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FFmpeg/libavcodec/cbrt_tablegen.h
Michael Niedermayer 59352a07d8 avcodec: improve precission for cbrtf() emulation
cbrtf() took floats but it represented 1/3 exactly
and even if not more precission should be better in theory
for the table generation

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
2013-10-15 21:03:03 +02:00

53 lines
1.5 KiB
C

/*
* Header file for hardcoded AAC cube-root table
*
* Copyright (c) 2010 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
*
* This file is part of FFmpeg.
*
* 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.
*
* 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 FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef AVCODEC_CBRT_TABLEGEN_H
#define AVCODEC_CBRT_TABLEGEN_H
#include <stdint.h>
#include <math.h>
#if CONFIG_HARDCODED_TABLES
#define cbrt_tableinit()
#include "libavcodec/cbrt_tables.h"
#else
static uint32_t cbrt_tab[1 << 13];
static void cbrt_tableinit(void)
{
if (!cbrt_tab[(1<<13) - 1]) {
int i;
/* cbrtf() isn't available on all systems, so we use powf(). */
for (i = 0; i < 1<<13; i++) {
union {
float f;
uint32_t i;
} f;
f.f = pow(i, 1.0 / 3.0) * i;
cbrt_tab[i] = f.i;
}
}
}
#endif /* CONFIG_HARDCODED_TABLES */
#endif /* AVCODEC_CBRT_TABLEGEN_H */