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334 lines
11 KiB
334 lines
11 KiB
/* |
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* jfdctfst.c |
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* |
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* This file is part of the Independent JPEG Group's software. |
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* |
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* The authors make NO WARRANTY or representation, either express or implied, |
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* with respect to this software, its quality, accuracy, merchantability, or |
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* fitness for a particular purpose. This software is provided "AS IS", and |
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* you, its user, assume the entire risk as to its quality and accuracy. |
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* |
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* This software is copyright (C) 1994-1996, Thomas G. Lane. |
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* All Rights Reserved except as specified below. |
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* |
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* Permission is hereby granted to use, copy, modify, and distribute this |
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* software (or portions thereof) for any purpose, without fee, subject to |
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* these conditions: |
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* (1) If any part of the source code for this software is distributed, then |
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* this README file must be included, with this copyright and no-warranty |
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* notice unaltered; and any additions, deletions, or changes to the original |
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* files must be clearly indicated in accompanying documentation. |
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* (2) If only executable code is distributed, then the accompanying |
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* documentation must state that "this software is based in part on the work |
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* of the Independent JPEG Group". |
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* (3) Permission for use of this software is granted only if the user accepts |
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* full responsibility for any undesirable consequences; the authors accept |
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* NO LIABILITY for damages of any kind. |
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* |
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* These conditions apply to any software derived from or based on the IJG |
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* code, not just to the unmodified library. If you use our work, you ought |
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* to acknowledge us. |
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* |
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* Permission is NOT granted for the use of any IJG author's name or company |
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* name in advertising or publicity relating to this software or products |
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* derived from it. This software may be referred to only as "the Independent |
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* JPEG Group's software". |
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* |
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* We specifically permit and encourage the use of this software as the basis |
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* of commercial products, provided that all warranty or liability claims are |
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* assumed by the product vendor. |
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* |
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* This file contains a fast, not so accurate integer implementation of the |
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* forward DCT (Discrete Cosine Transform). |
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* |
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* A 2-D DCT can be done by 1-D DCT on each row followed by 1-D DCT |
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* on each column. Direct algorithms are also available, but they are |
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* much more complex and seem not to be any faster when reduced to code. |
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* |
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* This implementation is based on Arai, Agui, and Nakajima's algorithm for |
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* scaled DCT. Their original paper (Trans. IEICE E-71(11):1095) is in |
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* Japanese, but the algorithm is described in the Pennebaker & Mitchell |
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* JPEG textbook (see REFERENCES section in file README). The following code |
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* is based directly on figure 4-8 in P&M. |
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* While an 8-point DCT cannot be done in less than 11 multiplies, it is |
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* possible to arrange the computation so that many of the multiplies are |
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* simple scalings of the final outputs. These multiplies can then be |
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* folded into the multiplications or divisions by the JPEG quantization |
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* table entries. The AA&N method leaves only 5 multiplies and 29 adds |
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* to be done in the DCT itself. |
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* The primary disadvantage of this method is that with fixed-point math, |
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* accuracy is lost due to imprecise representation of the scaled |
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* quantization values. The smaller the quantization table entry, the less |
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* precise the scaled value, so this implementation does worse with high- |
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* quality-setting files than with low-quality ones. |
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*/ |
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/** |
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* @file |
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* Independent JPEG Group's fast AAN dct. |
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*/ |
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#include <stdlib.h> |
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#include <stdio.h> |
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#include "libavutil/common.h" |
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#include "dsputil.h" |
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#define DCTSIZE 8 |
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#define GLOBAL(x) x |
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#define RIGHT_SHIFT(x, n) ((x) >> (n)) |
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/* |
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* This module is specialized to the case DCTSIZE = 8. |
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*/ |
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#if DCTSIZE != 8 |
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Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */ |
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#endif |
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/* Scaling decisions are generally the same as in the LL&M algorithm; |
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* see jfdctint.c for more details. However, we choose to descale |
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* (right shift) multiplication products as soon as they are formed, |
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* rather than carrying additional fractional bits into subsequent additions. |
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* This compromises accuracy slightly, but it lets us save a few shifts. |
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* More importantly, 16-bit arithmetic is then adequate (for 8-bit samples) |
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* everywhere except in the multiplications proper; this saves a good deal |
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* of work on 16-bit-int machines. |
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* |
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* Again to save a few shifts, the intermediate results between pass 1 and |
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* pass 2 are not upscaled, but are represented only to integral precision. |
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* |
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* A final compromise is to represent the multiplicative constants to only |
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* 8 fractional bits, rather than 13. This saves some shifting work on some |
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* machines, and may also reduce the cost of multiplication (since there |
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* are fewer one-bits in the constants). |
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*/ |
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#define CONST_BITS 8 |
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/* Some C compilers fail to reduce "FIX(constant)" at compile time, thus |
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* causing a lot of useless floating-point operations at run time. |
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* To get around this we use the following pre-calculated constants. |
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* If you change CONST_BITS you may want to add appropriate values. |
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* (With a reasonable C compiler, you can just rely on the FIX() macro...) |
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*/ |
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#if CONST_BITS == 8 |
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#define FIX_0_382683433 ((int32_t) 98) /* FIX(0.382683433) */ |
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#define FIX_0_541196100 ((int32_t) 139) /* FIX(0.541196100) */ |
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#define FIX_0_707106781 ((int32_t) 181) /* FIX(0.707106781) */ |
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#define FIX_1_306562965 ((int32_t) 334) /* FIX(1.306562965) */ |
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#else |
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#define FIX_0_382683433 FIX(0.382683433) |
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#define FIX_0_541196100 FIX(0.541196100) |
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#define FIX_0_707106781 FIX(0.707106781) |
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#define FIX_1_306562965 FIX(1.306562965) |
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#endif |
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/* We can gain a little more speed, with a further compromise in accuracy, |
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* by omitting the addition in a descaling shift. This yields an incorrectly |
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* rounded result half the time... |
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*/ |
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#ifndef USE_ACCURATE_ROUNDING |
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#undef DESCALE |
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#define DESCALE(x,n) RIGHT_SHIFT(x, n) |
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#endif |
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/* Multiply a DCTELEM variable by an int32_t constant, and immediately |
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* descale to yield a DCTELEM result. |
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*/ |
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#define MULTIPLY(var,const) ((DCTELEM) DESCALE((var) * (const), CONST_BITS)) |
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static av_always_inline void row_fdct(DCTELEM * data){ |
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int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7; |
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int tmp10, tmp11, tmp12, tmp13; |
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int z1, z2, z3, z4, z5, z11, z13; |
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DCTELEM *dataptr; |
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int ctr; |
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/* Pass 1: process rows. */ |
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dataptr = data; |
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for (ctr = DCTSIZE-1; ctr >= 0; ctr--) { |
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tmp0 = dataptr[0] + dataptr[7]; |
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tmp7 = dataptr[0] - dataptr[7]; |
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tmp1 = dataptr[1] + dataptr[6]; |
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tmp6 = dataptr[1] - dataptr[6]; |
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tmp2 = dataptr[2] + dataptr[5]; |
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tmp5 = dataptr[2] - dataptr[5]; |
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tmp3 = dataptr[3] + dataptr[4]; |
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tmp4 = dataptr[3] - dataptr[4]; |
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/* Even part */ |
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tmp10 = tmp0 + tmp3; /* phase 2 */ |
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tmp13 = tmp0 - tmp3; |
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tmp11 = tmp1 + tmp2; |
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tmp12 = tmp1 - tmp2; |
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dataptr[0] = tmp10 + tmp11; /* phase 3 */ |
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dataptr[4] = tmp10 - tmp11; |
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z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */ |
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dataptr[2] = tmp13 + z1; /* phase 5 */ |
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dataptr[6] = tmp13 - z1; |
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/* Odd part */ |
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tmp10 = tmp4 + tmp5; /* phase 2 */ |
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tmp11 = tmp5 + tmp6; |
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tmp12 = tmp6 + tmp7; |
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/* The rotator is modified from fig 4-8 to avoid extra negations. */ |
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z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */ |
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z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5; /* c2-c6 */ |
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z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5; /* c2+c6 */ |
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z3 = MULTIPLY(tmp11, FIX_0_707106781); /* c4 */ |
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z11 = tmp7 + z3; /* phase 5 */ |
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z13 = tmp7 - z3; |
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dataptr[5] = z13 + z2; /* phase 6 */ |
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dataptr[3] = z13 - z2; |
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dataptr[1] = z11 + z4; |
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dataptr[7] = z11 - z4; |
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dataptr += DCTSIZE; /* advance pointer to next row */ |
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} |
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} |
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/* |
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* Perform the forward DCT on one block of samples. |
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*/ |
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GLOBAL(void) |
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fdct_ifast (DCTELEM * data) |
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{ |
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int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7; |
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int tmp10, tmp11, tmp12, tmp13; |
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int z1, z2, z3, z4, z5, z11, z13; |
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DCTELEM *dataptr; |
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int ctr; |
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row_fdct(data); |
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/* Pass 2: process columns. */ |
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dataptr = data; |
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for (ctr = DCTSIZE-1; ctr >= 0; ctr--) { |
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tmp0 = dataptr[DCTSIZE*0] + dataptr[DCTSIZE*7]; |
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tmp7 = dataptr[DCTSIZE*0] - dataptr[DCTSIZE*7]; |
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tmp1 = dataptr[DCTSIZE*1] + dataptr[DCTSIZE*6]; |
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tmp6 = dataptr[DCTSIZE*1] - dataptr[DCTSIZE*6]; |
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tmp2 = dataptr[DCTSIZE*2] + dataptr[DCTSIZE*5]; |
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tmp5 = dataptr[DCTSIZE*2] - dataptr[DCTSIZE*5]; |
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tmp3 = dataptr[DCTSIZE*3] + dataptr[DCTSIZE*4]; |
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tmp4 = dataptr[DCTSIZE*3] - dataptr[DCTSIZE*4]; |
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/* Even part */ |
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tmp10 = tmp0 + tmp3; /* phase 2 */ |
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tmp13 = tmp0 - tmp3; |
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tmp11 = tmp1 + tmp2; |
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tmp12 = tmp1 - tmp2; |
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dataptr[DCTSIZE*0] = tmp10 + tmp11; /* phase 3 */ |
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dataptr[DCTSIZE*4] = tmp10 - tmp11; |
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z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */ |
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dataptr[DCTSIZE*2] = tmp13 + z1; /* phase 5 */ |
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dataptr[DCTSIZE*6] = tmp13 - z1; |
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/* Odd part */ |
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tmp10 = tmp4 + tmp5; /* phase 2 */ |
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tmp11 = tmp5 + tmp6; |
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tmp12 = tmp6 + tmp7; |
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/* The rotator is modified from fig 4-8 to avoid extra negations. */ |
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z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */ |
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z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5; /* c2-c6 */ |
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z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5; /* c2+c6 */ |
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z3 = MULTIPLY(tmp11, FIX_0_707106781); /* c4 */ |
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z11 = tmp7 + z3; /* phase 5 */ |
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z13 = tmp7 - z3; |
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dataptr[DCTSIZE*5] = z13 + z2; /* phase 6 */ |
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dataptr[DCTSIZE*3] = z13 - z2; |
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dataptr[DCTSIZE*1] = z11 + z4; |
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dataptr[DCTSIZE*7] = z11 - z4; |
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dataptr++; /* advance pointer to next column */ |
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} |
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} |
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/* |
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* Perform the forward 2-4-8 DCT on one block of samples. |
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*/ |
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GLOBAL(void) |
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fdct_ifast248 (DCTELEM * data) |
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{ |
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int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7; |
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int tmp10, tmp11, tmp12, tmp13; |
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int z1; |
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DCTELEM *dataptr; |
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int ctr; |
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row_fdct(data); |
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/* Pass 2: process columns. */ |
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dataptr = data; |
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for (ctr = DCTSIZE-1; ctr >= 0; ctr--) { |
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tmp0 = dataptr[DCTSIZE*0] + dataptr[DCTSIZE*1]; |
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tmp1 = dataptr[DCTSIZE*2] + dataptr[DCTSIZE*3]; |
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tmp2 = dataptr[DCTSIZE*4] + dataptr[DCTSIZE*5]; |
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tmp3 = dataptr[DCTSIZE*6] + dataptr[DCTSIZE*7]; |
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tmp4 = dataptr[DCTSIZE*0] - dataptr[DCTSIZE*1]; |
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tmp5 = dataptr[DCTSIZE*2] - dataptr[DCTSIZE*3]; |
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tmp6 = dataptr[DCTSIZE*4] - dataptr[DCTSIZE*5]; |
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tmp7 = dataptr[DCTSIZE*6] - dataptr[DCTSIZE*7]; |
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/* Even part */ |
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tmp10 = tmp0 + tmp3; |
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tmp11 = tmp1 + tmp2; |
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tmp12 = tmp1 - tmp2; |
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tmp13 = tmp0 - tmp3; |
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dataptr[DCTSIZE*0] = tmp10 + tmp11; |
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dataptr[DCTSIZE*4] = tmp10 - tmp11; |
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z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); |
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dataptr[DCTSIZE*2] = tmp13 + z1; |
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dataptr[DCTSIZE*6] = tmp13 - z1; |
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tmp10 = tmp4 + tmp7; |
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tmp11 = tmp5 + tmp6; |
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tmp12 = tmp5 - tmp6; |
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tmp13 = tmp4 - tmp7; |
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dataptr[DCTSIZE*1] = tmp10 + tmp11; |
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dataptr[DCTSIZE*5] = tmp10 - tmp11; |
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z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); |
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dataptr[DCTSIZE*3] = tmp13 + z1; |
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dataptr[DCTSIZE*7] = tmp13 - z1; |
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dataptr++; /* advance pointer to next column */ |
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} |
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} |
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#undef GLOBAL |
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#undef CONST_BITS |
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#undef DESCALE |
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#undef FIX_0_541196100 |
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#undef FIX_1_306562965
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