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rt-thread/bsp/stm32_radio/mp3/real/imdct.c

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add stm32 radio git-svn-id: https://rt-thread.googlecode.com/svn/trunk@9 bbd45198-f89e-11dd-88c7-29a3b14d5316
2009-07-28 07:28:26 +08:00
/* ***** BEGIN LICENSE BLOCK *****
* Version: RCSL 1.0/RPSL 1.0
*
* Portions Copyright (c) 1995-2002 RealNetworks, Inc. All Rights Reserved.
*
* The contents of this file, and the files included with this file, are
* subject to the current version of the RealNetworks Public Source License
* Version 1.0 (the "RPSL") available at
* http://www.helixcommunity.org/content/rpsl unless you have licensed
* the file under the RealNetworks Community Source License Version 1.0
* (the "RCSL") available at http://www.helixcommunity.org/content/rcsl,
* in which case the RCSL will apply. You may also obtain the license terms
* directly from RealNetworks. You may not use this file except in
* compliance with the RPSL or, if you have a valid RCSL with RealNetworks
* applicable to this file, the RCSL. Please see the applicable RPSL or
* RCSL for the rights, obligations and limitations governing use of the
* contents of the file.
*
* This file is part of the Helix DNA Technology. RealNetworks is the
* developer of the Original Code and owns the copyrights in the portions
* it created.
*
* This file, and the files included with this file, is distributed and made
* available on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
* EXPRESS OR IMPLIED, AND REALNETWORKS HEREBY DISCLAIMS ALL SUCH WARRANTIES,
* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
*
* Technology Compatibility Kit Test Suite(s) Location:
* http://www.helixcommunity.org/content/tck
*
* Contributor(s):
*
* ***** END LICENSE BLOCK ***** */
/**************************************************************************************
* Fixed-point MP3 decoder
* Jon Recker (jrecker@real.com), Ken Cooke (kenc@real.com)
* June 2003
*
* imdct.c - antialias, inverse transform (short/long/mixed), windowing,
* overlap-add, frequency inversion
**************************************************************************************/
#include "coder.h"
#include "assembly.h"
/**************************************************************************************
* Function: AntiAlias
*
* Description: smooth transition across DCT block boundaries (every 18 coefficients)
*
* Inputs: vector of dequantized coefficients, length = (nBfly+1) * 18
* number of "butterflies" to perform (one butterfly means one
* inter-block smoothing operation)
*
* Outputs: updated coefficient vector x
*
* Return: none
*
* Notes: weighted average of opposite bands (pairwise) from the 8 samples
* before and after each block boundary
* nBlocks = (nonZeroBound + 7) / 18, since nZB is the first ZERO sample
* above which all other samples are also zero
* max gain per sample = 1.372
* MAX(i) (abs(csa[i][0]) + abs(csa[i][1]))
* bits gained = 0
* assume at least 1 guard bit in x[] to avoid overflow
* (should be guaranteed from dequant, and max gain from stproc * max
* gain from AntiAlias < 2.0)
**************************************************************************************/
static void AntiAlias(int *x, int nBfly)
{
int k, a0, b0, c0, c1;
const int *c;
/* csa = Q31 */
for (k = nBfly; k > 0; k--) {
c = csa[0];
x += 18;
a0 = x[-1]; c0 = *c; c++; b0 = x[0]; c1 = *c; c++;
x[-1] = (MULSHIFT32(c0, a0) - MULSHIFT32(c1, b0)) << 1;
x[0] = (MULSHIFT32(c0, b0) + MULSHIFT32(c1, a0)) << 1;
a0 = x[-2]; c0 = *c; c++; b0 = x[1]; c1 = *c; c++;
x[-2] = (MULSHIFT32(c0, a0) - MULSHIFT32(c1, b0)) << 1;
x[1] = (MULSHIFT32(c0, b0) + MULSHIFT32(c1, a0)) << 1;
a0 = x[-3]; c0 = *c; c++; b0 = x[2]; c1 = *c; c++;
x[-3] = (MULSHIFT32(c0, a0) - MULSHIFT32(c1, b0)) << 1;
x[2] = (MULSHIFT32(c0, b0) + MULSHIFT32(c1, a0)) << 1;
a0 = x[-4]; c0 = *c; c++; b0 = x[3]; c1 = *c; c++;
x[-4] = (MULSHIFT32(c0, a0) - MULSHIFT32(c1, b0)) << 1;
x[3] = (MULSHIFT32(c0, b0) + MULSHIFT32(c1, a0)) << 1;
a0 = x[-5]; c0 = *c; c++; b0 = x[4]; c1 = *c; c++;
x[-5] = (MULSHIFT32(c0, a0) - MULSHIFT32(c1, b0)) << 1;
x[4] = (MULSHIFT32(c0, b0) + MULSHIFT32(c1, a0)) << 1;
a0 = x[-6]; c0 = *c; c++; b0 = x[5]; c1 = *c; c++;
x[-6] = (MULSHIFT32(c0, a0) - MULSHIFT32(c1, b0)) << 1;
x[5] = (MULSHIFT32(c0, b0) + MULSHIFT32(c1, a0)) << 1;
a0 = x[-7]; c0 = *c; c++; b0 = x[6]; c1 = *c; c++;
x[-7] = (MULSHIFT32(c0, a0) - MULSHIFT32(c1, b0)) << 1;
x[6] = (MULSHIFT32(c0, b0) + MULSHIFT32(c1, a0)) << 1;
a0 = x[-8]; c0 = *c; c++; b0 = x[7]; c1 = *c; c++;
x[-8] = (MULSHIFT32(c0, a0) - MULSHIFT32(c1, b0)) << 1;
x[7] = (MULSHIFT32(c0, b0) + MULSHIFT32(c1, a0)) << 1;
}
}
/**************************************************************************************
* Function: WinPrevious
*
* Description: apply specified window to second half of previous IMDCT (overlap part)
*
* Inputs: vector of 9 coefficients (xPrev)
*
* Outputs: 18 windowed output coefficients (gain 1 integer bit)
* window type (0, 1, 2, 3)
*
* Return: none
*
* Notes: produces 9 output samples from 18 input samples via symmetry
* all blocks gain at least 1 guard bit via window (long blocks get extra
* sign bit, short blocks can have one addition but max gain < 1.0)
**************************************************************************************/
static void WinPrevious(int *xPrev, int *xPrevWin, int btPrev)
{
int i, x, *xp, *xpwLo, *xpwHi, wLo, wHi;
const int *wpLo, *wpHi;
xp = xPrev;
/* mapping (see IMDCT12x3): xPrev[0-2] = sum[6-8], xPrev[3-8] = sum[12-17] */
if (btPrev == 2) {
/* this could be reordered for minimum loads/stores */
wpLo = imdctWin[btPrev];
xPrevWin[ 0] = MULSHIFT32(wpLo[ 6], xPrev[2]) + MULSHIFT32(wpLo[0], xPrev[6]);
xPrevWin[ 1] = MULSHIFT32(wpLo[ 7], xPrev[1]) + MULSHIFT32(wpLo[1], xPrev[7]);
xPrevWin[ 2] = MULSHIFT32(wpLo[ 8], xPrev[0]) + MULSHIFT32(wpLo[2], xPrev[8]);
xPrevWin[ 3] = MULSHIFT32(wpLo[ 9], xPrev[0]) + MULSHIFT32(wpLo[3], xPrev[8]);
xPrevWin[ 4] = MULSHIFT32(wpLo[10], xPrev[1]) + MULSHIFT32(wpLo[4], xPrev[7]);
xPrevWin[ 5] = MULSHIFT32(wpLo[11], xPrev[2]) + MULSHIFT32(wpLo[5], xPrev[6]);
xPrevWin[ 6] = MULSHIFT32(wpLo[ 6], xPrev[5]);
xPrevWin[ 7] = MULSHIFT32(wpLo[ 7], xPrev[4]);
xPrevWin[ 8] = MULSHIFT32(wpLo[ 8], xPrev[3]);
xPrevWin[ 9] = MULSHIFT32(wpLo[ 9], xPrev[3]);
xPrevWin[10] = MULSHIFT32(wpLo[10], xPrev[4]);
xPrevWin[11] = MULSHIFT32(wpLo[11], xPrev[5]);
xPrevWin[12] = xPrevWin[13] = xPrevWin[14] = xPrevWin[15] = xPrevWin[16] = xPrevWin[17] = 0;
} else {
/* use ARM-style pointers (*ptr++) so that ADS compiles well */
wpLo = imdctWin[btPrev] + 18;
wpHi = wpLo + 17;
xpwLo = xPrevWin;
xpwHi = xPrevWin + 17;
for (i = 9; i > 0; i--) {
x = *xp++; wLo = *wpLo++; wHi = *wpHi--;
*xpwLo++ = MULSHIFT32(wLo, x);
*xpwHi-- = MULSHIFT32(wHi, x);
}
}
}
/**************************************************************************************
* Function: FreqInvertRescale
*
* Description: do frequency inversion (odd samples of odd blocks) and rescale
* if necessary (extra guard bits added before IMDCT)
*
* Inputs: output vector y (18 new samples, spaced NBANDS apart)
* previous sample vector xPrev (9 samples)
* index of current block
* number of extra shifts added before IMDCT (usually 0)
*
* Outputs: inverted and rescaled (as necessary) outputs
* rescaled (as necessary) previous samples
*
* Return: updated mOut (from new outputs y)
**************************************************************************************/
static int FreqInvertRescale(int *y, int *xPrev, int blockIdx, int es)
{
int i, d, mOut;
int y0, y1, y2, y3, y4, y5, y6, y7, y8;
if (es == 0) {
/* fast case - frequency invert only (no rescaling) - can fuse into overlap-add for speed, if desired */
if (blockIdx & 0x01) {
y += NBANDS;
y0 = *y; y += 2*NBANDS;
y1 = *y; y += 2*NBANDS;
y2 = *y; y += 2*NBANDS;
y3 = *y; y += 2*NBANDS;
y4 = *y; y += 2*NBANDS;
y5 = *y; y += 2*NBANDS;
y6 = *y; y += 2*NBANDS;
y7 = *y; y += 2*NBANDS;
y8 = *y; y += 2*NBANDS;
y -= 18*NBANDS;
*y = -y0; y += 2*NBANDS;
*y = -y1; y += 2*NBANDS;
*y = -y2; y += 2*NBANDS;
*y = -y3; y += 2*NBANDS;
*y = -y4; y += 2*NBANDS;
*y = -y5; y += 2*NBANDS;
*y = -y6; y += 2*NBANDS;
*y = -y7; y += 2*NBANDS;
*y = -y8; y += 2*NBANDS;
}
return 0;
} else {
/* undo pre-IMDCT scaling, clipping if necessary */
mOut = 0;
if (blockIdx & 0x01) {
/* frequency invert */
for (i = 0; i < 18; i+=2) {
d = *y; CLIP_2N(d, 31 - es); *y = d << es; mOut |= FASTABS(*y); y += NBANDS;
d = -*y; CLIP_2N(d, 31 - es); *y = d << es; mOut |= FASTABS(*y); y += NBANDS;
d = *xPrev; CLIP_2N(d, 31 - es); *xPrev++ = d << es;
}
} else {
for (i = 0; i < 18; i+=2) {
d = *y; CLIP_2N(d, 31 - es); *y = d << es; mOut |= FASTABS(*y); y += NBANDS;
d = *y; CLIP_2N(d, 31 - es); *y = d << es; mOut |= FASTABS(*y); y += NBANDS;
d = *xPrev; CLIP_2N(d, 31 - es); *xPrev++ = d << es;
}
}
return mOut;
}
}
/* format = Q31
* #define M_PI 3.14159265358979323846
* double u = 2.0 * M_PI / 9.0;
* float c0 = sqrt(3.0) / 2.0;
* float c1 = cos(u);
* float c2 = cos(2*u);
* float c3 = sin(u);
* float c4 = sin(2*u);
*/
static const int c9_0 = 0x6ed9eba1;
static const int c9_1 = 0x620dbe8b;
static const int c9_2 = 0x163a1a7e;
static const int c9_3 = 0x5246dd49;
static const int c9_4 = 0x7e0e2e32;
/* format = Q31
* cos(((0:8) + 0.5) * (pi/18))
*/
static const int c18[9] = {
0x7f834ed0, 0x7ba3751d, 0x7401e4c1, 0x68d9f964, 0x5a82799a, 0x496af3e2, 0x36185aee, 0x2120fb83, 0x0b27eb5c,
};
/* require at least 3 guard bits in x[] to ensure no overflow */
static __inline void idct9(int *x)
{
int a1, a2, a3, a4, a5, a6, a7, a8, a9;
int a10, a11, a12, a13, a14, a15, a16, a17, a18;
int a19, a20, a21, a22, a23, a24, a25, a26, a27;
int m1, m3, m5, m6, m7, m8, m9, m10, m11, m12;
int x0, x1, x2, x3, x4, x5, x6, x7, x8;
x0 = x[0]; x1 = x[1]; x2 = x[2]; x3 = x[3]; x4 = x[4];
x5 = x[5]; x6 = x[6]; x7 = x[7]; x8 = x[8];
a1 = x0 - x6;
a2 = x1 - x5;
a3 = x1 + x5;
a4 = x2 - x4;
a5 = x2 + x4;
a6 = x2 + x8;
a7 = x1 + x7;
a8 = a6 - a5; /* ie x[8] - x[4] */
a9 = a3 - a7; /* ie x[5] - x[7] */
a10 = a2 - x7; /* ie x[1] - x[5] - x[7] */
a11 = a4 - x8; /* ie x[2] - x[4] - x[8] */
/* do the << 1 as constant shifts where mX is actually used (free, no stall or extra inst.) */
m1 = MULSHIFT32(c9_0, x3);
m3 = MULSHIFT32(c9_0, a10);
m5 = MULSHIFT32(c9_1, a5);
m6 = MULSHIFT32(c9_2, a6);
m7 = MULSHIFT32(c9_1, a8);
m8 = MULSHIFT32(c9_2, a5);
m9 = MULSHIFT32(c9_3, a9);
m10 = MULSHIFT32(c9_4, a7);
m11 = MULSHIFT32(c9_3, a3);
m12 = MULSHIFT32(c9_4, a9);
a12 = x[0] + (x[6] >> 1);
a13 = a12 + ( m1 << 1);
a14 = a12 - ( m1 << 1);
a15 = a1 + ( a11 >> 1);
a16 = ( m5 << 1) + (m6 << 1);
a17 = ( m7 << 1) - (m8 << 1);
a18 = a16 + a17;
a19 = ( m9 << 1) + (m10 << 1);
a20 = (m11 << 1) - (m12 << 1);
a21 = a20 - a19;
a22 = a13 + a16;
a23 = a14 + a16;
a24 = a14 + a17;
a25 = a13 + a17;
a26 = a14 - a18;
a27 = a13 - a18;
x0 = a22 + a19; x[0] = x0;
x1 = a15 + (m3 << 1); x[1] = x1;
x2 = a24 + a20; x[2] = x2;
x3 = a26 - a21; x[3] = x3;
x4 = a1 - a11; x[4] = x4;
x5 = a27 + a21; x[5] = x5;
x6 = a25 - a20; x[6] = x6;
x7 = a15 - (m3 << 1); x[7] = x7;
x8 = a23 - a19; x[8] = x8;
}
/* let c(j) = cos(M_PI/36 * ((j)+0.5)), s(j) = sin(M_PI/36 * ((j)+0.5))
* then fastWin[2*j+0] = c(j)*(s(j) + c(j)), j = [0, 8]
* fastWin[2*j+1] = c(j)*(s(j) - c(j))
* format = Q30
*/
static const int fastWin36[18] = {
0x42aace8b, 0xc2e92724, 0x47311c28, 0xc95f619a, 0x4a868feb, 0xd0859d8c,
0x4c913b51, 0xd8243ea0, 0x4d413ccc, 0xe0000000, 0x4c913b51, 0xe7dbc161,
0x4a868feb, 0xef7a6275, 0x47311c28, 0xf6a09e67, 0x42aace8b, 0xfd16d8dd,
};
/**************************************************************************************
* Function: IMDCT36
*
* Description: 36-point modified DCT, with windowing and overlap-add (50% overlap)
*
* Inputs: vector of 18 coefficients (N/2 inputs produces N outputs, by symmetry)
* overlap part of last IMDCT (9 samples - see output comments)
* window type (0,1,2,3) of current and previous block
* current block index (for deciding whether to do frequency inversion)
* number of guard bits in input vector
*
* Outputs: 18 output samples, after windowing and overlap-add with last frame
* second half of (unwindowed) 36-point IMDCT - save for next time
* only save 9 xPrev samples, using symmetry (see WinPrevious())
*
* Notes: this is Ken's hyper-fast algorithm, including symmetric sin window
* optimization, if applicable
* total number of multiplies, general case:
* 2*10 (idct9) + 9 (last stage imdct) + 36 (for windowing) = 65
* total number of multiplies, btCurr == 0 && btPrev == 0:
* 2*10 (idct9) + 9 (last stage imdct) + 18 (for windowing) = 47
*
* blockType == 0 is by far the most common case, so it should be
* possible to use the fast path most of the time
* this is the fastest known algorithm for performing
* long IMDCT + windowing + overlap-add in MP3
*
* Return: mOut (OR of abs(y) for all y calculated here)
*
* TODO: optimize for ARM (reorder window coefs, ARM-style pointers in C,
* inline asm may or may not be helpful)
**************************************************************************************/
static int IMDCT36(int *xCurr, int *xPrev, int *y, int btCurr, int btPrev, int blockIdx, int gb)
{
int i, es, xBuf[18], xPrevWin[18];
int acc1, acc2, s, d, t, mOut;
int xo, xe, c, *xp, yLo, yHi;
const int *cp, *wp;
acc1 = acc2 = 0;
xCurr += 17;
/* 7 gb is always adequate for antialias + accumulator loop + idct9 */
if (gb < 7) {
/* rarely triggered - 5% to 10% of the time on normal clips (with Q25 input) */
es = 7 - gb;
for (i = 8; i >= 0; i--) {
acc1 = ((*xCurr--) >> es) - acc1;
acc2 = acc1 - acc2;
acc1 = ((*xCurr--) >> es) - acc1;
xBuf[i+9] = acc2; /* odd */
xBuf[i+0] = acc1; /* even */
xPrev[i] >>= es;
}
} else {
es = 0;
/* max gain = 18, assume adequate guard bits */
for (i = 8; i >= 0; i--) {
acc1 = (*xCurr--) - acc1;
acc2 = acc1 - acc2;
acc1 = (*xCurr--) - acc1;
xBuf[i+9] = acc2; /* odd */
xBuf[i+0] = acc1; /* even */
}
}
/* xEven[0] and xOdd[0] scaled by 0.5 */
xBuf[9] >>= 1;
xBuf[0] >>= 1;
/* do 9-point IDCT on even and odd */
idct9(xBuf+0); /* even */
idct9(xBuf+9); /* odd */
xp = xBuf + 8;
cp = c18 + 8;
mOut = 0;
if (btPrev == 0 && btCurr == 0) {
/* fast path - use symmetry of sin window to reduce windowing multiplies to 18 (N/2) */
wp = fastWin36;
for (i = 0; i < 9; i++) {
/* do ARM-style pointer arithmetic (i still needed for y[] indexing - compiler spills if 2 y pointers) */
c = *cp--; xo = *(xp + 9); xe = *xp--;
/* gain 2 int bits here */
xo = MULSHIFT32(c, xo); /* 2*c18*xOdd (mul by 2 implicit in scaling) */
xe >>= 2;
s = -(*xPrev); /* sum from last block (always at least 2 guard bits) */
d = -(xe - xo); /* gain 2 int bits, don't shift xo (effective << 1 to eat sign bit, << 1 for mul by 2) */
(*xPrev++) = xe + xo; /* symmetry - xPrev[i] = xPrev[17-i] for long blocks */
t = s - d;
yLo = (d + (MULSHIFT32(t, *wp++) << 2));
yHi = (s + (MULSHIFT32(t, *wp++) << 2));
y[(i)*NBANDS] = yLo;
y[(17-i)*NBANDS] = yHi;
mOut |= FASTABS(yLo);
mOut |= FASTABS(yHi);
}
} else {
/* slower method - either prev or curr is using window type != 0 so do full 36-point window
* output xPrevWin has at least 3 guard bits (xPrev has 2, gain 1 in WinPrevious)
*/
WinPrevious(xPrev, xPrevWin, btPrev);
wp = imdctWin[btCurr];
for (i = 0; i < 9; i++) {
c = *cp--; xo = *(xp + 9); xe = *xp--;
/* gain 2 int bits here */
xo = MULSHIFT32(c, xo); /* 2*c18*xOdd (mul by 2 implicit in scaling) */
xe >>= 2;
d = xe - xo;
(*xPrev++) = xe + xo; /* symmetry - xPrev[i] = xPrev[17-i] for long blocks */
yLo = (xPrevWin[i] + MULSHIFT32(d, wp[i])) << 2;
yHi = (xPrevWin[17-i] + MULSHIFT32(d, wp[17-i])) << 2;
y[(i)*NBANDS] = yLo;
y[(17-i)*NBANDS] = yHi;
mOut |= FASTABS(yLo);
mOut |= FASTABS(yHi);
}
}
xPrev -= 9;
mOut |= FreqInvertRescale(y, xPrev, blockIdx, es);
return mOut;
}
static const int c3_0 = 0x6ed9eba1; /* format = Q31, cos(pi/6) */
static const int c6[3] = { 0x7ba3751d, 0x5a82799a, 0x2120fb83 }; /* format = Q31, cos(((0:2) + 0.5) * (pi/6)) */
/* 12-point inverse DCT, used in IMDCT12x3()
* 4 input guard bits will ensure no overflow
*/
static __inline void imdct12 (int *x, int *out)
{
int a0, a1, a2;
int x0, x1, x2, x3, x4, x5;
x0 = *x; x+=3; x1 = *x; x+=3;
x2 = *x; x+=3; x3 = *x; x+=3;
x4 = *x; x+=3; x5 = *x; x+=3;
x4 -= x5;
x3 -= x4;
x2 -= x3;
x3 -= x5;
x1 -= x2;
x0 -= x1;
x1 -= x3;
x0 >>= 1;
x1 >>= 1;
a0 = MULSHIFT32(c3_0, x2) << 1;
a1 = x0 + (x4 >> 1);
a2 = x0 - x4;
x0 = a1 + a0;
x2 = a2;
x4 = a1 - a0;
a0 = MULSHIFT32(c3_0, x3) << 1;
a1 = x1 + (x5 >> 1);
a2 = x1 - x5;
/* cos window odd samples, mul by 2, eat sign bit */
x1 = MULSHIFT32(c6[0], a1 + a0) << 2;
x3 = MULSHIFT32(c6[1], a2) << 2;
x5 = MULSHIFT32(c6[2], a1 - a0) << 2;
*out = x0 + x1; out++;
*out = x2 + x3; out++;
*out = x4 + x5; out++;
*out = x4 - x5; out++;
*out = x2 - x3; out++;
*out = x0 - x1;
}
/**************************************************************************************
* Function: IMDCT12x3
*
* Description: three 12-point modified DCT's for short blocks, with windowing,
* short block concatenation, and overlap-add
*
* Inputs: 3 interleaved vectors of 6 samples each
* (block0[0], block1[0], block2[0], block0[1], block1[1]....)
* overlap part of last IMDCT (9 samples - see output comments)
* window type (0,1,2,3) of previous block
* current block index (for deciding whether to do frequency inversion)
* number of guard bits in input vector
*
* Outputs: updated sample vector x, net gain of 1 integer bit
* second half of (unwindowed) IMDCT's - save for next time
* only save 9 xPrev samples, using symmetry (see WinPrevious())
*
* Return: mOut (OR of abs(y) for all y calculated here)
*
* TODO: optimize for ARM
**************************************************************************************/
static int IMDCT12x3(int *xCurr, int *xPrev, int *y, int btPrev, int blockIdx, int gb)
{
int i, es, mOut, yLo, xBuf[18], xPrevWin[18]; /* need temp buffer for reordering short blocks */
const int *wp;
es = 0;
/* 7 gb is always adequate for accumulator loop + idct12 + window + overlap */
if (gb < 7) {
es = 7 - gb;
for (i = 0; i < 18; i+=2) {
xCurr[i+0] >>= es;
xCurr[i+1] >>= es;
*xPrev++ >>= es;
}
xPrev -= 9;
}
/* requires 4 input guard bits for each imdct12 */
imdct12(xCurr + 0, xBuf + 0);
imdct12(xCurr + 1, xBuf + 6);
imdct12(xCurr + 2, xBuf + 12);
/* window previous from last time */
WinPrevious(xPrev, xPrevWin, btPrev);
/* could unroll this for speed, minimum loads (short blocks usually rare, so doesn't make much overall difference)
* xPrevWin[i] << 2 still has 1 gb always, max gain of windowed xBuf stuff also < 1.0 and gain the sign bit
* so y calculations won't overflow
*/
wp = imdctWin[2];
mOut = 0;
for (i = 0; i < 3; i++) {
yLo = (xPrevWin[ 0+i] << 2);
mOut |= FASTABS(yLo); y[( 0+i)*NBANDS] = yLo;
yLo = (xPrevWin[ 3+i] << 2);
mOut |= FASTABS(yLo); y[( 3+i)*NBANDS] = yLo;
yLo = (xPrevWin[ 6+i] << 2) + (MULSHIFT32(wp[0+i], xBuf[3+i]));
mOut |= FASTABS(yLo); y[( 6+i)*NBANDS] = yLo;
yLo = (xPrevWin[ 9+i] << 2) + (MULSHIFT32(wp[3+i], xBuf[5-i]));
mOut |= FASTABS(yLo); y[( 9+i)*NBANDS] = yLo;
yLo = (xPrevWin[12+i] << 2) + (MULSHIFT32(wp[6+i], xBuf[2-i]) + MULSHIFT32(wp[0+i], xBuf[(6+3)+i]));
mOut |= FASTABS(yLo); y[(12+i)*NBANDS] = yLo;
yLo = (xPrevWin[15+i] << 2) + (MULSHIFT32(wp[9+i], xBuf[0+i]) + MULSHIFT32(wp[3+i], xBuf[(6+5)-i]));
mOut |= FASTABS(yLo); y[(15+i)*NBANDS] = yLo;
}
/* save previous (unwindowed) for overlap - only need samples 6-8, 12-17 */
for (i = 6; i < 9; i++)
*xPrev++ = xBuf[i] >> 2;
for (i = 12; i < 18; i++)
*xPrev++ = xBuf[i] >> 2;
xPrev -= 9;
mOut |= FreqInvertRescale(y, xPrev, blockIdx, es);
return mOut;
}
/**************************************************************************************
* Function: HybridTransform
*
* Description: IMDCT's, windowing, and overlap-add on long/short/mixed blocks
*
* Inputs: vector of input coefficients, length = nBlocksTotal * 18)
* vector of overlap samples from last time, length = nBlocksPrev * 9)
* buffer for output samples, length = MAXNSAMP
* SideInfoSub struct for this granule/channel
* BlockCount struct with necessary info
* number of non-zero input and overlap blocks
* number of long blocks in input vector (rest assumed to be short blocks)
* number of blocks which use long window (type) 0 in case of mixed block
* (bc->currWinSwitch, 0 for non-mixed blocks)
*
* Outputs: transformed, windowed, and overlapped sample buffer
* does frequency inversion on odd blocks
* updated buffer of samples for overlap
*
* Return: number of non-zero IMDCT blocks calculated in this call
* (including overlap-add)
*
* TODO: examine mixedBlock/winSwitch logic carefully (test he_mode.bit)
**************************************************************************************/
static int HybridTransform(int *xCurr, int *xPrev, int y[BLOCK_SIZE][NBANDS], SideInfoSub *sis, BlockCount *bc)
{
int xPrevWin[18], currWinIdx, prevWinIdx;
int i, j, nBlocksOut, nonZero, mOut;
int fiBit, xp;
ASSERT(bc->nBlocksLong <= NBANDS);
ASSERT(bc->nBlocksTotal <= NBANDS);
ASSERT(bc->nBlocksPrev <= NBANDS);
mOut = 0;
/* do long blocks, if any */
for(i = 0; i < bc->nBlocksLong; i++) {
/* currWinIdx picks the right window for long blocks (if mixed, long blocks use window type 0) */
currWinIdx = sis->blockType;
if (sis->mixedBlock && i < bc->currWinSwitch)
currWinIdx = 0;
prevWinIdx = bc->prevType;
if (i < bc->prevWinSwitch)
prevWinIdx = 0;
/* do 36-point IMDCT, including windowing and overlap-add */
mOut |= IMDCT36(xCurr, xPrev, &(y[0][i]), currWinIdx, prevWinIdx, i, bc->gbIn);
xCurr += 18;
xPrev += 9;
}
/* do short blocks (if any) */
for ( ; i < bc->nBlocksTotal; i++) {
ASSERT(sis->blockType == 2);
prevWinIdx = bc->prevType;
if (i < bc->prevWinSwitch)
prevWinIdx = 0;
mOut |= IMDCT12x3(xCurr, xPrev, &(y[0][i]), prevWinIdx, i, bc->gbIn);
xCurr += 18;
xPrev += 9;
}
nBlocksOut = i;
/* window and overlap prev if prev longer that current */
for ( ; i < bc->nBlocksPrev; i++) {
prevWinIdx = bc->prevType;
if (i < bc->prevWinSwitch)
prevWinIdx = 0;
WinPrevious(xPrev, xPrevWin, prevWinIdx);
nonZero = 0;
fiBit = i << 31;
for (j = 0; j < 9; j++) {
xp = xPrevWin[2*j+0] << 2; /* << 2 temp for scaling */
nonZero |= xp;
y[2*j+0][i] = xp;
mOut |= FASTABS(xp);
/* frequency inversion on odd blocks/odd samples (flip sign if i odd, j odd) */
xp = xPrevWin[2*j+1] << 2;
xp = (xp ^ (fiBit >> 31)) + (i & 0x01);
nonZero |= xp;
y[2*j+1][i] = xp;
mOut |= FASTABS(xp);
xPrev[j] = 0;
}
xPrev += 9;
if (nonZero)
nBlocksOut = i;
}
/* clear rest of blocks */
for ( ; i < 32; i++) {
for (j = 0; j < 18; j++)
y[j][i] = 0;
}
bc->gbOut = CLZ(mOut) - 1;
return nBlocksOut;
}
/**************************************************************************************
* Function: IMDCT
*
* Description: do alias reduction, inverse MDCT, overlap-add, and frequency inversion
*
* Inputs: MP3DecInfo structure filled by UnpackFrameHeader(), UnpackSideInfo(),
* UnpackScaleFactors(), and DecodeHuffman() (for this granule, channel)
* includes PCM samples in overBuf (from last call to IMDCT) for OLA
* index of current granule and channel
*
* Outputs: PCM samples in outBuf, for input to subband transform
* PCM samples in overBuf, for OLA next time
* updated hi->nonZeroBound index for this channel
*
* Return: 0 on success, -1 if null input pointers
**************************************************************************************/
int IMDCT(MP3DecInfo *mp3DecInfo, int gr, int ch)
{
int nBfly, blockCutoff;
FrameHeader *fh;
SideInfo *si;
HuffmanInfo *hi;
IMDCTInfo *mi;
BlockCount bc;
/* validate pointers */
if (!mp3DecInfo || !mp3DecInfo->FrameHeaderPS || !mp3DecInfo->SideInfoPS ||
!mp3DecInfo->HuffmanInfoPS || !mp3DecInfo->IMDCTInfoPS)
return -1;
/* si is an array of up to 4 structs, stored as gr0ch0, gr0ch1, gr1ch0, gr1ch1 */
fh = (FrameHeader *)(mp3DecInfo->FrameHeaderPS);
si = (SideInfo *)(mp3DecInfo->SideInfoPS);
hi = (HuffmanInfo*)(mp3DecInfo->HuffmanInfoPS);
mi = (IMDCTInfo *)(mp3DecInfo->IMDCTInfoPS);
/* anti-aliasing done on whole long blocks only
* for mixed blocks, nBfly always 1, except 3 for 8 kHz MPEG 2.5 (see sfBandTab)
* nLongBlocks = number of blocks with (possibly) non-zero power
* nBfly = number of butterflies to do (nLongBlocks - 1, unless no long blocks)
*/
blockCutoff = fh->sfBand->l[(fh->ver == MPEG1 ? 8 : 6)] / 18; /* same as 3* num short sfb's in spec */
if (si->sis[gr][ch].blockType != 2) {
/* all long transforms */
bc.nBlocksLong = MIN((hi->nonZeroBound[ch] + 7) / 18 + 1, 32);
nBfly = bc.nBlocksLong - 1;
} else if (si->sis[gr][ch].blockType == 2 && si->sis[gr][ch].mixedBlock) {
/* mixed block - long transforms until cutoff, then short transforms */
bc.nBlocksLong = blockCutoff;
nBfly = bc.nBlocksLong - 1;
} else {
/* all short transforms */
bc.nBlocksLong = 0;
nBfly = 0;
}
AntiAlias(hi->huffDecBuf[ch], nBfly);
hi->nonZeroBound[ch] = MAX(hi->nonZeroBound[ch], (nBfly * 18) + 8);
ASSERT(hi->nonZeroBound[ch] <= MAX_NSAMP);
/* for readability, use a struct instead of passing a million parameters to HybridTransform() */
bc.nBlocksTotal = (hi->nonZeroBound[ch] + 17) / 18;
bc.nBlocksPrev = mi->numPrevIMDCT[ch];
bc.prevType = mi->prevType[ch];
bc.prevWinSwitch = mi->prevWinSwitch[ch];
bc.currWinSwitch = (si->sis[gr][ch].mixedBlock ? blockCutoff : 0); /* where WINDOW switches (not nec. transform) */
bc.gbIn = hi->gb[ch];
mi->numPrevIMDCT[ch] = HybridTransform(hi->huffDecBuf[ch], mi->overBuf[ch], mi->outBuf[ch], &si->sis[gr][ch], &bc);
mi->prevType[ch] = si->sis[gr][ch].blockType;
mi->prevWinSwitch[ch] = bc.currWinSwitch; /* 0 means not a mixed block (either all short or all long) */
mi->gb[ch] = bc.gbOut;
ASSERT(mi->numPrevIMDCT[ch] <= NBANDS);
/* output has gained 2 int bits */
return 0;
}