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 Libav.
   6  *
   7  * Libav 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  * Libav 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 Libav; 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 #include "internal.h"
  24
  25 #define BITSTREAM_READER_LE
  26 #include "get_bits.h"
  27
  28 typedef union MacroBlock {
  29     uint16_t pixels[4];
  30     uint32_t pixels32[2];
  31 } MacroBlock;
  32
  33 typedef union SuperBlock {
  34     uint16_t pixels[64];
  35     uint32_t pixels32[32];
  36 } SuperBlock;
  37
  38 typedef struct CodeBook {
  39     unsigned depth;
  40     unsigned size;
  41     MacroBlock* blocks;
  42 } CodeBook;
  43
  44 typedef struct Escape124Context {
  45     AVFrame *frame;
  46
  47     unsigned num_superblocks;
  48
  49     CodeBook codebooks[3];
  50 } Escape124Context;
  51
  52 static int can_safely_read(GetBitContext* gb, int bits) {
  53     return get_bits_left(gb) >= bits;
  54 }
  55
  56 /**
  57  * Initialize the decoder
  58  * @param avctx decoder context
  59  * @return 0 success, negative on error
  60  */
  61 static av_cold int escape124_decode_init(AVCodecContext *avctx)
  62 {
  63     Escape124Context *s = avctx->priv_data;
  64
  65     avctx->pix_fmt = AV_PIX_FMT_RGB555;
  66
  67     s->num_superblocks = ((unsigned)avctx->width / 8) *
  68                          ((unsigned)avctx->height / 8);
  69
  70     s->frame = av_frame_alloc();
  71     if (!s->frame)
  72         return AVERROR(ENOMEM);
  73
  74     return 0;
  75 }
  76
  77 static av_cold int escape124_decode_close(AVCodecContext *avctx)
  78 {
  79     unsigned i;
  80     Escape124Context *s = avctx->priv_data;
  81
  82     for (i = 0; i < 3; i++)
  83         av_free(s->codebooks[i].blocks);
  84
  85     av_frame_free(&s->frame);
  86
  87     return 0;
  88 }
  89
  90 static CodeBook unpack_codebook(GetBitContext* gb, unsigned depth,
  91                                  unsigned size)
  92 {
  93     unsigned i, j;
  94     CodeBook cb = { 0 };
  95
  96     if (!can_safely_read(gb, size * 34))
  97         return cb;
  98
  99     if (size >= INT_MAX / sizeof(MacroBlock))
 100         return cb;
 101     cb.blocks = av_malloc(size ? size * sizeof(MacroBlock) : 1);
 102     if (!cb.blocks)
 103         return cb;
 104
 105     cb.depth = depth;
 106     cb.size = size;
 107     for (i = 0; i < size; i++) {
 108         unsigned mask_bits = get_bits(gb, 4);
 109         unsigned color0 = get_bits(gb, 15);
 110         unsigned color1 = get_bits(gb, 15);
 111
 112         for (j = 0; j < 4; j++) {
 113             if (mask_bits & (1 << j))
 114                 cb.blocks[i].pixels[j] = color1;
 115             else
 116                 cb.blocks[i].pixels[j] = color0;
 117         }
 118     }
 119     return cb;
 120 }
 121
 122 static unsigned decode_skip_count(GetBitContext* gb)
 123 {
 124     unsigned value;
 125     // This function reads a maximum of 23 bits,
 126     // which is within the padding space
 127     if (!can_safely_read(gb, 1))
 128         return -1;
 129     value = get_bits1(gb);
 130     if (!value)
 131         return value;
 132
 133     value += get_bits(gb, 3);
 134     if (value != (1 + ((1 << 3) - 1)))
 135         return value;
 136
 137     value += get_bits(gb, 7);
 138     if (value != (1 + ((1 << 3) - 1)) + ((1 << 7) - 1))
 139         return value;
 140
 141     return value + get_bits(gb, 12);
 142 }
 143
 144 static MacroBlock decode_macroblock(Escape124Context* s, GetBitContext* gb,
 145                                     int* codebook_index, int superblock_index)
 146 {
 147     // This function reads a maximum of 22 bits; the callers
 148     // guard this function appropriately
 149     unsigned block_index, depth;
 150     int value = get_bits1(gb);
 151     if (value) {
 152         static const char transitions[3][2] = { {2, 1}, {0, 2}, {1, 0} };
 153         value = get_bits1(gb);
 154         *codebook_index = transitions[*codebook_index][value];
 155     }
 156
 157     depth = s->codebooks[*codebook_index].depth;
 158
 159     // depth = 0 means that this shouldn't read any bits;
 160     // in theory, this is the same as get_bits(gb, 0), but
 161     // that doesn't actually work.
 162     block_index = depth ? get_bits(gb, depth) : 0;
 163
 164     if (*codebook_index == 1) {
 165         block_index += superblock_index << s->codebooks[1].depth;
 166     }
 167
 168     // This condition can occur with invalid bitstreams and
 169     // *codebook_index == 2
 170     if (block_index >= s->codebooks[*codebook_index].size)
 171         return (MacroBlock) { { 0 } };
 172
 173     return s->codebooks[*codebook_index].blocks[block_index];
 174 }
 175
 176 static void insert_mb_into_sb(SuperBlock* sb, MacroBlock mb, unsigned index) {
 177    // Formula: ((index / 4) * 16 + (index % 4) * 2) / 2
 178    uint32_t *dst = sb->pixels32 + index + (index & -4);
 179
 180    // This technically violates C99 aliasing rules, but it should be safe.
 181    dst[0] = mb.pixels32[0];
 182    dst[4] = mb.pixels32[1];
 183 }
 184
 185 static void copy_superblock(uint16_t* dest, unsigned dest_stride,
 186                             uint16_t* src, unsigned src_stride)
 187 {
 188     unsigned y;
 189     if (src)
 190         for (y = 0; y < 8; y++)
 191             memcpy(dest + y * dest_stride, src + y * src_stride,
 192                    sizeof(uint16_t) * 8);
 193     else
 194         for (y = 0; y < 8; y++)
 195             memset(dest + y * dest_stride, 0, sizeof(uint16_t) * 8);
 196 }
 197
 198 static const uint16_t mask_matrix[] = {0x1,   0x2,   0x10,   0x20,
 199                                        0x4,   0x8,   0x40,   0x80,
 200                                        0x100, 0x200, 0x1000, 0x2000,
 201                                        0x400, 0x800, 0x4000, 0x8000};
 202
 203 static int escape124_decode_frame(AVCodecContext *avctx,
 204                                   void *data, int *got_frame,
 205                                   AVPacket *avpkt)
 206 {
 207     const uint8_t *buf = avpkt->data;
 208     int buf_size = avpkt->size;
 209     Escape124Context *s = avctx->priv_data;
 210     AVFrame *frame = data;
 211
 212     GetBitContext gb;
 213     unsigned frame_flags, frame_size;
 214     unsigned i;
 215
 216     unsigned superblock_index, cb_index = 1,
 217              superblock_col_index = 0,
 218              superblocks_per_row = avctx->width / 8, skip = -1;
 219
 220     uint16_t* old_frame_data, *new_frame_data;
 221     unsigned old_stride, new_stride;
 222     int ret;
 223
 224     init_get_bits(&gb, buf, buf_size * 8);
 225
 226     // This call also guards the potential depth reads for the
 227     // codebook unpacking.
 228     if (!can_safely_read(&gb, 64))
 229         return -1;
 230
 231     frame_flags = get_bits_long(&gb, 32);
 232     frame_size  = get_bits_long(&gb, 32);
 233
 234     // Leave last frame unchanged
 235     // FIXME: Is this necessary?  I haven't seen it in any real samples
 236     if (!(frame_flags & 0x114) || !(frame_flags & 0x7800000)) {
 237         if (!s->frame->data[0])
 238             return AVERROR_INVALIDDATA;
 239
 240         av_log(NULL, AV_LOG_DEBUG, "Skipping frame\n");
 241
 242         *got_frame = 1;
 243         if ((ret = av_frame_ref(frame, s->frame)) < 0)
 244             return ret;
 245
 246         return frame_size;
 247     }
 248
 249     for (i = 0; i < 3; i++) {
 250         if (frame_flags & (1 << (17 + i))) {
 251             unsigned cb_depth, cb_size;
 252             if (i == 2) {
 253                 // This codebook can be cut off at places other than
 254                 // powers of 2, leaving some of the entries undefined.
 255                 cb_size = get_bits_long(&gb, 20);
 256                 cb_depth = av_log2(cb_size - 1) + 1;
 257             } else {
 258                 cb_depth = get_bits(&gb, 4);
 259                 if (i == 0) {
 260                     // This is the most basic codebook: pow(2,depth) entries
 261                     // for a depth-length key
 262                     cb_size = 1 << cb_depth;
 263                 } else {
 264                     // This codebook varies per superblock
 265                     // FIXME: I don't think this handles integer overflow
 266                     // properly
 267                     cb_size = s->num_superblocks << cb_depth;
 268                 }
 269             }
 270             av_free(s->codebooks[i].blocks);
 271             s->codebooks[i] = unpack_codebook(&gb, cb_depth, cb_size);
 272             if (!s->codebooks[i].blocks)
 273                 return -1;
 274         }
 275     }
 276
 277     if ((ret = ff_get_buffer(avctx, frame, AV_GET_BUFFER_FLAG_REF)) < 0) {
 278         av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
 279         return ret;
 280     }
 281
 282     new_frame_data = (uint16_t*)frame->data[0];
 283     new_stride = frame->linesize[0] / 2;
 284     old_frame_data = (uint16_t*)s->frame->data[0];
 285     old_stride = s->frame->linesize[0] / 2;
 286
 287     for (superblock_index = 0; superblock_index < s->num_superblocks;
 288          superblock_index++) {
 289         MacroBlock mb;
 290         SuperBlock sb;
 291         unsigned multi_mask = 0;
 292
 293         if (skip == -1) {
 294             // Note that this call will make us skip the rest of the blocks
 295             // if the frame prematurely ends
 296             skip = decode_skip_count(&gb);
 297         }
 298
 299         if (skip) {
 300             copy_superblock(new_frame_data, new_stride,
 301                             old_frame_data, old_stride);
 302         } else {
 303             copy_superblock(sb.pixels, 8,
 304                             old_frame_data, old_stride);
 305
 306             while (can_safely_read(&gb, 1) && !get_bits1(&gb)) {
 307                 unsigned mask;
 308                 mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
 309                 mask = get_bits(&gb, 16);
 310                 multi_mask |= mask;
 311                 for (i = 0; i < 16; i++) {
 312                     if (mask & mask_matrix[i]) {
 313                         insert_mb_into_sb(&sb, mb, i);
 314                     }
 315                 }
 316             }
 317
 318             if (can_safely_read(&gb, 1) && !get_bits1(&gb)) {
 319                 unsigned inv_mask = get_bits(&gb, 4);
 320                 for (i = 0; i < 4; i++) {
 321                     if (inv_mask & (1 << i)) {
 322                         multi_mask ^= 0xF << i*4;
 323                     } else {
 324                         multi_mask ^= get_bits(&gb, 4) << i*4;
 325                     }
 326                 }
 327
 328                 for (i = 0; i < 16; i++) {
 329                     if (multi_mask & mask_matrix[i]) {
 330                         if (!can_safely_read(&gb, 1))
 331                             break;
 332                         mb = decode_macroblock(s, &gb, &cb_index,
 333                                                superblock_index);
 334                         insert_mb_into_sb(&sb, mb, i);
 335                     }
 336                 }
 337             } else if (frame_flags & (1 << 16)) {
 338                 while (can_safely_read(&gb, 1) && !get_bits1(&gb)) {
 339                     mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
 340                     insert_mb_into_sb(&sb, mb, get_bits(&gb, 4));
 341                 }
 342             }
 343
 344             copy_superblock(new_frame_data, new_stride, sb.pixels, 8);
 345         }
 346
 347         superblock_col_index++;
 348         new_frame_data += 8;
 349         if (old_frame_data)
 350             old_frame_data += 8;
 351         if (superblock_col_index == superblocks_per_row) {
 352             new_frame_data += new_stride * 8 - superblocks_per_row * 8;
 353             if (old_frame_data)
 354                 old_frame_data += old_stride * 8 - superblocks_per_row * 8;
 355             superblock_col_index = 0;
 356         }
 357         skip--;
 358     }
 359
 360     av_log(NULL, AV_LOG_DEBUG,
 361            "Escape sizes: %i, %i, %i\n",
 362            frame_size, buf_size, get_bits_count(&gb) / 8);
 363
 364     av_frame_unref(s->frame);
 365     if ((ret = av_frame_ref(s->frame, frame)) < 0)
 366         return ret;
 367
 368     *got_frame = 1;
 369
 370     return frame_size;
 371 }
 372
 373
 374 AVCodec ff_escape124_decoder = {
 375     .name           = "escape124",
 376     .long_name      = NULL_IF_CONFIG_SMALL("Escape 124"),
 377     .type           = AVMEDIA_TYPE_VIDEO,
 378     .id             = AV_CODEC_ID_ESCAPE124,
 379     .priv_data_size = sizeof(Escape124Context),
 380     .init           = escape124_decode_init,
 381     .close          = escape124_decode_close,
 382     .decode         = escape124_decode_frame,
 383     .capabilities   = AV_CODEC_CAP_DR1,
 384 };