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| 2 | pj | 1 | /* idctref.c, Inverse Discrete Fourier Transform, double precision */ |
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| 3 | /* Copyright (C) 1994, MPEG Software Simulation Group. All Rights Reserved. */ |
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| 4 | |||
| 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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| 33 | |||
| 34 | |||
| 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 | #ifndef __STDC__ |
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| 41 | #define _ANSI_ARGS_(x) () |
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| 42 | #else |
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| 43 | #define _ANSI_ARGS_(x) x |
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| 44 | #endif |
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| 45 | |||
| 46 | #define RB "rb" |
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| 47 | #define WB "wb" |
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| 48 | |||
| 49 | #ifndef O_BINARY |
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| 50 | #define O_BINARY 0 |
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| 51 | #endif |
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| 52 | |||
| 53 | #ifndef PI |
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| 54 | # ifdef M_PI |
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| 55 | # define PI M_PI |
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| 56 | # else |
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| 57 | # define PI 3.14159265358979323846 |
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| 58 | # endif |
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| 59 | #endif |
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| 60 | |||
| 61 | /* global declarations */ |
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| 62 | void init_float_idct _ANSI_ARGS_((void)); |
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| 63 | void float_idct _ANSI_ARGS_((short *block)); |
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| 64 | |||
| 65 | /* private data */ |
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| 66 | |||
| 67 | /* cosine transform matrix for 8x1 IDCT */ |
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| 68 | static double c[8][8]; |
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| 69 | |||
| 70 | /* initialize DCT coefficient matrix */ |
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| 71 | |||
| 72 | void init_float_idct() |
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| 73 | { |
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| 74 | int freq, time; |
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| 75 | double scale; |
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| 76 | |||
| 77 | for (freq=0; freq < 8; freq++) |
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| 78 | { |
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| 79 | scale = (freq == 0) ? sqrt(0.125) : 0.5; |
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| 80 | for (time=0; time<8; time++) |
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| 81 | c[freq][time] = scale*cos((PI/8.0)*freq*(time + 0.5)); |
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| 82 | } |
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| 83 | } |
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| 84 | |||
| 85 | /* perform IDCT matrix multiply for 8x8 coefficient block */ |
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| 86 | |||
| 87 | void float_idct(block) |
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| 88 | short *block; |
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| 89 | { |
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| 90 | int i, j, k, v; |
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| 91 | double partial_product; |
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| 92 | double tmp[64]; |
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| 93 | |||
| 94 | for (i=0; i<8; i++) |
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| 95 | for (j=0; j<8; j++) |
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| 96 | { |
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| 97 | partial_product = 0.0; |
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| 98 | |||
| 99 | for (k=0; k<8; k++) |
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| 100 | partial_product+= c[k][j]*block[8*i+k]; |
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| 101 | |||
| 102 | tmp[8*i+j] = partial_product; |
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| 103 | } |
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| 104 | |||
| 105 | /* Transpose operation is integrated into address mapping by switching |
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| 106 | loop order of i and j */ |
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| 107 | |||
| 108 | for (j=0; j<8; j++) |
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| 109 | for (i=0; i<8; i++) |
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| 110 | { |
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| 111 | partial_product = 0.0; |
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| 112 | |||
| 113 | for (k=0; k<8; k++) |
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| 114 | partial_product+= c[k][i]*tmp[8*k+j]; |
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| 115 | |||
| 116 | v = floor(partial_product+0.5); |
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| 117 | block[8*i+j] = (v<-256) ? -256 : ((v>255) ? 255 : v); |
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| 118 | } |
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| 119 | } |