mirror of
https://git.ffmpeg.org/ffmpeg.git
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137 lines
3.9 KiB
C
137 lines
3.9 KiB
C
/*
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* Copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef AVUTIL_SOFTFLOAT_H
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#define AVUTIL_SOFTFLOAT_H
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#include <stdint.h>
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#include "common.h"
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#include "avassert.h"
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#define MIN_EXP -126
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#define MAX_EXP 126
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#define ONE_BITS 29
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typedef struct SoftFloat{
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int32_t mant;
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int32_t exp;
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}SoftFloat;
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static av_const SoftFloat av_normalize_sf(SoftFloat a){
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if(a.mant){
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#if 1
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while((a.mant + 0x20000000U)<0x40000000U){
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a.mant += a.mant;
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a.exp -= 1;
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}
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#else
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int s=ONE_BITS + 1 - av_log2(a.mant ^ (a.mant<<1));
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a.exp -= s;
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a.mant <<= s;
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#endif
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if(a.exp < MIN_EXP){
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a.exp = MIN_EXP;
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a.mant= 0;
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}
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}else{
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a.exp= MIN_EXP;
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}
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return a;
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}
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static inline av_const SoftFloat av_normalize1_sf(SoftFloat a){
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#if 1
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if((int32_t)(a.mant + 0x40000000U) < 0){
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a.exp++;
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a.mant>>=1;
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}
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av_assert2(a.mant < 0x40000000 && a.mant > -0x40000000);
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return a;
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#elif 1
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int t= a.mant + 0x40000000 < 0;
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return (SoftFloat){ a.mant>>t, a.exp+t};
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#else
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int t= (a.mant + 0x40000000U)>>31;
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return (SoftFloat){a.mant>>t, a.exp+t};
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#endif
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}
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/**
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* @return Will not be more denormalized than a+b. So if either input is
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* normalized, then the output will not be worse then the other input.
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* If both are normalized, then the output will be normalized.
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*/
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static inline av_const SoftFloat av_mul_sf(SoftFloat a, SoftFloat b){
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a.exp += b.exp;
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av_assert2((int32_t)((a.mant * (int64_t)b.mant) >> ONE_BITS) == (a.mant * (int64_t)b.mant) >> ONE_BITS);
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a.mant = (a.mant * (int64_t)b.mant) >> ONE_BITS;
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return av_normalize1_sf(a);
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}
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/**
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* b has to be normalized and not zero.
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* @return Will not be more denormalized than a.
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*/
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static av_const SoftFloat av_div_sf(SoftFloat a, SoftFloat b){
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a.exp -= b.exp+1;
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a.mant = ((int64_t)a.mant<<(ONE_BITS+1)) / b.mant;
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return av_normalize1_sf(a);
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}
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static inline av_const int av_cmp_sf(SoftFloat a, SoftFloat b){
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int t= a.exp - b.exp;
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if(t<0) return (a.mant >> (-t)) - b.mant ;
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else return a.mant - (b.mant >> t);
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}
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static inline av_const SoftFloat av_add_sf(SoftFloat a, SoftFloat b){
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int t= a.exp - b.exp;
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if (t <-31) return b;
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else if (t < 0) return av_normalize1_sf((SoftFloat){b.mant + (a.mant >> (-t)), b.exp});
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else if (t < 32) return av_normalize1_sf((SoftFloat){a.mant + (b.mant >> t ), a.exp});
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else return a;
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}
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static inline av_const SoftFloat av_sub_sf(SoftFloat a, SoftFloat b){
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return av_add_sf(a, (SoftFloat){ -b.mant, b.exp});
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}
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//FIXME sqrt, log, exp, pow, sin, cos
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/**
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* Converts a mantisse and exponent to a SoftFloat
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* @returns a SoftFloat with value v * 2^frac_bits
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*/
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static inline av_const SoftFloat av_int2sf(int v, int frac_bits){
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return av_normalize_sf((SoftFloat){v, ONE_BITS-frac_bits});
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}
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/**
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* Rounding is to -inf.
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*/
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static inline av_const int av_sf2int(SoftFloat v, int frac_bits){
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v.exp += frac_bits - ONE_BITS;
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if(v.exp >= 0) return v.mant << v.exp ;
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else return v.mant >>(-v.exp);
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}
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#endif /* AVUTIL_SOFTFLOAT_H */
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