mirror of
https://github.com/ZDoom/qzdoom.git
synced 2024-12-12 21:52:01 +00:00
390 lines
14 KiB
C
390 lines
14 KiB
C
|
/*
|
||
|
* jidctint.c
|
||
|
*
|
||
|
* Copyright (C) 1991-1998, 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 a slow-but-accurate integer implementation of the
|
||
|
* inverse DCT (Discrete Cosine Transform). In the IJG code, this routine
|
||
|
* must also perform dequantization of the input coefficients.
|
||
|
*
|
||
|
* A 2-D IDCT can be done by 1-D IDCT on each column followed by 1-D IDCT
|
||
|
* on each row (or vice versa, but it's more convenient to emit a row at
|
||
|
* a time). 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.
|
||
|
*/
|
||
|
|
||
|
#define JPEG_INTERNALS
|
||
|
#include "jinclude.h"
|
||
|
#include "jpeglib.h"
|
||
|
#include "jdct.h" /* Private declarations for DCT subsystem */
|
||
|
|
||
|
#ifdef DCT_ISLOW_SUPPORTED
|
||
|
|
||
|
|
||
|
/*
|
||
|
* 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 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.
|
||
|
*/
|
||
|
|
||
|
#if BITS_IN_JSAMPLE == 8
|
||
|
#define CONST_BITS 13
|
||
|
#define PASS1_BITS 2
|
||
|
#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) 2446) /* FIX(0.298631336) */
|
||
|
#define FIX_0_390180644 ((INT32) 3196) /* FIX(0.390180644) */
|
||
|
#define FIX_0_541196100 ((INT32) 4433) /* FIX(0.541196100) */
|
||
|
#define FIX_0_765366865 ((INT32) 6270) /* FIX(0.765366865) */
|
||
|
#define FIX_0_899976223 ((INT32) 7373) /* FIX(0.899976223) */
|
||
|
#define FIX_1_175875602 ((INT32) 9633) /* FIX(1.175875602) */
|
||
|
#define FIX_1_501321110 ((INT32) 12299) /* FIX(1.501321110) */
|
||
|
#define FIX_1_847759065 ((INT32) 15137) /* FIX(1.847759065) */
|
||
|
#define FIX_1_961570560 ((INT32) 16069) /* FIX(1.961570560) */
|
||
|
#define FIX_2_053119869 ((INT32) 16819) /* FIX(2.053119869) */
|
||
|
#define FIX_2_562915447 ((INT32) 20995) /* FIX(2.562915447) */
|
||
|
#define FIX_3_072711026 ((INT32) 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 variable by an INT32 constant to yield an INT32 result.
|
||
|
* For 8-bit samples with the recommended scaling, all the variable
|
||
|
* and constant values involved are no more than 16 bits wide, so a
|
||
|
* 16x16->32 bit multiply can be used instead of a full 32x32 multiply.
|
||
|
* For 12-bit samples, a full 32-bit multiplication will be needed.
|
||
|
*/
|
||
|
|
||
|
#if BITS_IN_JSAMPLE == 8
|
||
|
#define MULTIPLY(var,const) MULTIPLY16C16(var,const)
|
||
|
#else
|
||
|
#define MULTIPLY(var,const) ((var) * (const))
|
||
|
#endif
|
||
|
|
||
|
|
||
|
/* Dequantize a coefficient by multiplying it by the multiplier-table
|
||
|
* entry; produce an int result. In this module, both inputs and result
|
||
|
* are 16 bits or less, so either int or short multiply will work.
|
||
|
*/
|
||
|
|
||
|
#define DEQUANTIZE(coef,quantval) (((ISLOW_MULT_TYPE) (coef)) * (quantval))
|
||
|
|
||
|
|
||
|
/*
|
||
|
* Perform dequantization and inverse DCT on one block of coefficients.
|
||
|
*/
|
||
|
|
||
|
GLOBAL(void)
|
||
|
jpeg_idct_islow (j_decompress_ptr cinfo, jpeg_component_info * compptr,
|
||
|
JCOEFPTR coef_block,
|
||
|
JSAMPARRAY output_buf, JDIMENSION output_col)
|
||
|
{
|
||
|
INT32 tmp0, tmp1, tmp2, tmp3;
|
||
|
INT32 tmp10, tmp11, tmp12, tmp13;
|
||
|
INT32 z1, z2, z3, z4, z5;
|
||
|
JCOEFPTR inptr;
|
||
|
ISLOW_MULT_TYPE * quantptr;
|
||
|
int * wsptr;
|
||
|
JSAMPROW outptr;
|
||
|
JSAMPLE *range_limit = IDCT_range_limit(cinfo);
|
||
|
int ctr;
|
||
|
int workspace[DCTSIZE2]; /* buffers data between passes */
|
||
|
SHIFT_TEMPS
|
||
|
|
||
|
/* Pass 1: process columns from input, store into work array. */
|
||
|
/* Note results are scaled up by sqrt(8) compared to a true IDCT; */
|
||
|
/* furthermore, we scale the results by 2**PASS1_BITS. */
|
||
|
|
||
|
inptr = coef_block;
|
||
|
quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
|
||
|
wsptr = workspace;
|
||
|
for (ctr = DCTSIZE; ctr > 0; ctr--) {
|
||
|
/* 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 column 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
|
||
|
* column DCT calculations can be simplified this way.
|
||
|
*/
|
||
|
|
||
|
if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 &&
|
||
|
inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*4] == 0 &&
|
||
|
inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*6] == 0 &&
|
||
|
inptr[DCTSIZE*7] == 0) {
|
||
|
/* AC terms all zero */
|
||
|
int dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]) << PASS1_BITS;
|
||
|
|
||
|
wsptr[DCTSIZE*0] = dcval;
|
||
|
wsptr[DCTSIZE*1] = dcval;
|
||
|
wsptr[DCTSIZE*2] = dcval;
|
||
|
wsptr[DCTSIZE*3] = dcval;
|
||
|
wsptr[DCTSIZE*4] = dcval;
|
||
|
wsptr[DCTSIZE*5] = dcval;
|
||
|
wsptr[DCTSIZE*6] = dcval;
|
||
|
wsptr[DCTSIZE*7] = dcval;
|
||
|
|
||
|
inptr++; /* advance pointers to next column */
|
||
|
quantptr++;
|
||
|
wsptr++;
|
||
|
continue;
|
||
|
}
|
||
|
|
||
|
/* Even part: reverse the even part of the forward DCT. */
|
||
|
/* The rotator is sqrt(2)*c(-6). */
|
||
|
|
||
|
z2 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]);
|
||
|
z3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]);
|
||
|
|
||
|
z1 = MULTIPLY(z2 + z3, FIX_0_541196100);
|
||
|
tmp2 = z1 + MULTIPLY(z3, - FIX_1_847759065);
|
||
|
tmp3 = z1 + MULTIPLY(z2, FIX_0_765366865);
|
||
|
|
||
|
z2 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
|
||
|
z3 = DEQUANTIZE(inptr[DCTSIZE*4], quantptr[DCTSIZE*4]);
|
||
|
|
||
|
tmp0 = (z2 + z3) << CONST_BITS;
|
||
|
tmp1 = (z2 - z3) << CONST_BITS;
|
||
|
|
||
|
tmp10 = tmp0 + tmp3;
|
||
|
tmp13 = tmp0 - tmp3;
|
||
|
tmp11 = tmp1 + tmp2;
|
||
|
tmp12 = tmp1 - tmp2;
|
||
|
|
||
|
/* Odd part per figure 8; the matrix is unitary and hence its
|
||
|
* transpose is its inverse. i0..i3 are y7,y5,y3,y1 respectively.
|
||
|
*/
|
||
|
|
||
|
tmp0 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
|
||
|
tmp1 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
|
||
|
tmp2 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
|
||
|
tmp3 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
|
||
|
|
||
|
z1 = tmp0 + tmp3;
|
||
|
z2 = tmp1 + tmp2;
|
||
|
z3 = tmp0 + tmp2;
|
||
|
z4 = tmp1 + tmp3;
|
||
|
z5 = MULTIPLY(z3 + z4, FIX_1_175875602); /* sqrt(2) * c3 */
|
||
|
|
||
|
tmp0 = MULTIPLY(tmp0, FIX_0_298631336); /* sqrt(2) * (-c1+c3+c5-c7) */
|
||
|
tmp1 = MULTIPLY(tmp1, FIX_2_053119869); /* sqrt(2) * ( c1+c3-c5+c7) */
|
||
|
tmp2 = MULTIPLY(tmp2, FIX_3_072711026); /* sqrt(2) * ( c1+c3+c5-c7) */
|
||
|
tmp3 = MULTIPLY(tmp3, 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;
|
||
|
|
||
|
tmp0 += z1 + z3;
|
||
|
tmp1 += z2 + z4;
|
||
|
tmp2 += z2 + z3;
|
||
|
tmp3 += z1 + z4;
|
||
|
|
||
|
/* Final output stage: inputs are tmp10..tmp13, tmp0..tmp3 */
|
||
|
|
||
|
wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp3, CONST_BITS-PASS1_BITS);
|
||
|
wsptr[DCTSIZE*7] = (int) DESCALE(tmp10 - tmp3, CONST_BITS-PASS1_BITS);
|
||
|
wsptr[DCTSIZE*1] = (int) DESCALE(tmp11 + tmp2, CONST_BITS-PASS1_BITS);
|
||
|
wsptr[DCTSIZE*6] = (int) DESCALE(tmp11 - tmp2, CONST_BITS-PASS1_BITS);
|
||
|
wsptr[DCTSIZE*2] = (int) DESCALE(tmp12 + tmp1, CONST_BITS-PASS1_BITS);
|
||
|
wsptr[DCTSIZE*5] = (int) DESCALE(tmp12 - tmp1, CONST_BITS-PASS1_BITS);
|
||
|
wsptr[DCTSIZE*3] = (int) DESCALE(tmp13 + tmp0, CONST_BITS-PASS1_BITS);
|
||
|
wsptr[DCTSIZE*4] = (int) DESCALE(tmp13 - tmp0, CONST_BITS-PASS1_BITS);
|
||
|
|
||
|
inptr++; /* advance pointers to next column */
|
||
|
quantptr++;
|
||
|
wsptr++;
|
||
|
}
|
||
|
|
||
|
/* Pass 2: process rows from work array, store into output array. */
|
||
|
/* Note that we must descale the results by a factor of 8 == 2**3, */
|
||
|
/* and also undo the PASS1_BITS scaling. */
|
||
|
|
||
|
wsptr = workspace;
|
||
|
for (ctr = 0; ctr < DCTSIZE; ctr++) {
|
||
|
outptr = output_buf[ctr] + output_col;
|
||
|
/* Rows of zeroes can be exploited in the same way as we did with columns.
|
||
|
* However, the column 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.
|
||
|
*/
|
||
|
|
||
|
#ifndef NO_ZERO_ROW_TEST
|
||
|
if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 && wsptr[4] == 0 &&
|
||
|
wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) {
|
||
|
/* AC terms all zero */
|
||
|
JSAMPLE dcval = range_limit[(int) DESCALE((INT32) wsptr[0], PASS1_BITS+3)
|
||
|
& RANGE_MASK];
|
||
|
|
||
|
outptr[0] = dcval;
|
||
|
outptr[1] = dcval;
|
||
|
outptr[2] = dcval;
|
||
|
outptr[3] = dcval;
|
||
|
outptr[4] = dcval;
|
||
|
outptr[5] = dcval;
|
||
|
outptr[6] = dcval;
|
||
|
outptr[7] = dcval;
|
||
|
|
||
|
wsptr += DCTSIZE; /* advance pointer to next row */
|
||
|
continue;
|
||
|
}
|
||
|
#endif
|
||
|
|
||
|
/* Even part: reverse the even part of the forward DCT. */
|
||
|
/* The rotator is sqrt(2)*c(-6). */
|
||
|
|
||
|
z2 = (INT32) wsptr[2];
|
||
|
z3 = (INT32) wsptr[6];
|
||
|
|
||
|
z1 = MULTIPLY(z2 + z3, FIX_0_541196100);
|
||
|
tmp2 = z1 + MULTIPLY(z3, - FIX_1_847759065);
|
||
|
tmp3 = z1 + MULTIPLY(z2, FIX_0_765366865);
|
||
|
|
||
|
tmp0 = ((INT32) wsptr[0] + (INT32) wsptr[4]) << CONST_BITS;
|
||
|
tmp1 = ((INT32) wsptr[0] - (INT32) wsptr[4]) << CONST_BITS;
|
||
|
|
||
|
tmp10 = tmp0 + tmp3;
|
||
|
tmp13 = tmp0 - tmp3;
|
||
|
tmp11 = tmp1 + tmp2;
|
||
|
tmp12 = tmp1 - tmp2;
|
||
|
|
||
|
/* Odd part per figure 8; the matrix is unitary and hence its
|
||
|
* transpose is its inverse. i0..i3 are y7,y5,y3,y1 respectively.
|
||
|
*/
|
||
|
|
||
|
tmp0 = (INT32) wsptr[7];
|
||
|
tmp1 = (INT32) wsptr[5];
|
||
|
tmp2 = (INT32) wsptr[3];
|
||
|
tmp3 = (INT32) wsptr[1];
|
||
|
|
||
|
z1 = tmp0 + tmp3;
|
||
|
z2 = tmp1 + tmp2;
|
||
|
z3 = tmp0 + tmp2;
|
||
|
z4 = tmp1 + tmp3;
|
||
|
z5 = MULTIPLY(z3 + z4, FIX_1_175875602); /* sqrt(2) * c3 */
|
||
|
|
||
|
tmp0 = MULTIPLY(tmp0, FIX_0_298631336); /* sqrt(2) * (-c1+c3+c5-c7) */
|
||
|
tmp1 = MULTIPLY(tmp1, FIX_2_053119869); /* sqrt(2) * ( c1+c3-c5+c7) */
|
||
|
tmp2 = MULTIPLY(tmp2, FIX_3_072711026); /* sqrt(2) * ( c1+c3+c5-c7) */
|
||
|
tmp3 = MULTIPLY(tmp3, 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;
|
||
|
|
||
|
tmp0 += z1 + z3;
|
||
|
tmp1 += z2 + z4;
|
||
|
tmp2 += z2 + z3;
|
||
|
tmp3 += z1 + z4;
|
||
|
|
||
|
/* Final output stage: inputs are tmp10..tmp13, tmp0..tmp3 */
|
||
|
|
||
|
outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp3,
|
||
|
CONST_BITS+PASS1_BITS+3)
|
||
|
& RANGE_MASK];
|
||
|
outptr[7] = range_limit[(int) DESCALE(tmp10 - tmp3,
|
||
|
CONST_BITS+PASS1_BITS+3)
|
||
|
& RANGE_MASK];
|
||
|
outptr[1] = range_limit[(int) DESCALE(tmp11 + tmp2,
|
||
|
CONST_BITS+PASS1_BITS+3)
|
||
|
& RANGE_MASK];
|
||
|
outptr[6] = range_limit[(int) DESCALE(tmp11 - tmp2,
|
||
|
CONST_BITS+PASS1_BITS+3)
|
||
|
& RANGE_MASK];
|
||
|
outptr[2] = range_limit[(int) DESCALE(tmp12 + tmp1,
|
||
|
CONST_BITS+PASS1_BITS+3)
|
||
|
& RANGE_MASK];
|
||
|
outptr[5] = range_limit[(int) DESCALE(tmp12 - tmp1,
|
||
|
CONST_BITS+PASS1_BITS+3)
|
||
|
& RANGE_MASK];
|
||
|
outptr[3] = range_limit[(int) DESCALE(tmp13 + tmp0,
|
||
|
CONST_BITS+PASS1_BITS+3)
|
||
|
& RANGE_MASK];
|
||
|
outptr[4] = range_limit[(int) DESCALE(tmp13 - tmp0,
|
||
|
CONST_BITS+PASS1_BITS+3)
|
||
|
& RANGE_MASK];
|
||
|
|
||
|
wsptr += DCTSIZE; /* advance pointer to next row */
|
||
|
}
|
||
|
}
|
||
|
|
||
|
#endif /* DCT_ISLOW_SUPPORTED */
|