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author | giraffedata <giraffedata@9d0c8265-081b-0410-96cb-a4ca84ce46f8> | 2006-08-19 03:12:28 +0000 |
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committer | giraffedata <giraffedata@9d0c8265-081b-0410-96cb-a4ca84ce46f8> | 2006-08-19 03:12:28 +0000 |
commit | 1fd361a1ea06e44286c213ca1f814f49306fdc43 (patch) | |
tree | 64c8c96cf54d8718847339a403e5e67b922e8c3f /converter/ppm/ppmtompeg/jrevdct.c | |
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git-svn-id: http://svn.code.sf.net/p/netpbm/code/trunk@1 9d0c8265-081b-0410-96cb-a4ca84ce46f8
Diffstat (limited to 'converter/ppm/ppmtompeg/jrevdct.c')
-rw-r--r-- | converter/ppm/ppmtompeg/jrevdct.c | 1278 |
1 files changed, 1278 insertions, 0 deletions
diff --git a/converter/ppm/ppmtompeg/jrevdct.c b/converter/ppm/ppmtompeg/jrevdct.c new file mode 100644 index 00000000..2e99a67a --- /dev/null +++ b/converter/ppm/ppmtompeg/jrevdct.c @@ -0,0 +1,1278 @@ +/* + * jrevdct.c + * + * Copyright (C) 1991, 1992, Thomas G. Lane. + * This file is part of the Independent JPEG Group's software. + * For conditions of distribution and use, see the accompanying README file. + * + * This file contains the basic inverse-DCT transformation subroutine. + * + * This implementation is based on an algorithm described in + * C. Loeffler, A. Ligtenberg and G. Moschytz, "Practical Fast 1-D DCT + * Algorithms with 11 Multiplications", Proc. Int'l. Conf. on Acoustics, + * Speech, and Signal Processing 1989 (ICASSP '89), pp. 988-991. + * The primary algorithm described there uses 11 multiplies and 29 adds. + * We use their alternate method with 12 multiplies and 32 adds. + * The advantage of this method is that no data path contains more than one + * multiplication; this allows a very simple and accurate implementation in + * scaled fixed-point arithmetic, with a minimal number of shifts. + * + * I've made lots of modifications to attempt to take advantage of the + * sparse nature of the DCT matrices we're getting. Although the logic + * is cumbersome, it's straightforward and the resulting code is much + * faster. + * + * A better way to do this would be to pass in the DCT block as a sparse + * matrix, perhaps with the difference cases encoded. + */ + +#include <memory.h> +#include "all.h" +#include "ansi.h" +#include "dct.h" + + +#define CONST_BITS 13 + +/* + * This routine is specialized to the case DCTSIZE = 8. + */ + +#if DCTSIZE != 8 + Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */ +#endif + + +/* + * A 2-D IDCT can be done by 1-D IDCT on each row followed by 1-D IDCT + * on each column. Direct algorithms are also available, but they are + * much more complex and seem not to be any faster when reduced to code. + * + * The poop on this scaling stuff is as follows: + * + * Each 1-D IDCT step produces outputs which are a factor of sqrt(N) + * larger than the true IDCT outputs. The final outputs are therefore + * a factor of N larger than desired; since N=8 this can be cured by + * a simple right shift at the end of the algorithm. The advantage of + * this arrangement is that we save two multiplications per 1-D IDCT, + * because the y0 and y4 inputs need not be divided by sqrt(N). + * + * We have to do addition and subtraction of the integer inputs, which + * is no problem, and multiplication by fractional constants, which is + * a problem to do in integer arithmetic. We multiply all the constants + * by CONST_SCALE and convert them to integer constants (thus retaining + * CONST_BITS bits of precision in the constants). After doing a + * multiplication we have to divide the product by CONST_SCALE, with proper + * rounding, to produce the correct output. This division can be done + * cheaply as a right shift of CONST_BITS bits. We postpone shifting + * as long as possible so that partial sums can be added together with + * full fractional precision. + * + * The outputs of the first pass are scaled up by PASS1_BITS bits so that + * they are represented to better-than-integral precision. These outputs + * require BITS_IN_JSAMPLE + PASS1_BITS + 3 bits; this fits in a 16-bit word + * with the recommended scaling. (To scale up 12-bit sample data further, an + * intermediate int32 array would be needed.) + * + * To avoid overflow of the 32-bit intermediate results in pass 2, we must + * have BITS_IN_JSAMPLE + CONST_BITS + PASS1_BITS <= 26. Error analysis + * shows that the values given below are the most effective. + */ + +#ifdef EIGHT_BIT_SAMPLES +#define PASS1_BITS 2 +#else +#define PASS1_BITS 1 /* lose a little precision to avoid overflow */ +#endif + +#define ONE ((int32) 1) + +#define CONST_SCALE (ONE << CONST_BITS) + +/* Convert a positive real constant to an integer scaled by CONST_SCALE. + * IMPORTANT: if your compiler doesn't do this arithmetic at compile time, + * you will pay a significant penalty in run time. In that case, figure + * the correct integer constant values and insert them by hand. + */ + +/* Actually FIX is no longer used, we precomputed them all */ +#define FIX(x) ((int32) ((x) * CONST_SCALE + 0.5)) + +/* Descale and correctly round an int32 value that's scaled by N bits. + * We assume RIGHT_SHIFT rounds towards minus infinity, so adding + * the fudge factor is correct for either sign of X. + */ + +#define DESCALE(x,n) RIGHT_SHIFT((x) + (ONE << ((n)-1)), n) + +/* Multiply an int32 variable by an int32 constant to yield an int32 result. + * For 8-bit samples with the recommended scaling, all the variable + * and constant values involved are no more than 16 bits wide, so a + * 16x16->32 bit multiply can be used instead of a full 32x32 multiply; + * this provides a useful speedup on many machines. + * There is no way to specify a 16x16->32 multiply in portable C, but + * some C compilers will do the right thing if you provide the correct + * combination of casts. + * NB: for 12-bit samples, a full 32-bit multiplication will be needed. + */ + +#ifdef EIGHT_BIT_SAMPLES +#ifdef SHORTxSHORT_32 /* may work if 'int' is 32 bits */ +#define MULTIPLY(var,const) (((INT16) (var)) * ((INT16) (const))) +#endif +#ifdef SHORTxLCONST_32 /* known to work with Microsoft C 6.0 */ +#define MULTIPLY(var,const) (((INT16) (var)) * ((int32) (const))) +#endif +#endif + +#ifndef MULTIPLY /* default definition */ +#define MULTIPLY(var,const) ((var) * (const)) +#endif + + +/* + Unlike our decoder where we approximate the FIXes, we need to use exact +ones here or successive P-frames will drift too much with Reference frame coding +*/ +#define FIX_0_211164243 1730 +#define FIX_0_275899380 2260 +#define FIX_0_298631336 2446 +#define FIX_0_390180644 3196 +#define FIX_0_509795579 4176 +#define FIX_0_541196100 4433 +#define FIX_0_601344887 4926 +#define FIX_0_765366865 6270 +#define FIX_0_785694958 6436 +#define FIX_0_899976223 7373 +#define FIX_1_061594337 8697 +#define FIX_1_111140466 9102 +#define FIX_1_175875602 9633 +#define FIX_1_306562965 10703 +#define FIX_1_387039845 11363 +#define FIX_1_451774981 11893 +#define FIX_1_501321110 12299 +#define FIX_1_662939225 13623 +#define FIX_1_847759065 15137 +#define FIX_1_961570560 16069 +#define FIX_2_053119869 16819 +#define FIX_2_172734803 17799 +#define FIX_2_562915447 20995 +#define FIX_3_072711026 25172 + +/* + Switch on reverse_dct choices +*/ +void reference_rev_dct _ANSI_ARGS_((int16 *block)); +void mpeg_jrevdct_quick _ANSI_ARGS_((int16 *block)); +void init_idctref _ANSI_ARGS_((void)); + +extern boolean pureDCT; + +void +mpeg_jrevdct(data) + DCTBLOCK data; +{ + if (pureDCT) reference_rev_dct(data); + else mpeg_jrevdct_quick(data); +} + +/* + * Perform the inverse DCT on one block of coefficients. + */ + +void +mpeg_jrevdct_quick(data) + DCTBLOCK data; +{ + int32 tmp0, tmp1, tmp2, tmp3; + int32 tmp10, tmp11, tmp12, tmp13; + int32 z1, z2, z3, z4, z5; + int32 d0, d1, d2, d3, d4, d5, d6, d7; + register DCTELEM *dataptr; + int rowctr; + SHIFT_TEMPS + + /* Pass 1: process rows. */ + /* Note results are scaled up by sqrt(8) compared to a true IDCT; */ + /* furthermore, we scale the results by 2**PASS1_BITS. */ + + dataptr = data; + + for (rowctr = DCTSIZE-1; rowctr >= 0; rowctr--) { + /* Due to quantization, we will usually find that many of the input + * coefficients are zero, especially the AC terms. We can exploit this + * by short-circuiting the IDCT calculation for any row in which all + * the AC terms are zero. In that case each output is equal to the + * DC coefficient (with scale factor as needed). + * With typical images and quantization tables, half or more of the + * row DCT calculations can be simplified this way. + */ + + register int *idataptr = (int*)dataptr; + d0 = dataptr[0]; + d1 = dataptr[1]; + if ((d1 == 0) && (idataptr[1] | idataptr[2] | idataptr[3]) == 0) { + /* AC terms all zero */ + if (d0) { + /* Compute a 32 bit value to assign. */ + DCTELEM dcval = (DCTELEM) (d0 << PASS1_BITS); + register int v = (dcval & 0xffff) | ((dcval << 16) & 0xffff0000); + + idataptr[0] = v; + idataptr[1] = v; + idataptr[2] = v; + idataptr[3] = v; + } + + dataptr += DCTSIZE; /* advance pointer to next row */ + continue; + } + d2 = dataptr[2]; + d3 = dataptr[3]; + d4 = dataptr[4]; + d5 = dataptr[5]; + d6 = dataptr[6]; + d7 = dataptr[7]; + + /* Even part: reverse the even part of the forward DCT. */ + /* The rotator is sqrt(2)*c(-6). */ +{ + if (d6) { + if (d4) { + if (d2) { + if (d0) { + /* d0 != 0, d2 != 0, d4 != 0, d6 != 0 */ + z1 = MULTIPLY(d2 + d6, FIX_0_541196100); + tmp2 = z1 + MULTIPLY(-d6, FIX_1_847759065); + tmp3 = z1 + MULTIPLY(d2, FIX_0_765366865); + + tmp0 = (d0 + d4) << CONST_BITS; + tmp1 = (d0 - d4) << CONST_BITS; + + tmp10 = tmp0 + tmp3; + tmp13 = tmp0 - tmp3; + tmp11 = tmp1 + tmp2; + tmp12 = tmp1 - tmp2; + } else { + /* d0 == 0, d2 != 0, d4 != 0, d6 != 0 */ + z1 = MULTIPLY(d2 + d6, FIX_0_541196100); + tmp2 = z1 + MULTIPLY(-d6, FIX_1_847759065); + tmp3 = z1 + MULTIPLY(d2, FIX_0_765366865); + + tmp0 = d4 << CONST_BITS; + + tmp10 = tmp0 + tmp3; + tmp13 = tmp0 - tmp3; + tmp11 = tmp2 - tmp0; + tmp12 = -(tmp0 + tmp2); + } + } else { + if (d0) { + /* d0 != 0, d2 == 0, d4 != 0, d6 != 0 */ + tmp2 = MULTIPLY(-d6, FIX_1_306562965); + tmp3 = MULTIPLY(d6, FIX_0_541196100); + + tmp0 = (d0 + d4) << CONST_BITS; + tmp1 = (d0 - d4) << CONST_BITS; + + tmp10 = tmp0 + tmp3; + tmp13 = tmp0 - tmp3; + tmp11 = tmp1 + tmp2; + tmp12 = tmp1 - tmp2; + } else { + /* d0 == 0, d2 == 0, d4 != 0, d6 != 0 */ + tmp2 = MULTIPLY(-d6, FIX_1_306562965); + tmp3 = MULTIPLY(d6, FIX_0_541196100); + + tmp0 = d4 << CONST_BITS; + + tmp10 = tmp0 + tmp3; + tmp13 = tmp0 - tmp3; + tmp11 = tmp2 - tmp0; + tmp12 = -(tmp0 + tmp2); + } + } + } else { + if (d2) { + if (d0) { + /* d0 != 0, d2 != 0, d4 == 0, d6 != 0 */ + z1 = MULTIPLY(d2 + d6, FIX_0_541196100); + tmp2 = z1 + MULTIPLY(-d6, FIX_1_847759065); + tmp3 = z1 + MULTIPLY(d2, FIX_0_765366865); + + tmp0 = d0 << CONST_BITS; + + tmp10 = tmp0 + tmp3; + tmp13 = tmp0 - tmp3; + tmp11 = tmp0 + tmp2; + tmp12 = tmp0 - tmp2; + } else { + /* d0 == 0, d2 != 0, d4 == 0, d6 != 0 */ + z1 = MULTIPLY(d2 + d6, FIX_0_541196100); + tmp2 = z1 + MULTIPLY(-d6, FIX_1_847759065); + tmp3 = z1 + MULTIPLY(d2, FIX_0_765366865); + + tmp10 = tmp3; + tmp13 = -tmp3; + tmp11 = tmp2; + tmp12 = -tmp2; + } + } else { + if (d0) { + /* d0 != 0, d2 == 0, d4 == 0, d6 != 0 */ + tmp2 = MULTIPLY(-d6, FIX_1_306562965); + tmp3 = MULTIPLY(d6, FIX_0_541196100); + + tmp0 = d0 << CONST_BITS; + + tmp10 = tmp0 + tmp3; + tmp13 = tmp0 - tmp3; + tmp11 = tmp0 + tmp2; + tmp12 = tmp0 - tmp2; + } else { + /* d0 == 0, d2 == 0, d4 == 0, d6 != 0 */ + tmp2 = MULTIPLY(-d6, FIX_1_306562965); + tmp3 = MULTIPLY(d6, FIX_0_541196100); + + tmp10 = tmp3; + tmp13 = -tmp3; + tmp11 = tmp2; + tmp12 = -tmp2; + } + } + } + } else { + if (d4) { + if (d2) { + if (d0) { + /* d0 != 0, d2 != 0, d4 != 0, d6 == 0 */ + tmp2 = MULTIPLY(d2, FIX_0_541196100); + tmp3 = MULTIPLY(d2, FIX_1_306562965); + + tmp0 = (d0 + d4) << CONST_BITS; + tmp1 = (d0 - d4) << CONST_BITS; + + tmp10 = tmp0 + tmp3; + tmp13 = tmp0 - tmp3; + tmp11 = tmp1 + tmp2; + tmp12 = tmp1 - tmp2; + } else { + /* d0 == 0, d2 != 0, d4 != 0, d6 == 0 */ + tmp2 = MULTIPLY(d2, FIX_0_541196100); + tmp3 = MULTIPLY(d2, FIX_1_306562965); + + tmp0 = d4 << CONST_BITS; + + tmp10 = tmp0 + tmp3; + tmp13 = tmp0 - tmp3; + tmp11 = tmp2 - tmp0; + tmp12 = -(tmp0 + tmp2); + } + } else { + if (d0) { + /* d0 != 0, d2 == 0, d4 != 0, d6 == 0 */ + tmp10 = tmp13 = (d0 + d4) << CONST_BITS; + tmp11 = tmp12 = (d0 - d4) << CONST_BITS; + } else { + /* d0 == 0, d2 == 0, d4 != 0, d6 == 0 */ + tmp10 = tmp13 = d4 << CONST_BITS; + tmp11 = tmp12 = -tmp10; + } + } + } else { + if (d2) { + if (d0) { + /* d0 != 0, d2 != 0, d4 == 0, d6 == 0 */ + tmp2 = MULTIPLY(d2, FIX_0_541196100); + tmp3 = MULTIPLY(d2, FIX_1_306562965); + + tmp0 = d0 << CONST_BITS; + + tmp10 = tmp0 + tmp3; + tmp13 = tmp0 - tmp3; + tmp11 = tmp0 + tmp2; + tmp12 = tmp0 - tmp2; + } else { + /* d0 == 0, d2 != 0, d4 == 0, d6 == 0 */ + tmp2 = MULTIPLY(d2, FIX_0_541196100); + tmp3 = MULTIPLY(d2, FIX_1_306562965); + + tmp10 = tmp3; + tmp13 = -tmp3; + tmp11 = tmp2; + tmp12 = -tmp2; + } + } else { + if (d0) { + /* d0 != 0, d2 == 0, d4 == 0, d6 == 0 */ + tmp10 = tmp13 = tmp11 = tmp12 = d0 << CONST_BITS; + } else { + /* d0 == 0, d2 == 0, d4 == 0, d6 == 0 */ + tmp10 = tmp13 = tmp11 = tmp12 = 0; + } + } + } + } + + /* Odd part per figure 8; the matrix is unitary and hence its + * transpose is its inverse. i0..i3 are y7,y5,y3,y1 respectively. + */ + + if (d7) { + if (d5) { + if (d3) { + if (d1) { + /* d1 != 0, d3 != 0, d5 != 0, d7 != 0 */ + z1 = d7 + d1; + z2 = d5 + d3; + z3 = d7 + d3; + z4 = d5 + d1; + z5 = MULTIPLY(z3 + z4, FIX_1_175875602); + + tmp0 = MULTIPLY(d7, FIX_0_298631336); + tmp1 = MULTIPLY(d5, FIX_2_053119869); + tmp2 = MULTIPLY(d3, FIX_3_072711026); + tmp3 = MULTIPLY(d1, FIX_1_501321110); + z1 = MULTIPLY(-z1, FIX_0_899976223); + z2 = MULTIPLY(-z2, FIX_2_562915447); + z3 = MULTIPLY(-z3, FIX_1_961570560); + z4 = MULTIPLY(-z4, FIX_0_390180644); + + z3 += z5; + z4 += z5; + + tmp0 += z1 + z3; + tmp1 += z2 + z4; + tmp2 += z2 + z3; + tmp3 += z1 + z4; + } else { + /* d1 == 0, d3 != 0, d5 != 0, d7 != 0 */ + z2 = d5 + d3; + z3 = d7 + d3; + z5 = MULTIPLY(z3 + d5, FIX_1_175875602); + + tmp0 = MULTIPLY(d7, FIX_0_298631336); + tmp1 = MULTIPLY(d5, FIX_2_053119869); + tmp2 = MULTIPLY(d3, FIX_3_072711026); + z1 = MULTIPLY(-d7, FIX_0_899976223); + z2 = MULTIPLY(-z2, FIX_2_562915447); + z3 = MULTIPLY(-z3, FIX_1_961570560); + z4 = MULTIPLY(-d5, FIX_0_390180644); + + z3 += z5; + z4 += z5; + + tmp0 += z1 + z3; + tmp1 += z2 + z4; + tmp2 += z2 + z3; + tmp3 = z1 + z4; + } + } else { + if (d1) { + /* d1 != 0, d3 == 0, d5 != 0, d7 != 0 */ + z1 = d7 + d1; + z4 = d5 + d1; + z5 = MULTIPLY(d7 + z4, FIX_1_175875602); + + tmp0 = MULTIPLY(d7, FIX_0_298631336); + tmp1 = MULTIPLY(d5, FIX_2_053119869); + tmp3 = MULTIPLY(d1, FIX_1_501321110); + z1 = MULTIPLY(-z1, FIX_0_899976223); + z2 = MULTIPLY(-d5, FIX_2_562915447); + z3 = MULTIPLY(-d7, FIX_1_961570560); + z4 = MULTIPLY(-z4, FIX_0_390180644); + + z3 += z5; + z4 += z5; + + tmp0 += z1 + z3; + tmp1 += z2 + z4; + tmp2 = z2 + z3; + tmp3 += z1 + z4; + } else { + /* d1 == 0, d3 == 0, d5 != 0, d7 != 0 */ + tmp0 = MULTIPLY(-d7, FIX_0_601344887); + z1 = MULTIPLY(-d7, FIX_0_899976223); + z3 = MULTIPLY(-d7, FIX_1_961570560); + tmp1 = MULTIPLY(-d5, FIX_0_509795579); + z2 = MULTIPLY(-d5, FIX_2_562915447); + z4 = MULTIPLY(-d5, FIX_0_390180644); + z5 = MULTIPLY(d5 + d7, FIX_1_175875602); + + z3 += z5; + z4 += z5; + + tmp0 += z3; + tmp1 += z4; + tmp2 = z2 + z3; + tmp3 = z1 + z4; + } + } + } else { + if (d3) { + if (d1) { + /* d1 != 0, d3 != 0, d5 == 0, d7 != 0 */ + z1 = d7 + d1; + z3 = d7 + d3; + z5 = MULTIPLY(z3 + d1, FIX_1_175875602); + + tmp0 = MULTIPLY(d7, FIX_0_298631336); + tmp2 = MULTIPLY(d3, FIX_3_072711026); + tmp3 = MULTIPLY(d1, FIX_1_501321110); + z1 = MULTIPLY(-z1, FIX_0_899976223); + z2 = MULTIPLY(-d3, FIX_2_562915447); + z3 = MULTIPLY(-z3, FIX_1_961570560); + z4 = MULTIPLY(-d1, FIX_0_390180644); + + z3 += z5; + z4 += z5; + + tmp0 += z1 + z3; + tmp1 = z2 + z4; + tmp2 += z2 + z3; + tmp3 += z1 + z4; + } else { + /* d1 == 0, d3 != 0, d5 == 0, d7 != 0 */ + z3 = d7 + d3; + + tmp0 = MULTIPLY(-d7, FIX_0_601344887); + z1 = MULTIPLY(-d7, FIX_0_899976223); + tmp2 = MULTIPLY(d3, FIX_0_509795579); + z2 = MULTIPLY(-d3, FIX_2_562915447); + z5 = MULTIPLY(z3, FIX_1_175875602); + z3 = MULTIPLY(-z3, FIX_0_785694958); + + tmp0 += z3; + tmp1 = z2 + z5; + tmp2 += z3; + tmp3 = z1 + z5; + } + } else { + if (d1) { + /* d1 != 0, d3 == 0, d5 == 0, d7 != 0 */ + z1 = d7 + d1; + z5 = MULTIPLY(z1, FIX_1_175875602); + + z1 = MULTIPLY(z1, FIX_0_275899380); + z3 = MULTIPLY(-d7, FIX_1_961570560); + tmp0 = MULTIPLY(-d7, FIX_1_662939225); + z4 = MULTIPLY(-d1, FIX_0_390180644); + tmp3 = MULTIPLY(d1, FIX_1_111140466); + + tmp0 += z1; + tmp1 = z4 + z5; + tmp2 = z3 + z5; + tmp3 += z1; + } else { + /* d1 == 0, d3 == 0, d5 == 0, d7 != 0 */ + tmp0 = MULTIPLY(-d7, FIX_1_387039845); + tmp1 = MULTIPLY(d7, FIX_1_175875602); + tmp2 = MULTIPLY(-d7, FIX_0_785694958); + tmp3 = MULTIPLY(d7, FIX_0_275899380); + } + } + } + } else { + if (d5) { + if (d3) { + if (d1) { + /* d1 != 0, d3 != 0, d5 != 0, d7 == 0 */ + z2 = d5 + d3; + z4 = d5 + d1; + z5 = MULTIPLY(d3 + z4, FIX_1_175875602); + + tmp1 = MULTIPLY(d5, FIX_2_053119869); + tmp2 = MULTIPLY(d3, FIX_3_072711026); + tmp3 = MULTIPLY(d1, FIX_1_501321110); + z1 = MULTIPLY(-d1, FIX_0_899976223); + z2 = MULTIPLY(-z2, FIX_2_562915447); + z3 = MULTIPLY(-d3, FIX_1_961570560); + z4 = MULTIPLY(-z4, FIX_0_390180644); + + z3 += z5; + z4 += z5; + + tmp0 = z1 + z3; + tmp1 += z2 + z4; + tmp2 += z2 + z3; + tmp3 += z1 + z4; + } else { + /* d1 == 0, d3 != 0, d5 != 0, d7 == 0 */ + z2 = d5 + d3; + + z5 = MULTIPLY(z2, FIX_1_175875602); + tmp1 = MULTIPLY(d5, FIX_1_662939225); + z4 = MULTIPLY(-d5, FIX_0_390180644); + z2 = MULTIPLY(-z2, FIX_1_387039845); + tmp2 = MULTIPLY(d3, FIX_1_111140466); + z3 = MULTIPLY(-d3, FIX_1_961570560); + + tmp0 = z3 + z5; + tmp1 += z2; + tmp2 += z2; + tmp3 = z4 + z5; + } + } else { + if (d1) { + /* d1 != 0, d3 == 0, d5 != 0, d7 == 0 */ + z4 = d5 + d1; + + z5 = MULTIPLY(z4, FIX_1_175875602); + z1 = MULTIPLY(-d1, FIX_0_899976223); + tmp3 = MULTIPLY(d1, FIX_0_601344887); + tmp1 = MULTIPLY(-d5, FIX_0_509795579); + z2 = MULTIPLY(-d5, FIX_2_562915447); + z4 = MULTIPLY(z4, FIX_0_785694958); + + tmp0 = z1 + z5; + tmp1 += z4; + tmp2 = z2 + z5; + tmp3 += z4; + } else { + /* d1 == 0, d3 == 0, d5 != 0, d7 == 0 */ + tmp0 = MULTIPLY(d5, FIX_1_175875602); + tmp1 = MULTIPLY(d5, FIX_0_275899380); + tmp2 = MULTIPLY(-d5, FIX_1_387039845); + tmp3 = MULTIPLY(d5, FIX_0_785694958); + } + } + } else { + if (d3) { + if (d1) { + /* d1 != 0, d3 != 0, d5 == 0, d7 == 0 */ + z5 = d1 + d3; + tmp3 = MULTIPLY(d1, FIX_0_211164243); + tmp2 = MULTIPLY(-d3, FIX_1_451774981); + z1 = MULTIPLY(d1, FIX_1_061594337); + z2 = MULTIPLY(-d3, FIX_2_172734803); + z4 = MULTIPLY(z5, FIX_0_785694958); + z5 = MULTIPLY(z5, FIX_1_175875602); + + tmp0 = z1 - z4; + tmp1 = z2 + z4; + tmp2 += z5; + tmp3 += z5; + } else { + /* d1 == 0, d3 != 0, d5 == 0, d7 == 0 */ + tmp0 = MULTIPLY(-d3, FIX_0_785694958); + tmp1 = MULTIPLY(-d3, FIX_1_387039845); + tmp2 = MULTIPLY(-d3, FIX_0_275899380); + tmp3 = MULTIPLY(d3, FIX_1_175875602); + } + } else { + if (d1) { + /* d1 != 0, d3 == 0, d5 == 0, d7 == 0 */ + tmp0 = MULTIPLY(d1, FIX_0_275899380); + tmp1 = MULTIPLY(d1, FIX_0_785694958); + tmp2 = MULTIPLY(d1, FIX_1_175875602); + tmp3 = MULTIPLY(d1, FIX_1_387039845); + } else { + /* d1 == 0, d3 == 0, d5 == 0, d7 == 0 */ + tmp0 = tmp1 = tmp2 = tmp3 = 0; + } + } + } + } +} + /* Final output stage: inputs are tmp10..tmp13, tmp0..tmp3 */ + + dataptr[0] = (DCTELEM) DESCALE(tmp10 + tmp3, CONST_BITS-PASS1_BITS); + dataptr[7] = (DCTELEM) DESCALE(tmp10 - tmp3, CONST_BITS-PASS1_BITS); + dataptr[1] = (DCTELEM) DESCALE(tmp11 + tmp2, CONST_BITS-PASS1_BITS); + dataptr[6] = (DCTELEM) DESCALE(tmp11 - tmp2, CONST_BITS-PASS1_BITS); + dataptr[2] = (DCTELEM) DESCALE(tmp12 + tmp1, CONST_BITS-PASS1_BITS); + dataptr[5] = (DCTELEM) DESCALE(tmp12 - tmp1, CONST_BITS-PASS1_BITS); + dataptr[3] = (DCTELEM) DESCALE(tmp13 + tmp0, CONST_BITS-PASS1_BITS); + dataptr[4] = (DCTELEM) DESCALE(tmp13 - tmp0, CONST_BITS-PASS1_BITS); + + dataptr += DCTSIZE; /* advance pointer to next row */ + } + + /* Pass 2: process columns. */ + /* Note that we must descale the results by a factor of 8 == 2**3, */ + /* and also undo the PASS1_BITS scaling. */ + + dataptr = data; + for (rowctr = DCTSIZE-1; rowctr >= 0; rowctr--) { + /* Columns of zeroes can be exploited in the same way as we did with rows. + * However, the row calculation has created many nonzero AC terms, so the + * simplification applies less often (typically 5% to 10% of the time). + * On machines with very fast multiplication, it's possible that the + * test takes more time than it's worth. In that case this section + * may be commented out. + */ + + d0 = dataptr[DCTSIZE*0]; + d1 = dataptr[DCTSIZE*1]; + d2 = dataptr[DCTSIZE*2]; + d3 = dataptr[DCTSIZE*3]; + d4 = dataptr[DCTSIZE*4]; + d5 = dataptr[DCTSIZE*5]; + d6 = dataptr[DCTSIZE*6]; + d7 = dataptr[DCTSIZE*7]; + + /* Even part: reverse the even part of the forward DCT. */ + /* The rotator is sqrt(2)*c(-6). */ + if (d6) { + if (d4) { + if (d2) { + if (d0) { + /* d0 != 0, d2 != 0, d4 != 0, d6 != 0 */ + z1 = MULTIPLY(d2 + d6, FIX_0_541196100); + tmp2 = z1 + MULTIPLY(-d6, FIX_1_847759065); + tmp3 = z1 + MULTIPLY(d2, FIX_0_765366865); + + tmp0 = (d0 + d4) << CONST_BITS; + tmp1 = (d0 - d4) << CONST_BITS; + + tmp10 = tmp0 + tmp3; + tmp13 = tmp0 - tmp3; + tmp11 = tmp1 + tmp2; + tmp12 = tmp1 - tmp2; + } else { + /* d0 == 0, d2 != 0, d4 != 0, d6 != 0 */ + z1 = MULTIPLY(d2 + d6, FIX_0_541196100); + tmp2 = z1 + MULTIPLY(-d6, FIX_1_847759065); + tmp3 = z1 + MULTIPLY(d2, FIX_0_765366865); + + tmp0 = d4 << CONST_BITS; + + tmp10 = tmp0 + tmp3; + tmp13 = tmp0 - tmp3; + tmp11 = tmp2 - tmp0; + tmp12 = -(tmp0 + tmp2); + } + } else { + if (d0) { + /* d0 != 0, d2 == 0, d4 != 0, d6 != 0 */ + tmp2 = MULTIPLY(-d6, FIX_1_306562965); + tmp3 = MULTIPLY(d6, FIX_0_541196100); + + tmp0 = (d0 + d4) << CONST_BITS; + tmp1 = (d0 - d4) << CONST_BITS; + + tmp10 = tmp0 + tmp3; + tmp13 = tmp0 - tmp3; + tmp11 = tmp1 + tmp2; + tmp12 = tmp1 - tmp2; + } else { + /* d0 == 0, d2 == 0, d4 != 0, d6 != 0 */ + tmp2 = MULTIPLY(-d6, FIX_1_306562965); + tmp3 = MULTIPLY(d6, FIX_0_541196100); + + tmp0 = d4 << CONST_BITS; + + tmp10 = tmp0 + tmp3; + tmp13 = tmp0 - tmp3; + tmp11 = tmp2 - tmp0; + tmp12 = -(tmp0 + tmp2); + } + } + } else { + if (d2) { + if (d0) { + /* d0 != 0, d2 != 0, d4 == 0, d6 != 0 */ + z1 = MULTIPLY(d2 + d6, FIX_0_541196100); + tmp2 = z1 + MULTIPLY(-d6, FIX_1_847759065); + tmp3 = z1 + MULTIPLY(d2, FIX_0_765366865); + + tmp0 = d0 << CONST_BITS; + + tmp10 = tmp0 + tmp3; + tmp13 = tmp0 - tmp3; + tmp11 = tmp0 + tmp2; + tmp12 = tmp0 - tmp2; + } else { + /* d0 == 0, d2 != 0, d4 == 0, d6 != 0 */ + z1 = MULTIPLY(d2 + d6, FIX_0_541196100); + tmp2 = z1 + MULTIPLY(-d6, FIX_1_847759065); + tmp3 = z1 + MULTIPLY(d2, FIX_0_765366865); + + tmp10 = tmp3; + tmp13 = -tmp3; + tmp11 = tmp2; + tmp12 = -tmp2; + } + } else { + if (d0) { + /* d0 != 0, d2 == 0, d4 == 0, d6 != 0 */ + tmp2 = MULTIPLY(-d6, FIX_1_306562965); + tmp3 = MULTIPLY(d6, FIX_0_541196100); + + tmp0 = d0 << CONST_BITS; + + tmp10 = tmp0 + tmp3; + tmp13 = tmp0 - tmp3; + tmp11 = tmp0 + tmp2; + tmp12 = tmp0 - tmp2; + } else { + /* d0 == 0, d2 == 0, d4 == 0, d6 != 0 */ + tmp2 = MULTIPLY(-d6, FIX_1_306562965); + tmp3 = MULTIPLY(d6, FIX_0_541196100); + + tmp10 = tmp3; + tmp13 = -tmp3; + tmp11 = tmp2; + tmp12 = -tmp2; + } + } + } + } else { + if (d4) { + if (d2) { + if (d0) { + /* d0 != 0, d2 != 0, d4 != 0, d6 == 0 */ + tmp2 = MULTIPLY(d2, FIX_0_541196100); + tmp3 = MULTIPLY(d2, FIX_1_306562965); + + tmp0 = (d0 + d4) << CONST_BITS; + tmp1 = (d0 - d4) << CONST_BITS; + + tmp10 = tmp0 + tmp3; + tmp13 = tmp0 - tmp3; + tmp11 = tmp1 + tmp2; + tmp12 = tmp1 - tmp2; + } else { + /* d0 == 0, d2 != 0, d4 != 0, d6 == 0 */ + tmp2 = MULTIPLY(d2, FIX_0_541196100); + tmp3 = MULTIPLY(d2, FIX_1_306562965); + + tmp0 = d4 << CONST_BITS; + + tmp10 = tmp0 + tmp3; + tmp13 = tmp0 - tmp3; + tmp11 = tmp2 - tmp0; + tmp12 = -(tmp0 + tmp2); + } + } else { + if (d0) { + /* d0 != 0, d2 == 0, d4 != 0, d6 == 0 */ + tmp10 = tmp13 = (d0 + d4) << CONST_BITS; + tmp11 = tmp12 = (d0 - d4) << CONST_BITS; + } else { + /* d0 == 0, d2 == 0, d4 != 0, d6 == 0 */ + tmp10 = tmp13 = d4 << CONST_BITS; + tmp11 = tmp12 = -tmp10; + } + } + } else { + if (d2) { + if (d0) { + /* d0 != 0, d2 != 0, d4 == 0, d6 == 0 */ + tmp2 = MULTIPLY(d2, FIX_0_541196100); + tmp3 = MULTIPLY(d2, FIX_1_306562965); + + tmp0 = d0 << CONST_BITS; + + tmp10 = tmp0 + tmp3; + tmp13 = tmp0 - tmp3; + tmp11 = tmp0 + tmp2; + tmp12 = tmp0 - tmp2; + } else { + /* d0 == 0, d2 != 0, d4 == 0, d6 == 0 */ + tmp2 = MULTIPLY(d2, FIX_0_541196100); + tmp3 = MULTIPLY(d2, FIX_1_306562965); + + tmp10 = tmp3; + tmp13 = -tmp3; + tmp11 = tmp2; + tmp12 = -tmp2; + } + } else { + if (d0) { + /* d0 != 0, d2 == 0, d4 == 0, d6 == 0 */ + tmp10 = tmp13 = tmp11 = tmp12 = d0 << CONST_BITS; + } else { + /* d0 == 0, d2 == 0, d4 == 0, d6 == 0 */ + tmp10 = tmp13 = tmp11 = tmp12 = 0; + } + } + } + } + + /* Odd part per figure 8; the matrix is unitary and hence its + * transpose is its inverse. i0..i3 are y7,y5,y3,y1 respectively. + */ + if (d7) { + if (d5) { + if (d3) { + if (d1) { + /* d1 != 0, d3 != 0, d5 != 0, d7 != 0 */ + z1 = d7 + d1; + z2 = d5 + d3; + z3 = d7 + d3; + z4 = d5 + d1; + z5 = MULTIPLY(z3 + z4, FIX_1_175875602); + + tmp0 = MULTIPLY(d7, FIX_0_298631336); + tmp1 = MULTIPLY(d5, FIX_2_053119869); + tmp2 = MULTIPLY(d3, FIX_3_072711026); + tmp3 = MULTIPLY(d1, FIX_1_501321110); + z1 = MULTIPLY(-z1, FIX_0_899976223); + z2 = MULTIPLY(-z2, FIX_2_562915447); + z3 = MULTIPLY(-z3, FIX_1_961570560); + z4 = MULTIPLY(-z4, FIX_0_390180644); + + z3 += z5; + z4 += z5; + + tmp0 += z1 + z3; + tmp1 += z2 + z4; + tmp2 += z2 + z3; + tmp3 += z1 + z4; + } else { + /* d1 == 0, d3 != 0, d5 != 0, d7 != 0 */ + z1 = d7; + z2 = d5 + d3; + z3 = d7 + d3; + z5 = MULTIPLY(z3 + d5, FIX_1_175875602); + + tmp0 = MULTIPLY(d7, FIX_0_298631336); + tmp1 = MULTIPLY(d5, FIX_2_053119869); + tmp2 = MULTIPLY(d3, FIX_3_072711026); + z1 = MULTIPLY(-d7, FIX_0_899976223); + z2 = MULTIPLY(-z2, FIX_2_562915447); + z3 = MULTIPLY(-z3, FIX_1_961570560); + z4 = MULTIPLY(-d5, FIX_0_390180644); + + z3 += z5; + z4 += z5; + + tmp0 += z1 + z3; + tmp1 += z2 + z4; + tmp2 += z2 + z3; + tmp3 = z1 + z4; + } + } else { + if (d1) { + /* d1 != 0, d3 == 0, d5 != 0, d7 != 0 */ + z1 = d7 + d1; + z2 = d5; + z3 = d7; + z4 = d5 + d1; + z5 = MULTIPLY(z3 + z4, FIX_1_175875602); + + tmp0 = MULTIPLY(d7, FIX_0_298631336); + tmp1 = MULTIPLY(d5, FIX_2_053119869); + tmp3 = MULTIPLY(d1, FIX_1_501321110); + z1 = MULTIPLY(-z1, FIX_0_899976223); + z2 = MULTIPLY(-d5, FIX_2_562915447); + z3 = MULTIPLY(-d7, FIX_1_961570560); + z4 = MULTIPLY(-z4, FIX_0_390180644); + + z3 += z5; + z4 += z5; + + tmp0 += z1 + z3; + tmp1 += z2 + z4; + tmp2 = z2 + z3; + tmp3 += z1 + z4; + } else { + /* d1 == 0, d3 == 0, d5 != 0, d7 != 0 */ + tmp0 = MULTIPLY(-d7, FIX_0_601344887); + z1 = MULTIPLY(-d7, FIX_0_899976223); + z3 = MULTIPLY(-d7, FIX_1_961570560); + tmp1 = MULTIPLY(-d5, FIX_0_509795579); + z2 = MULTIPLY(-d5, FIX_2_562915447); + z4 = MULTIPLY(-d5, FIX_0_390180644); + z5 = MULTIPLY(d5 + d7, FIX_1_175875602); + + z3 += z5; + z4 += z5; + + tmp0 += z3; + tmp1 += z4; + tmp2 = z2 + z3; + tmp3 = z1 + z4; + } + } + } else { + if (d3) { + if (d1) { + /* d1 != 0, d3 != 0, d5 == 0, d7 != 0 */ + z1 = d7 + d1; + z3 = d7 + d3; + z5 = MULTIPLY(z3 + d1, FIX_1_175875602); + + tmp0 = MULTIPLY(d7, FIX_0_298631336); + tmp2 = MULTIPLY(d3, FIX_3_072711026); + tmp3 = MULTIPLY(d1, FIX_1_501321110); + z1 = MULTIPLY(-z1, FIX_0_899976223); + z2 = MULTIPLY(-d3, FIX_2_562915447); + z3 = MULTIPLY(-z3, FIX_1_961570560); + z4 = MULTIPLY(-d1, FIX_0_390180644); + + z3 += z5; + z4 += z5; + + tmp0 += z1 + z3; + tmp1 = z2 + z4; + tmp2 += z2 + z3; + tmp3 += z1 + z4; + } else { + /* d1 == 0, d3 != 0, d5 == 0, d7 != 0 */ + z3 = d7 + d3; + + tmp0 = MULTIPLY(-d7, FIX_0_601344887); + z1 = MULTIPLY(-d7, FIX_0_899976223); + tmp2 = MULTIPLY(d3, FIX_0_509795579); + z2 = MULTIPLY(-d3, FIX_2_562915447); + z5 = MULTIPLY(z3, FIX_1_175875602); + z3 = MULTIPLY(-z3, FIX_0_785694958); + + tmp0 += z3; + tmp1 = z2 + z5; + tmp2 += z3; + tmp3 = z1 + z5; + } + } else { + if (d1) { + /* d1 != 0, d3 == 0, d5 == 0, d7 != 0 */ + z1 = d7 + d1; + z5 = MULTIPLY(z1, FIX_1_175875602); + + z1 = MULTIPLY(z1, FIX_0_275899380); + z3 = MULTIPLY(-d7, FIX_1_961570560); + tmp0 = MULTIPLY(-d7, FIX_1_662939225); + z4 = MULTIPLY(-d1, FIX_0_390180644); + tmp3 = MULTIPLY(d1, FIX_1_111140466); + + tmp0 += z1; + tmp1 = z4 + z5; + tmp2 = z3 + z5; + tmp3 += z1; + } else { + /* d1 == 0, d3 == 0, d5 == 0, d7 != 0 */ + tmp0 = MULTIPLY(-d7, FIX_1_387039845); + tmp1 = MULTIPLY(d7, FIX_1_175875602); + tmp2 = MULTIPLY(-d7, FIX_0_785694958); + tmp3 = MULTIPLY(d7, FIX_0_275899380); + } + } + } + } else { + if (d5) { + if (d3) { + if (d1) { + /* d1 != 0, d3 != 0, d5 != 0, d7 == 0 */ + z2 = d5 + d3; + z4 = d5 + d1; + z5 = MULTIPLY(d3 + z4, FIX_1_175875602); + + tmp1 = MULTIPLY(d5, FIX_2_053119869); + tmp2 = MULTIPLY(d3, FIX_3_072711026); + tmp3 = MULTIPLY(d1, FIX_1_501321110); + z1 = MULTIPLY(-d1, FIX_0_899976223); + z2 = MULTIPLY(-z2, FIX_2_562915447); + z3 = MULTIPLY(-d3, FIX_1_961570560); + z4 = MULTIPLY(-z4, FIX_0_390180644); + + z3 += z5; + z4 += z5; + + tmp0 = z1 + z3; + tmp1 += z2 + z4; + tmp2 += z2 + z3; + tmp3 += z1 + z4; + } else { + /* d1 == 0, d3 != 0, d5 != 0, d7 == 0 */ + z2 = d5 + d3; + + z5 = MULTIPLY(z2, FIX_1_175875602); + tmp1 = MULTIPLY(d5, FIX_1_662939225); + z4 = MULTIPLY(-d5, FIX_0_390180644); + z2 = MULTIPLY(-z2, FIX_1_387039845); + tmp2 = MULTIPLY(d3, FIX_1_111140466); + z3 = MULTIPLY(-d3, FIX_1_961570560); + + tmp0 = z3 + z5; + tmp1 += z2; + tmp2 += z2; + tmp3 = z4 + z5; + } + } else { + if (d1) { + /* d1 != 0, d3 == 0, d5 != 0, d7 == 0 */ + z4 = d5 + d1; + + z5 = MULTIPLY(z4, FIX_1_175875602); + z1 = MULTIPLY(-d1, FIX_0_899976223); + tmp3 = MULTIPLY(d1, FIX_0_601344887); + tmp1 = MULTIPLY(-d5, FIX_0_509795579); + z2 = MULTIPLY(-d5, FIX_2_562915447); + z4 = MULTIPLY(z4, FIX_0_785694958); + + tmp0 = z1 + z5; + tmp1 += z4; + tmp2 = z2 + z5; + tmp3 += z4; + } else { + /* d1 == 0, d3 == 0, d5 != 0, d7 == 0 */ + tmp0 = MULTIPLY(d5, FIX_1_175875602); + tmp1 = MULTIPLY(d5, FIX_0_275899380); + tmp2 = MULTIPLY(-d5, FIX_1_387039845); + tmp3 = MULTIPLY(d5, FIX_0_785694958); + } + } + } else { + if (d3) { + if (d1) { + /* d1 != 0, d3 != 0, d5 == 0, d7 == 0 */ + z5 = d1 + d3; + tmp3 = MULTIPLY(d1, FIX_0_211164243); + tmp2 = MULTIPLY(-d3, FIX_1_451774981); + z1 = MULTIPLY(d1, FIX_1_061594337); + z2 = MULTIPLY(-d3, FIX_2_172734803); + z4 = MULTIPLY(z5, FIX_0_785694958); + z5 = MULTIPLY(z5, FIX_1_175875602); + + tmp0 = z1 - z4; + tmp1 = z2 + z4; + tmp2 += z5; + tmp3 += z5; + } else { + /* d1 == 0, d3 != 0, d5 == 0, d7 == 0 */ + tmp0 = MULTIPLY(-d3, FIX_0_785694958); + tmp1 = MULTIPLY(-d3, FIX_1_387039845); + tmp2 = MULTIPLY(-d3, FIX_0_275899380); + tmp3 = MULTIPLY(d3, FIX_1_175875602); + } + } else { + if (d1) { + /* d1 != 0, d3 == 0, d5 == 0, d7 == 0 */ + tmp0 = MULTIPLY(d1, FIX_0_275899380); + tmp1 = MULTIPLY(d1, FIX_0_785694958); + tmp2 = MULTIPLY(d1, FIX_1_175875602); + tmp3 = MULTIPLY(d1, FIX_1_387039845); + } else { + /* d1 == 0, d3 == 0, d5 == 0, d7 == 0 */ + tmp0 = tmp1 = tmp2 = tmp3 = 0; + } + } + } + } + + /* Final output stage: inputs are tmp10..tmp13, tmp0..tmp3 */ + + dataptr[DCTSIZE*0] = (DCTELEM) DESCALE(tmp10 + tmp3, + CONST_BITS+PASS1_BITS+3); + dataptr[DCTSIZE*7] = (DCTELEM) DESCALE(tmp10 - tmp3, + CONST_BITS+PASS1_BITS+3); + dataptr[DCTSIZE*1] = (DCTELEM) DESCALE(tmp11 + tmp2, + CONST_BITS+PASS1_BITS+3); + dataptr[DCTSIZE*6] = (DCTELEM) DESCALE(tmp11 - tmp2, + CONST_BITS+PASS1_BITS+3); + dataptr[DCTSIZE*2] = (DCTELEM) DESCALE(tmp12 + tmp1, + CONST_BITS+PASS1_BITS+3); + dataptr[DCTSIZE*5] = (DCTELEM) DESCALE(tmp12 - tmp1, + CONST_BITS+PASS1_BITS+3); + dataptr[DCTSIZE*3] = (DCTELEM) DESCALE(tmp13 + tmp0, + CONST_BITS+PASS1_BITS+3); + dataptr[DCTSIZE*4] = (DCTELEM) DESCALE(tmp13 - tmp0, + CONST_BITS+PASS1_BITS+3); + + dataptr++; /* advance pointer to next column */ + } +} + + +/* here is the reference one, in case of problems with the normal one */ + +/* idctref.c, Inverse Discrete Fourier Transform, double precision */ + +/* Copyright (C) 1994, 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. + * + */ + +/* Perform IEEE 1180 reference (64-bit floating point, separable 8x1 + * direct matrix multiply) Inverse Discrete Cosine Transform +*/ + + +/* Here we use math.h to generate constants. Compiler results may + vary a little */ + +#ifndef PI +#ifdef M_PI +#define PI M_PI +#else +#define PI 3.14159265358979323846 +#endif +#endif + +/* cosine transform matrix for 8x1 IDCT */ +static double itrans_coef[8][8]; + +/* initialize DCT coefficient matrix */ + +void init_idctref() +{ + int freq, time; + double scale; + + for (freq=0; freq < 8; freq++) + { + scale = (freq == 0) ? sqrt(0.125) : 0.5; + for (time=0; time<8; time++) + itrans_coef[freq][time] = scale*cos((PI/8.0)*freq*(time + 0.5)); + } +} + +/* perform IDCT matrix multiply for 8x8 coefficient block */ + +void reference_rev_dct(block) +int16 *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+= itrans_coef[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+= itrans_coef[k][i]*tmp[8*k+j]; + + v = floor(partial_product+0.5); + block[8*i+j] = (v<-256) ? -256 : ((v>255) ? 255 : v); + } +} |