/* * Various fixed-point math operations * * Copyright (c) 2008 Vladimir Voroshilov * * This file is part of Libav. * * Libav is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * Libav is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with Libav; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ #include <inttypes.h> #include <limits.h> #include <assert.h> #include "avcodec.h" #include "celp_math.h" #include "libavutil/common.h" static const uint16_t exp2a[]= { 0, 1435, 2901, 4400, 5931, 7496, 9096, 10730, 12400, 14106, 15850, 17632, 19454, 21315, 23216, 25160, 27146, 29175, 31249, 33368, 35534, 37747, 40009, 42320, 44682, 47095, 49562, 52082, 54657, 57289, 59979, 62727, }; static const uint16_t exp2b[]= { 3, 712, 1424, 2134, 2845, 3557, 4270, 4982, 5696, 6409, 7124, 7839, 8554, 9270, 9986, 10704, 11421, 12138, 12857, 13576, 14295, 15014, 15734, 16455, 17176, 17898, 18620, 19343, 20066, 20790, 21514, 22238, }; int ff_exp2(uint16_t power) { unsigned int result= exp2a[power>>10] + 0x10000; assert(power <= 0x7fff); result= (result<<3) + ((result*exp2b[(power>>5)&31])>>17); return result + ((result*(power&31)*89)>>22); } /** * Table used to compute log2(x) * * tab_log2[i] = (1<<15) * log2(1 + i/32), i=0..32 */ static const uint16_t tab_log2[33] = { 4, 1459, 2870, 4240, 5572, 6867, 8127, 9355, 10552, 11719, 12858, 13971, 15057, 16120, 17158, 18175, 19170, 20145, 21100, 22036, 22954, 23854, 24738, 25605, 26457, 27294, 28116, 28924, 29719, 30500, 31269, 32025, 32769, }; int ff_log2_q15(uint32_t value) { uint8_t power_int; uint8_t frac_x0; uint16_t frac_dx; // Stripping zeros from beginning power_int = av_log2(value); value <<= (31 - power_int); // b31 is always non-zero now frac_x0 = (value & 0x7c000000) >> 26; // b26-b31 and [32..63] -> [0..31] frac_dx = (value & 0x03fff800) >> 11; value = tab_log2[frac_x0]; value += (frac_dx * (tab_log2[frac_x0+1] - tab_log2[frac_x0])) >> 15; return (power_int << 15) + value; }