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## ffmpeg / libavcodec / jrevdct.c @ 8a01fc47

 1 ```/* ``` ``` * 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. ``` ``` */ ``` ``` ``` ```/** ``` ``` * @file jrevdct.c ``` ``` * Independent JPEG Group's LLM idct. ``` ``` */ ``` ``` ``` ```#include "common.h" ``` ```#include "dsputil.h" ``` ```#define EIGHT_BIT_SAMPLES ``` ```#define DCTSIZE 8 ``` ```#define DCTSIZE2 64 ``` ```#define GLOBAL ``` ```#define RIGHT_SHIFT(x, n) ((x) >> (n)) ``` ```typedef DCTELEM DCTBLOCK[DCTSIZE2]; ``` ```#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_t) 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_t) ((x) * CONST_SCALE + 0.5)) ``` ```/* Descale and correctly round an int32_t 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_t variable by an int32_t constant to yield an int32_t 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_t) (var)) * ((int16_t) (const))) ``` ```#endif ``` ```#ifdef SHORTxLCONST_32 /* known to work with Microsoft C 6.0 */ ``` ```#define MULTIPLY(var,const) (((int16_t) (var)) * ((int32_t) (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 ``` ```/* ``` ``` * Perform the inverse DCT on one block of coefficients. ``` ``` */ ``` ```void j_rev_dct(DCTBLOCK data) ``` ```{ ``` ``` int32_t tmp0, tmp1, tmp2, tmp3; ``` ``` int32_t tmp10, tmp11, tmp12, tmp13; ``` ``` int32_t z1, z2, z3, z4, z5; ``` ``` int32_t d0, d1, d2, d3, d4, d5, d6, d7; ``` ``` register DCTELEM *dataptr; ``` ``` int rowctr; ``` ``` ``` ``` /* 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; ``` ``` /* WARNING: we do the same permutation as MMX idct to simplify the ``` ``` video core */ ``` ``` d0 = dataptr[0]; ``` ``` d2 = dataptr[1]; ``` ``` d4 = dataptr[2]; ``` ``` d6 = dataptr[3]; ``` ``` d1 = dataptr[4]; ``` ``` d3 = dataptr[5]; ``` ``` d5 = dataptr[6]; ``` ``` d7 = dataptr[7]; ``` ``` if ((d1 | d2 | d3 | d4 | d5 | d6 | d7) == 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; ``` ``` } ``` ``` /* Even part: reverse the even part of the forward DCT. */ ``` ``` /* The rotator is sqrt(2)*c(-6). */ ``` ```{ ``` ``` if (d6) { ``` ``` if (d2) { ``` ``` /* 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 */ ``` ``` 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 { ``` ``` if (d2) { ``` ``` /* 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 */ ``` ``` tmp10 = tmp13 = (d0 + d4) << CONST_BITS; ``` ``` tmp11 = tmp12 = (d0 - d4) << CONST_BITS; ``` ``` } ``` ``` } ``` ``` /* 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 (d2) { ``` ``` /* 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 */ ``` ``` 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 { ``` ``` if (d2) { ``` ``` /* 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 */ ``` ``` tmp10 = tmp13 = (d0 + d4) << CONST_BITS; ``` ``` tmp11 = tmp12 = (d0 - d4) << CONST_BITS; ``` ``` } ``` ``` } ``` ``` /* 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 */ ``` ``` } ``` ```} ``` ```#undef DCTSIZE ``` ```#define DCTSIZE 4 ``` ```#define DCTSTRIDE 8 ``` ```void j_rev_dct4(DCTBLOCK data) ``` ```{ ``` ``` int32_t tmp0, tmp1, tmp2, tmp3; ``` ``` int32_t tmp10, tmp11, tmp12, tmp13; ``` ``` int32_t z1; ``` ``` int32_t d0, d2, d4, d6; ``` ``` register DCTELEM *dataptr; ``` ``` int rowctr; ``` ``` /* 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. */ ``` ``` data[0] += 4; ``` ``` ``` ``` 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]; ``` ``` d2 = dataptr[1]; ``` ``` d4 = dataptr[2]; ``` ``` d6 = dataptr[3]; ``` ``` if ((d2 | d4 | d6) == 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; ``` ``` } ``` ``` ``` ``` dataptr += DCTSTRIDE; /* advance pointer to next row */ ``` ``` continue; ``` ``` } ``` ``` ``` ``` /* Even part: reverse the even part of the forward DCT. */ ``` ``` /* The rotator is sqrt(2)*c(-6). */ ``` ``` if (d6) { ``` ``` if (d2) { ``` ``` /* 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 */ ``` ``` 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 { ``` ``` if (d2) { ``` ``` /* 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 */ ``` ``` tmp10 = tmp13 = (d0 + d4) << CONST_BITS; ``` ``` tmp11 = tmp12 = (d0 - d4) << CONST_BITS; ``` ``` } ``` ``` } ``` ``` /* Final output stage: inputs are tmp10..tmp13, tmp0..tmp3 */ ``` ``` dataptr[0] = (DCTELEM) DESCALE(tmp10, CONST_BITS-PASS1_BITS); ``` ``` dataptr[1] = (DCTELEM) DESCALE(tmp11, CONST_BITS-PASS1_BITS); ``` ``` dataptr[2] = (DCTELEM) DESCALE(tmp12, CONST_BITS-PASS1_BITS); ``` ``` dataptr[3] = (DCTELEM) DESCALE(tmp13, CONST_BITS-PASS1_BITS); ``` ``` dataptr += DCTSTRIDE; /* 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[DCTSTRIDE*0]; ``` ``` d2 = dataptr[DCTSTRIDE*1]; ``` ``` d4 = dataptr[DCTSTRIDE*2]; ``` ``` d6 = dataptr[DCTSTRIDE*3]; ``` ``` /* Even part: reverse the even part of the forward DCT. */ ``` ``` /* The rotator is sqrt(2)*c(-6). */ ``` ``` if (d6) { ``` ``` if (d2) { ``` ``` /* 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 */ ``` ``` 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 { ``` ``` if (d2) { ``` ``` /* 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 */ ``` ``` tmp10 = tmp13 = (d0 + d4) << CONST_BITS; ``` ``` tmp11 = tmp12 = (d0 - d4) << CONST_BITS; ``` ``` } ``` ``` } ``` ``` /* Final output stage: inputs are tmp10..tmp13, tmp0..tmp3 */ ``` ``` dataptr[DCTSTRIDE*0] = tmp10 >> (CONST_BITS+PASS1_BITS+3); ``` ``` dataptr[DCTSTRIDE*1] = tmp11 >> (CONST_BITS+PASS1_BITS+3); ``` ``` dataptr[DCTSTRIDE*2] = tmp12 >> (CONST_BITS+PASS1_BITS+3); ``` ``` dataptr[DCTSTRIDE*3] = tmp13 >> (CONST_BITS+PASS1_BITS+3); ``` ``` ``` ``` dataptr++; /* advance pointer to next column */ ``` ``` } ``` ```} ``` ```void j_rev_dct2(DCTBLOCK data){ ``` ``` int d00, d01, d10, d11; ``` ``` data[0] += 4; ``` ``` d00 = data[0+0*DCTSTRIDE] + data[1+0*DCTSTRIDE]; ``` ``` d01 = data[0+0*DCTSTRIDE] - data[1+0*DCTSTRIDE]; ``` ``` d10 = data[0+1*DCTSTRIDE] + data[1+1*DCTSTRIDE]; ``` ``` d11 = data[0+1*DCTSTRIDE] - data[1+1*DCTSTRIDE]; ``` ``` ``` ``` data[0+0*DCTSTRIDE]= (d00 + d10)>>3; ``` ``` data[1+0*DCTSTRIDE]= (d01 + d11)>>3; ``` ``` data[0+1*DCTSTRIDE]= (d00 - d10)>>3; ``` ``` data[1+1*DCTSTRIDE]= (d01 - d11)>>3; ``` ```} ``` ```void j_rev_dct1(DCTBLOCK data){ ``` ``` data[0] = (data[0] + 4)>>3; ``` ```} ``` ```#undef FIX ``` ```#undef CONST_BITS ```