libavcodec/escape124.c

   1 /*
   2  * Escape 124 Video Decoder
   3  * Copyright (C) 2008 Eli Friedman (eli.friedman@gmail.com)
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 #include "avcodec.h"
  23
  24 #define ALT_BITSTREAM_READER_LE
  25 #include "bitstream.h"
  26
  27 typedef union MacroBlock {
  28     uint16_t pixels[4];
  29     uint32_t pixels32[2];
  30 } MacroBlock;
  31
  32 typedef union SuperBlock {
  33     uint16_t pixels[64];
  34     uint32_t pixels32[32];
  35 } SuperBlock;
  36
  37 typedef struct CodeBook {
  38     unsigned depth;
  39     unsigned size;
  40     MacroBlock* blocks;
  41 } CodeBook;
  42
  43 typedef struct Escape124Context {
  44     AVFrame frame;
  45
  46     unsigned num_superblocks;
  47
  48     CodeBook codebooks[3];
  49 } Escape124Context;
  50
  51 static int can_safely_read(GetBitContext* gb, int bits) {
  52     return get_bits_count(gb) + bits <= gb->size_in_bits;
  53 }
  54
  55 /**
  56  * Initialize the decoder
  57  * @param avctx decoder context
  58  * @return 0 success, negative on error
  59  */
  60 static av_cold int escape124_decode_init(AVCodecContext *avctx)
  61 {
  62     Escape124Context *s = avctx->priv_data;
  63
  64     avctx->pix_fmt = PIX_FMT_RGB555;
  65
  66     s->num_superblocks = ((unsigned)avctx->width / 8) *
  67                          ((unsigned)avctx->height / 8);
  68
  69     return 0;
  70 }
  71
  72 static av_cold int escape124_decode_close(AVCodecContext *avctx)
  73 {
  74     unsigned i;
  75     Escape124Context *s = avctx->priv_data;
  76
  77     for (i = 0; i < 3; i++)
  78         av_free(s->codebooks[i].blocks);
  79
  80     if (s->frame.data[0])
  81         avctx->release_buffer(avctx, &s->frame);
  82
  83     return 0;
  84 }
  85
  86 static CodeBook unpack_codebook(GetBitContext* gb, unsigned depth,
  87                                  unsigned size)
  88 {
  89     unsigned i, j;
  90     CodeBook cb = { 0 };
  91
  92     if (!can_safely_read(gb, size * 34))
  93         return cb;
  94
  95     if (size >= INT_MAX / sizeof(MacroBlock))
  96         return cb;
  97     cb.blocks = av_malloc(size ? size * sizeof(MacroBlock) : 1);
  98     if (!cb.blocks)
  99         return cb;
 100
 101     cb.depth = depth;
 102     cb.size = size;
 103     for (i = 0; i < size; i++) {
 104         unsigned mask_bits = get_bits(gb, 4);
 105         unsigned color0 = get_bits(gb, 15);
 106         unsigned color1 = get_bits(gb, 15);
 107
 108         for (j = 0; j < 4; j++) {
 109             if (mask_bits & (1 << j))
 110                 cb.blocks[i].pixels[j] = color1;
 111             else
 112                 cb.blocks[i].pixels[j] = color0;
 113         }
 114     }
 115     return cb;
 116 }
 117
 118 static unsigned decode_skip_count(GetBitContext* gb)
 119 {
 120     unsigned value;
 121     // This function reads a maximum of 23 bits,
 122     // which is within the padding space
 123     if (!can_safely_read(gb, 1))
 124         return -1;
 125     value = get_bits1(gb);
 126     if (!value)
 127         return value;
 128
 129     value += get_bits(gb, 3);
 130     if (value != (1 + ((1 << 3) - 1)))
 131         return value;
 132
 133     value += get_bits(gb, 7);
 134     if (value != (1 + ((1 << 3) - 1)) + ((1 << 7) - 1))
 135         return value;
 136
 137     return value + get_bits(gb, 12);
 138 }
 139
 140 static MacroBlock decode_macroblock(Escape124Context* s, GetBitContext* gb,
 141                                     int* codebook_index, int superblock_index)
 142 {
 143     // This function reads a maximum of 22 bits; the callers
 144     // guard this function appropriately
 145     unsigned block_index, depth;
 146
 147     if (get_bits1(gb)) {
 148         static const char transitions[3][2] = { {2, 1}, {0, 2}, {1, 0} };
 149         *codebook_index = transitions[*codebook_index][get_bits1(gb)];
 150     }
 151
 152     depth = s->codebooks[*codebook_index].depth;
 153
 154     // depth = 0 means that this shouldn't read any bits;
 155     // in theory, this is the same as get_bits(gb, 0), but
 156     // that doesn't actually work.
 157     block_index = depth ? get_bits(gb, depth) : 0;
 158
 159     if (*codebook_index == 1) {
 160         block_index += superblock_index << s->codebooks[1].depth;
 161     }
 162
 163     // This condition can occur with invalid bitstreams and
 164     // *codebook_index == 2
 165     if (block_index >= s->codebooks[*codebook_index].size)
 166         return (MacroBlock) { { 0 } };
 167
 168     return s->codebooks[*codebook_index].blocks[block_index];
 169 }
 170
 171 static void insert_mb_into_sb(SuperBlock* sb, MacroBlock mb, unsigned index) {
 172    // Formula: ((index / 4) * 16 + (index % 4) * 2) / 2
 173    uint32_t *dst = sb->pixels32 + index + (index & -4);
 174
 175    // This technically violates C99 aliasing rules, but it should be safe.
 176    dst[0] = mb.pixels32[0];
 177    dst[4] = mb.pixels32[1];
 178 }
 179
 180 static void copy_superblock(uint16_t* dest, unsigned dest_stride,
 181                             uint16_t* src, unsigned src_stride)
 182 {
 183     unsigned y;
 184     if (src)
 185         for (y = 0; y < 8; y++)
 186             memcpy(dest + y * dest_stride, src + y * src_stride,
 187                    sizeof(uint16_t) * 8);
 188     else
 189         for (y = 0; y < 8; y++)
 190             memset(dest + y * dest_stride, 0, sizeof(uint16_t) * 8);
 191 }
 192
 193 static const uint16_t mask_matrix[] = {0x1,   0x2,   0x10,   0x20,
 194                                        0x4,   0x8,   0x40,   0x80,
 195                                        0x100, 0x200, 0x1000, 0x2000,
 196                                        0x400, 0x800, 0x4000, 0x8000};
 197
 198 /**
 199  * Decode a single frame
 200  * @param avctx decoder context
 201  * @param data decoded frame
 202  * @param data_size size of the decoded frame
 203  * @param buf input buffer
 204  * @param buf_size input buffer size
 205  * @return 0 success, -1 on error
 206  */
 207 static int escape124_decode_frame(AVCodecContext *avctx,
 208                                   void *data, int *data_size,
 209                                   const uint8_t *buf, int buf_size)
 210 {
 211     Escape124Context *s = avctx->priv_data;
 212
 213     GetBitContext gb;
 214     unsigned frame_flags, frame_size;
 215     unsigned i;
 216
 217     unsigned superblock_index, cb_index = 1,
 218              superblock_col_index = 0,
 219              superblocks_per_row = avctx->width / 8, skip = -1;
 220
 221     uint16_t* old_frame_data, *new_frame_data;
 222     unsigned old_stride, new_stride;
 223
 224     AVFrame new_frame = { { 0 } };
 225
 226     init_get_bits(&gb, buf, buf_size * 8);
 227
 228     // This call also guards the potential depth reads for the
 229     // codebook unpacking.
 230     if (!can_safely_read(&gb, 64))
 231         return -1;
 232
 233     frame_flags = get_bits_long(&gb, 32);
 234     frame_size  = get_bits_long(&gb, 32);
 235
 236     // Leave last frame unchanged
 237     // FIXME: Is this necessary?  I haven't seen it in any real samples
 238     if (!(frame_flags & 0x114) || !(frame_flags & 0x7800000)) {
 239         av_log(NULL, AV_LOG_DEBUG, "Skipping frame\n");
 240
 241         *data_size = sizeof(AVFrame);
 242         *(AVFrame*)data = s->frame;
 243
 244         return frame_size;
 245     }
 246
 247     for (i = 0; i < 3; i++) {
 248         if (frame_flags & (1 << (17 + i))) {
 249             unsigned cb_depth, cb_size;
 250             if (i == 2) {
 251                 // This codebook can be cut off at places other than
 252                 // powers of 2, leaving some of the entries undefined.
 253                 cb_size = get_bits_long(&gb, 20);
 254                 cb_depth = av_log2(cb_size - 1) + 1;
 255             } else {
 256                 cb_depth = get_bits(&gb, 4);
 257                 if (i == 0) {
 258                     // This is the most basic codebook: pow(2,depth) entries
 259                     // for a depth-length key
 260                     cb_size = 1 << cb_depth;
 261                 } else {
 262                     // This codebook varies per superblock
 263                     // FIXME: I don't think this handles integer overflow
 264                     // properly
 265                     cb_size = s->num_superblocks << cb_depth;
 266                 }
 267             }
 268             av_free(s->codebooks[i].blocks);
 269             s->codebooks[i] = unpack_codebook(&gb, cb_depth, cb_size);
 270             if (!s->codebooks[i].blocks)
 271                 return -1;
 272         }
 273     }
 274
 275     new_frame.reference = 3;
 276     if (avctx->get_buffer(avctx, &new_frame)) {
 277         av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
 278         return -1;
 279     }
 280
 281     new_frame_data = (uint16_t*)new_frame.data[0];
 282     new_stride = new_frame.linesize[0] / 2;
 283     old_frame_data = (uint16_t*)s->frame.data[0];
 284     old_stride = s->frame.linesize[0] / 2;
 285
 286     for (superblock_index = 0; superblock_index < s->num_superblocks;
 287          superblock_index++) {
 288         MacroBlock mb;
 289         SuperBlock sb;
 290         unsigned multi_mask = 0;
 291
 292         if (skip == -1) {
 293             // Note that this call will make us skip the rest of the blocks
 294             // if the frame prematurely ends
 295             skip = decode_skip_count(&gb);
 296         }
 297
 298         if (skip) {
 299             copy_superblock(new_frame_data, new_stride,
 300                             old_frame_data, old_stride);
 301         } else {
 302             copy_superblock(sb.pixels, 8,
 303                             old_frame_data, old_stride);
 304
 305             while (can_safely_read(&gb, 1) && !get_bits1(&gb)) {
 306                 unsigned mask;
 307                 mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
 308                 mask = get_bits(&gb, 16);
 309                 multi_mask |= mask;
 310                 for (i = 0; i < 16; i++) {
 311                     if (mask & mask_matrix[i]) {
 312                         insert_mb_into_sb(&sb, mb, i);
 313                     }
 314                 }
 315             }
 316
 317             if (can_safely_read(&gb, 1) && !get_bits1(&gb)) {
 318                 unsigned inv_mask = get_bits(&gb, 4);
 319                 for (i = 0; i < 4; i++) {
 320                     if (inv_mask & (1 << i)) {
 321                         multi_mask ^= 0xF << i*4;
 322                     } else {
 323                         multi_mask ^= get_bits(&gb, 4) << i*4;
 324                     }
 325                 }
 326
 327                 for (i = 0; i < 16; i++) {
 328                     if (multi_mask & mask_matrix[i]) {
 329                         if (!can_safely_read(&gb, 1))
 330                             break;
 331                         mb = decode_macroblock(s, &gb, &cb_index,
 332                                                superblock_index);
 333                         insert_mb_into_sb(&sb, mb, i);
 334                     }
 335                 }
 336             } else if (frame_flags & (1 << 16)) {
 337                 while (can_safely_read(&gb, 1) && !get_bits1(&gb)) {
 338                     mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
 339                     insert_mb_into_sb(&sb, mb, get_bits(&gb, 4));
 340                 }
 341             }
 342
 343             copy_superblock(new_frame_data, new_stride, sb.pixels, 8);
 344         }
 345
 346         superblock_col_index++;
 347         new_frame_data += 8;
 348         if (old_frame_data)
 349             old_frame_data += 8;
 350         if (superblock_col_index == superblocks_per_row) {
 351             new_frame_data += new_stride * 8 - superblocks_per_row * 8;
 352             if (old_frame_data)
 353                 old_frame_data += old_stride * 8 - superblocks_per_row * 8;
 354             superblock_col_index = 0;
 355         }
 356         skip--;
 357     }
 358
 359     av_log(NULL, AV_LOG_DEBUG,
 360            "Escape sizes: %i, %i, %i\n",
 361            frame_size, buf_size, get_bits_count(&gb) / 8);
 362
 363     if (s->frame.data[0])
 364         avctx->release_buffer(avctx, &s->frame);
 365
 366     *(AVFrame*)data = s->frame = new_frame;
 367     *data_size = sizeof(AVFrame);
 368
 369     return frame_size;
 370 }
 371
 372
 373 AVCodec escape124_decoder = {
 374     "escape124",
 375     CODEC_TYPE_VIDEO,
 376     CODEC_ID_ESCAPE124,
 377     sizeof(Escape124Context),
 378     escape124_decode_init,
 379     NULL,
 380     escape124_decode_close,
 381     escape124_decode_frame,
 382     CODEC_CAP_DR1,
 383     .long_name = NULL_IF_CONFIG_SMALL("Escape 124"),
 384 };
 385