0] += x2[0];
+    r1 = x2[1] - x1[1]; x1[1] += x2[1];
+    XPROD31( r1, r0, T[0], T[1], &x2[0], &x2[1] ); T+=step;
+
+    x1-=8; x2-=8;
   }while(T<sincos_lookup0+1024);
   do{
-    r0 = x1[0] - x1[1]; x1[0] += x1[1];
-    r1 = x1[2] - x1[3]; x1[2] += x1[3];
-    r2 = x2[0] - x2[1]; x1[1]  = x2[1] + x2[0];
-    r3 = x2[3] - x2[2]; x1[3]  = x2[3] + x2[2];
-    XNPROD31( r0, r1, T[0], T[1], &x2[0], &x2[2] );
-    XNPROD31( r3, r2, T[0], T[1], &x2[1], &x2[3] ); T-=step;
-    x1-=4; 
-    x2-=4; 
+    r0 = x1[6] - x2[6]; x1[6] += x2[6];
+    r1 = x1[7] - x2[7]; x1[7] += x2[7];
+    XNPROD31( r0, r1, T[0], T[1], &x2[6], &x2[7] ); T-=step;
+
+    r0 = x1[4] - x2[4]; x1[4] += x2[4];
+    r1 = x1[5] - x2[5]; x1[5] += x2[5];
+    XNPROD31( r0, r1, T[0], T[1], &x2[4], &x2[5] ); T-=step;
+
+    r0 = x1[2] - x2[2]; x1[2] += x2[2];
+    r1 = x1[3] - x2[3]; x1[3] += x2[3];
+    XNPROD31( r0, r1, T[0], T[1], &x2[2], &x2[3] ); T-=step;
+
+    r0 = x1[0] - x2[0]; x1[0] += x2[0];
+    r1 = x1[1] - x2[1]; x1[1] += x2[1];
+    XNPROD31( r0, r1, T[0], T[1], &x2[0], &x2[1] ); T-=step;
+
+    x1-=8; x2-=8;
+  }while(T>sincos_lookup0);
+  do{
+    r0 = x2[6] - x1[6]; x1[6] += x2[6];
+    r1 = x2[7] - x1[7]; x1[7] += x2[7];
+    XPROD31( r0, r1, T[0], T[1], &x2[6], &x2[7] ); T+=step;
+
+    r0 = x2[4] - x1[4]; x1[4] += x2[4];
+    r1 = x2[5] - x1[5]; x1[5] += x2[5];
+    XPROD31( r0, r1, T[0], T[1], &x2[4], &x2[5] ); T+=step;
+
+    r0 = x2[2] - x1[2]; x1[2] += x2[2];
+    r1 = x2[3] - x1[3]; x1[3] += x2[3];
+    XPROD31( r0, r1, T[0], T[1], &x2[2], &x2[3] ); T+=step;
+
+    r0 = x2[0] - x1[0]; x1[0] += x2[0];
+    r1 = x2[1] - x1[1]; x1[1] += x2[1];
+    XPROD31( r0, r1, T[0], T[1], &x2[0], &x2[1] ); T+=step;
+
+    x1-=8; x2-=8;
+  }while(T<sincos_lookup0+1024);
+  do{
+    r0 = x1[6] - x2[6]; x1[6] += x2[6];
+    r1 = x2[7] - x1[7]; x1[7] += x2[7];
+    XNPROD31( r1, r0, T[0], T[1], &x2[6], &x2[7] ); T-=step;
+
+    r0 = x1[4] - x2[4]; x1[4] += x2[4];
+    r1 = x2[5] - x1[5]; x1[5] += x2[5];
+    XNPROD31( r1, r0, T[0], T[1], &x2[4], &x2[5] ); T-=step;
+
+    r0 = x1[2] - x2[2]; x1[2] += x2[2];
+    r1 = x2[3] - x1[3]; x1[3] += x2[3];
+    XNPROD31( r1, r0, T[0], T[1], &x2[2], &x2[3] ); T-=step;
+
+    r0 = x1[0] - x2[0]; x1[0] += x2[0];
+    r1 = x2[1] - x1[1]; x1[1] += x2[1];
+    XNPROD31( r1, r0, T[0], T[1], &x2[0], &x2[1] ); T-=step;
+
+    x1-=8; x2-=8;
   }while(T>sincos_lookup0);
 }
 
@@ -205,14 +235,15 @@
 
   int stages=8-shift;
   int i,j;
-
+  
   for(i=0;--stages>0;i++){
     for(j=0;j<(1<<i);j++)
       mdct_butterfly_generic(x+(points>>i)*j,points>>i,4<<(i+shift));
   }
-  
+
   for(j=0;j<points;j+=32)
     mdct_butterfly_32(x+j);
+
 }
 
 static unsigned char bitrev[16]={0,8,4,12,2,10,6,14,1,9,5,13,3,11,7,15};
@@ -221,266 +252,259 @@
   return bitrev[x>>8]|(bitrev[(x&0x0f0)>>4]<<4)|(((int)bitrev[x&0x00f])<<8);
 }
 
-STIN void mdct_bitreverse(DATA_TYPE *x,int n,int shift){
+STIN void mdct_bitreverse(DATA_TYPE *x,int n,int step,int shift){
+
   int          bit   = 0;
-  DATA_TYPE   *w     = x+(n>>1);
+  DATA_TYPE   *w0    = x;
+  DATA_TYPE   *w1    = x = w0+(n>>1);
+  LOOKUP_T    *T = (step>=4)?(sincos_lookup0+(step>>1)):sincos_lookup1;
+  LOOKUP_T    *Ttop  = T+1024;
+  DATA_TYPE    r2;
 
   do{
-    DATA_TYPE  b     = bitrev12(bit++);
-    DATA_TYPE *xx    = x + (b>>shift);
-    REG_TYPE  r;
-
-               w    -= 2;
-
-	       if(w>xx){
+    DATA_TYPE r3     = bitrev12(bit++);
+    DATA_TYPE *x0    = x + ((r3 ^ 0xfff)>>shift) -1;
+    DATA_TYPE *x1    = x + (r3>>shift);
 
-		 r      = xx[0];
-		 xx[0]  = w[0];
-		 w[0]   = r;
-		 
-		 r      = xx[1];
-		 xx[1]  = w[1];
-		 w[1]   = r;
-	       }
-  }while(w>x);
-}
+    REG_TYPE  r0     = x0[0]  + x1[0];
+    REG_TYPE  r1     = x1[1]  - x0[1];
 
-STIN void mdct_step7(DATA_TYPE *x,int n,int step){
-  DATA_TYPE   *w0    = x;
-  DATA_TYPE   *w1    = x+(n>>1);
-  LOOKUP_T    *T = (step>=4)?(sincos_lookup0+(step>>1)):sincos_lookup1;
-  LOOKUP_T    *Ttop  = T+1024;
-  REG_TYPE     r0, r1, r2, r3;
-  
-  do{
-	      w1    -= 2;
+	      XPROD32( r0, r1, T[1], T[0], &r2, &r3 ); T+=step;
 
-              r0     = w0[0]  + w1[0];
-              r1     = w1[1]  - w0[1];	      
-	      r2     = MULT32(r0, T[1]) + MULT32(r1, T[0]);
-	      r3     = MULT32(r1, T[1]) - MULT32(r0, T[0]);
-	      T+=step;
+	      w1    -= 4;
 
-	      r0     = (w0[1] + w1[1])>>1;
-              r1     = (w0[0] - w1[0])>>1;
+	      r0     = (x0[1] + x1[1])>>1;
+              r1     = (x0[0] - x1[0])>>1;
 	      w0[0]  = r0     + r2;
 	      w0[1]  = r1     + r3;
+	      w1[2]  = r0     - r2;
+	      w1[3]  = r3     - r1;
+
+	      r3     = bitrev12(bit++);
+              x0     = x + ((r3 ^ 0xfff)>>shift) -1;
+              x1     = x + (r3>>shift);
+
+              r0     = x0[0]  + x1[0];
+              r1     = x1[1]  - x0[1];
+
+	      XPROD32( r0, r1, T[1], T[0], &r2, &r3 ); T+=step;
+
+              r0     = (x0[1] + x1[1])>>1;
+              r1     = (x0[0] - x1[0])>>1;
+	      w0[2]  = r0     + r2;
+	      w0[3]  = r1     + r3;
 	      w1[0]  = r0     - r2;
 	      w1[1]  = r3     - r1;
 
-	      w0    += 2;
+	      w0    += 4;
   }while(T<Ttop);
   do{
-	      w1    -= 2;
+    DATA_TYPE r3     = bitrev12(bit++);
+    DATA_TYPE *x0    = x + ((r3 ^ 0xfff)>>shift) -1;
+    DATA_TYPE *x1    = x + (r3>>shift);
+
+    REG_TYPE  r0     = x0[0]  + x1[0];
+    REG_TYPE  r1     = x1[1]  - x0[1];
 
-              r0     = w0[0]  + w1[0];
-              r1     = w1[1]  - w0[1];	
-	      T-=step;
-	      r2     = MULT32(r0, T[0]) + MULT32(r1, T[1]);
-	      r3     = MULT32(r1, T[0]) - MULT32(r0, T[1]);      
+	      T-=step; XPROD32( r0, r1, T[0], T[1], &r2, &r3 );
 
-	      r0     = (w0[1] + w1[1])>>1;
-              r1     = (w0[0] - w1[0])>>1;
+	      w1    -= 4;
+
+	      r0     = (x0[1] + x1[1])>>1;
+              r1     = (x0[0] - x1[0])>>1;
 	      w0[0]  = r0     + r2;
 	      w0[1]  = r1     + r3;
+	      w1[2]  = r0     - r2;
+	      w1[3]  = r3     - r1;
+
+	      r3     = bitrev12(bit++);
+              x0     = x + ((r3 ^ 0xfff)>>shift) -1;
+              x1     = x + (r3>>shift);
+
+              r0     = x0[0]  + x1[0];
+              r1     = x1[1]  - x0[1];
+
+	      T-=step; XPROD32( r0, r1, T[0], T[1], &r2, &r3 );
+
+              r0     = (x0[1] + x1[1])>>1;
+              r1     = (x0[0] - x1[0])>>1;
+	      w0[2]  = r0     + r2;
+	      w0[3]  = r1     + r3;
 	      w1[0]  = r0     - r2;
 	      w1[1]  = r3     - r1;
 
-	      w0    += 2;
+	      w0    += 4;
   }while(w0<w1);
 }
 
-STIN void mdct_step8(DATA_TYPE *x, int n, int step){
+void mdct_backward(int n, DATA_TYPE *in, DATA_TYPE *out){
+  int n2=n>>1;
+  int n4=n>>2;
+  DATA_TYPE *iX;
+  DATA_TYPE *oX;
   LOOKUP_T *T;
   LOOKUP_T *V;
-  DATA_TYPE *iX =x+(n>>1);
-  step>>=2;
-
-  switch(step) {
-  default: 
-    T=(step>=4)?(sincos_lookup0+(step>>1)):sincos_lookup1;
-    do{
-      REG_TYPE     r0  =  x[0];
-      REG_TYPE     r1  = -x[1];
-                   XPROD31( r0, r1, T[0], T[1], x, x+1); T+=step;
-                   x  +=2;
-    }while(x<iX);
-    break;
-  
-  case 1: 
-    {
-      /* linear interpolation between table values: offset=0.5, step=1 */
-      REG_TYPE    t0,t1,v0,v1,r0,r1;
-      T         = sincos_lookup0;
-      V         = sincos_lookup1;
-      t0        = (*T++)>>1;
-      t1        = (*T++)>>1;
-      do{
-	    r0  =  x[0];
-	    r1  = -x[1];	
-	    t0 += (v0 = (*V++)>>1);
-	    t1 += (v1 = (*V++)>>1);
-	    XPROD31( r0, r1, t0, t1, x, x+1 );
-	    
-	    r0  =  x[2];
-	    r1  = -x[3];
-	    v0 += (t0 = (*T++)>>1);
-	    v1 += (t1 = (*T++)>>1);
-	    XPROD31( r0, r1, v0, v1, x+2, x+3 );
-	    
-	    x += 4;
-      }while(x<iX);
-      break;
-    }
-    
-  case 0: 
-    {
-      /* linear interpolation between table values: offset=0.25, step=0.5 */
-      REG_TYPE    t0,t1,v0,v1,q0,q1,r0,r1;
-      T         = sincos_lookup0;
-      V         = sincos_lookup1;
-      t0        = *T++;
-      t1        = *T++;
-      do{
-
-	
-	v0  = *V++;
-	v1  = *V++;
-	t0 +=  (q0 = (v0-t0)>>2);
-	t1 +=  (q1 = (v1-t1)>>2);
-	r0  =  x[0];
-	r1  = -x[1];	
-	XPROD31( r0, r1, t0, t1, x, x+1 );
-	t0  = v0-q0;
-	t1  = v1-q1;
-	r0  =  x[2];
-	r1  = -x[3];	
-	XPROD31( r0, r1, t0, t1, x+2, x+3 );
-	
-	t0  = *T++;
-	t1  = *T++;
-	v0 += (q0 = (t0-v0)>>2);
-	v1 += (q1 = (t1-v1)>>2);
-	r0  =  x[4];
-	r1  = -x[5];	
-	XPROD31( r0, r1, v0, v1, x+4, x+5 );
-	v0  = t0-q0;
-	v1  = t1-q1;
-	r0  =  x[6];
-	r1  = -x[7];	
-	XPROD31( r0, r1, v0, v1, x+5, x+6 );
-
-	x+=8;
-      }while(x<iX);
-      break;
-    }
-  }
-}
-
-/* partial; doesn't perform last-step deinterleave/unrolling.  That
-   can be done more efficiently during pcm output */
-void mdct_backward(int n, DATA_TYPE *in){
   int shift;
   int step;
-  
-  for (shift=4;!(n&(1<<shift));shift++);
+
+  for (shift=6;!(n&(1<<shift));shift++);
   shift=13-shift;
   step=2<<shift;
    
-  presymmetry(in,n>>1,step);
-  mdct_butterflies(in,n>>1,shift);
-  mdct_bitreverse(in,n,shift);
-  mdct_step7(in,n,step);
-  mdct_step8(in,n,step);
-}
+  /* rotate */
+
+  iX            = in+n2-7;
+  oX            = out+n2+n4;
+  T             = sincos_lookup0;
 
-void mdct_shift_right(int n, DATA_TYPE *in, DATA_TYPE *right){
-  int i;
-  n>>=2;
-  in+=1;
+  do{
+    oX-=4;
+    XPROD31( iX[4], iX[6], T[0], T[1], &oX[2], &oX[3] ); T+=step;
+    XPROD31( iX[0], iX[2], T[0], T[1], &oX[0], &oX[1] ); T+=step;
+    iX-=8;
+  }while(iX>=in+n4);
+  do{
+    oX-=4;
+    XPROD31( iX[4], iX[6], T[1], T[0], &oX[2], &oX[3] ); T-=step;
+    XPROD31( iX[0], iX[2], T[1], T[0], &oX[0], &oX[1] ); T-=step;
+    iX-=8;
+  }while(iX>=in);
 
-  for(i=0;i<n;i++)
-    right[i]=in[i<<1];
-}
+  iX            = in+n2-8;
+  oX            = out+n2+n4;
+  T             = sincos_lookup0;
+
+  do{
+    T+=step; XNPROD31( iX[6], iX[4], T[0], T[1], &oX[0], &oX[1] );
+    T+=step; XNPROD31( iX[2], iX[0], T[0], T[1], &oX[2], &oX[3] );
+    iX-=8;
+    oX+=4;
+  }while(iX>=in+n4);
+  do{
+    T-=step; XNPROD31( iX[6], iX[4], T[1], T[0], &oX[0], &oX[1] );
+    T-=step; XNPROD31( iX[2], iX[0], T[1], T[0], &oX[2], &oX[3] );
+    iX-=8;
+    oX+=4;
+  }while(iX>=in);
 
-void mdct_unroll_lap(int n0,int n1,
-		     int lW,int W,
-		     DATA_TYPE *in,
-		     DATA_TYPE *right,
-		     LOOKUP_T *w0,
-		     LOOKUP_T *w1,
-		     ogg_int16_t *out,
-		     int step,
-		     int start, /* samples, this frame */
-		     int end    /* samples, this frame */){
+  mdct_butterflies(out+n2,n2,shift);
+  mdct_bitreverse(out,n,step,shift);
+
+  /* rotate + window */
+
+  step>>=2;
+  {
+    DATA_TYPE *oX1=out+n2+n4;
+    DATA_TYPE *oX2=out+n2+n4;
+    DATA_TYPE *iX =out;
 
-  DATA_TYPE *l=in+(W&&lW ? n1>>1 : n0>>1);
-  DATA_TYPE *r=right+(lW ? n1>>2 : n0>>2);
-  DATA_TYPE *post;
-  LOOKUP_T *wR=(W && lW ? w1+(n1>>1) : w0+(n0>>1));
-  LOOKUP_T *wL=(W && lW ? w1         : w0        );
+    switch(step) {
+      default: {
+        T=(step>=4)?(sincos_lookup0+(step>>1)):sincos_lookup1;
+        do{
+          oX1-=4;
+	  XPROD31( iX[0], -iX[1], T[0], T[1], &oX1[3], &oX2[0] ); T+=step;
+	  XPROD31( iX[2], -iX[3], T[0], T[1], &oX1[2], &oX2[1] ); T+=step;
+	  XPROD31( iX[4], -iX[5], T[0], T[1], &oX1[1], &oX2[2] ); T+=step;
+	  XPROD31( iX[6], -iX[7], T[0], T[1], &oX1[0], &oX2[3] ); T+=step;
+	  oX2+=4;
+	  iX+=8;
+	}while(iX<oX1);
+	break;
+      }
 
-  int preLap=(lW && !W ? (n1>>2)-(n0>>2) : 0 );
-  int halfLap=(lW && W ? (n1>>2) : (n0>>2) );
-  int postLap=(!lW && W ? (n1>>2)-(n0>>2) : 0 );
-  int n,off;
+      case 1: {
+        /* linear interpolation between table values: offset=0.5, step=1 */
+	REG_TYPE  t0,t1,v0,v1;
+        T         = sincos_lookup0;
+        V         = sincos_lookup1;
+	t0        = (*T++)>>1;
+	t1        = (*T++)>>1;
+        do{
+          oX1-=4;
 
-  /* preceeding direct-copy lapping from previous frame, if any */
-  if(preLap){
-    n      = (end<preLap?end:preLap);
-    off    = (start<preLap?start:preLap);
-    post   = r-n;
-    r     -= off;
-    start -= off;
-    end   -= n;
-    while(r>post){
-      *out = CLIP_TO_15((*--r)>>9);
-      out+=step;
+	  t0 += (v0 = (*V++)>>1);
+	  t1 += (v1 = (*V++)>>1);
+	  XPROD31( iX[0], -iX[1], t0, t1, &oX1[3], &oX2[0] );
+	  v0 += (t0 = (*T++)>>1);
+	  v1 += (t1 = (*T++)>>1);
+	  XPROD31( iX[2], -iX[3], v0, v1, &oX1[2], &oX2[1] );
+	  t0 += (v0 = (*V++)>>1);
+	  t1 += (v1 = (*V++)>>1);
+	  XPROD31( iX[4], -iX[5], t0, t1, &oX1[1], &oX2[2] );
+	  v0 += (t0 = (*T++)>>1);
+	  v1 += (t1 = (*T++)>>1);
+	  XPROD31( iX[6], -iX[7], v0, v1, &oX1[0], &oX2[3] );
+
+	  oX2+=4;
+	  iX+=8;
+	}while(iX<oX1);
+	break;
+      }
+
+      case 0: {
+        /* linear interpolation between table values: offset=0.25, step=0.5 */
+	REG_TYPE  t0,t1,v0,v1,q0,q1;
+        T         = sincos_lookup0;
+        V         = sincos_lookup1;
+	t0        = *T++;
+	t1        = *T++;
+        do{
+          oX1-=4;
+
+	  v0  = *V++;
+	  v1  = *V++;
+	  t0 +=  (q0 = (v0-t0)>>2);
+	  t1 +=  (q1 = (v1-t1)>>2);
+	  XPROD31( iX[0], -iX[1], t0, t1, &oX1[3], &oX2[0] );
+	  t0  = v0-q0;
+	  t1  = v1-q1;
+	  XPROD31( iX[2], -iX[3], t0, t1, &oX1[2], &oX2[1] );
+
+	  t0  = *T++;
+	  t1  = *T++;
+	  v0 += (q0 = (t0-v0)>>2);
+	  v1 += (q1 = (t1-v1)>>2);
+	  XPROD31( iX[4], -iX[5], v0, v1, &oX1[1], &oX2[2] );
+	  v0  = t0-q0;
+	  v1  = t1-q1;
+	  XPROD31( iX[6], -iX[7], v0, v1, &oX1[0], &oX2[3] );
+
+	  oX2+=4;
+	  iX+=8;
+	}while(iX<oX1);
+	break;
+      }
     }
-  }
-  
-  /* cross-lap; two halves due to wrap-around */
-  n      = (end<halfLap?end:halfLap);
-  off    = (start<halfLap?start:halfLap);
-  post   = r-n;
-  r     -= off;
-  l     -= off*2;
-  start -= off;
-  wR    -= off;
-  wL    += off;
-  end   -= n;
-  while(r>post){
-    l-=2;
-    *out = CLIP_TO_15((MULT31(*--r,*--wR) + MULT31(*l,*wL++))>>9);
-    out+=step;
-  }
+
+    iX=out+n2+n4;
+    oX1=out+n4;
+    oX2=oX1;
+
+    do{
+      oX1-=4;
+      iX-=4;
+
+      oX2[0] = -(oX1[3] = iX[3]);
+      oX2[1] = -(oX1[2] = iX[2]);
+      oX2[2] = -(oX1[1] = iX[1]);
+      oX2[3] = -(oX1[0] = iX[0]);
 
-  n      = (end<halfLap?end:halfLap);
-  off    = (start<halfLap?start:halfLap);
-  post   = r+n;
-  r     += off;
-  l     += off*2;
-  start -= off;
-  end   -= n;
-  wR    -= off;
-  wL    += off;
-  while(r<post){
-    *out = CLIP_TO_15((MULT31(*r++,*--wR) - MULT31(*l,*wL++))>>9);
-    out+=step;
-    l+=2;
-  }
+      oX2+=4;
+    }while(oX2<iX);
+
+    iX=out+n2+n4;
+    oX1=out+n2+n4;
+    oX2=out+n2;
 
-  /* preceeding direct-copy lapping from previous frame, if any */
-  if(postLap){
-    n      = (end<postLap?end:postLap);
-    off    = (start<postLap?start:postLap);
-    post   = l+n*2;
-    l     += off*2;
-    while(l<post){
-      *out = CLIP_TO_15((-*l)>>9);
-      out+=step;
-      l+=2;
-    }
+    do{
+      oX1-=4;
+      oX1[0]= iX[3];
+      oX1[1]= iX[2];
+      oX1[2]= iX[1];
+      oX1[3]= iX[0];
+      iX+=4;
+    }while(oX1>oX2);
   }
 }