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FFmpeg/libavutil/lfg.h
Michael Niedermayer 55c49afc42 Merge remote-tracking branch 'qatar/master'
* qatar/master:
  yuv4mpeg: return proper error codes.
  Give all anonymously typedeffed structs in headers a name
  fate: Add parseutils test
  parseutils-test: Drop random colors from parsing test
  vf_pad/scale: use double precision for aspect ratios.
  build: error on variable-length arrays
  ppc: swscale: rework yuv2planeX_altivec()
  ppc: fmtconvert: kill VLA in float_to_int16_interleave_altivec()
  x86: dsputil: kill VLA in gmc_mmx()
  libspeexenc: Updated commentary to reflect recent changes
  libspeexenc: Add an option for enabling DTX
  doc/APIchanges: fill in missing dates and hashes.
  lavr: bump major to 1 and declare it stable.
  lavr: change the type of the data buffers to uint8_t**.
  lavc: deprecate the audio resampling API.

Conflicts:
	cmdutils.h
	configure
	doc/APIchanges
	ffplay.c
	libavcodec/dwt.h
	libavcodec/libspeexenc.c
	libavfilter/vf_pad.c
	libavfilter/vf_scale.c
	libavformat/asf.h
	tests/fate/libavutil.mak
	tests/ref/fate/parseutils

Merged-by: Michael Niedermayer <michaelni@gmx.at>
2012-10-06 13:45:08 +02:00

63 lines
1.9 KiB
C

/*
* 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 AVLFG {
unsigned int state[64];
int index;
} AVLFG;
void av_lfg_init(AVLFG *c, unsigned int seed);
/**
* Get 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];
}
/**
* Get 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;
}
/**
* Get the next two numbers generated by a Box-Muller Gaussian
* generator using the random numbers issued by lfg.
*
* @param out array where the two generated numbers are placed
*/
void av_bmg_get(AVLFG *lfg, double out[2]);
#endif /* AVUTIL_LFG_H */