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- /*
- * jfdctint.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) 1991-1996, 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 a slow-but-accurate integer implementation of the
- * forward DCT (Discrete Cosine Transform).
- *
- * A 2-D DCT can be done by 1-D DCT on each row followed by 1-D DCT
- * 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.
- *
- * 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.
- */
- /**
- * @file libavcodec/jfdctint.c
- * Independent JPEG Group's slow & accurate dct.
- */
- #include <stdlib.h>
- #include <stdio.h>
- #include "libavutil/common.h"
- #include "dsputil.h"
- #define SHIFT_TEMPS
- #define DCTSIZE 8
- #define BITS_IN_JSAMPLE 8
- #define GLOBAL(x) x
- #define RIGHT_SHIFT(x, n) ((x) >> (n))
- #define MULTIPLY16C16(var,const) ((var)*(const))
- #if 1 //def USE_ACCURATE_ROUNDING
- #define DESCALE(x,n) RIGHT_SHIFT((x) + (1 << ((n) - 1)), n)
- #else
- #define DESCALE(x,n) RIGHT_SHIFT(x, n)
- #endif
- /*
- * This module is specialized to the case DCTSIZE = 8.
- */
- #if DCTSIZE != 8
- Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
- #endif
- /*
- * The poop on this scaling stuff is as follows:
- *
- * Each 1-D DCT step produces outputs which are a factor of sqrt(N)
- * larger than the true DCT 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 DCT,
- * because the y0 and y4 outputs need not be divided by sqrt(N).
- * In the IJG code, this factor of 8 is removed by the quantization step
- * (in jcdctmgr.c), NOT in this module.
- *
- * 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. (For 12-bit sample data, the intermediate
- * array is int32_t anyway.)
- *
- * 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.
- */
- #if BITS_IN_JSAMPLE == 8
- #define CONST_BITS 13
- #define PASS1_BITS 4 /* set this to 2 if 16x16 multiplies are faster */
- #else
- #define CONST_BITS 13
- #define PASS1_BITS 1 /* lose a little precision to avoid overflow */
- #endif
- /* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
- * causing a lot of useless floating-point operations at run time.
- * To get around this we use the following pre-calculated constants.
- * If you change CONST_BITS you may want to add appropriate values.
- * (With a reasonable C compiler, you can just rely on the FIX() macro...)
- */
- #if CONST_BITS == 13
- #define FIX_0_298631336 ((int32_t) 2446) /* FIX(0.298631336) */
- #define FIX_0_390180644 ((int32_t) 3196) /* FIX(0.390180644) */
- #define FIX_0_541196100 ((int32_t) 4433) /* FIX(0.541196100) */
- #define FIX_0_765366865 ((int32_t) 6270) /* FIX(0.765366865) */
- #define FIX_0_899976223 ((int32_t) 7373) /* FIX(0.899976223) */
- #define FIX_1_175875602 ((int32_t) 9633) /* FIX(1.175875602) */
- #define FIX_1_501321110 ((int32_t) 12299) /* FIX(1.501321110) */
- #define FIX_1_847759065 ((int32_t) 15137) /* FIX(1.847759065) */
- #define FIX_1_961570560 ((int32_t) 16069) /* FIX(1.961570560) */
- #define FIX_2_053119869 ((int32_t) 16819) /* FIX(2.053119869) */
- #define FIX_2_562915447 ((int32_t) 20995) /* FIX(2.562915447) */
- #define FIX_3_072711026 ((int32_t) 25172) /* FIX(3.072711026) */
- #else
- #define FIX_0_298631336 FIX(0.298631336)
- #define FIX_0_390180644 FIX(0.390180644)
- #define FIX_0_541196100 FIX(0.541196100)
- #define FIX_0_765366865 FIX(0.765366865)
- #define FIX_0_899976223 FIX(0.899976223)
- #define FIX_1_175875602 FIX(1.175875602)
- #define FIX_1_501321110 FIX(1.501321110)
- #define FIX_1_847759065 FIX(1.847759065)
- #define FIX_1_961570560 FIX(1.961570560)
- #define FIX_2_053119869 FIX(2.053119869)
- #define FIX_2_562915447 FIX(2.562915447)
- #define FIX_3_072711026 FIX(3.072711026)
- #endif
- /* 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.
- * For 12-bit samples, a full 32-bit multiplication will be needed.
- */
- #if BITS_IN_JSAMPLE == 8 && CONST_BITS<=13 && PASS1_BITS<=2
- #define MULTIPLY(var,const) MULTIPLY16C16(var,const)
- #else
- #define MULTIPLY(var,const) ((var) * (const))
- #endif
- static av_always_inline void row_fdct(DCTELEM * data){
- int_fast32_t tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
- int_fast32_t tmp10, tmp11, tmp12, tmp13;
- int_fast32_t z1, z2, z3, z4, z5;
- DCTELEM *dataptr;
- int ctr;
- SHIFT_TEMPS
- /* Pass 1: process rows. */
- /* Note results are scaled up by sqrt(8) compared to a true DCT; */
- /* furthermore, we scale the results by 2**PASS1_BITS. */
- dataptr = data;
- for (ctr = DCTSIZE-1; ctr >= 0; ctr--) {
- tmp0 = dataptr[0] + dataptr[7];
- tmp7 = dataptr[0] - dataptr[7];
- tmp1 = dataptr[1] + dataptr[6];
- tmp6 = dataptr[1] - dataptr[6];
- tmp2 = dataptr[2] + dataptr[5];
- tmp5 = dataptr[2] - dataptr[5];
- tmp3 = dataptr[3] + dataptr[4];
- tmp4 = dataptr[3] - dataptr[4];
- /* Even part per LL&M figure 1 --- note that published figure is faulty;
- * rotator "sqrt(2)*c1" should be "sqrt(2)*c6".
- */
- tmp10 = tmp0 + tmp3;
- tmp13 = tmp0 - tmp3;
- tmp11 = tmp1 + tmp2;
- tmp12 = tmp1 - tmp2;
- dataptr[0] = (DCTELEM) ((tmp10 + tmp11) << PASS1_BITS);
- dataptr[4] = (DCTELEM) ((tmp10 - tmp11) << PASS1_BITS);
- z1 = MULTIPLY(tmp12 + tmp13, FIX_0_541196100);
- dataptr[2] = (DCTELEM) DESCALE(z1 + MULTIPLY(tmp13, FIX_0_765366865),
- CONST_BITS-PASS1_BITS);
- dataptr[6] = (DCTELEM) DESCALE(z1 + MULTIPLY(tmp12, - FIX_1_847759065),
- CONST_BITS-PASS1_BITS);
- /* Odd part per figure 8 --- note paper omits factor of sqrt(2).
- * cK represents cos(K*pi/16).
- * i0..i3 in the paper are tmp4..tmp7 here.
- */
- z1 = tmp4 + tmp7;
- z2 = tmp5 + tmp6;
- z3 = tmp4 + tmp6;
- z4 = tmp5 + tmp7;
- z5 = MULTIPLY(z3 + z4, FIX_1_175875602); /* sqrt(2) * c3 */
- tmp4 = MULTIPLY(tmp4, FIX_0_298631336); /* sqrt(2) * (-c1+c3+c5-c7) */
- tmp5 = MULTIPLY(tmp5, FIX_2_053119869); /* sqrt(2) * ( c1+c3-c5+c7) */
- tmp6 = MULTIPLY(tmp6, FIX_3_072711026); /* sqrt(2) * ( c1+c3+c5-c7) */
- tmp7 = MULTIPLY(tmp7, FIX_1_501321110); /* sqrt(2) * ( c1+c3-c5-c7) */
- z1 = MULTIPLY(z1, - FIX_0_899976223); /* sqrt(2) * (c7-c3) */
- z2 = MULTIPLY(z2, - FIX_2_562915447); /* sqrt(2) * (-c1-c3) */
- z3 = MULTIPLY(z3, - FIX_1_961570560); /* sqrt(2) * (-c3-c5) */
- z4 = MULTIPLY(z4, - FIX_0_390180644); /* sqrt(2) * (c5-c3) */
- z3 += z5;
- z4 += z5;
- dataptr[7] = (DCTELEM) DESCALE(tmp4 + z1 + z3, CONST_BITS-PASS1_BITS);
- dataptr[5] = (DCTELEM) DESCALE(tmp5 + z2 + z4, CONST_BITS-PASS1_BITS);
- dataptr[3] = (DCTELEM) DESCALE(tmp6 + z2 + z3, CONST_BITS-PASS1_BITS);
- dataptr[1] = (DCTELEM) DESCALE(tmp7 + z1 + z4, CONST_BITS-PASS1_BITS);
- dataptr += DCTSIZE; /* advance pointer to next row */
- }
- }
- /*
- * Perform the forward DCT on one block of samples.
- */
- GLOBAL(void)
- ff_jpeg_fdct_islow (DCTELEM * data)
- {
- int_fast32_t tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
- int_fast32_t tmp10, tmp11, tmp12, tmp13;
- int_fast32_t z1, z2, z3, z4, z5;
- DCTELEM *dataptr;
- int ctr;
- SHIFT_TEMPS
- row_fdct(data);
- /* Pass 2: process columns.
- * We remove the PASS1_BITS scaling, but leave the results scaled up
- * by an overall factor of 8.
- */
- dataptr = data;
- for (ctr = DCTSIZE-1; ctr >= 0; ctr--) {
- tmp0 = dataptr[DCTSIZE*0] + dataptr[DCTSIZE*7];
- tmp7 = dataptr[DCTSIZE*0] - dataptr[DCTSIZE*7];
- tmp1 = dataptr[DCTSIZE*1] + dataptr[DCTSIZE*6];
- tmp6 = dataptr[DCTSIZE*1] - dataptr[DCTSIZE*6];
- tmp2 = dataptr[DCTSIZE*2] + dataptr[DCTSIZE*5];
- tmp5 = dataptr[DCTSIZE*2] - dataptr[DCTSIZE*5];
- tmp3 = dataptr[DCTSIZE*3] + dataptr[DCTSIZE*4];
- tmp4 = dataptr[DCTSIZE*3] - dataptr[DCTSIZE*4];
- /* Even part per LL&M figure 1 --- note that published figure is faulty;
- * rotator "sqrt(2)*c1" should be "sqrt(2)*c6".
- */
- tmp10 = tmp0 + tmp3;
- tmp13 = tmp0 - tmp3;
- tmp11 = tmp1 + tmp2;
- tmp12 = tmp1 - tmp2;
- dataptr[DCTSIZE*0] = (DCTELEM) DESCALE(tmp10 + tmp11, PASS1_BITS);
- dataptr[DCTSIZE*4] = (DCTELEM) DESCALE(tmp10 - tmp11, PASS1_BITS);
- z1 = MULTIPLY(tmp12 + tmp13, FIX_0_541196100);
- dataptr[DCTSIZE*2] = (DCTELEM) DESCALE(z1 + MULTIPLY(tmp13, FIX_0_765366865),
- CONST_BITS+PASS1_BITS);
- dataptr[DCTSIZE*6] = (DCTELEM) DESCALE(z1 + MULTIPLY(tmp12, - FIX_1_847759065),
- CONST_BITS+PASS1_BITS);
- /* Odd part per figure 8 --- note paper omits factor of sqrt(2).
- * cK represents cos(K*pi/16).
- * i0..i3 in the paper are tmp4..tmp7 here.
- */
- z1 = tmp4 + tmp7;
- z2 = tmp5 + tmp6;
- z3 = tmp4 + tmp6;
- z4 = tmp5 + tmp7;
- z5 = MULTIPLY(z3 + z4, FIX_1_175875602); /* sqrt(2) * c3 */
- tmp4 = MULTIPLY(tmp4, FIX_0_298631336); /* sqrt(2) * (-c1+c3+c5-c7) */
- tmp5 = MULTIPLY(tmp5, FIX_2_053119869); /* sqrt(2) * ( c1+c3-c5+c7) */
- tmp6 = MULTIPLY(tmp6, FIX_3_072711026); /* sqrt(2) * ( c1+c3+c5-c7) */
- tmp7 = MULTIPLY(tmp7, FIX_1_501321110); /* sqrt(2) * ( c1+c3-c5-c7) */
- z1 = MULTIPLY(z1, - FIX_0_899976223); /* sqrt(2) * (c7-c3) */
- z2 = MULTIPLY(z2, - FIX_2_562915447); /* sqrt(2) * (-c1-c3) */
- z3 = MULTIPLY(z3, - FIX_1_961570560); /* sqrt(2) * (-c3-c5) */
- z4 = MULTIPLY(z4, - FIX_0_390180644); /* sqrt(2) * (c5-c3) */
- z3 += z5;
- z4 += z5;
- dataptr[DCTSIZE*7] = (DCTELEM) DESCALE(tmp4 + z1 + z3,
- CONST_BITS+PASS1_BITS);
- dataptr[DCTSIZE*5] = (DCTELEM) DESCALE(tmp5 + z2 + z4,
- CONST_BITS+PASS1_BITS);
- dataptr[DCTSIZE*3] = (DCTELEM) DESCALE(tmp6 + z2 + z3,
- CONST_BITS+PASS1_BITS);
- dataptr[DCTSIZE*1] = (DCTELEM) DESCALE(tmp7 + z1 + z4,
- CONST_BITS+PASS1_BITS);
- dataptr++; /* advance pointer to next column */
- }
- }
- /*
- * The secret of DCT2-4-8 is really simple -- you do the usual 1-DCT
- * on the rows and then, instead of doing even and odd, part on the colums
- * you do even part two times.
- */
- GLOBAL(void)
- ff_fdct248_islow (DCTELEM * data)
- {
- int_fast32_t tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
- int_fast32_t tmp10, tmp11, tmp12, tmp13;
- int_fast32_t z1;
- DCTELEM *dataptr;
- int ctr;
- SHIFT_TEMPS
- row_fdct(data);
- /* Pass 2: process columns.
- * We remove the PASS1_BITS scaling, but leave the results scaled up
- * by an overall factor of 8.
- */
- dataptr = data;
- for (ctr = DCTSIZE-1; ctr >= 0; ctr--) {
- tmp0 = dataptr[DCTSIZE*0] + dataptr[DCTSIZE*1];
- tmp1 = dataptr[DCTSIZE*2] + dataptr[DCTSIZE*3];
- tmp2 = dataptr[DCTSIZE*4] + dataptr[DCTSIZE*5];
- tmp3 = dataptr[DCTSIZE*6] + dataptr[DCTSIZE*7];
- tmp4 = dataptr[DCTSIZE*0] - dataptr[DCTSIZE*1];
- tmp5 = dataptr[DCTSIZE*2] - dataptr[DCTSIZE*3];
- tmp6 = dataptr[DCTSIZE*4] - dataptr[DCTSIZE*5];
- tmp7 = dataptr[DCTSIZE*6] - dataptr[DCTSIZE*7];
- tmp10 = tmp0 + tmp3;
- tmp11 = tmp1 + tmp2;
- tmp12 = tmp1 - tmp2;
- tmp13 = tmp0 - tmp3;
- dataptr[DCTSIZE*0] = (DCTELEM) DESCALE(tmp10 + tmp11, PASS1_BITS);
- dataptr[DCTSIZE*4] = (DCTELEM) DESCALE(tmp10 - tmp11, PASS1_BITS);
- z1 = MULTIPLY(tmp12 + tmp13, FIX_0_541196100);
- dataptr[DCTSIZE*2] = (DCTELEM) DESCALE(z1 + MULTIPLY(tmp13, FIX_0_765366865),
- CONST_BITS+PASS1_BITS);
- dataptr[DCTSIZE*6] = (DCTELEM) DESCALE(z1 + MULTIPLY(tmp12, - FIX_1_847759065),
- CONST_BITS+PASS1_BITS);
- tmp10 = tmp4 + tmp7;
- tmp11 = tmp5 + tmp6;
- tmp12 = tmp5 - tmp6;
- tmp13 = tmp4 - tmp7;
- dataptr[DCTSIZE*1] = (DCTELEM) DESCALE(tmp10 + tmp11, PASS1_BITS);
- dataptr[DCTSIZE*5] = (DCTELEM) DESCALE(tmp10 - tmp11, PASS1_BITS);
- z1 = MULTIPLY(tmp12 + tmp13, FIX_0_541196100);
- dataptr[DCTSIZE*3] = (DCTELEM) DESCALE(z1 + MULTIPLY(tmp13, FIX_0_765366865),
- CONST_BITS+PASS1_BITS);
- dataptr[DCTSIZE*7] = (DCTELEM) DESCALE(z1 + MULTIPLY(tmp12, - FIX_1_847759065),
- CONST_BITS+PASS1_BITS);
- dataptr++; /* advance pointer to next column */
- }
- }
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