nest-open-source / manifest_repos / ffmpeg / 62cf23d89db2251203d6207e2261ddc5498167c6 / . / libavcodec / jfdctfst.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) 1994-1996, 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 fast, not so 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 Arai, Agui, and Nakajima's algorithm for | |

* scaled DCT. Their original paper (Trans. IEICE E-71(11):1095) is in | |

* Japanese, but the algorithm is described in the Pennebaker & Mitchell | |

* JPEG textbook (see REFERENCES section in file README). The following code | |

* is based directly on figure 4-8 in P&M. | |

* While an 8-point DCT cannot be done in less than 11 multiplies, it is | |

* possible to arrange the computation so that many of the multiplies are | |

* simple scalings of the final outputs. These multiplies can then be | |

* folded into the multiplications or divisions by the JPEG quantization | |

* table entries. The AA&N method leaves only 5 multiplies and 29 adds | |

* to be done in the DCT itself. | |

* The primary disadvantage of this method is that with fixed-point math, | |

* accuracy is lost due to imprecise representation of the scaled | |

* quantization values. The smaller the quantization table entry, the less | |

* precise the scaled value, so this implementation does worse with high- | |

* quality-setting files than with low-quality ones. | |

*/ | |

/** | |

* @file | |

* Independent JPEG Group's fast AAN dct. | |

*/ | |

#include <stdlib.h> | |

#include <stdio.h> | |

#include "libavutil/common.h" | |

#include "dct.h" | |

#define DCTSIZE 8 | |

#define GLOBAL(x) x | |

#define RIGHT_SHIFT(x, n) ((x) >> (n)) | |

/* | |

* This module is specialized to the case DCTSIZE = 8. | |

*/ | |

#if DCTSIZE != 8 | |

Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */ | |

#endif | |

/* Scaling decisions are generally the same as in the LL&M algorithm; | |

* see jfdctint.c for more details. However, we choose to descale | |

* (right shift) multiplication products as soon as they are formed, | |

* rather than carrying additional fractional bits into subsequent additions. | |

* This compromises accuracy slightly, but it lets us save a few shifts. | |

* More importantly, 16-bit arithmetic is then adequate (for 8-bit samples) | |

* everywhere except in the multiplications proper; this saves a good deal | |

* of work on 16-bit-int machines. | |

* | |

* Again to save a few shifts, the intermediate results between pass 1 and | |

* pass 2 are not upscaled, but are represented only to integral precision. | |

* | |

* A final compromise is to represent the multiplicative constants to only | |

* 8 fractional bits, rather than 13. This saves some shifting work on some | |

* machines, and may also reduce the cost of multiplication (since there | |

* are fewer one-bits in the constants). | |

*/ | |

#define CONST_BITS 8 | |

/* 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 == 8 | |

#define FIX_0_382683433 ((int32_t) 98) /* FIX(0.382683433) */ | |

#define FIX_0_541196100 ((int32_t) 139) /* FIX(0.541196100) */ | |

#define FIX_0_707106781 ((int32_t) 181) /* FIX(0.707106781) */ | |

#define FIX_1_306562965 ((int32_t) 334) /* FIX(1.306562965) */ | |

#else | |

#define FIX_0_382683433 FIX(0.382683433) | |

#define FIX_0_541196100 FIX(0.541196100) | |

#define FIX_0_707106781 FIX(0.707106781) | |

#define FIX_1_306562965 FIX(1.306562965) | |

#endif | |

/* We can gain a little more speed, with a further compromise in accuracy, | |

* by omitting the addition in a descaling shift. This yields an incorrectly | |

* rounded result half the time... | |

*/ | |

#ifndef USE_ACCURATE_ROUNDING | |

#undef DESCALE | |

#define DESCALE(x,n) RIGHT_SHIFT(x, n) | |

#endif | |

/* Multiply a int16_t variable by an int32_t constant, and immediately | |

* descale to yield a int16_t result. | |

*/ | |

#define MULTIPLY(var,const) ((int16_t) DESCALE((var) * (const), CONST_BITS)) | |

static av_always_inline void row_fdct(int16_t * data){ | |

int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7; | |

int tmp10, tmp11, tmp12, tmp13; | |

int z1, z2, z3, z4, z5, z11, z13; | |

int16_t *dataptr; | |

int ctr; | |

/* Pass 1: process rows. */ | |

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 */ | |

tmp10 = tmp0 + tmp3; /* phase 2 */ | |

tmp13 = tmp0 - tmp3; | |

tmp11 = tmp1 + tmp2; | |

tmp12 = tmp1 - tmp2; | |

dataptr[0] = tmp10 + tmp11; /* phase 3 */ | |

dataptr[4] = tmp10 - tmp11; | |

z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */ | |

dataptr[2] = tmp13 + z1; /* phase 5 */ | |

dataptr[6] = tmp13 - z1; | |

/* Odd part */ | |

tmp10 = tmp4 + tmp5; /* phase 2 */ | |

tmp11 = tmp5 + tmp6; | |

tmp12 = tmp6 + tmp7; | |

/* The rotator is modified from fig 4-8 to avoid extra negations. */ | |

z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */ | |

z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5; /* c2-c6 */ | |

z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5; /* c2+c6 */ | |

z3 = MULTIPLY(tmp11, FIX_0_707106781); /* c4 */ | |

z11 = tmp7 + z3; /* phase 5 */ | |

z13 = tmp7 - z3; | |

dataptr[5] = z13 + z2; /* phase 6 */ | |

dataptr[3] = z13 - z2; | |

dataptr[1] = z11 + z4; | |

dataptr[7] = z11 - z4; | |

dataptr += DCTSIZE; /* advance pointer to next row */ | |

} | |

} | |

/* | |

* Perform the forward DCT on one block of samples. | |

*/ | |

GLOBAL(void) | |

ff_fdct_ifast (int16_t * data) | |

{ | |

int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7; | |

int tmp10, tmp11, tmp12, tmp13; | |

int z1, z2, z3, z4, z5, z11, z13; | |

int16_t *dataptr; | |

int ctr; | |

row_fdct(data); | |

/* Pass 2: process columns. */ | |

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 */ | |

tmp10 = tmp0 + tmp3; /* phase 2 */ | |

tmp13 = tmp0 - tmp3; | |

tmp11 = tmp1 + tmp2; | |

tmp12 = tmp1 - tmp2; | |

dataptr[DCTSIZE*0] = tmp10 + tmp11; /* phase 3 */ | |

dataptr[DCTSIZE*4] = tmp10 - tmp11; | |

z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */ | |

dataptr[DCTSIZE*2] = tmp13 + z1; /* phase 5 */ | |

dataptr[DCTSIZE*6] = tmp13 - z1; | |

/* Odd part */ | |

tmp10 = tmp4 + tmp5; /* phase 2 */ | |

tmp11 = tmp5 + tmp6; | |

tmp12 = tmp6 + tmp7; | |

/* The rotator is modified from fig 4-8 to avoid extra negations. */ | |

z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */ | |

z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5; /* c2-c6 */ | |

z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5; /* c2+c6 */ | |

z3 = MULTIPLY(tmp11, FIX_0_707106781); /* c4 */ | |

z11 = tmp7 + z3; /* phase 5 */ | |

z13 = tmp7 - z3; | |

dataptr[DCTSIZE*5] = z13 + z2; /* phase 6 */ | |

dataptr[DCTSIZE*3] = z13 - z2; | |

dataptr[DCTSIZE*1] = z11 + z4; | |

dataptr[DCTSIZE*7] = z11 - z4; | |

dataptr++; /* advance pointer to next column */ | |

} | |

} | |

/* | |

* Perform the forward 2-4-8 DCT on one block of samples. | |

*/ | |

GLOBAL(void) | |

ff_fdct_ifast248 (int16_t * data) | |

{ | |

int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7; | |

int tmp10, tmp11, tmp12, tmp13; | |

int z1; | |

int16_t *dataptr; | |

int ctr; | |

row_fdct(data); | |

/* Pass 2: process columns. */ | |

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]; | |

/* Even part */ | |

tmp10 = tmp0 + tmp3; | |

tmp11 = tmp1 + tmp2; | |

tmp12 = tmp1 - tmp2; | |

tmp13 = tmp0 - tmp3; | |

dataptr[DCTSIZE*0] = tmp10 + tmp11; | |

dataptr[DCTSIZE*4] = tmp10 - tmp11; | |

z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); | |

dataptr[DCTSIZE*2] = tmp13 + z1; | |

dataptr[DCTSIZE*6] = tmp13 - z1; | |

tmp10 = tmp4 + tmp7; | |

tmp11 = tmp5 + tmp6; | |

tmp12 = tmp5 - tmp6; | |

tmp13 = tmp4 - tmp7; | |

dataptr[DCTSIZE*1] = tmp10 + tmp11; | |

dataptr[DCTSIZE*5] = tmp10 - tmp11; | |

z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); | |

dataptr[DCTSIZE*3] = tmp13 + z1; | |

dataptr[DCTSIZE*7] = tmp13 - z1; | |

dataptr++; /* advance pointer to next column */ | |

} | |

} | |

#undef GLOBAL | |

#undef CONST_BITS | |

#undef DESCALE | |

#undef FIX_0_541196100 | |

#undef FIX_1_306562965 |