mirror of
https://github.com/FFmpeg/FFmpeg.git
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152 lines
4.4 KiB
C
152 lines
4.4 KiB
C
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/*
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* AAC decoder
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* Copyright (c) 2005-2006 Oded Shimon ( ods15 ods15 dyndns org )
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* Copyright (c) 2006-2007 Maxim Gavrilov ( maxim.gavrilov gmail com )
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* Copyright (c) 2008-2013 Alex Converse <alex.converse@gmail.com>
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*
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* AAC LATM decoder
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* Copyright (c) 2008-2010 Paul Kendall <paul@kcbbs.gen.nz>
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* Copyright (c) 2010 Janne Grunau <janne-libav@jannau.net>
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*
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* AAC decoder fixed-point implementation
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* Copyright (c) 2013
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* MIPS Technologies, Inc., California.
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef AVCODEC_AAC_AACDEC_FIXED_PREDICTION_H
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#define AVCODEC_AAC_AACDEC_FIXED_PREDICTION_H
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static av_always_inline SoftFloat flt16_round(SoftFloat pf)
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{
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SoftFloat tmp;
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int s;
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tmp.exp = pf.exp;
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s = pf.mant >> 31;
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tmp.mant = (pf.mant ^ s) - s;
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tmp.mant = (tmp.mant + 0x00200000U) & 0xFFC00000U;
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tmp.mant = (tmp.mant ^ s) - s;
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return tmp;
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}
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static av_always_inline SoftFloat flt16_even(SoftFloat pf)
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{
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SoftFloat tmp;
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int s;
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tmp.exp = pf.exp;
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s = pf.mant >> 31;
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tmp.mant = (pf.mant ^ s) - s;
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tmp.mant = (tmp.mant + 0x001FFFFFU + (tmp.mant & 0x00400000U >> 16)) & 0xFFC00000U;
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tmp.mant = (tmp.mant ^ s) - s;
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return tmp;
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}
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static av_always_inline SoftFloat flt16_trunc(SoftFloat pf)
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{
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SoftFloat pun;
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int s;
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pun.exp = pf.exp;
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s = pf.mant >> 31;
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pun.mant = (pf.mant ^ s) - s;
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pun.mant = pun.mant & 0xFFC00000U;
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pun.mant = (pun.mant ^ s) - s;
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return pun;
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}
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static av_always_inline void predict(PredictorState *ps, int *coef,
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int output_enable)
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{
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const SoftFloat a = { 1023410176, 0 }; // 61.0 / 64
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const SoftFloat alpha = { 973078528, 0 }; // 29.0 / 32
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SoftFloat e0, e1;
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SoftFloat pv;
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SoftFloat k1, k2;
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SoftFloat r0 = ps->r0, r1 = ps->r1;
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SoftFloat cor0 = ps->cor0, cor1 = ps->cor1;
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SoftFloat var0 = ps->var0, var1 = ps->var1;
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SoftFloat tmp;
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if (var0.exp > 1 || (var0.exp == 1 && var0.mant > 0x20000000)) {
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k1 = av_mul_sf(cor0, flt16_even(av_div_sf(a, var0)));
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}
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else {
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k1.mant = 0;
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k1.exp = 0;
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}
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if (var1.exp > 1 || (var1.exp == 1 && var1.mant > 0x20000000)) {
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k2 = av_mul_sf(cor1, flt16_even(av_div_sf(a, var1)));
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}
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else {
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k2.mant = 0;
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k2.exp = 0;
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}
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tmp = av_mul_sf(k1, r0);
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pv = flt16_round(av_add_sf(tmp, av_mul_sf(k2, r1)));
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if (output_enable) {
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int shift = 28 - pv.exp;
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if (shift < 31) {
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if (shift > 0) {
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*coef += (unsigned)((pv.mant + (1 << (shift - 1))) >> shift);
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} else
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*coef += (unsigned)pv.mant << -shift;
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}
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}
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e0 = av_int2sf(*coef, 2);
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e1 = av_sub_sf(e0, tmp);
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ps->cor1 = flt16_trunc(av_add_sf(av_mul_sf(alpha, cor1), av_mul_sf(r1, e1)));
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tmp = av_add_sf(av_mul_sf(r1, r1), av_mul_sf(e1, e1));
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tmp.exp--;
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ps->var1 = flt16_trunc(av_add_sf(av_mul_sf(alpha, var1), tmp));
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ps->cor0 = flt16_trunc(av_add_sf(av_mul_sf(alpha, cor0), av_mul_sf(r0, e0)));
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tmp = av_add_sf(av_mul_sf(r0, r0), av_mul_sf(e0, e0));
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tmp.exp--;
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ps->var0 = flt16_trunc(av_add_sf(av_mul_sf(alpha, var0), tmp));
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ps->r1 = flt16_trunc(av_mul_sf(a, av_sub_sf(r0, av_mul_sf(k1, e0))));
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ps->r0 = flt16_trunc(av_mul_sf(a, e0));
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}
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static av_always_inline void reset_predict_state(PredictorState *ps)
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{
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ps->r0.mant = 0;
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ps->r0.exp = 0;
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ps->r1.mant = 0;
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ps->r1.exp = 0;
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ps->cor0.mant = 0;
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ps->cor0.exp = 0;
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ps->cor1.mant = 0;
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ps->cor1.exp = 0;
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ps->var0.mant = 0x20000000;
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ps->var0.exp = 1;
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ps->var1.mant = 0x20000000;
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ps->var1.exp = 1;
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}
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#endif /* AVCODEC_AAC_AACDEC_FIXED_PREDICTION_H */
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