libavutil/mathematics.c File Reference

miscellaneous math routines and tables More...

`#include <assert.h>`
`#include <stdint.h>`
`#include <limits.h>`
`#include "mathematics.h"`

Go to the source code of this file.

Functions

int64_t av_gcd (int64_t a, int64_t b)
Returns the greatest common divisor of a and b.
int64_t av_rescale_rnd (int64_t a, int64_t b, int64_t c, enum AVRounding rnd)
Rescales a 64-bit integer with specified rounding.
int64_t av_rescale (int64_t a, int64_t b, int64_t c)
Rescales a 64-bit integer with rounding to nearest.
int64_t av_rescale_q (int64_t a, AVRational bq, AVRational cq)
Rescales a 64-bit integer by 2 rational numbers.
int av_compare_ts (int64_t ts_a, AVRational tb_a, int64_t ts_b, AVRational tb_b)
Compares 2 timestamps each in its own timebases.

Variables

const uint8_t ff_sqrt_tab [256]
const uint8_t ff_log2_tab [256]
const uint8_t av_reverse [256]

Detailed Description

miscellaneous math routines and tables

Definition in file mathematics.c.

Function Documentation

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

Compares 2 timestamps each in its own timebases.

The result of the function is undefined if one of the timestamps is outside the int64_t range when represented in the others timebase.

Returns:
-1 if ts_a is before ts_b, 1 if ts_a is after ts_b or 0 if they represent the same position

Definition at line 139 of file mathematics.c.

Referenced by av_transcode(), ff_gen_syncpoint_search(), and search_hi_lo_keyframes().

 int64_t av_gcd ( int64_t a, int64_t b )

Returns the greatest common divisor of a and b.

If both a and b are 0 or either or both are <0 then behavior is undefined.

Definition at line 72 of file mathematics.c.

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

Rescales a 64-bit integer with rounding to nearest.

A simple a*b/c isn't possible as it can overflow.

Definition at line 129 of file mathematics.c.

 int64_t av_rescale_q ( int64_t a, AVRational bq, AVRational cq )

Rescales a 64-bit integer by 2 rational numbers.

Definition at line 133 of file mathematics.c.

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

Rescales a 64-bit integer with specified rounding.

A simple a*b/c isn't possible as it can overflow.

Definition at line 77 of file mathematics.c.

Variable Documentation

 const uint8_t av_reverse[256]

Initial value:

```{
0x00,0x80,0x40,0xC0,0x20,0xA0,0x60,0xE0,0x10,0x90,0x50,0xD0,0x30,0xB0,0x70,0xF0,
0x08,0x88,0x48,0xC8,0x28,0xA8,0x68,0xE8,0x18,0x98,0x58,0xD8,0x38,0xB8,0x78,0xF8,
0x04,0x84,0x44,0xC4,0x24,0xA4,0x64,0xE4,0x14,0x94,0x54,0xD4,0x34,0xB4,0x74,0xF4,
0x0C,0x8C,0x4C,0xCC,0x2C,0xAC,0x6C,0xEC,0x1C,0x9C,0x5C,0xDC,0x3C,0xBC,0x7C,0xFC,
0x02,0x82,0x42,0xC2,0x22,0xA2,0x62,0xE2,0x12,0x92,0x52,0xD2,0x32,0xB2,0x72,0xF2,
0x0A,0x8A,0x4A,0xCA,0x2A,0xAA,0x6A,0xEA,0x1A,0x9A,0x5A,0xDA,0x3A,0xBA,0x7A,0xFA,
0x06,0x86,0x46,0xC6,0x26,0xA6,0x66,0xE6,0x16,0x96,0x56,0xD6,0x36,0xB6,0x76,0xF6,
0x0E,0x8E,0x4E,0xCE,0x2E,0xAE,0x6E,0xEE,0x1E,0x9E,0x5E,0xDE,0x3E,0xBE,0x7E,0xFE,
0x01,0x81,0x41,0xC1,0x21,0xA1,0x61,0xE1,0x11,0x91,0x51,0xD1,0x31,0xB1,0x71,0xF1,
0x09,0x89,0x49,0xC9,0x29,0xA9,0x69,0xE9,0x19,0x99,0x59,0xD9,0x39,0xB9,0x79,0xF9,
0x05,0x85,0x45,0xC5,0x25,0xA5,0x65,0xE5,0x15,0x95,0x55,0xD5,0x35,0xB5,0x75,0xF5,
0x03,0x83,0x43,0xC3,0x23,0xA3,0x63,0xE3,0x13,0x93,0x53,0xD3,0x33,0xB3,0x73,0xF3,
0x0B,0x8B,0x4B,0xCB,0x2B,0xAB,0x6B,0xEB,0x1B,0x9B,0x5B,0xDB,0x3B,0xBB,0x7B,0xFB,
0x07,0x87,0x47,0xC7,0x27,0xA7,0x67,0xE7,0x17,0x97,0x57,0xD7,0x37,0xB7,0x77,0xF7,
0x0F,0x8F,0x4F,0xCF,0x2F,0xAF,0x6F,0xEF,0x1F,0x9F,0x5F,0xDF,0x3F,0xBF,0x7F,0xFF,
}
```

Definition at line 53 of file mathematics.c.

 const uint8_t ff_log2_tab[256]

Initial value:

```{
0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7
}
```

Definition at line 42 of file mathematics.c.

Referenced by av_log2_16bit_c(), av_log2_c(), ff_ps_read_data(), put_xsub_rle(), and seq_decode_op1().

 const uint8_t ff_sqrt_tab[256]

Initial value:

```{
0, 16, 23, 28, 32, 36, 40, 43, 46, 48, 51, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 77, 79, 80, 82, 84, 85, 87, 88, 90,
91, 92, 94, 95, 96, 98, 99,100,102,103,104,105,107,108,109,110,111,112,114,115,116,117,118,119,120,121,122,123,124,125,126,127,
128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,144,144,145,146,147,148,149,150,151,151,152,153,154,155,156,156,
157,158,159,160,160,161,162,163,164,164,165,166,167,168,168,169,170,171,171,172,173,174,174,175,176,176,177,178,179,179,180,181,
182,182,183,184,184,185,186,186,187,188,188,189,190,190,191,192,192,193,194,194,195,196,196,197,198,198,199,200,200,201,202,202,
203,204,204,205,205,206,207,207,208,208,209,210,210,211,212,212,213,213,214,215,215,216,216,217,218,218,219,219,220,220,221,222,
222,223,223,224,224,225,226,226,227,227,228,228,229,230,230,231,231,232,232,233,233,234,235,235,236,236,237,237,238,238,239,239,
240,240,241,242,242,243,243,244,244,245,245,246,246,247,247,248,248,249,249,250,250,251,251,252,252,253,253,254,254,255,255,255
}
```

Definition at line 31 of file mathematics.c.

Referenced by ff_sqrt().

Generated on Fri Oct 26 02:36:55 2012 for FFmpeg by  1.5.8