imdct.c
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- /* ***** 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;
- }