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194 lines
5.3 KiB
C
Executable File
194 lines
5.3 KiB
C
Executable File
/*
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* rational numbers
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* Copyright (c) 2003 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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/**
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* @file
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* rational numbers
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* @author Michael Niedermayer <michaelni@gmx.at>
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*/
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#include "avassert.h"
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#include <limits.h>
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#include "common.h"
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#include "mathematics.h"
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#include "rational.h"
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int av_reduce(int *dst_num, int *dst_den,
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int64_t num, int64_t den, int64_t max)
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{
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AVRational a0 = { 0, 1 }, a1 = { 1, 0 };
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int sign = (num < 0) ^ (den < 0);
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int64_t gcd = av_gcd(FFABS(num), FFABS(den));
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if (gcd) {
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num = FFABS(num) / gcd;
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den = FFABS(den) / gcd;
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}
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if (num <= max && den <= max) {
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a1 = (AVRational) { num, den };
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den = 0;
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}
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while (den) {
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uint64_t x = num / den;
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int64_t next_den = num - den * x;
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int64_t a2n = x * a1.num + a0.num;
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int64_t a2d = x * a1.den + a0.den;
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if (a2n > max || a2d > max) {
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if (a1.num) x = (max - a0.num) / a1.num;
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if (a1.den) x = FFMIN(x, (max - a0.den) / a1.den);
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if (den * (2 * x * a1.den + a0.den) > num * a1.den)
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a1 = (AVRational) { x * a1.num + a0.num, x * a1.den + a0.den };
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break;
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}
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a0 = a1;
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a1 = (AVRational) { a2n, a2d };
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num = den;
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den = next_den;
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}
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av_assert2(av_gcd(a1.num, a1.den) <= 1U);
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av_assert2(a1.num <= max && a1.den <= max);
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*dst_num = sign ? -a1.num : a1.num;
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*dst_den = a1.den;
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return den == 0;
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}
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AVRational av_mul_q(AVRational b, AVRational c)
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{
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av_reduce(&b.num, &b.den,
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b.num * (int64_t) c.num,
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b.den * (int64_t) c.den, INT_MAX);
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return b;
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}
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AVRational av_div_q(AVRational b, AVRational c)
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{
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return av_mul_q(b, (AVRational) { c.den, c.num });
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}
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AVRational av_add_q(AVRational b, AVRational c) {
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av_reduce(&b.num, &b.den,
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b.num * (int64_t) c.den +
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c.num * (int64_t) b.den,
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b.den * (int64_t) c.den, INT_MAX);
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return b;
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}
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AVRational av_sub_q(AVRational b, AVRational c)
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{
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return av_add_q(b, (AVRational) { -c.num, c.den });
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}
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AVRational av_d2q(double d, int max)
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{
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AVRational a;
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int exponent;
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int64_t den;
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if (isnan(d))
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return (AVRational) { 0,0 };
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if (fabs(d) > INT_MAX + 3LL)
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return (AVRational) { d < 0 ? -1 : 1, 0 };
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frexp(d, &exponent);
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exponent = FFMAX(exponent-1, 0);
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den = 1LL << (61 - exponent);
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// (int64_t)rint() and llrint() do not work with gcc on ia64 and sparc64,
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// see Ticket2713 for affected gcc/glibc versions
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av_reduce(&a.num, &a.den, floor(d * den + 0.5), den, max);
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if ((!a.num || !a.den) && d && max>0 && max<INT_MAX)
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av_reduce(&a.num, &a.den, floor(d * den + 0.5), den, INT_MAX);
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return a;
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}
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int av_nearer_q(AVRational q, AVRational q1, AVRational q2)
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{
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/* n/d is q, a/b is the median between q1 and q2 */
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int64_t a = q1.num * (int64_t)q2.den + q2.num * (int64_t)q1.den;
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int64_t b = 2 * (int64_t)q1.den * q2.den;
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/* rnd_up(a*d/b) > n => a*d/b > n */
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int64_t x_up = av_rescale_rnd(a, q.den, b, AV_ROUND_UP);
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/* rnd_down(a*d/b) < n => a*d/b < n */
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int64_t x_down = av_rescale_rnd(a, q.den, b, AV_ROUND_DOWN);
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return ((x_up > q.num) - (x_down < q.num)) * av_cmp_q(q2, q1);
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}
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int av_find_nearest_q_idx(AVRational q, const AVRational* q_list)
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{
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int i, nearest_q_idx = 0;
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for (i = 0; q_list[i].den; i++)
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if (av_nearer_q(q, q_list[i], q_list[nearest_q_idx]) > 0)
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nearest_q_idx = i;
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return nearest_q_idx;
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}
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uint32_t av_q2intfloat(AVRational q) {
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int64_t n;
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int shift;
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int sign = 0;
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if (q.den < 0) {
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q.den *= -1;
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q.num *= -1;
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}
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if (q.num < 0) {
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q.num *= -1;
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sign = 1;
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}
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if (!q.num && !q.den) return 0xFFC00000;
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if (!q.num) return 0;
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if (!q.den) return 0x7F800000 | (q.num & 0x80000000);
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shift = 23 + av_log2(q.den) - av_log2(q.num);
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if (shift >= 0) n = av_rescale(q.num, 1LL<<shift, q.den);
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else n = av_rescale(q.num, 1, ((int64_t)q.den) << -shift);
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shift -= n >= (1<<24);
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shift += n < (1<<23);
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if (shift >= 0) n = av_rescale(q.num, 1LL<<shift, q.den);
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else n = av_rescale(q.num, 1, ((int64_t)q.den) << -shift);
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av_assert1(n < (1<<24));
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av_assert1(n >= (1<<23));
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return sign<<31 | (150-shift)<<23 | (n - (1<<23));
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}
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AVRational av_gcd_q(AVRational a, AVRational b, int max_den, AVRational def)
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{
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int64_t gcd, lcm;
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gcd = av_gcd(a.den, b.den);
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lcm = (a.den / gcd) * b.den;
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return lcm < max_den ? av_make_q(av_gcd(a.num, b.num), lcm) : def;
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}
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