136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane/*
236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * jidctfst.c
336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane *
45ead57a34a398aa798f35bd7a6abad19b2e453e2Thomas G. Lane * Copyright (C) 1994-1998, Thomas G. Lane.
536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * This file is part of the Independent JPEG Group's software.
636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * For conditions of distribution and use, see the accompanying README file.
736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane *
836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * This file contains a fast, not so accurate integer implementation of the
936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * inverse DCT (Discrete Cosine Transform).  In the IJG code, this routine
1036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * must also perform dequantization of the input coefficients.
1136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane *
1236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * A 2-D IDCT can be done by 1-D IDCT on each column followed by 1-D IDCT
1336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * on each row (or vice versa, but it's more convenient to emit a row at
1436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * a time).  Direct algorithms are also available, but they are much more
1536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * complex and seem not to be any faster when reduced to code.
1636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane *
1736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * This implementation is based on Arai, Agui, and Nakajima's algorithm for
1836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * scaled DCT.  Their original paper (Trans. IEICE E-71(11):1095) is in
1936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * Japanese, but the algorithm is described in the Pennebaker & Mitchell
2036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * JPEG textbook (see REFERENCES section in file README).  The following code
2136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * is based directly on figure 4-8 in P&M.
2236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * While an 8-point DCT cannot be done in less than 11 multiplies, it is
2336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * possible to arrange the computation so that many of the multiplies are
2436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * simple scalings of the final outputs.  These multiplies can then be
2536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * folded into the multiplications or divisions by the JPEG quantization
2636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * table entries.  The AA&N method leaves only 5 multiplies and 29 adds
2736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * to be done in the DCT itself.
2836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * The primary disadvantage of this method is that with fixed-point math,
2936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * accuracy is lost due to imprecise representation of the scaled
3036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * quantization values.  The smaller the quantization table entry, the less
3136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * precise the scaled value, so this implementation does worse with high-
3236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * quality-setting files than with low-quality ones.
3336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane */
3436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
3536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#define JPEG_INTERNALS
3636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#include "jinclude.h"
3736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#include "jpeglib.h"
38e5eaf37440b8e337ab150c017df7c03faf846c51DRC#include "jdct.h"               /* Private declarations for DCT subsystem */
3936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
4036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#ifdef DCT_IFAST_SUPPORTED
4136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
4236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
4336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane/*
4436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * This module is specialized to the case DCTSIZE = 8.
4536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane */
4636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
4736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#if DCTSIZE != 8
4836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane  Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
4936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#endif
5036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
5136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
5236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane/* Scaling decisions are generally the same as in the LL&M algorithm;
5336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * see jidctint.c for more details.  However, we choose to descale
5436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * (right shift) multiplication products as soon as they are formed,
5536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * rather than carrying additional fractional bits into subsequent additions.
5636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * This compromises accuracy slightly, but it lets us save a few shifts.
5736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * More importantly, 16-bit arithmetic is then adequate (for 8-bit samples)
5836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * everywhere except in the multiplications proper; this saves a good deal
5936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * of work on 16-bit-int machines.
6036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane *
6136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * The dequantized coefficients are not integers because the AA&N scaling
6236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * factors have been incorporated.  We represent them scaled up by PASS1_BITS,
6336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * so that the first and second IDCT rounds have the same input scaling.
6436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * For 8-bit JSAMPLEs, we choose IFAST_SCALE_BITS = PASS1_BITS so as to
6536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * avoid a descaling shift; this compromises accuracy rather drastically
6636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * for small quantization table entries, but it saves a lot of shifts.
6736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * For 12-bit JSAMPLEs, there's no hope of using 16x16 multiplies anyway,
6836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * so we use a much larger scaling factor to preserve accuracy.
6936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane *
7036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * A final compromise is to represent the multiplicative constants to only
7136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * 8 fractional bits, rather than 13.  This saves some shifting work on some
7236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * machines, and may also reduce the cost of multiplication (since there
7336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * are fewer one-bits in the constants).
7436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane */
7536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
7636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#if BITS_IN_JSAMPLE == 8
7736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#define CONST_BITS  8
7836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#define PASS1_BITS  2
7936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#else
8036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#define CONST_BITS  8
81e5eaf37440b8e337ab150c017df7c03faf846c51DRC#define PASS1_BITS  1           /* lose a little precision to avoid overflow */
8236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#endif
8336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
8436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane/* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
8536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * causing a lot of useless floating-point operations at run time.
8636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * To get around this we use the following pre-calculated constants.
8736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * If you change CONST_BITS you may want to add appropriate values.
8836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * (With a reasonable C compiler, you can just rely on the FIX() macro...)
8936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane */
9036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
9136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#if CONST_BITS == 8
92e5eaf37440b8e337ab150c017df7c03faf846c51DRC#define FIX_1_082392200  ((INT32)  277)         /* FIX(1.082392200) */
93e5eaf37440b8e337ab150c017df7c03faf846c51DRC#define FIX_1_414213562  ((INT32)  362)         /* FIX(1.414213562) */
94e5eaf37440b8e337ab150c017df7c03faf846c51DRC#define FIX_1_847759065  ((INT32)  473)         /* FIX(1.847759065) */
95e5eaf37440b8e337ab150c017df7c03faf846c51DRC#define FIX_2_613125930  ((INT32)  669)         /* FIX(2.613125930) */
9636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#else
9736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#define FIX_1_082392200  FIX(1.082392200)
9836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#define FIX_1_414213562  FIX(1.414213562)
9936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#define FIX_1_847759065  FIX(1.847759065)
10036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#define FIX_2_613125930  FIX(2.613125930)
10136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#endif
10236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
10336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
10436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane/* We can gain a little more speed, with a further compromise in accuracy,
10536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * by omitting the addition in a descaling shift.  This yields an incorrectly
10636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * rounded result half the time...
10736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane */
10836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
10936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#ifndef USE_ACCURATE_ROUNDING
11036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#undef DESCALE
11136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#define DESCALE(x,n)  RIGHT_SHIFT(x, n)
11236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#endif
11336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
11436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
11536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane/* Multiply a DCTELEM variable by an INT32 constant, and immediately
11636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * descale to yield a DCTELEM result.
11736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane */
11836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
11936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#define MULTIPLY(var,const)  ((DCTELEM) DESCALE((var) * (const), CONST_BITS))
12036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
12136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
12236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane/* Dequantize a coefficient by multiplying it by the multiplier-table
12336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * entry; produce a DCTELEM result.  For 8-bit data a 16x16->16
12436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * multiplication will do.  For 12-bit data, the multiplier table is
12536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * declared INT32, so a 32-bit multiply will be used.
12636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane */
12736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
12836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#if BITS_IN_JSAMPLE == 8
12936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#define DEQUANTIZE(coef,quantval)  (((IFAST_MULT_TYPE) (coef)) * (quantval))
13036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#else
13136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#define DEQUANTIZE(coef,quantval)  \
132e5eaf37440b8e337ab150c017df7c03faf846c51DRC        DESCALE((coef)*(quantval), IFAST_SCALE_BITS-PASS1_BITS)
13336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#endif
13436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
13536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
13636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane/* Like DESCALE, but applies to a DCTELEM and produces an int.
13736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * We assume that int right shift is unsigned if INT32 right shift is.
13836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane */
13936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
14036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#ifdef RIGHT_SHIFT_IS_UNSIGNED
141e5eaf37440b8e337ab150c017df7c03faf846c51DRC#define ISHIFT_TEMPS    DCTELEM ishift_temp;
142bc79e0680a45d1ca330d690dae0340c8e17ab5e3Thomas G. Lane#if BITS_IN_JSAMPLE == 8
143e5eaf37440b8e337ab150c017df7c03faf846c51DRC#define DCTELEMBITS  16         /* DCTELEM may be 16 or 32 bits */
144bc79e0680a45d1ca330d690dae0340c8e17ab5e3Thomas G. Lane#else
145e5eaf37440b8e337ab150c017df7c03faf846c51DRC#define DCTELEMBITS  32         /* DCTELEM must be 32 bits */
146bc79e0680a45d1ca330d690dae0340c8e17ab5e3Thomas G. Lane#endif
14736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#define IRIGHT_SHIFT(x,shft)  \
148bc79e0680a45d1ca330d690dae0340c8e17ab5e3Thomas G. Lane    ((ishift_temp = (x)) < 0 ? \
149bc79e0680a45d1ca330d690dae0340c8e17ab5e3Thomas G. Lane     (ishift_temp >> (shft)) | ((~((DCTELEM) 0)) << (DCTELEMBITS-(shft))) : \
150bc79e0680a45d1ca330d690dae0340c8e17ab5e3Thomas G. Lane     (ishift_temp >> (shft)))
15136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#else
15236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#define ISHIFT_TEMPS
153e5eaf37440b8e337ab150c017df7c03faf846c51DRC#define IRIGHT_SHIFT(x,shft)    ((x) >> (shft))
15436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#endif
15536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
15636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#ifdef USE_ACCURATE_ROUNDING
15736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#define IDESCALE(x,n)  ((int) IRIGHT_SHIFT((x) + (1 << ((n)-1)), n))
15836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#else
15936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#define IDESCALE(x,n)  ((int) IRIGHT_SHIFT(x, n))
16036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#endif
16136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
16236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
16336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane/*
16436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane * Perform dequantization and inverse DCT on one block of coefficients.
16536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane */
16636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
167489583f5165e05d37302e8eeec58104ea0109127Thomas G. LaneGLOBAL(void)
16836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lanejpeg_idct_ifast (j_decompress_ptr cinfo, jpeg_component_info * compptr,
169e5eaf37440b8e337ab150c017df7c03faf846c51DRC                 JCOEFPTR coef_block,
170e5eaf37440b8e337ab150c017df7c03faf846c51DRC                 JSAMPARRAY output_buf, JDIMENSION output_col)
17136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane{
17236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane  DCTELEM tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
17336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane  DCTELEM tmp10, tmp11, tmp12, tmp13;
17436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane  DCTELEM z5, z10, z11, z12, z13;
17536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane  JCOEFPTR inptr;
17636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane  IFAST_MULT_TYPE * quantptr;
17736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane  int * wsptr;
17836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane  JSAMPROW outptr;
17936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane  JSAMPLE *range_limit = IDCT_range_limit(cinfo);
18036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane  int ctr;
181e5eaf37440b8e337ab150c017df7c03faf846c51DRC  int workspace[DCTSIZE2];      /* buffers data between passes */
182e5eaf37440b8e337ab150c017df7c03faf846c51DRC  SHIFT_TEMPS                   /* for DESCALE */
183e5eaf37440b8e337ab150c017df7c03faf846c51DRC  ISHIFT_TEMPS                  /* for IDESCALE */
18436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
18536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane  /* Pass 1: process columns from input, store into work array. */
18636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
18736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane  inptr = coef_block;
18836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane  quantptr = (IFAST_MULT_TYPE *) compptr->dct_table;
18936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane  wsptr = workspace;
19036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane  for (ctr = DCTSIZE; ctr > 0; ctr--) {
19136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    /* Due to quantization, we will usually find that many of the input
19236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane     * coefficients are zero, especially the AC terms.  We can exploit this
19336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane     * by short-circuiting the IDCT calculation for any column in which all
19436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane     * the AC terms are zero.  In that case each output is equal to the
19536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane     * DC coefficient (with scale factor as needed).
19636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane     * With typical images and quantization tables, half or more of the
19736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane     * column DCT calculations can be simplified this way.
19836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane     */
199e5eaf37440b8e337ab150c017df7c03faf846c51DRC
2005ead57a34a398aa798f35bd7a6abad19b2e453e2Thomas G. Lane    if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 &&
201e5eaf37440b8e337ab150c017df7c03faf846c51DRC        inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*4] == 0 &&
202e5eaf37440b8e337ab150c017df7c03faf846c51DRC        inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*6] == 0 &&
203e5eaf37440b8e337ab150c017df7c03faf846c51DRC        inptr[DCTSIZE*7] == 0) {
20436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      /* AC terms all zero */
20536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      int dcval = (int) DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
20636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
20736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      wsptr[DCTSIZE*0] = dcval;
20836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      wsptr[DCTSIZE*1] = dcval;
20936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      wsptr[DCTSIZE*2] = dcval;
21036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      wsptr[DCTSIZE*3] = dcval;
21136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      wsptr[DCTSIZE*4] = dcval;
21236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      wsptr[DCTSIZE*5] = dcval;
21336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      wsptr[DCTSIZE*6] = dcval;
21436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      wsptr[DCTSIZE*7] = dcval;
215e5eaf37440b8e337ab150c017df7c03faf846c51DRC
216e5eaf37440b8e337ab150c017df7c03faf846c51DRC      inptr++;                  /* advance pointers to next column */
21736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      quantptr++;
21836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      wsptr++;
21936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      continue;
22036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    }
221e5eaf37440b8e337ab150c017df7c03faf846c51DRC
22236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    /* Even part */
22336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
22436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp0 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
22536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp1 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]);
22636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp2 = DEQUANTIZE(inptr[DCTSIZE*4], quantptr[DCTSIZE*4]);
22736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]);
22836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
229e5eaf37440b8e337ab150c017df7c03faf846c51DRC    tmp10 = tmp0 + tmp2;        /* phase 3 */
23036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp11 = tmp0 - tmp2;
23136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
232e5eaf37440b8e337ab150c017df7c03faf846c51DRC    tmp13 = tmp1 + tmp3;        /* phases 5-3 */
23336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp12 = MULTIPLY(tmp1 - tmp3, FIX_1_414213562) - tmp13; /* 2*c4 */
23436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
235e5eaf37440b8e337ab150c017df7c03faf846c51DRC    tmp0 = tmp10 + tmp13;       /* phase 2 */
23636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp3 = tmp10 - tmp13;
23736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp1 = tmp11 + tmp12;
23836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp2 = tmp11 - tmp12;
239e5eaf37440b8e337ab150c017df7c03faf846c51DRC
24036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    /* Odd part */
24136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
24236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp4 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
24336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp5 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
24436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp6 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
24536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp7 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
24636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
247e5eaf37440b8e337ab150c017df7c03faf846c51DRC    z13 = tmp6 + tmp5;          /* phase 6 */
24836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    z10 = tmp6 - tmp5;
24936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    z11 = tmp4 + tmp7;
25036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    z12 = tmp4 - tmp7;
25136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
252e5eaf37440b8e337ab150c017df7c03faf846c51DRC    tmp7 = z11 + z13;           /* phase 5 */
25336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp11 = MULTIPLY(z11 - z13, FIX_1_414213562); /* 2*c4 */
25436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
25536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    z5 = MULTIPLY(z10 + z12, FIX_1_847759065); /* 2*c2 */
25636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp10 = MULTIPLY(z12, FIX_1_082392200) - z5; /* 2*(c2-c6) */
25736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp12 = MULTIPLY(z10, - FIX_2_613125930) + z5; /* -2*(c2+c6) */
25836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
259e5eaf37440b8e337ab150c017df7c03faf846c51DRC    tmp6 = tmp12 - tmp7;        /* phase 2 */
26036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp5 = tmp11 - tmp6;
26136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp4 = tmp10 + tmp5;
26236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
26336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    wsptr[DCTSIZE*0] = (int) (tmp0 + tmp7);
26436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    wsptr[DCTSIZE*7] = (int) (tmp0 - tmp7);
26536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    wsptr[DCTSIZE*1] = (int) (tmp1 + tmp6);
26636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    wsptr[DCTSIZE*6] = (int) (tmp1 - tmp6);
26736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    wsptr[DCTSIZE*2] = (int) (tmp2 + tmp5);
26836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    wsptr[DCTSIZE*5] = (int) (tmp2 - tmp5);
26936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    wsptr[DCTSIZE*4] = (int) (tmp3 + tmp4);
27036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    wsptr[DCTSIZE*3] = (int) (tmp3 - tmp4);
27136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
272e5eaf37440b8e337ab150c017df7c03faf846c51DRC    inptr++;                    /* advance pointers to next column */
27336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    quantptr++;
27436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    wsptr++;
27536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane  }
276e5eaf37440b8e337ab150c017df7c03faf846c51DRC
27736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane  /* Pass 2: process rows from work array, store into output array. */
27836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane  /* Note that we must descale the results by a factor of 8 == 2**3, */
27936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane  /* and also undo the PASS1_BITS scaling. */
28036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
28136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane  wsptr = workspace;
28236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane  for (ctr = 0; ctr < DCTSIZE; ctr++) {
28336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    outptr = output_buf[ctr] + output_col;
28436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    /* Rows of zeroes can be exploited in the same way as we did with columns.
28536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane     * However, the column calculation has created many nonzero AC terms, so
28636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane     * the simplification applies less often (typically 5% to 10% of the time).
28736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane     * On machines with very fast multiplication, it's possible that the
28836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane     * test takes more time than it's worth.  In that case this section
28936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane     * may be commented out.
29036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane     */
291e5eaf37440b8e337ab150c017df7c03faf846c51DRC
29236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#ifndef NO_ZERO_ROW_TEST
2935ead57a34a398aa798f35bd7a6abad19b2e453e2Thomas G. Lane    if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 && wsptr[4] == 0 &&
294e5eaf37440b8e337ab150c017df7c03faf846c51DRC        wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) {
29536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      /* AC terms all zero */
29636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      JSAMPLE dcval = range_limit[IDESCALE(wsptr[0], PASS1_BITS+3)
297e5eaf37440b8e337ab150c017df7c03faf846c51DRC                                  & RANGE_MASK];
298e5eaf37440b8e337ab150c017df7c03faf846c51DRC
29936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      outptr[0] = dcval;
30036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      outptr[1] = dcval;
30136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      outptr[2] = dcval;
30236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      outptr[3] = dcval;
30336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      outptr[4] = dcval;
30436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      outptr[5] = dcval;
30536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      outptr[6] = dcval;
30636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      outptr[7] = dcval;
30736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
308e5eaf37440b8e337ab150c017df7c03faf846c51DRC      wsptr += DCTSIZE;         /* advance pointer to next row */
30936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane      continue;
31036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    }
31136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#endif
312e5eaf37440b8e337ab150c017df7c03faf846c51DRC
31336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    /* Even part */
31436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
31536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp10 = ((DCTELEM) wsptr[0] + (DCTELEM) wsptr[4]);
31636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp11 = ((DCTELEM) wsptr[0] - (DCTELEM) wsptr[4]);
31736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
31836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp13 = ((DCTELEM) wsptr[2] + (DCTELEM) wsptr[6]);
31936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp12 = MULTIPLY((DCTELEM) wsptr[2] - (DCTELEM) wsptr[6], FIX_1_414213562)
320e5eaf37440b8e337ab150c017df7c03faf846c51DRC            - tmp13;
32136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
32236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp0 = tmp10 + tmp13;
32336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp3 = tmp10 - tmp13;
32436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp1 = tmp11 + tmp12;
32536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp2 = tmp11 - tmp12;
32636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
32736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    /* Odd part */
32836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
32936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    z13 = (DCTELEM) wsptr[5] + (DCTELEM) wsptr[3];
33036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    z10 = (DCTELEM) wsptr[5] - (DCTELEM) wsptr[3];
33136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    z11 = (DCTELEM) wsptr[1] + (DCTELEM) wsptr[7];
33236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    z12 = (DCTELEM) wsptr[1] - (DCTELEM) wsptr[7];
33336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
334e5eaf37440b8e337ab150c017df7c03faf846c51DRC    tmp7 = z11 + z13;           /* phase 5 */
33536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp11 = MULTIPLY(z11 - z13, FIX_1_414213562); /* 2*c4 */
33636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
33736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    z5 = MULTIPLY(z10 + z12, FIX_1_847759065); /* 2*c2 */
33836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp10 = MULTIPLY(z12, FIX_1_082392200) - z5; /* 2*(c2-c6) */
33936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp12 = MULTIPLY(z10, - FIX_2_613125930) + z5; /* -2*(c2+c6) */
34036a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
341e5eaf37440b8e337ab150c017df7c03faf846c51DRC    tmp6 = tmp12 - tmp7;        /* phase 2 */
34236a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp5 = tmp11 - tmp6;
34336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    tmp4 = tmp10 + tmp5;
34436a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
34536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    /* Final output stage: scale down by a factor of 8 and range-limit */
34636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
34736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    outptr[0] = range_limit[IDESCALE(tmp0 + tmp7, PASS1_BITS+3)
348e5eaf37440b8e337ab150c017df7c03faf846c51DRC                            & RANGE_MASK];
34936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    outptr[7] = range_limit[IDESCALE(tmp0 - tmp7, PASS1_BITS+3)
350e5eaf37440b8e337ab150c017df7c03faf846c51DRC                            & RANGE_MASK];
35136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    outptr[1] = range_limit[IDESCALE(tmp1 + tmp6, PASS1_BITS+3)
352e5eaf37440b8e337ab150c017df7c03faf846c51DRC                            & RANGE_MASK];
35336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    outptr[6] = range_limit[IDESCALE(tmp1 - tmp6, PASS1_BITS+3)
354e5eaf37440b8e337ab150c017df7c03faf846c51DRC                            & RANGE_MASK];
35536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    outptr[2] = range_limit[IDESCALE(tmp2 + tmp5, PASS1_BITS+3)
356e5eaf37440b8e337ab150c017df7c03faf846c51DRC                            & RANGE_MASK];
35736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    outptr[5] = range_limit[IDESCALE(tmp2 - tmp5, PASS1_BITS+3)
358e5eaf37440b8e337ab150c017df7c03faf846c51DRC                            & RANGE_MASK];
35936a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    outptr[4] = range_limit[IDESCALE(tmp3 + tmp4, PASS1_BITS+3)
360e5eaf37440b8e337ab150c017df7c03faf846c51DRC                            & RANGE_MASK];
36136a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane    outptr[3] = range_limit[IDESCALE(tmp3 - tmp4, PASS1_BITS+3)
362e5eaf37440b8e337ab150c017df7c03faf846c51DRC                            & RANGE_MASK];
36336a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
364e5eaf37440b8e337ab150c017df7c03faf846c51DRC    wsptr += DCTSIZE;           /* advance pointer to next row */
36536a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane  }
36636a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane}
36736a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane
36836a4ccccd33f5cc9df62949554af87129ced7f84Thomas G. Lane#endif /* DCT_IFAST_SUPPORTED */
369