aboutsummaryrefslogtreecommitdiffstats
path: root/libavcodec/escape124.c
blob: 6c4654cd351b9620086a3737de67ba0ca64501ad (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
/*
 * Escape 124 Video Decoder
 * Copyright (C) 2008 Eli Friedman (eli.friedman@gmail.com)
 *
 * This file is part of Libav.
 *
 * Libav is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * Libav is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with Libav; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "avcodec.h"
#include "internal.h"

#define BITSTREAM_READER_LE
#include "get_bits.h"

typedef union MacroBlock {
    uint16_t pixels[4];
    uint32_t pixels32[2];
} MacroBlock;

typedef union SuperBlock {
    uint16_t pixels[64];
    uint32_t pixels32[32];
} SuperBlock;

typedef struct CodeBook {
    unsigned depth;
    unsigned size;
    MacroBlock* blocks;
} CodeBook;

typedef struct Escape124Context {
    AVFrame *frame;

    unsigned num_superblocks;

    CodeBook codebooks[3];
} Escape124Context;

static int can_safely_read(GetBitContext* gb, int bits) {
    return get_bits_left(gb) >= bits;
}

/**
 * Initialize the decoder
 * @param avctx decoder context
 * @return 0 success, negative on error
 */
static av_cold int escape124_decode_init(AVCodecContext *avctx)
{
    Escape124Context *s = avctx->priv_data;

    avctx->pix_fmt = AV_PIX_FMT_RGB555;

    s->num_superblocks = ((unsigned)avctx->width / 8) *
                         ((unsigned)avctx->height / 8);

    s->frame = av_frame_alloc();
    if (!s->frame)
        return AVERROR(ENOMEM);

    return 0;
}

static av_cold int escape124_decode_close(AVCodecContext *avctx)
{
    unsigned i;
    Escape124Context *s = avctx->priv_data;

    for (i = 0; i < 3; i++)
        av_free(s->codebooks[i].blocks);

    av_frame_free(&s->frame);

    return 0;
}

static CodeBook unpack_codebook(GetBitContext* gb, unsigned depth,
                                 unsigned size)
{
    unsigned i, j;
    CodeBook cb = { 0 };

    if (!can_safely_read(gb, size * 34))
        return cb;

    if (size >= INT_MAX / sizeof(MacroBlock))
        return cb;
    cb.blocks = av_malloc(size ? size * sizeof(MacroBlock) : 1);
    if (!cb.blocks)
        return cb;

    cb.depth = depth;
    cb.size = size;
    for (i = 0; i < size; i++) {
        unsigned mask_bits = get_bits(gb, 4);
        unsigned color0 = get_bits(gb, 15);
        unsigned color1 = get_bits(gb, 15);

        for (j = 0; j < 4; j++) {
            if (mask_bits & (1 << j))
                cb.blocks[i].pixels[j] = color1;
            else
                cb.blocks[i].pixels[j] = color0;
        }
    }
    return cb;
}

static unsigned decode_skip_count(GetBitContext* gb)
{
    unsigned value;
    // This function reads a maximum of 23 bits,
    // which is within the padding space
    if (!can_safely_read(gb, 1))
        return -1;
    value = get_bits1(gb);
    if (!value)
        return value;

    value += get_bits(gb, 3);
    if (value != (1 + ((1 << 3) - 1)))
        return value;

    value += get_bits(gb, 7);
    if (value != (1 + ((1 << 3) - 1)) + ((1 << 7) - 1))
        return value;

    return value + get_bits(gb, 12);
}

static MacroBlock decode_macroblock(Escape124Context* s, GetBitContext* gb,
                                    int* codebook_index, int superblock_index)
{
    // This function reads a maximum of 22 bits; the callers
    // guard this function appropriately
    unsigned block_index, depth;
    int value = get_bits1(gb);
    if (value) {
        static const char transitions[3][2] = { {2, 1}, {0, 2}, {1, 0} };
        value = get_bits1(gb);
        *codebook_index = transitions[*codebook_index][value];
    }

    depth = s->codebooks[*codebook_index].depth;

    // depth = 0 means that this shouldn't read any bits;
    // in theory, this is the same as get_bits(gb, 0), but
    // that doesn't actually work.
    block_index = depth ? get_bits(gb, depth) : 0;

    if (*codebook_index == 1) {
        block_index += superblock_index << s->codebooks[1].depth;
    }

    // This condition can occur with invalid bitstreams and
    // *codebook_index == 2
    if (block_index >= s->codebooks[*codebook_index].size)
        return (MacroBlock) { { 0 } };

    return s->codebooks[*codebook_index].blocks[block_index];
}

static void insert_mb_into_sb(SuperBlock* sb, MacroBlock mb, unsigned index) {
   // Formula: ((index / 4) * 16 + (index % 4) * 2) / 2
   uint32_t *dst = sb->pixels32 + index + (index & -4);

   // This technically violates C99 aliasing rules, but it should be safe.
   dst[0] = mb.pixels32[0];
   dst[4] = mb.pixels32[1];
}

static void copy_superblock(uint16_t* dest, unsigned dest_stride,
                            uint16_t* src, unsigned src_stride)
{
    unsigned y;
    if (src)
        for (y = 0; y < 8; y++)
            memcpy(dest + y * dest_stride, src + y * src_stride,
                   sizeof(uint16_t) * 8);
    else
        for (y = 0; y < 8; y++)
            memset(dest + y * dest_stride, 0, sizeof(uint16_t) * 8);
}

static const uint16_t mask_matrix[] = {0x1,   0x2,   0x10,   0x20,
                                       0x4,   0x8,   0x40,   0x80,
                                       0x100, 0x200, 0x1000, 0x2000,
                                       0x400, 0x800, 0x4000, 0x8000};

static int escape124_decode_frame(AVCodecContext *avctx,
                                  void *data, int *got_frame,
                                  AVPacket *avpkt)
{
    const uint8_t *buf = avpkt->data;
    int buf_size = avpkt->size;
    Escape124Context *s = avctx->priv_data;
    AVFrame *frame = data;

    GetBitContext gb;
    unsigned frame_flags, frame_size;
    unsigned i;

    unsigned superblock_index, cb_index = 1,
             superblock_col_index = 0,
             superblocks_per_row = avctx->width / 8, skip = -1;

    uint16_t* old_frame_data, *new_frame_data;
    unsigned old_stride, new_stride;
    int ret;

    init_get_bits(&gb, buf, buf_size * 8);

    // This call also guards the potential depth reads for the
    // codebook unpacking.
    if (!can_safely_read(&gb, 64))
        return -1;

    frame_flags = get_bits_long(&gb, 32);
    frame_size  = get_bits_long(&gb, 32);

    // Leave last frame unchanged
    // FIXME: Is this necessary?  I haven't seen it in any real samples
    if (!(frame_flags & 0x114) || !(frame_flags & 0x7800000)) {
        if (!s->frame->data[0])
            return AVERROR_INVALIDDATA;

        av_log(NULL, AV_LOG_DEBUG, "Skipping frame\n");

        *got_frame = 1;
        if ((ret = av_frame_ref(frame, s->frame)) < 0)
            return ret;

        return frame_size;
    }

    for (i = 0; i < 3; i++) {
        if (frame_flags & (1 << (17 + i))) {
            unsigned cb_depth, cb_size;
            if (i == 2) {
                // This codebook can be cut off at places other than
                // powers of 2, leaving some of the entries undefined.
                cb_size = get_bits_long(&gb, 20);
                cb_depth = av_log2(cb_size - 1) + 1;
            } else {
                cb_depth = get_bits(&gb, 4);
                if (i == 0) {
                    // This is the most basic codebook: pow(2,depth) entries
                    // for a depth-length key
                    cb_size = 1 << cb_depth;
                } else {
                    // This codebook varies per superblock
                    // FIXME: I don't think this handles integer overflow
                    // properly
                    cb_size = s->num_superblocks << cb_depth;
                }
            }
            av_free(s->codebooks[i].blocks);
            s->codebooks[i] = unpack_codebook(&gb, cb_depth, cb_size);
            if (!s->codebooks[i].blocks)
                return -1;
        }
    }

    if ((ret = ff_get_buffer(avctx, frame, AV_GET_BUFFER_FLAG_REF)) < 0) {
        av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
        return ret;
    }

    new_frame_data = (uint16_t*)frame->data[0];
    new_stride = frame->linesize[0] / 2;
    old_frame_data = (uint16_t*)s->frame->data[0];
    old_stride = s->frame->linesize[0] / 2;

    for (superblock_index = 0; superblock_index < s->num_superblocks;
         superblock_index++) {
        MacroBlock mb;
        SuperBlock sb;
        unsigned multi_mask = 0;

        if (skip == -1) {
            // Note that this call will make us skip the rest of the blocks
            // if the frame prematurely ends
            skip = decode_skip_count(&gb);
        }

        if (skip) {
            copy_superblock(new_frame_data, new_stride,
                            old_frame_data, old_stride);
        } else {
            copy_superblock(sb.pixels, 8,
                            old_frame_data, old_stride);

            while (can_safely_read(&gb, 1) && !get_bits1(&gb)) {
                unsigned mask;
                mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
                mask = get_bits(&gb, 16);
                multi_mask |= mask;
                for (i = 0; i < 16; i++) {
                    if (mask & mask_matrix[i]) {
                        insert_mb_into_sb(&sb, mb, i);
                    }
                }
            }

            if (can_safely_read(&gb, 1) && !get_bits1(&gb)) {
                unsigned inv_mask = get_bits(&gb, 4);
                for (i = 0; i < 4; i++) {
                    if (inv_mask & (1 << i)) {
                        multi_mask ^= 0xF << i*4;
                    } else {
                        multi_mask ^= get_bits(&gb, 4) << i*4;
                    }
                }

                for (i = 0; i < 16; i++) {
                    if (multi_mask & mask_matrix[i]) {
                        if (!can_safely_read(&gb, 1))
                            break;
                        mb = decode_macroblock(s, &gb, &cb_index,
                                               superblock_index);
                        insert_mb_into_sb(&sb, mb, i);
                    }
                }
            } else if (frame_flags & (1 << 16)) {
                while (can_safely_read(&gb, 1) && !get_bits1(&gb)) {
                    mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
                    insert_mb_into_sb(&sb, mb, get_bits(&gb, 4));
                }
            }

            copy_superblock(new_frame_data, new_stride, sb.pixels, 8);
        }

        superblock_col_index++;
        new_frame_data += 8;
        if (old_frame_data)
            old_frame_data += 8;
        if (superblock_col_index == superblocks_per_row) {
            new_frame_data += new_stride * 8 - superblocks_per_row * 8;
            if (old_frame_data)
                old_frame_data += old_stride * 8 - superblocks_per_row * 8;
            superblock_col_index = 0;
        }
        skip--;
    }

    av_log(NULL, AV_LOG_DEBUG,
           "Escape sizes: %i, %i, %i\n",
           frame_size, buf_size, get_bits_count(&gb) / 8);

    av_frame_unref(s->frame);
    if ((ret = av_frame_ref(s->frame, frame)) < 0)
        return ret;

    *got_frame = 1;

    return frame_size;
}


AVCodec ff_escape124_decoder = {
    .name           = "escape124",
    .long_name      = NULL_IF_CONFIG_SMALL("Escape 124"),
    .type           = AVMEDIA_TYPE_VIDEO,
    .id             = AV_CODEC_ID_ESCAPE124,
    .priv_data_size = sizeof(Escape124Context),
    .init           = escape124_decode_init,
    .close          = escape124_decode_close,
    .decode         = escape124_decode_frame,
    .capabilities   = CODEC_CAP_DR1,
};