AVRational

Граф связей класса AVRational:

Файлы
файл	rational.h

Классы
struct	AVRational

Определения типов
typedef struct AVRational	AVRational

Функции
static AVRational	av_make_q (int num, int den)
static int	av_cmp_q (AVRational a, AVRational b)
static double	av_q2d (AVRational a)
int	av_reduce (int *dst_num, int *dst_den, int64_t num, int64_t den, int64_t max)
AVRational	av_mul_q (AVRational b, AVRational c) av_const
AVRational	av_div_q (AVRational b, AVRational c) av_const
AVRational	av_add_q (AVRational b, AVRational c) av_const
AVRational	av_sub_q (AVRational b, AVRational c) av_const
static av_always_inline AVRational	av_inv_q (AVRational q)
AVRational	av_d2q (double d, int max) av_const
int	av_nearer_q (AVRational q, AVRational q1, AVRational q2)
int	av_find_nearest_q_idx (AVRational q, const AVRational *q_list)
uint32_t	av_q2intfloat (AVRational q)

Подробное описание

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.

Типы

AVRational

typedef struct AVRational AVRational

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/rational.h>

Rational number (pair of numerator and denominator).

Функции

av_make_q()

static AVRational av_make_q ( int  num, int  den  )

inlinestatic

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/rational.h>

Create an AVRational.

Useful for compilers that do not support compound literals.

Заметки

The return value is not reduced.

См. также

av_reduce()

См. определение в файле rational.h строка 71

{
    AVRational r = { num, den };
    return r;
}

av_cmp_q()

static int av_cmp_q ( AVRational  a, AVRational  b  )

inlinestatic

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/rational.h>

Compare two rationals.

Аргументы

a	First rational
b	Second rational

Возвращает

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

См. определение в файле rational.h строка 89

                                                      {
    const int64_t tmp= a.num * (int64_t)b.den - b.num * (int64_t)a.den;
 
    if(tmp) return (int)((tmp ^ a.den ^ b.den)>>63)|1;
    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;
}

av_q2d()

static double av_q2d ( AVRational  a )

inlinestatic

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/rational.h>

Convert an AVRational to a double.

Аргументы

a	AVRational to convert

Возвращает

a in floating-point form

См. также

av_d2q()

См. определение в файле rational.h строка 104

                                         {
    return a.num / (double) a.den;
}

Используется в av_ts_make_time_string() и AVVideoStream::open().

Граф вызова функции:

av_reduce()

int av_reduce	(	int *	dst_num,
		int *	dst_den,
		int64_t	num,
		int64_t	den,
		int64_t	max
	)

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/rational.h>

Reduce a fraction.

This is useful for framerate calculations.

Аргументы

[out]	dst_num	Destination numerator
[out]	dst_den	Destination denominator
[in]	num	Source numerator
[in]	den	Source denominator
[in]	max	Maximum allowed values for dst_num & dst_den

Возвращает

1 if the operation is exact, 0 otherwise

av_mul_q()

AVRational av_mul_q	(	AVRational	b,
		AVRational	c
	)		const

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/rational.h>

Multiply two rationals.

Аргументы

b	First rational
c	Second rational

Возвращает

b*c

av_div_q()

AVRational av_div_q	(	AVRational	b,
		AVRational	c
	)		const

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/rational.h>

Divide one rational by another.

Аргументы

b	First rational
c	Second rational

Возвращает

b/c

av_add_q()

AVRational av_add_q	(	AVRational	b,
		AVRational	c
	)		const

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/rational.h>

Add two rationals.

Аргументы

b	First rational
c	Second rational

Возвращает

b+c

av_sub_q()

AVRational av_sub_q	(	AVRational	b,
		AVRational	c
	)		const

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/rational.h>

Subtract one rational from another.

Аргументы

b	First rational
c	Second rational

Возвращает

b-c

av_inv_q()

static av_always_inline AVRational av_inv_q ( AVRational  q )

static

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/rational.h>

Invert a rational.

Аргументы

q

value

Возвращает

1 / q

См. определение в файле rational.h строка 159

{
    AVRational r = { q.den, q.num };
    return r;
}

Перекрестные ссылки AVRational::den.

av_d2q()

AVRational av_d2q	(	double	d,
		int	max
	)		const

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/rational.h>

Convert a double precision floating point number to a rational.

In case of infinity, the returned value is expressed as {1, 0} or {-1, 0} depending on the sign.

Аргументы

d	double to convert
max	Maximum allowed numerator and denominator

Возвращает

d in AVRational form

См. также

av_q2d()

av_nearer_q()

int av_nearer_q	(	AVRational	q,
		AVRational	q1,
		AVRational	q2
	)

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/rational.h>

Find which of the two rationals is closer to another rational.

Аргументы

q	Rational to be compared against
q1,q2	Rationals to be tested

Возвращает

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

av_find_nearest_q_idx()

int av_find_nearest_q_idx	(	AVRational	q,
		const AVRational *	q_list
	)

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/rational.h>

Find the value in a list of rationals nearest a given reference rational.

Аргументы

q	Reference rational
q_list	Array of rationals terminated by {0, 0}

Возвращает

Index of the nearest value found in the array

av_q2intfloat()

uint32_t av_q2intfloat

(

AVRational

q

)

#include <C:/git/world-of-might-and-magic/lib/win32/x86/ffmpeg-4.2.2/include/libavutil/rational.h>

Convert an AVRational to a IEEE 32-bit float expressed in fixed-point format.

Аргументы

q	Rational to be converted

Возвращает

Equivalent floating-point value, expressed as an unsigned 32-bit integer.

Заметки

The returned value is platform-indepedant.