/* ***** 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; }