FFmpeg
half2float.h
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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  *
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11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12  * Lesser General Public License for more details.
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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 #ifndef AVCODEC_HALF2FLOAT_H
20 #define AVCODEC_HALF2FLOAT_H
21 
22 #include <stdint.h>
23 
24 static uint32_t convertmantissa(uint32_t i)
25 {
26  int32_t m = i << 13; // Zero pad mantissa bits
27  int32_t e = 0; // Zero exponent
28 
29  while (!(m & 0x00800000)) { // While not normalized
30  e -= 0x00800000; // Decrement exponent (1<<23)
31  m <<= 1; // Shift mantissa
32  }
33 
34  m &= ~0x00800000; // Clear leading 1 bit
35  e += 0x38800000; // Adjust bias ((127-14)<<23)
36 
37  return m | e; // Return combined number
38 }
39 
40 static void half2float_table(uint32_t *mantissatable, uint32_t *exponenttable,
41  uint16_t *offsettable)
42 {
43  mantissatable[0] = 0;
44  for (int i = 1; i < 1024; i++)
45  mantissatable[i] = convertmantissa(i);
46  for (int i = 1024; i < 2048; i++)
47  mantissatable[i] = 0x38000000UL + ((i - 1024) << 13UL);
48 
49  exponenttable[0] = 0;
50  for (int i = 1; i < 31; i++)
51  exponenttable[i] = i << 23;
52  for (int i = 33; i < 63; i++)
53  exponenttable[i] = 0x80000000UL + ((i - 32) << 23UL);
54  exponenttable[31]= 0x47800000UL;
55  exponenttable[32]= 0x80000000UL;
56  exponenttable[63]= 0xC7800000UL;
57 
58  offsettable[0] = 0;
59  for (int i = 1; i < 64; i++)
60  offsettable[i] = 1024;
61  offsettable[32] = 0;
62 }
63 
64 static uint32_t half2float(uint16_t h, uint32_t *mantissatable, uint32_t *exponenttable,
65  uint16_t *offsettable)
66 {
67  uint32_t f;
68 
69  f = mantissatable[offsettable[h >> 10] + (h & 0x3ff)] + exponenttable[h >> 10];
70 
71  return f;
72 }
73 
74 #endif /* AVCODEC_HALF2FLOAT_H */
f
#define f(width, name)
Definition: cbs_vp9.c:255
half2float_table
static void half2float_table(uint32_t *mantissatable, uint32_t *exponenttable, uint16_t *offsettable)
Definition: half2float.h:40
half2float
static uint32_t half2float(uint16_t h, uint32_t *mantissatable, uint32_t *exponenttable, uint16_t *offsettable)
Definition: half2float.h:64
i
int i
Definition: input.c:407
int32_t
int32_t
Definition: audioconvert.c:56
convertmantissa
static uint32_t convertmantissa(uint32_t i)
Definition: half2float.h:24
h
h
Definition: vp9dsp_template.c:2038