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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.  
  31. void ff_jpegls_init_state(JLSState *state)
  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.  
  62. void ff_jpegls_reset_coding_parameters(JLSState *s, int reset_all)
  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. }
  102.