FFmpeg
Mathematics

## Modules

Colorspace Utility

AVRational

## Macros

#define ff_ctz   ff_ctz_c

#define ff_ctzll   ff_ctzll_c

#define ff_clz   ff_clz_c

## Enumerations

enum  AVRounding {
AV_ROUND_ZERO = 0, AV_ROUND_INF = 1, AV_ROUND_DOWN = 2, AV_ROUND_UP = 3,
AV_ROUND_NEAR_INF = 5, AV_ROUND_PASS_MINMAX = 8192
}
Rounding methods. More...

## Functions

static av_always_inline av_const int ff_ctz_c (int v)
Trailing zero bit count. More...

static av_always_inline av_const int ff_ctzll_c (long long v)

static av_always_inline av_const unsigned ff_clz_c (unsigned x)

int64_t av_const av_gcd (int64_t a, int64_t b)
Compute the greatest common divisor of two integer operands. More...

int64_t av_rescale (int64_t a, int64_t b, int64_t c) av_const
Rescale a 64-bit integer with rounding to nearest. More...

int64_t av_rescale_rnd (int64_t a, int64_t b, int64_t c, enum AVRounding rnd) av_const
Rescale a 64-bit integer with specified rounding. More...

int64_t av_rescale_q (int64_t a, AVRational bq, AVRational cq) av_const
Rescale a 64-bit integer by 2 rational numbers. More...

int64_t av_rescale_q_rnd (int64_t a, AVRational bq, AVRational cq, enum AVRounding rnd) av_const
Rescale a 64-bit integer by 2 rational numbers with specified rounding. More...

int av_compare_ts (int64_t ts_a, AVRational tb_a, int64_t ts_b, AVRational tb_b)
Compare two timestamps each in its own time base. More...

int64_t av_compare_mod (uint64_t a, uint64_t b, uint64_t mod)
Compare the remainders of two integer operands divided by a common divisor. More...

int64_t av_rescale_delta (AVRational in_tb, int64_t in_ts, AVRational fs_tb, int duration, int64_t *last, AVRational out_tb)
Rescale a timestamp while preserving known durations. More...

int64_t av_add_stable (AVRational ts_tb, int64_t ts, AVRational inc_tb, int64_t inc)
Add a value to a timestamp. More...

double av_bessel_i0 (double x)
0th order modified bessel function of the first kind. More...

## Detailed Description

Mathematical utilities for working with timestamp and time base.

## ◆ ff_ctz

 #define ff_ctz   ff_ctz_c

Definition at line 107 of file intmath.h.

## ◆ ff_ctzll

 #define ff_ctzll   ff_ctzll_c

Definition at line 127 of file intmath.h.

## ◆ ff_clz

 #define ff_clz   ff_clz_c

Definition at line 143 of file intmath.h.

## ◆ AVRounding

 enum AVRounding

Rounding methods.

Enumerator
AV_ROUND_ZERO

Round toward zero.

AV_ROUND_INF

Round away from zero.

AV_ROUND_DOWN

Round toward -infinity.

AV_ROUND_UP

Round toward +infinity.

AV_ROUND_NEAR_INF

Round to nearest and halfway cases away from zero.

AV_ROUND_PASS_MINMAX

Flag telling rescaling functions to pass `INT64_MIN`/`MAX` through unchanged, avoiding special cases for AV_NOPTS_VALUE.

Unlike other values of the enumeration AVRounding, this value is a bitmask that must be used in conjunction with another value of the enumeration through a bitwise OR, in order to set behavior for normal cases.

// Rescaling 3:
// Calculating 3 * 1 / 2
// 3 / 2 is rounded up to 2
// => 2
// Rescaling AV_NOPTS_VALUE:
// AV_NOPTS_VALUE == INT64_MIN
// AV_NOPTS_VALUE is passed through
// => AV_NOPTS_VALUE

Definition at line 130 of file mathematics.h.

## ◆ ff_ctz_c()

 static av_always_inline av_const int ff_ctz_c ( int v )
static

Trailing zero bit count.

Parameters
 v input value. If v is 0, the result is undefined.
Returns
the number of trailing 0-bits

Definition at line 116 of file intmath.h.

## ◆ ff_ctzll_c()

 static av_always_inline av_const int ff_ctzll_c ( long long v )
static

Definition at line 130 of file intmath.h.

## ◆ ff_clz_c()

 static av_always_inline av_const unsigned ff_clz_c ( unsigned x )
static

Definition at line 144 of file intmath.h.

## ◆ av_gcd()

 int64_t av_const av_gcd ( int64_t a, int64_t b )

Compute the greatest common divisor of two integer operands.

Parameters
 a Operand b Operand
Returns
GCD of a and b up to sign; if a >= 0 and b >= 0, return value is >= 0; if a == 0 and b == 0, returns 0.

Definition at line 37 of file mathematics.c.

## ◆ av_rescale()

 int64_t av_rescale ( int64_t a, int64_t b, int64_t c ) const

## ◆ av_rescale_rnd()

 int64_t av_rescale_rnd ( int64_t a, int64_t b, int64_t c, enum AVRounding rnd ) const

Rescale a 64-bit integer with specified rounding.

The operation is mathematically equivalent to `a * b / c`, but writing that directly can overflow, and does not support different rounding methods. If the result is not representable then INT64_MIN is returned.

av_rescale(), av_rescale_q(), av_rescale_q_rnd()

Definition at line 58 of file mathematics.c.

## ◆ av_rescale_q_rnd()

 int64_t av_rescale_q_rnd ( int64_t a, AVRational bq, AVRational cq, enum AVRounding rnd ) const

Rescale a 64-bit integer by 2 rational numbers with specified rounding.

The operation is mathematically equivalent to `a * bq / cq`.

av_rescale(), av_rescale_rnd(), av_rescale_q()

Definition at line 134 of file mathematics.c.

## ◆ av_compare_ts()

 int av_compare_ts ( int64_t ts_a, AVRational tb_a, int64_t ts_b, AVRational tb_b )

Compare two timestamps each in its own time base.

Returns
One of the following values:
• -1 if `ts_a` is before `ts_b`
• 1 if `ts_a` is after `ts_b`
• 0 if they represent the same position
Warning
The result of the function is undefined if one of the timestamps is outside the `int64_t` range when represented in the other's timebase.

Definition at line 147 of file mathematics.c.

## ◆ av_compare_mod()

 int64_t av_compare_mod ( uint64_t a, uint64_t b, uint64_t mod )

Compare the remainders of two integer operands divided by a common divisor.

In other words, compare the least significant `log2(mod)` bits of integers `a` and `b`.

av_compare_mod(0x11, 0x02, 0x10) < 0 // since 0x11 % 0x10 (0x1) < 0x02 % 0x10 (0x2)
av_compare_mod(0x11, 0x02, 0x20) > 0 // since 0x11 % 0x20 (0x11) > 0x02 % 0x20 (0x02)
Parameters
 a Operand b Operand mod Divisor; must be a power of 2
Returns
• a negative value if `a % mod < b % mod`
• a positive value if `a % mod > b % mod`
• zero if `a % mod == b % mod`

Definition at line 160 of file mathematics.c.

## ◆ av_rescale_delta()

 int64_t av_rescale_delta ( AVRational in_tb, int64_t in_ts, AVRational fs_tb, int duration, int64_t * last, AVRational out_tb )

Rescale a timestamp while preserving known durations.

This function is designed to be called per audio packet to scale the input timestamp to a different time base. Compared to a simple av_rescale_q() call, this function is robust against possible inconsistent frame durations.

The `last` parameter is a state variable that must be preserved for all subsequent calls for the same stream. For the first call, `*last` should be initialized to AV_NOPTS_VALUE.

Parameters
 [in] in_tb Input time base [in] in_ts Input timestamp [in] fs_tb Duration time base; typically this is finer-grained (greater) than `in_tb` and `out_tb` [in] duration Duration till the next call to this function (i.e. duration of the current packet/frame) [in,out] last Pointer to a timestamp expressed in terms of `fs_tb`, acting as a state variable [in] out_tb Output timebase
Returns
Timestamp expressed in terms of `out_tb`
Note
In the context of this function, "duration" is in term of samples, not seconds.

Definition at line 168 of file mathematics.c.

Referenced by audio_ts_process(), and mux_fixup_ts().

 int64_t av_add_stable ( AVRational ts_tb, int64_t ts, AVRational inc_tb, int64_t inc )

Add a value to a timestamp.

This function guarantees that when the same value is repeatly added that no accumulation of rounding errors occurs.

Parameters
 [in] ts Input timestamp [in] ts_tb Input timestamp time base [in] inc Value to be added [in] inc_tb Time base of `inc`

Definition at line 191 of file mathematics.c.

Referenced by compute_pkt_fields(), and main().

## ◆ av_bessel_i0()

 double av_bessel_i0 ( double x )

0th order modified bessel function of the first kind.

Algorithm taken from the Boost project, source: https://searchcode.com/codesearch/view/14918379/ Use, modification and distribution are subject to the Boost Software License, Version 1.0 (see notice below). Boost Software License - Version 1.0 - August 17th, 2003 Permission is hereby granted, free of charge, to any person or organization obtaining a copy of the software and accompanying documentation covered by this license (the "Software") to use, reproduce, display, distribute, execute, and transmit the Software, and to prepare derivative works of the Software, and to permit third-parties to whom the Software is furnished to do so, all subject to the following:

The copyright notices in the Software and this entire statement, including the above license grant, this restriction and the following disclaimer, must be included in all copies of the Software, in whole or in part, and all derivative works of the Software, unless such copies or derivative works are solely in the form of machine-executable object code generated by a source language processor.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Definition at line 257 of file mathematics.c.

Referenced by build_filter(), generate_window_func(), kbd_window_init(), and make_lpf().

AV_ROUND_UP
@ AV_ROUND_UP
Round toward +infinity.
Definition: mathematics.h:134
av_rescale_rnd
int64_t av_rescale_rnd(int64_t a, int64_t b, int64_t c, enum AVRounding rnd)
Rescale a 64-bit integer with specified rounding.
Definition: mathematics.c:58
AV_NOPTS_VALUE
#define AV_NOPTS_VALUE
Undefined timestamp value.
Definition: avutil.h:248
av_compare_mod
int64_t av_compare_mod(uint64_t a, uint64_t b, uint64_t mod)
Compare the remainders of two integer operands divided by a common divisor.
Definition: mathematics.c:160
AV_ROUND_PASS_MINMAX
@ AV_ROUND_PASS_MINMAX
Flag telling rescaling functions to pass INT64_MIN/MAX through unchanged, avoiding special cases for ...
Definition: mathematics.h:159