1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
|
/*
dsp/White.h
Copyright 2004 Tim Goetze <tim@quitte.de>
simple white noise generator, based on Jon Dattorro's 3/2002 JAES
paper. quite an elegant design; consumes next to no CPU on a processor
providing a decent binary shift operator. most of all, no random() calls.
*/
/*
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA or point your web browser to http://www.gnu.org.
*/
#ifndef _DSP_WHITE_H_
#define _DSP_WHITE_H_
namespace DSP {
/* after initializing, call either get() or get_31() to get a sample, don't
* mix them. (get_31 output goes out of range if called after get()).
*/
class White
{
public:
uint32 b;
White()
{
b = 0x1fff7777;
}
void init (float f)
{
b = (uint32) (f * (float) 0x1fff7777);
}
d_sample abs()
{
return fabs (get());
}
/* 32-bit version */
d_sample get()
{
# define BIT(y) ((b << (31 - y)) & 0x80000000)
b = ((BIT (28) ^ BIT (27) ^ BIT (1) ^ BIT (0))) | (b >> 1);
return (4.6566128730773926e-10 * (d_sample) b) - 1;
# undef BIT
}
/* 31-bit version, at least 6 instructions less / sample. probably only
* pays off on a processor not providing a decent binary shift. */
d_sample get_31()
{
# define BIT(y) ((b << (30 - y)) & 0x40000000)
b = ((BIT (3) ^ BIT (0))) | (b >> 1);
return (9.3132257461547852e-10 * (d_sample) b) - 1;
# undef BIT
}
};
} /* namespace DSP */
#endif /* _DSP_WHITE_H_ */
|