diff options
Diffstat (limited to 'libavcodec/mpegaudio_tablegen.h')
| -rw-r--r-- | libavcodec/mpegaudio_tablegen.h | 43 |
1 files changed, 30 insertions, 13 deletions
diff --git a/libavcodec/mpegaudio_tablegen.h b/libavcodec/mpegaudio_tablegen.h index 8a3e51ae60..0b0ea40682 100644 --- a/libavcodec/mpegaudio_tablegen.h +++ b/libavcodec/mpegaudio_tablegen.h @@ -3,20 +3,20 @@ * * Copyright (c) 2009 Reimar Döffinger <Reimar.Doeffinger@gmx.de> * - * This file is part of Libav. + * This file is part of FFmpeg. * - * Libav is free software; you can redistribute it and/or + * FFmpeg 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, + * FFmpeg 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 + * License along with FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ @@ -25,6 +25,7 @@ #include <stdint.h> #include <math.h> +#include "libavutil/attributes.h" #define TABLE_4_3_SIZE (8191 + 16)*4 #if CONFIG_HARDCODED_TABLES @@ -39,18 +40,33 @@ static float exp_table_float[512]; static float expval_table_float[512][16]; #define FRAC_BITS 23 +#define IMDCT_SCALAR 1.759 -static void mpegaudio_tableinit(void) +static av_cold void mpegaudio_tableinit(void) { int i, value, exponent; + static const double exp2_lut[4] = { + 1.00000000000000000000, /* 2 ^ (0 * 0.25) */ + 1.18920711500272106672, /* 2 ^ (1 * 0.25) */ + M_SQRT2 , /* 2 ^ (2 * 0.25) */ + 1.68179283050742908606, /* 2 ^ (3 * 0.25) */ + }; + static double pow43_lut[16]; + double exp2_base = 2.11758236813575084767080625169910490512847900390625e-22; // 2^(-72) + double exp2_val; + double pow43_val = 0; + for (i = 0; i < 16; ++i) + pow43_lut[i] = i * cbrt(i); + for (i = 1; i < TABLE_4_3_SIZE; i++) { - double value = i / 4; double f, fm; int e, m; - /* cbrtf() isn't available on all systems, so we use powf(). */ - f = value * powf(value, 1.0 / 3.0) * pow(2, (i & 3) * 0.25); + double value = i / 4; + if ((i & 3) == 0) + pow43_val = value / IMDCT_SCALAR * cbrt(value); + f = pow43_val * exp2_lut[i & 3]; fm = frexp(f, &e); - m = (uint32_t)(fm * (1LL << 31) + 0.5); + m = llrint(fm * (1LL << 31)); e += FRAC_BITS - 31 + 5 - 100; /* normalized to FRAC_BITS */ @@ -58,11 +74,12 @@ static void mpegaudio_tableinit(void) table_4_3_exp[i] = -e; } for (exponent = 0; exponent < 512; exponent++) { + if (exponent && (exponent & 3) == 0) + exp2_base *= 2; + exp2_val = exp2_base * exp2_lut[exponent & 3] / IMDCT_SCALAR; for (value = 0; value < 16; value++) { - /* cbrtf() isn't available on all systems, so we use powf(). */ - double f = (double)value * powf(value, 1.0 / 3.0) * pow(2, (exponent - 400) * 0.25 + FRAC_BITS + 5); - /* llrint() isn't always available, so round and cast manually. */ - expval_table_fixed[exponent][value] = (long long int) (f >= 0 ? floor(f + 0.5) : ceil(f - 0.5)); + double f = pow43_lut[value] * exp2_val; + expval_table_fixed[exponent][value] = (f < 0xFFFFFFFF ? llrint(f) : 0xFFFFFFFF); expval_table_float[exponent][value] = f; } exp_table_fixed[exponent] = expval_table_fixed[exponent][1]; |