FreeCalypso > hg > gsm-codec-lib

annotate libtwamr/inv_sqrt.h @ 287:f00925b533b7

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
gsmfr-encode: convert to libgsmfr2
author Mychaela Falconia <falcon@freecalypso.org>
date Sun, 14 Apr 2024 06:16:47 +0000
parents 54f6bc41ed10
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
253
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
1 /*
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
2 ********************************************************************************
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
3 *
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
4 * GSM AMR-NB speech codec R98 Version 7.6.0 December 12, 2001
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
5 * R99 Version 3.3.0
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
6 * REL-4 Version 4.1.0
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
7 *
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
8 ********************************************************************************
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
9 *
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
10 * File : inv_sqrt.h
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
11 * Purpose : Computes 1/sqrt(L_x), where L_x is positive.
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
12 * : If L_x is negative or zero, the result is
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
13 * : 1 (3fff ffff).
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
14 * Description : The function 1/sqrt(L_x) is approximated by a table
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
15 * : and linear interpolation. The inverse square root is
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
16 * : computed using the following steps:
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
17 * 1- Normalization of L_x.
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
18 * 2- If (30-exponent) is even then shift right once.
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
19 * 3- exponent = (30-exponent)/2 +1
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
20 * 4- i = bit25-b31 of L_x; 16<=i<=63 because of normalization.
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
21 * 5- a = bit10-b24
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
22 * 6- i -=16
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
23 * 7- L_y = table[i]<<16 - (table[i] - table[i+1]) * a * 2
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
24 * 8- L_y >>= exponent
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
25 *
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
26 ********************************************************************************
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
27 */
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
28 #ifndef inv_sqrt_h
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
29 #define inv_sqrt_h "$Id $"
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
30
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
31 /*
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
32 ********************************************************************************
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
33 * INCLUDE FILES
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
34 ********************************************************************************
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
35 */
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
36 #include "typedef.h"
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
37
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
38 /*
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
39 ********************************************************************************
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
40 * DEFINITION OF DATA TYPES
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
41 ********************************************************************************
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
42 */
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
43
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
44 /*
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
45 ********************************************************************************
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
46 * DECLARATION OF PROTOTYPES
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
47 ********************************************************************************
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
48 */
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
49
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
50 Word32 Inv_sqrt ( /* (o) : output value (range: 0<=val<1) */
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
51 Word32 L_x /* (i) : input value (range: 0<=val<=7fffffff) */
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
52 );
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
53
54f6bc41ed10 libtwamr: integrate a* modules
Mychaela Falconia <falcon@freecalypso.org>
parents:
diff changeset
54 #endif