mirror of https://github.com/FFmpeg/FFmpeg.git
patch by Dylan Yudaken, dyudaken gmail com Originally committed as revision 18274 to svn://svn.ffmpeg.org/ffmpeg/trunkrelease/0.6
Dylan Yudaken
16 years ago
committed by
Diego Biurrun
parent
41b4dbbb0e
commit
3ba153f8da
4 changed files with 1 additions and 163 deletions
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/**
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* @file libavcodec/fdctref.c |
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* forward discrete cosine transform, double precision. |
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*/ |
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/* Copyright (C) 1996, MPEG Software Simulation Group. All Rights Reserved. */ |
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/*
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* Disclaimer of Warranty |
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* |
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* These software programs are available to the user without any license fee or |
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* royalty on an "as is" basis. The MPEG Software Simulation Group disclaims |
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* any and all warranties, whether express, implied, or statuary, including any |
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* implied warranties or merchantability or of fitness for a particular |
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* purpose. In no event shall the copyright-holder be liable for any |
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* incidental, punitive, or consequential damages of any kind whatsoever |
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* arising from the use of these programs. |
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* |
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* This disclaimer of warranty extends to the user of these programs and user's |
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* customers, employees, agents, transferees, successors, and assigns. |
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* |
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* The MPEG Software Simulation Group does not represent or warrant that the |
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* programs furnished hereunder are free of infringement of any third-party |
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* patents. |
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* |
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* Commercial implementations of MPEG-1 and MPEG-2 video, including shareware, |
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* are subject to royalty fees to patent holders. Many of these patents are |
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* general enough such that they are unavoidable regardless of implementation |
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* design. |
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*/ |
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#include <math.h> |
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#ifndef PI |
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# ifdef M_PI |
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# define PI M_PI |
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# else |
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# define PI 3.14159265358979323846 |
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# endif |
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#endif |
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/* global declarations */ |
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void ff_ref_dct_init (void); |
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void ff_ref_fdct (short *block); |
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/* private data */ |
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static double c[8][8]; /* transform coefficients */ |
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void ff_ref_dct_init(void) |
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{ |
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int i, j; |
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double s; |
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for (i=0; i<8; i++) |
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{ |
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s = (i==0) ? sqrt(0.125) : 0.5; |
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for (j=0; j<8; j++) |
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c[i][j] = s * cos((PI/8.0)*i*(j+0.5)); |
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} |
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} |
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void ff_ref_fdct(block) |
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short *block; |
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{ |
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register int i, j; |
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double s; |
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double tmp[64]; |
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for(i = 0; i < 8; i++) |
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for(j = 0; j < 8; j++) |
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{ |
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s = 0.0; |
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/*
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* for(k = 0; k < 8; k++) |
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* s += c[j][k] * block[8 * i + k]; |
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*/ |
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s += c[j][0] * block[8 * i + 0]; |
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s += c[j][1] * block[8 * i + 1]; |
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s += c[j][2] * block[8 * i + 2]; |
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s += c[j][3] * block[8 * i + 3]; |
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s += c[j][4] * block[8 * i + 4]; |
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s += c[j][5] * block[8 * i + 5]; |
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s += c[j][6] * block[8 * i + 6]; |
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s += c[j][7] * block[8 * i + 7]; |
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tmp[8 * i + j] = s; |
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} |
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for(j = 0; j < 8; j++) |
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for(i = 0; i < 8; i++) |
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{ |
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s = 0.0; |
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/*
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* for(k = 0; k < 8; k++) |
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* s += c[i][k] * tmp[8 * k + j]; |
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*/ |
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s += c[i][0] * tmp[8 * 0 + j]; |
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s += c[i][1] * tmp[8 * 1 + j]; |
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s += c[i][2] * tmp[8 * 2 + j]; |
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s += c[i][3] * tmp[8 * 3 + j]; |
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s += c[i][4] * tmp[8 * 4 + j]; |
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s += c[i][5] * tmp[8 * 5 + j]; |
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s += c[i][6] * tmp[8 * 6 + j]; |
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s += c[i][7] * tmp[8 * 7 + j]; |
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s*=8.0; |
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block[8 * i + j] = (short)floor(s + 0.499999); |
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/*
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* reason for adding 0.499999 instead of 0.5: |
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* s is quite often x.5 (at least for i and/or j = 0 or 4) |
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* and setting the rounding threshold exactly to 0.5 leads to an |
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* extremely high arithmetic implementation dependency of the result; |
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* s being between x.5 and x.500001 (which is now incorrectly rounded |
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* downwards instead of upwards) is assumed to occur less often |
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* (if at all) |
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*/ |
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} |
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} |
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/* perform IDCT matrix multiply for 8x8 coefficient block */ |
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void ff_ref_idct(block) |
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short *block; |
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{ |
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int i, j, k, v; |
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double partial_product; |
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double tmp[64]; |
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for (i=0; i<8; i++) |
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for (j=0; j<8; j++) |
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{ |
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partial_product = 0.0; |
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for (k=0; k<8; k++) |
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partial_product+= c[k][j]*block[8*i+k]; |
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tmp[8*i+j] = partial_product; |
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} |
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/* Transpose operation is integrated into address mapping by switching
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loop order of i and j */ |
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for (j=0; j<8; j++) |
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for (i=0; i<8; i++) |
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{ |
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partial_product = 0.0; |
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for (k=0; k<8; k++) |
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partial_product+= c[k][i]*tmp[8*k+j]; |
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v = (int) floor(partial_product+0.5); |
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block[8*i+j] = v; |
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} |
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} |
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