gfiber / vendor / opensource / ffmpeg / 3d15d128df6c42df883fe3aedbbd2ef50085217f / . / libavcodec / fdctref.c

/** | |

* @file libavcodec/fdctref.c | |

* forward discrete cosine transform, double precision. | |

*/ | |

/* Copyright (C) 1996, MPEG Software Simulation Group. All Rights Reserved. */ | |

/* | |

* Disclaimer of Warranty | |

* | |

* These software programs are available to the user without any license fee or | |

* royalty on an "as is" basis. The MPEG Software Simulation Group disclaims | |

* any and all warranties, whether express, implied, or statuary, including any | |

* implied warranties or merchantability or of fitness for a particular | |

* purpose. In no event shall the copyright-holder be liable for any | |

* incidental, punitive, or consequential damages of any kind whatsoever | |

* arising from the use of these programs. | |

* | |

* This disclaimer of warranty extends to the user of these programs and user's | |

* customers, employees, agents, transferees, successors, and assigns. | |

* | |

* The MPEG Software Simulation Group does not represent or warrant that the | |

* programs furnished hereunder are free of infringement of any third-party | |

* patents. | |

* | |

* Commercial implementations of MPEG-1 and MPEG-2 video, including shareware, | |

* are subject to royalty fees to patent holders. Many of these patents are | |

* general enough such that they are unavoidable regardless of implementation | |

* design. | |

*/ | |

#include <math.h> | |

#ifndef PI | |

# ifdef M_PI | |

# define PI M_PI | |

# else | |

# define PI 3.14159265358979323846 | |

# endif | |

#endif | |

/* global declarations */ | |

void init_fdct (void); | |

void fdct (short *block); | |

/* private data */ | |

static double c[8][8]; /* transform coefficients */ | |

void init_fdct(void) | |

{ | |

int i, j; | |

double s; | |

for (i=0; i<8; i++) | |

{ | |

s = (i==0) ? sqrt(0.125) : 0.5; | |

for (j=0; j<8; j++) | |

c[i][j] = s * cos((PI/8.0)*i*(j+0.5)); | |

} | |

} | |

void fdct(block) | |

short *block; | |

{ | |

register int i, j; | |

double s; | |

double tmp[64]; | |

for(i = 0; i < 8; i++) | |

for(j = 0; j < 8; j++) | |

{ | |

s = 0.0; | |

/* | |

* for(k = 0; k < 8; k++) | |

* s += c[j][k] * block[8 * i + k]; | |

*/ | |

s += c[j][0] * block[8 * i + 0]; | |

s += c[j][1] * block[8 * i + 1]; | |

s += c[j][2] * block[8 * i + 2]; | |

s += c[j][3] * block[8 * i + 3]; | |

s += c[j][4] * block[8 * i + 4]; | |

s += c[j][5] * block[8 * i + 5]; | |

s += c[j][6] * block[8 * i + 6]; | |

s += c[j][7] * block[8 * i + 7]; | |

tmp[8 * i + j] = s; | |

} | |

for(j = 0; j < 8; j++) | |

for(i = 0; i < 8; i++) | |

{ | |

s = 0.0; | |

/* | |

* for(k = 0; k < 8; k++) | |

* s += c[i][k] * tmp[8 * k + j]; | |

*/ | |

s += c[i][0] * tmp[8 * 0 + j]; | |

s += c[i][1] * tmp[8 * 1 + j]; | |

s += c[i][2] * tmp[8 * 2 + j]; | |

s += c[i][3] * tmp[8 * 3 + j]; | |

s += c[i][4] * tmp[8 * 4 + j]; | |

s += c[i][5] * tmp[8 * 5 + j]; | |

s += c[i][6] * tmp[8 * 6 + j]; | |

s += c[i][7] * tmp[8 * 7 + j]; | |

s*=8.0; | |

block[8 * i + j] = (short)floor(s + 0.499999); | |

/* | |

* reason for adding 0.499999 instead of 0.5: | |

* s is quite often x.5 (at least for i and/or j = 0 or 4) | |

* and setting the rounding threshold exactly to 0.5 leads to an | |

* extremely high arithmetic implementation dependency of the result; | |

* s being between x.5 and x.500001 (which is now incorrectly rounded | |

* downwards instead of upwards) is assumed to occur less often | |

* (if at all) | |

*/ | |

} | |

} | |

/* perform IDCT matrix multiply for 8x8 coefficient block */ | |

void idct(block) | |

short *block; | |

{ | |

int i, j, k, v; | |

double partial_product; | |

double tmp[64]; | |

for (i=0; i<8; i++) | |

for (j=0; j<8; j++) | |

{ | |

partial_product = 0.0; | |

for (k=0; k<8; k++) | |

partial_product+= c[k][j]*block[8*i+k]; | |

tmp[8*i+j] = partial_product; | |

} | |

/* Transpose operation is integrated into address mapping by switching | |

loop order of i and j */ | |

for (j=0; j<8; j++) | |

for (i=0; i<8; i++) | |

{ | |

partial_product = 0.0; | |

for (k=0; k<8; k++) | |

partial_product+= c[k][i]*tmp[8*k+j]; | |

v = (int) floor(partial_product+0.5); | |

block[8*i+j] = v; | |

} | |

} |