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jpegls.c
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1 /*
2  * JPEG-LS common code
3  * Copyright (c) 2003 Michael Niedermayer
4  * Copyright (c) 2006 Konstantin Shishkov
5  *
6  * This file is part of FFmpeg.
7  *
8  * FFmpeg is free software; you can redistribute it and/or
9  * modify it under the terms of the GNU Lesser General Public
10  * License as published by the Free Software Foundation; either
11  * version 2.1 of the License, or (at your option) any later version.
12  *
13  * FFmpeg is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16  * Lesser General Public License for more details.
17  *
18  * You should have received a copy of the GNU Lesser General Public
19  * License along with FFmpeg; if not, write to the Free Software
20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21  */
22 
23 /**
24  * @file
25  * JPEG-LS common code.
26  */
27 
28 #include "internal.h"
29 #include "jpegls.h"
30 
32 {
33  int i;
34 
35  state->twonear = state->near * 2 + 1;
36  state->range = (state->maxval + state->twonear - 1) / state->twonear + 1;
37 
38  // QBPP = ceil(log2(RANGE))
39  for (state->qbpp = 0; (1 << state->qbpp) < state->range; state->qbpp++)
40  ;
41 
42  state->bpp = FFMAX(av_log2(state->maxval) + 1, 2);
43  state->limit = 2*(state->bpp + FFMAX(state->bpp, 8)) - state->qbpp;
44 
45  for (i = 0; i < 367; i++) {
46  state->A[i] = FFMAX(state->range + 32 >> 6, 2);
47  state->N[i] = 1;
48  }
49 }
50 
51 /**
52  * Custom value clipping function used in T1, T2, T3 calculation
53  */
54 static inline int iso_clip(int v, int vmin, int vmax)
55 {
56  if (v > vmax || v < vmin)
57  return vmin;
58  else
59  return v;
60 }
61 
63 {
64  const int basic_t1 = 3;
65  const int basic_t2 = 7;
66  const int basic_t3 = 21;
67  int factor;
68 
69  if (s->maxval == 0 || reset_all)
70  s->maxval = (1 << s->bpp) - 1;
71 
72  if (s->maxval >= 128) {
73  factor = FFMIN(s->maxval, 4095) + 128 >> 8;
74 
75  if (s->T1 == 0 || reset_all)
76  s->T1 = iso_clip(factor * (basic_t1 - 2) + 2 + 3 * s->near,
77  s->near + 1, s->maxval);
78  if (s->T2 == 0 || reset_all)
79  s->T2 = iso_clip(factor * (basic_t2 - 3) + 3 + 5 * s->near,
80  s->T1, s->maxval);
81  if (s->T3 == 0 || reset_all)
82  s->T3 = iso_clip(factor * (basic_t3 - 4) + 4 + 7 * s->near,
83  s->T2, s->maxval);
84  } else {
85  factor = 256 / (s->maxval + 1);
86 
87  if (s->T1 == 0 || reset_all)
88  s->T1 = iso_clip(FFMAX(2, basic_t1 / factor + 3 * s->near),
89  s->near + 1, s->maxval);
90  if (s->T2 == 0 || reset_all)
91  s->T2 = iso_clip(FFMAX(3, basic_t2 / factor + 5 * s->near),
92  s->T1, s->maxval);
93  if (s->T3 == 0 || reset_all)
94  s->T3 = iso_clip(FFMAX(4, basic_t3 / factor + 7 * s->near),
95  s->T2, s->maxval);
96  }
97 
98  if (s->reset == 0 || reset_all)
99  s->reset = 64;
100  ff_dlog(NULL, "[JPEG-LS RESET] T=%i,%i,%i\n", s->T1, s->T2, s->T3);
101 }