FFmpeg
float2half.c
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1 /*
2  * This file is part of FFmpeg.
3  *
4  * FFmpeg is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU Lesser General Public
6  * License as published by the Free Software Foundation; either
7  * version 2.1 of the License, or (at your option) any later version.
8  *
9  * FFmpeg is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12  * Lesser General Public License for more details.
13  *
14  * You should have received a copy of the GNU Lesser General Public
15  * License along with FFmpeg; if not, write to the Free Software
16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17  */
18 
19 #include "libavutil/float2half.h"
20 
22 {
23 #if !HAVE_FAST_FLOAT16
24  for (int i = 0; i < 256; i++) {
25  int e = i - 127;
26 
27  if (e < -24) { // Very small numbers map to zero
28  t->basetable[i|0x000] = 0x0000;
29  t->basetable[i|0x100] = 0x8000;
30  t->shifttable[i|0x000] = 24;
31  t->shifttable[i|0x100] = 24;
32  } else if (e < -14) { // Small numbers map to denorms
33  t->basetable[i|0x000] = (0x0400>>(-e-14));
34  t->basetable[i|0x100] = (0x0400>>(-e-14)) | 0x8000;
35  t->shifttable[i|0x000] = -e-1;
36  t->shifttable[i|0x100] = -e-1;
37  } else if (e <= 15) { // Normal numbers just lose precision
38  t->basetable[i|0x000] = ((e + 15) << 10);
39  t->basetable[i|0x100] = ((e + 15) << 10) | 0x8000;
40  t->shifttable[i|0x000] = 13;
41  t->shifttable[i|0x100] = 13;
42  } else if (e < 128) { // Large numbers map to Infinity
43  t->basetable[i|0x000] = 0x7C00;
44  t->basetable[i|0x100] = 0xFC00;
45  t->shifttable[i|0x000] = 24;
46  t->shifttable[i|0x100] = 24;
47  } else { // Infinity and NaN's stay Infinity and NaN's
48  t->basetable[i|0x000] = 0x7C00;
49  t->basetable[i|0x100] = 0xFC00;
50  t->shifttable[i|0x000] = 13;
51  t->shifttable[i|0x100] = 13;
52  }
53  }
54 #endif
55 }
Float2HalfTables
Definition: float2half.h:27
ff_init_float2half_tables
void ff_init_float2half_tables(Float2HalfTables *t)
Definition: float2half.c:21
Float2HalfTables::shifttable
uint8_t shifttable[512]
Definition: float2half.h:32
i
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:255
Float2HalfTables::basetable
uint16_t basetable[512]
Definition: float2half.h:31
float2half.h