FFmpeg
half2float.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/half2float.h"
20 
21 #if !HAVE_FAST_FLOAT16
22 static uint32_t convertmantissa(uint32_t i)
23 {
24  int32_t m = i << 13; // Zero pad mantissa bits
25  int32_t e = 0; // Zero exponent
26 
27  while (!(m & 0x00800000)) { // While not normalized
28  e -= 0x00800000; // Decrement exponent (1<<23)
29  m <<= 1; // Shift mantissa
30  }
31 
32  m &= ~0x00800000; // Clear leading 1 bit
33  e += 0x38800000; // Adjust bias ((127-14)<<23)
34 
35  return m | e; // Return combined number
36 }
37 #endif
38 
40 {
41 #if !HAVE_FAST_FLOAT16
42  t->mantissatable[0] = 0;
43  for (int i = 1; i < 1024; i++)
45  for (int i = 1024; i < 2048; i++)
46  t->mantissatable[i] = 0x38000000UL + ((i - 1024) << 13UL);
47  for (int i = 2048; i < 3072; i++)
48  t->mantissatable[i] = t->mantissatable[i - 1024] | 0x400000UL;
49  t->mantissatable[2048] = t->mantissatable[1024];
50 
51  t->exponenttable[0] = 0;
52  for (int i = 1; i < 31; i++)
53  t->exponenttable[i] = i << 23;
54  for (int i = 33; i < 63; i++)
55  t->exponenttable[i] = 0x80000000UL + ((i - 32) << 23UL);
56  t->exponenttable[31]= 0x47800000UL;
57  t->exponenttable[32]= 0x80000000UL;
58  t->exponenttable[63]= 0xC7800000UL;
59 
60  t->offsettable[0] = 0;
61  for (int i = 1; i < 64; i++)
62  t->offsettable[i] = 1024;
63  t->offsettable[31] = 2048;
64  t->offsettable[32] = 0;
65  t->offsettable[63] = 2048;
66 #endif
67 }
Half2FloatTables
Definition: half2float.h:27
convertmantissa
static uint32_t convertmantissa(uint32_t i)
Definition: half2float.c:22
Half2FloatTables::offsettable
uint16_t offsettable[64]
Definition: half2float.h:33
for
for(k=2;k<=8;++k)
Definition: h264pred_template.c:425
half2float.h
i
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:256
ff_init_half2float_tables
void ff_init_half2float_tables(Half2FloatTables *t)
Definition: half2float.c:39
Half2FloatTables::exponenttable
uint32_t exponenttable[64]
Definition: half2float.h:32
Half2FloatTables::mantissatable
uint32_t mantissatable[3072]
Definition: half2float.h:31
int32_t
int32_t
Definition: audioconvert.c:56