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FFmpeg/libavcodec/mpegaudio_tablegen.c
Ganesh Ajjanagadde 16d4c28cbb avcodec/mpegaudio_tablegen: speed up dynamic table creation
This does some miscellaneous stuff mainly avoiding the usage of pow to
achieve significant speedups. This is not speed critical, but is
unnecessary latency and cycles wasted for a user.

All tables tested and are identical to the old ones
(bit-exact even in floating point case).

Sample benchmark (x86-64, Haswell, GNU/Linux):
old:
102329530 decicycles in mpegaudio_tableinit,       1 runs,      0 skips

new:
34111900 decicycles in mpegaudio_tableinit,       1 runs,      0 skips

Reviewed-by: Ronald S. Bultje <rsbultje@gmail.com>
Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
2015-12-01 19:05:19 -05:00

44 lines
1.5 KiB
C

/*
* Generate a header file for hardcoded mpegaudiodec tables
*
* Copyright (c) 2009 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
*/
#include <stdlib.h>
#define CONFIG_HARDCODED_TABLES 0
#include "mpegaudio_tablegen.h"
#include "libavutil/tablegen.h"
#include "tableprint.h"
int main(void)
{
mpegaudio_tableinit();
write_fileheader();
WRITE_ARRAY("static const", int8_t, table_4_3_exp);
WRITE_ARRAY("static const", uint32_t, table_4_3_value);
WRITE_ARRAY("static const", uint32_t, exp_table_fixed);
WRITE_ARRAY("static const", float, exp_table_float);
WRITE_2D_ARRAY("static const", uint32_t, expval_table_fixed);
WRITE_2D_ARRAY("static const", float, expval_table_float);
return 0;
}