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   1 /*
   2  * Copyright (c) 2012 Konstantin Shishkov
   3  *
   4  * This file is part of FFmpeg.
   5  *
   6  * FFmpeg is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * FFmpeg is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with FFmpeg; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19  */
  20
  21 /**
  22  * @file
  23  * Common header for Microsoft Screen 1 and 2
  24  */
  25
  26 #ifndef AVCODEC_MSS12_H
  27 #define AVCODEC_MSS12_H
  28
  29 #include "libavutil/intreadwrite.h"
  30 #include "avcodec.h"
  31 #include "get_bits.h"
  32 #include "bytestream.h"
  33
  34 #define MODEL_MIN_SYMS    2
  35 #define MODEL_MAX_SYMS  256
  36 #define THRESH_ADAPTIVE  -1
  37 #define THRESH_LOW       15
  38 #define THRESH_HIGH      50
  39
  40 typedef struct Model {
  41     int16_t cum_prob[MODEL_MAX_SYMS + 1];
  42     int16_t weights[MODEL_MAX_SYMS + 1];
  43     uint8_t idx2sym[MODEL_MAX_SYMS + 1];
  44     int num_syms;
  45     int thr_weight, threshold;
  46 } Model;
  47
  48 typedef struct ArithCoder {
  49     int low, high, value;
  50     union {
  51         GetBitContext *gb;
  52         GetByteContext *gB;
  53     } gbc;
  54     int (*get_model_sym)(struct ArithCoder *c, Model *m);
  55     int (*get_number)   (struct ArithCoder *c, int n);
  56 } ArithCoder;
  57
  58 typedef struct PixContext {
  59     int cache_size, num_syms;
  60     uint8_t cache[12];
  61     Model cache_model, full_model;
  62     Model sec_models[15][4];
  63     int special_initial_cache;
  64 } PixContext;
  65
  66 struct MSS12Context;
  67
  68 typedef struct SliceContext {
  69     struct MSS12Context *c;
  70     Model      intra_region, inter_region;
  71     Model      pivot, edge_mode, split_mode;
  72     PixContext intra_pix_ctx, inter_pix_ctx;
  73 } SliceContext;
  74
  75 typedef struct MSS12Context {
  76     AVCodecContext *avctx;
  77     uint32_t       pal[256];
  78     uint8_t        *pal_pic;
  79     uint8_t        *last_pal_pic;
  80     ptrdiff_t      pal_stride;
  81     uint8_t        *mask;
  82     ptrdiff_t      mask_stride;
  83     uint8_t        *rgb_pic;
  84     uint8_t        *last_rgb_pic;
  85     ptrdiff_t      rgb_stride;
  86     int            free_colours;
  87     int            keyframe;
  88     int            mvX, mvY;
  89     int            corrupted;
  90     int            slice_split;
  91     int            full_model_syms;
  92 } MSS12Context;
  93
  94 int ff_mss12_decode_rect(SliceContext *ctx, ArithCoder *acoder,
  95                          int x, int y, int width, int height);
  96 void ff_mss12_model_update(Model *m, int val);
  97 void ff_mss12_slicecontext_reset(SliceContext *sc);
  98 int ff_mss12_decode_init(MSS12Context *c, int version,
  99                          SliceContext *sc1, SliceContext *sc2);
 100 int ff_mss12_decode_end(MSS12Context *ctx);
 101
 102 #define ARITH_GET_BIT(prefix)                                           \
 103 static int prefix ## _get_bit(ArithCoder *c)                            \
 104 {                                                                       \
 105     int range = c->high - c->low + 1;                                   \
 106     int bit   = 2 * c->value - c->low >= c->high;                       \
 107                                                                         \
 108     if (bit)                                                            \
 109         c->low += range >> 1;                                           \
 110     else                                                                \
 111         c->high = c->low + (range >> 1) - 1;                            \
 112                                                                         \
 113     prefix ## _normalise(c);                                            \
 114                                                                         \
 115     return bit;                                                         \
 116 }
 117
 118 #define ARITH_GET_MODEL_SYM(prefix)                                     \
 119 static int prefix ## _get_model_sym(ArithCoder *c, Model *m)            \
 120 {                                                                       \
 121     int idx, val;                                                       \
 122                                                                         \
 123     idx = prefix ## _get_prob(c, m->cum_prob);                          \
 124                                                                         \
 125     val = m->idx2sym[idx];                                              \
 126     ff_mss12_model_update(m, idx);                                      \
 127                                                                         \
 128     prefix ## _normalise(c);                                            \
 129                                                                         \
 130     return val;                                                         \
 131 }
 132
 133 #endif /* AVCODEC_MSS12_H */