mirror of https://github.com/FFmpeg/FFmpeg.git
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
60 lines
1.7 KiB
60 lines
1.7 KiB
/* |
|
* Lagged Fibonacci PRNG |
|
* Copyright (c) 2008 Michael Niedermayer |
|
* |
|
* This file is part of Libav. |
|
* |
|
* Libav is free software; you can redistribute it and/or |
|
* modify it under the terms of the GNU Lesser General Public |
|
* License as published by the Free Software Foundation; either |
|
* version 2.1 of the License, or (at your option) any later version. |
|
* |
|
* Libav 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 |
|
* Lesser General Public License for more details. |
|
* |
|
* You should have received a copy of the GNU Lesser General Public |
|
* License along with Libav; if not, write to the Free Software |
|
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
|
*/ |
|
|
|
#include <inttypes.h> |
|
#include <limits.h> |
|
#include <math.h> |
|
#include "lfg.h" |
|
#include "md5.h" |
|
#include "intreadwrite.h" |
|
#include "attributes.h" |
|
|
|
av_cold void av_lfg_init(AVLFG *c, unsigned int seed) |
|
{ |
|
uint8_t tmp[16] = { 0 }; |
|
int i; |
|
|
|
for (i = 8; i < 64; i += 4) { |
|
AV_WL32(tmp, seed); |
|
tmp[4] = i; |
|
av_md5_sum(tmp, tmp, 16); |
|
c->state[i ] = AV_RL32(tmp); |
|
c->state[i + 1] = AV_RL32(tmp + 4); |
|
c->state[i + 2] = AV_RL32(tmp + 8); |
|
c->state[i + 3] = AV_RL32(tmp + 12); |
|
} |
|
c->index = 0; |
|
} |
|
|
|
void av_bmg_get(AVLFG *lfg, double out[2]) |
|
{ |
|
double x1, x2, w; |
|
|
|
do { |
|
x1 = 2.0 / UINT_MAX * av_lfg_get(lfg) - 1.0; |
|
x2 = 2.0 / UINT_MAX * av_lfg_get(lfg) - 1.0; |
|
w = x1 * x1 + x2 * x2; |
|
} while (w >= 1.0); |
|
|
|
w = sqrt((-2.0 * log(w)) / w); |
|
out[0] = x1 * w; |
|
out[1] = x2 * w; |
|
}
|
|
|