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1085 | pj | 1 | `/* Reference_IDCT.c, Inverse Discrete Fourier Transform, double precision */` |

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3 | `/* Copyright (C) 1996, MPEG Software Simulation Group. All Rights Reserved. */` |
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5 | `/*` |
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6 | ` * Disclaimer of Warranty` |
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7 | ` *` |
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8 | ` * These software programs are available to the user without any license fee or` |
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9 | ` * royalty on an "as is" basis. The MPEG Software Simulation Group disclaims` |
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10 | ` * any and all warranties, whether express, implied, or statuary, including any` |
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11 | ` * implied warranties or merchantability or of fitness for a particular` |
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12 | ` * purpose. In no event shall the copyright-holder be liable for any` |
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13 | ` * incidental, punitive, or consequential damages of any kind whatsoever` |
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14 | ` * arising from the use of these programs.` |
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15 | ` *` |
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16 | ` * This disclaimer of warranty extends to the user of these programs and user's` |
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17 | ` * customers, employees, agents, transferees, successors, and assigns.` |
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18 | ` *` |
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19 | ` * The MPEG Software Simulation Group does not represent or warrant that the` |
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20 | ` * programs furnished hereunder are free of infringement of any third-party` |
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21 | ` * patents.` |
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22 | ` *` |
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23 | ` * Commercial implementations of MPEG-1 and MPEG-2 video, including shareware,` |
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24 | ` * are subject to royalty fees to patent holders. Many of these patents are` |
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25 | ` * general enough such that they are unavoidable regardless of implementation` |
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26 | ` * design.` |
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27 | ` *` |
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28 | ` */` |
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29 | |||

30 | `/* Perform IEEE 1180 reference (64-bit floating point, separable 8x1` |
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31 | ` * direct matrix multiply) Inverse Discrete Cosine Transform` |
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32 | `*/` |
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35 | `/* Here we use math.h to generate constants. Compiler results may` |
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36 | ` vary a little */` |
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37 | |||

38 | `#include <math.h>` |
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39 | |||

40 | `#include "config.h"` |
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41 | |||

42 | `#ifndef PI` |
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43 | `# ifdef M_PI` |
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44 | `# define PI M_PI` |
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45 | `# else` |
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46 | `# define PI 3.14159265358979323846` |
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47 | `# endif` |
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48 | `#endif` |
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49 | |||

50 | `/* global declarations */` |
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51 | void Initialize_Fast_IDCTref _ANSI_ARGS_((void)); |
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52 | void Reference_IDCT _ANSI_ARGS_((short *block)); |
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54 | `/* private data */` |
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56 | `/* cosine transform matrix for 8x1 IDCT */` |
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57 | static double c[8][8]; |
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59 | `/* initialize DCT coefficient matrix */` |
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61 | void Initialize_Reference_IDCT() |
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62 | `{` |
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63 | int freq, time; |
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64 | double scale; |
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65 | |||

66 | for (freq=0; freq < 8; freq++) |
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67 | ` {` |
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68 | scale = (freq == 0) ? sqrt(0.125) : 0.5; |
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69 | for (time=0; time<8; time++) |
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70 | c[freq][time] = scale*cos((PI/8.0)*freq*(time + 0.5)); |
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71 | ` }` |
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72 | `}` |
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73 | |||

74 | `/* perform IDCT matrix multiply for 8x8 coefficient block */` |
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76 | void Reference_IDCT(block) |
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77 | short *block; |
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78 | `{` |
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79 | int i, j, k, v; |
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80 | double partial_product; |
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81 | double tmp[64]; |
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82 | |||

83 | for (i=0; i<8; i++) |
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84 | for (j=0; j<8; j++) |
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85 | ` {` |
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86 | partial_product = 0.0; |
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87 | |||

88 | for (k=0; k<8; k++) |
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89 | partial_product+= c[k][j]*block[8*i+k]; |
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90 | |||

91 | tmp[8*i+j] = partial_product; |
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92 | ` }` |
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93 | |||

94 | ` /* Transpose operation is integrated into address mapping by switching` |
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95 | ` loop order of i and j */` |
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96 | |||

97 | for (j=0; j<8; j++) |
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98 | for (i=0; i<8; i++) |
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99 | ` {` |
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100 | partial_product = 0.0; |
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101 | |||

102 | for (k=0; k<8; k++) |
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103 | partial_product+= c[k][i]*tmp[8*k+j]; |
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104 | |||

105 | v = (int) floor(partial_product+0.5); |
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106 | block[8*i+j] = (v<-256) ? -256 : ((v>255) ? 255 : v); |
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107 | ` }` |
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108 | `}` |