/* dsp/White.h Copyright 2004 Tim Goetze 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_ */