jrevdct.c
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- /*
- * jrevdct.c
- *
- * This file is part of the Independent JPEG Group's software.
- *
- * The authors make NO WARRANTY or representation, either express or implied,
- * with respect to this software, its quality, accuracy, merchantability, or
- * fitness for a particular purpose. This software is provided "AS IS", and
- * you, its user, assume the entire risk as to its quality and accuracy.
- *
- * This software is copyright (C) 1991, 1992, Thomas G. Lane.
- * All Rights Reserved except as specified below.
- *
- * Permission is hereby granted to use, copy, modify, and distribute this
- * software (or portions thereof) for any purpose, without fee, subject to
- * these conditions:
- * (1) If any part of the source code for this software is distributed, then
- * this README file must be included, with this copyright and no-warranty
- * notice unaltered; and any additions, deletions, or changes to the original
- * files must be clearly indicated in accompanying documentation.
- * (2) If only executable code is distributed, then the accompanying
- * documentation must state that "this software is based in part on the work
- * of the Independent JPEG Group".
- * (3) Permission for use of this software is granted only if the user accepts
- * full responsibility for any undesirable consequences; the authors accept
- * NO LIABILITY for damages of any kind.
- *
- * These conditions apply to any software derived from or based on the IJG
- * code, not just to the unmodified library. If you use our work, you ought
- * to acknowledge us.
- *
- * Permission is NOT granted for the use of any IJG author's name or company
- * name in advertising or publicity relating to this software or products
- * derived from it. This software may be referred to only as "the Independent
- * JPEG Group's software".
- *
- * We specifically permit and encourage the use of this software as the basis
- * of commercial products, provided that all warranty or liability claims are
- * assumed by the product vendor.
- *
- * 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 "dsputil.h"
- //#include "internal.h"
- //#include "integer.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