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/* |
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* rational numbers |
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* Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
* |
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* This file is part of FFmpeg.
*
* 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
* 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
* 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 |
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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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/** |
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* @file |
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* @ingroup lavu_math_rational
* Utilties for rational number calculation. |
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* @author Michael Niedermayer <michaelni@gmx.at>
*/
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#ifndef AVUTIL_RATIONAL_H
#define AVUTIL_RATIONAL_H |
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|
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#include <stdint.h> |
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#include <limits.h> |
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#include "attributes.h" |
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|
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/** |
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* @defgroup lavu_math_rational AVRational
* @ingroup lavu_math
* Rational number calculation.
*
* While rational numbers can be expressed as floating-point numbers, the
* conversion process is a lossy one, so are floating-point operations. On the
* other hand, the nature of FFmpeg demands highly accurate calculation of
* timestamps. This set of rational number utilities serves as a generic
* interface for manipulating rational numbers as pairs of numerators and
* denominators.
*
* Many of the functions that operate on AVRational's have the suffix `_q`, in
* reference to the mathematical symbol "ℚ" (Q) which denotes the set of all
* rational numbers.
* |
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* @{
*/
/** |
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* Rational number (pair of numerator and denominator). |
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*/ |
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typedef struct AVRational{ |
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int num; ///< Numerator
int den; ///< Denominator |
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} AVRational;
|
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/** |
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* Create an AVRational.
* |
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* Useful for compilers that do not support compound literals. |
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*
* @note The return value is not reduced.
* @see av_reduce() |
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*/
static inline AVRational av_make_q(int num, int den)
{
AVRational r = { num, den };
return r;
}
/** |
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* Compare two rationals. |
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*
* @param a First rational
* @param b Second rational
*
* @return One of the following values:
* - 0 if `a == b`
* - 1 if `a > b`
* - -1 if `a < b`
* - `INT_MIN` if one of the values is of the form `0 / 0` |
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*/ |
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static inline int av_cmp_q(AVRational a, AVRational b){
const int64_t tmp= a.num * (int64_t)b.den - b.num * (int64_t)a.den;
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if(tmp) return (int)((tmp ^ a.den ^ b.den)>>63)|1; |
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else if(b.den && a.den) return 0;
else if(a.num && b.num) return (a.num>>31) - (b.num>>31);
else return INT_MIN; |
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}
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/** |
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* Convert an AVRational to a `double`.
* @param a AVRational to convert
* @return `a` in floating-point form
* @see av_d2q() |
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*/ |
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static inline double av_q2d(AVRational a){
return a.num / (double) a.den;
}
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/** |
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* Reduce a fraction. |
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* |
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* This is useful for framerate calculations. |
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*
* @param[out] dst_num Destination numerator
* @param[out] dst_den Destination denominator
* @param[in] num Source numerator
* @param[in] den Source denominator
* @param[in] max Maximum allowed values for `dst_num` & `dst_den`
* @return 1 if the operation is exact, 0 otherwise |
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*/ |
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int av_reduce(int *dst_num, int *dst_den, int64_t num, int64_t den, int64_t max); |
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|
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/** |
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* Multiply two rationals. |
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* @param b First rational
* @param c Second rational |
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* @return b*c |
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*/ |
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AVRational av_mul_q(AVRational b, AVRational c) av_const; |
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/** |
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* Divide one rational by another. |
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* @param b First rational
* @param c Second rational |
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* @return b/c |
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*/ |
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AVRational av_div_q(AVRational b, AVRational c) av_const; |
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/** |
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* Add two rationals. |
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* @param b First rational
* @param c Second rational |
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* @return b+c |
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*/ |
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AVRational av_add_q(AVRational b, AVRational c) av_const; |
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/** |
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* Subtract one rational from another. |
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* @param b First rational
* @param c Second rational |
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* @return b-c |
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*/ |
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AVRational av_sub_q(AVRational b, AVRational c) av_const; |
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/** |
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* Invert a rational.
* @param q value
* @return 1 / q
*/
static av_always_inline AVRational av_inv_q(AVRational q)
{
AVRational r = { q.den, q.num };
return r;
}
/** |
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* Convert a double precision floating point number to a rational. |
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* |
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* In case of infinity, the returned value is expressed as `{1, 0}` or
* `{-1, 0}` depending on the sign.
*
* @param d `double` to convert
* @param max Maximum allowed numerator and denominator
* @return `d` in AVRational form
* @see av_q2d() |
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*/ |
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AVRational av_d2q(double d, int max) av_const; |
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|
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/** |
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* Find which of the two rationals is closer to another rational.
*
* @param q Rational to be compared against
* @param q1,q2 Rationals to be tested
* @return One of the following values:
* - 1 if `q1` is nearer to `q` than `q2`
* - -1 if `q2` is nearer to `q` than `q1`
* - 0 if they have the same distance |
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*/
int av_nearer_q(AVRational q, AVRational q1, AVRational q2);
/** |
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* Find the value in a list of rationals nearest a given reference rational.
*
* @param q Reference rational
* @param q_list Array of rationals terminated by `{0, 0}`
* @return Index of the nearest value found in the array |
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*/
int av_find_nearest_q_idx(AVRational q, const AVRational* q_list);
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/** |
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* Convert an AVRational to a IEEE 32-bit `float` expressed in fixed-point
* format. |
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* |
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* @param q Rational to be converted
* @return Equivalent floating-point value, expressed as an unsigned 32-bit
* integer.
* @note The returned value is platform-indepedant. |
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*/
uint32_t av_q2intfloat(AVRational q);
/** |
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* @}
*/
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#endif /* AVUTIL_RATIONAL_H */ |