From 69db01e72f2de91d35703919bfc9d0700df83e85 Mon Sep 17 00:00:00 2001 From: Dave Chapman Date: Sat, 9 May 2009 01:04:20 +0000 Subject: Initial commit of the minimal set of ffmpeg (r18079) files required for Cook (realaudio) decoding. These are the unmodified versions from ffmpeg, committed as a base for future changes. git-svn-id: svn://svn.rockbox.org/rockbox/trunk@20882 a1c6a512-1295-4272-9138-f99709370657 --- apps/codecs/libcook/libavutil/lfg.h | 54 +++++++++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) create mode 100644 apps/codecs/libcook/libavutil/lfg.h (limited to 'apps/codecs/libcook/libavutil/lfg.h') diff --git a/apps/codecs/libcook/libavutil/lfg.h b/apps/codecs/libcook/libavutil/lfg.h new file mode 100644 index 0000000000..3250c18e79 --- /dev/null +++ b/apps/codecs/libcook/libavutil/lfg.h @@ -0,0 +1,54 @@ +/* + * Lagged Fibonacci PRNG + * Copyright (c) 2008 Michael Niedermayer + * + * This file is part of FFmpeg. + * + * FFmpeg 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. + * + * FFmpeg 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 FFmpeg; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +#ifndef AVUTIL_LFG_H +#define AVUTIL_LFG_H + +typedef struct { + unsigned int state[64]; + int index; +} AVLFG; + +void av_lfg_init(AVLFG *c, unsigned int seed); + +/** + * Gets the next random unsigned 32-bit number using an ALFG. + * + * Please also consider a simple LCG like state= state*1664525+1013904223, + * it may be good enough and faster for your specific use case. + */ +static inline unsigned int av_lfg_get(AVLFG *c){ + c->state[c->index & 63] = c->state[(c->index-24) & 63] + c->state[(c->index-55) & 63]; + return c->state[c->index++ & 63]; +} + +/** + * Gets the next random unsigned 32-bit number using a MLFG. + * + * Please also consider av_lfg_get() above, it is faster. + */ +static inline unsigned int av_mlfg_get(AVLFG *c){ + unsigned int a= c->state[(c->index-55) & 63]; + unsigned int b= c->state[(c->index-24) & 63]; + return c->state[c->index++ & 63] = 2*a*b+a+b; +} + +#endif /* AVUTIL_LFG_H */ -- cgit v1.2.3