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use LFG instead of Mersenne Twister for AC-3 PRNG

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Originally committed as revision 14815 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles 2008-08-17 17:41:48 +00:00
parent defa0cd6f5
commit ec0350c983
3 changed files with 5 additions and 5 deletions
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5
libavcodec/ac3dec.c
View File

@ -33,7 +33,6 @@
#include <string.h>
#include "libavutil/crc.h"
#include "libavutil/random.h"
#include "avcodec.h"
#include "ac3_parser.h"
#include "bitstream.h"
@ -198,7 +197,7 @@ static av_cold int ac3_decode_init(AVCodecContext *avctx)
ff_mdct_init(&s->imdct_512, 9, 1);
ff_kbd_window_init(s->window, 5.0, 256);
dsputil_init(&s->dsp, avctx);
av_init_random(0, &s->dith_state);
av_lfg_init(&s->dith_state, 0);
/* set bias values for float to int16 conversion */
if(s->dsp.float_to_int16_interleave == ff_float_to_int16_interleave_c) {
@ -450,7 +449,7 @@ static void get_transform_coeffs_ch(AC3DecodeContext *s, int ch_index, mant_grou
tbap = bap[i];
switch (tbap) {
case 0:
coeffs[i] = (av_random(&s->dith_state) & 0x7FFFFF) - 0x400000;
coeffs[i] = (av_lfg_get(&s->dith_state) & 0x7FFFFF) - 0x400000;
break;
case 1:

4
libavcodec/ac3dec.h
View File

@ -27,7 +27,7 @@
#ifndef FFMPEG_AC3DEC_H
#define FFMPEG_AC3DEC_H
#include "libavutil/random.h"
#include "libavutil/lfg.h"
#include "ac3tab.h"
#include "ac3.h"
#include "bitstream.h"
@ -143,7 +143,7 @@ typedef struct {
///@defgroup dithering zero-mantissa dithering
int dither_all; ///< true if all channels are dithered
int dither_flag[AC3_MAX_CHANNELS]; ///< dither flags (dithflg)
AVRandomState dith_state; ///< for dither generation
AVLFG dith_state; ///< for dither generation
///@}
///@defgroup imdct IMDCT

1
libavutil/Makefile
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@ -9,6 +9,7 @@ OBJS = adler32.o \
des.o \
fifo.o \
intfloat_readwrite.o \
lfg.o \
lls.o \
log.o \
lzo.o \