FFmpeg
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
cbrt_tablegen.h
Go to the documentation of this file.
1 /*
2  * Header file for hardcoded AAC cube-root table
3  *
4  * Copyright (c) 2010 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
5  *
6  * This file is part of FFmpeg.
7  *
8  * FFmpeg is free software; you can redistribute it and/or
9  * modify it under the terms of the GNU Lesser General Public
10  * License as published by the Free Software Foundation; either
11  * version 2.1 of the License, or (at your option) any later version.
12  *
13  * FFmpeg is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16  * Lesser General Public License for more details.
17  *
18  * You should have received a copy of the GNU Lesser General Public
19  * License along with FFmpeg; if not, write to the Free Software
20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21  */
22 
23 #ifndef AVCODEC_CBRT_TABLEGEN_H
24 #define AVCODEC_CBRT_TABLEGEN_H
25 
26 #include <stdint.h>
27 #include <math.h>
28 #include "libavutil/attributes.h"
29 
30 #if CONFIG_HARDCODED_TABLES
31 #define cbrt_tableinit()
32 #include "libavcodec/cbrt_tables.h"
33 #else
34 static uint32_t cbrt_tab[1 << 13];
35 
36 static av_cold void cbrt_tableinit(void)
37 {
38  if (!cbrt_tab[(1<<13) - 1]) {
39  int i;
40  /* cbrtf() isn't available on all systems, so we use powf(). */
41  for (i = 0; i < 1<<13; i++) {
42  union {
43  float f;
44  uint32_t i;
45  } f;
46  f.f = pow(i, 1.0 / 3.0) * i;
47  cbrt_tab[i] = f.i;
48  }
49  }
50 }
51 #endif /* CONFIG_HARDCODED_TABLES */
52 
53 #endif /* AVCODEC_CBRT_TABLEGEN_H */