FFmpeg coverage

Directory: ../../../ffmpeg/
File: src/libavcodec/escape124.c
Date: 2026-01-23 19:11:46
Exec Total Coverage
Lines: 139 161 86.3%
Functions: 8 8 100.0%
Branches: 81 106 76.4%
Line Branch Exec Source
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 #define BITSTREAM_READER_LE
23 #include "libavutil/mem.h"
24 #include "avcodec.h"
25 #include "codec_internal.h"
26 #include "decode.h"
27 #include "get_bits.h"
28
29 typedef union MacroBlock {
30 uint16_t pixels[4];
31 uint32_t pixels32[2];
32 } MacroBlock;
33
34 typedef union SuperBlock {
35 uint16_t pixels[64];
36 uint32_t pixels32[32];
37 } SuperBlock;
38
39 typedef struct CodeBook {
40 unsigned depth;
41 unsigned size;
42 MacroBlock* blocks;
43 } CodeBook;
44
45 typedef struct Escape124Context {
46 AVFrame *frame;
47
48 unsigned num_superblocks;
49
50 CodeBook codebooks[3];
51 } Escape124Context;
52
53 /**
54 * Initialize the decoder
55 * @param avctx decoder context
56 * @return 0 success, negative on error
57 */
58 2 static av_cold int escape124_decode_init(AVCodecContext *avctx)
59 {
60 2 Escape124Context *s = avctx->priv_data;
61
62 2 avctx->pix_fmt = AV_PIX_FMT_RGB555;
63
64 2 s->num_superblocks = ((unsigned)avctx->width / 8) *
65 2 ((unsigned)avctx->height / 8);
66
67 2 s->frame = av_frame_alloc();
68
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 2 if (!s->frame)
69 ✗ return AVERROR(ENOMEM);
70
71 2 return 0;
72 }
73
74 2 static av_cold int escape124_decode_close(AVCodecContext *avctx)
75 {
76 unsigned i;
77 2 Escape124Context *s = avctx->priv_data;
78
79
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 8 for (i = 0; i < 3; i++)
80 6 av_freep(&s->codebooks[i].blocks);
81
82 2 av_frame_free(&s->frame);
83
84 2 return 0;
85 }
86
87 12 static CodeBook unpack_codebook(GetBitContext* gb, unsigned depth,
88 unsigned size)
89 {
90 unsigned i, j;
91 12 CodeBook cb = { 0 };
92
93
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 12 cb.blocks = av_malloc(size ? size * sizeof(MacroBlock) : 1);
94
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 12 if (!cb.blocks)
95 ✗ return cb;
96
97 12 cb.depth = depth;
98 12 cb.size = size;
99
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 21255 for (i = 0; i < size; i++) {
100 21243 unsigned mask_bits = get_bits(gb, 4);
101 unsigned color[2];
102 21243 color[0] = get_bits(gb, 15);
103 21243 color[1] = get_bits(gb, 15);
104
105
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 106215 for (j = 0; j < 4; j++)
106 84972 cb.blocks[i].pixels[j] = color[(mask_bits>>j) & 1];
107 }
108 12 return cb;
109 }
110
111 69095 static unsigned decode_skip_count(GetBitContext* gb)
112 {
113 unsigned value;
114 // This function reads a maximum of 23 bits,
115 // which is within the padding space
116
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 69095 if (get_bits_left(gb) < 1)
117 ✗ return -1;
118 69095 value = get_bits1(gb);
119
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 69095 if (!value)
120 59778 return value;
121
122 9317 value += get_bits(gb, 3);
123
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 9317 if (value != (1 + ((1 << 3) - 1)))
124 8204 return value;
125
126 1113 value += get_bits(gb, 7);
127
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 1113 if (value != (1 + ((1 << 3) - 1)) + ((1 << 7) - 1))
128 1086 return value;
129
130 27 return value + get_bits(gb, 12);
131 }
132
133 339543 static MacroBlock decode_macroblock(Escape124Context* s, GetBitContext* gb,
134 int* codebook_index, int superblock_index)
135 {
136 // This function reads a maximum of 22 bits; the callers
137 // guard this function appropriately
138 unsigned block_index, depth;
139 339543 int value = get_bits1(gb);
140
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 339543 if (value) {
141 static const int8_t transitions[3][2] = { {2, 1}, {0, 2}, {1, 0} };
142 131966 value = get_bits1(gb);
143 131966 *codebook_index = transitions[*codebook_index][value];
144 }
145
146 339543 depth = s->codebooks[*codebook_index].depth;
147
148 // depth = 0 means that this shouldn't read any bits;
149 // in theory, this is the same as get_bits(gb, 0), but
150 // that doesn't actually work.
151 339543 block_index = get_bitsz(gb, depth);
152
153
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 339543 if (*codebook_index == 1) {
154 33088 block_index += superblock_index << s->codebooks[1].depth;
155 }
156
157 // This condition can occur with invalid bitstreams and
158 // *codebook_index == 2
159
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 339543 if (block_index >= s->codebooks[*codebook_index].size || !s->codebooks[*codebook_index].blocks)
160 ✗ return (MacroBlock) { { 0 } };
161
162 339543 return s->codebooks[*codebook_index].blocks[block_index];
163 }
164
165 492736 static void insert_mb_into_sb(SuperBlock* sb, MacroBlock mb, unsigned index) {
166 // Formula: ((index / 4) * 16 + (index % 4) * 2) / 2
167 492736 uint32_t *dst = sb->pixels32 + index + (index & -4);
168
169 // This technically violates C99 aliasing rules, but it should be safe.
170 492736 dst[0] = mb.pixels32[0];
171 492736 dst[4] = mb.pixels32[1];
172 492736 }
173
174 189026 static void copy_superblock(uint16_t* dest, ptrdiff_t dest_stride,
175 uint16_t* src, ptrdiff_t src_stride)
176 {
177 unsigned y;
178
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 189026 if (src)
179
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 1690434 for (y = 0; y < 8; y++)
180 1502608 memcpy(dest + y * dest_stride, src + y * src_stride,
181 sizeof(uint16_t) * 8);
182 else
183
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 10800 for (y = 0; y < 8; y++)
184 9600 memset(dest + y * dest_stride, 0, sizeof(uint16_t) * 8);
185 189026 }
186
187 static const uint16_t mask_matrix[] = {0x1, 0x2, 0x10, 0x20,
188 0x4, 0x8, 0x40, 0x80,
189 0x100, 0x200, 0x1000, 0x2000,
190 0x400, 0x800, 0x4000, 0x8000};
191
192 100 static int escape124_decode_frame(AVCodecContext *avctx, AVFrame *frame,
193 int *got_frame, AVPacket *avpkt)
194 {
195 100 int buf_size = avpkt->size;
196 100 Escape124Context *s = avctx->priv_data;
197
198 GetBitContext gb;
199 unsigned frame_flags, frame_size;
200 unsigned i;
201
202 100 unsigned superblock_index, cb_index = 1,
203 100 superblock_col_index = 0,
204 100 superblocks_per_row = avctx->width / 8, skip = -1;
205
206 uint16_t* old_frame_data, *new_frame_data;
207 ptrdiff_t old_stride, new_stride;
208
209 int ret;
210
211
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 100 if ((ret = init_get_bits8(&gb, avpkt->data, avpkt->size)) < 0)
212 ✗ return ret;
213
214 // This call also guards the potential depth reads for the
215 // codebook unpacking.
216 // Check if the amount we will read minimally is available on input.
217 // The 64 represent the immediately next 2 frame_* elements read, the 23/4320
218 // represent a lower bound of the space needed for skipped superblocks. Non
219 // skipped SBs need more space.
220
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 100 if (get_bits_left(&gb) < 64 + s->num_superblocks * 23LL / 4320)
221 ✗ return AVERROR_INVALIDDATA;
222
223 100 frame_flags = get_bits_long(&gb, 32);
224 100 frame_size = get_bits_long(&gb, 32);
225
226 // Leave last frame unchanged
227 // FIXME: Is this necessary? I haven't seen it in any real samples
228
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 100 if (!(frame_flags & 0x114) || !(frame_flags & 0x7800000)) {
229 ✗ if (!s->frame->data[0])
230 ✗ return AVERROR_INVALIDDATA;
231
232 ✗ av_log(avctx, AV_LOG_DEBUG, "Skipping frame\n");
233
234 ✗ *got_frame = 1;
235 ✗ if ((ret = av_frame_ref(frame, s->frame)) < 0)
236 ✗ return ret;
237
238 ✗ return 0;
239 }
240
241
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 400 for (i = 0; i < 3; i++) {
242
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 300 if (frame_flags & (1 << (17 + i))) {
243 unsigned cb_depth, cb_size;
244
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 12 if (i == 2) {
245 // This codebook can be cut off at places other than
246 // powers of 2, leaving some of the entries undefined.
247 4 cb_size = get_bits(&gb, 20);
248
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 4 if (!cb_size) {
249 ✗ av_log(avctx, AV_LOG_ERROR, "Invalid codebook size 0.\n");
250 ✗ return AVERROR_INVALIDDATA;
251 }
252 4 cb_depth = av_log2(cb_size - 1) + 1;
253 } else {
254 8 cb_depth = get_bits(&gb, 4);
255
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 8 if (i == 0) {
256 // This is the most basic codebook: pow(2,depth) entries
257 // for a depth-length key
258 4 cb_size = 1 << cb_depth;
259 } else {
260 // This codebook varies per superblock
261 // FIXME: I don't think this handles integer overflow
262 // properly
263 4 cb_size = s->num_superblocks << cb_depth;
264 }
265 }
266
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 12 if (s->num_superblocks >= INT_MAX >> cb_depth) {
267 ✗ av_log(avctx, AV_LOG_ERROR, "Depth or num_superblocks are too large\n");
268 ✗ return AVERROR_INVALIDDATA;
269 }
270
271 12 av_freep(&s->codebooks[i].blocks);
272
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 12 if (cb_size >= INT_MAX / 34 || get_bits_left(&gb) < (int)cb_size * 34)
273 ✗ return AVERROR_INVALIDDATA;
274
275
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 12 if (cb_size >= INT_MAX / sizeof(MacroBlock))
276 ✗ return AVERROR_INVALIDDATA;
277 12 s->codebooks[i] = unpack_codebook(&gb, cb_depth, cb_size);
278
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 12 if (!s->codebooks[i].blocks)
279 ✗ return AVERROR(ENOMEM);
280 }
281 }
282
283
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 100 if ((ret = ff_get_buffer(avctx, frame, AV_GET_BUFFER_FLAG_REF)) < 0)
284 ✗ return ret;
285
286 100 new_frame_data = (uint16_t*)frame->data[0];
287 100 new_stride = frame->linesize[0] / 2;
288 100 old_frame_data = (uint16_t*)s->frame->data[0];
289 100 old_stride = s->frame->linesize[0] / 2;
290
291
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 120100 for (superblock_index = 0; superblock_index < s->num_superblocks;
292 120000 superblock_index++) {
293 MacroBlock mb;
294 SuperBlock sb;
295 120000 unsigned multi_mask = 0;
296
297
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 120000 if (skip == -1) {
298 // Note that this call will make us skip the rest of the blocks
299 // if the frame prematurely ends
300 69095 skip = decode_skip_count(&gb);
301 }
302
303
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 120000 if (skip) {
304 50974 copy_superblock(new_frame_data, new_stride,
305 old_frame_data, old_stride);
306 } else {
307 69026 copy_superblock(sb.pixels, 8,
308 old_frame_data, old_stride);
309
310
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 100930 while (get_bits_left(&gb) >= 1 && !get_bits1(&gb)) {
311 unsigned mask;
312 31904 mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
313 31904 mask = get_bits(&gb, 16);
314 31904 multi_mask |= mask;
315
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 542368 for (i = 0; i < 16; i++) {
316
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 510464 if (mask & mask_matrix[i]) {
317 185097 insert_mb_into_sb(&sb, mb, i);
318 }
319 }
320 }
321
322
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 69026 if (!get_bits1(&gb)) {
323 29605 unsigned inv_mask = get_bits(&gb, 4);
324
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 148025 for (i = 0; i < 4; i++) {
325
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 118420 if (inv_mask & (1 << i)) {
326 45362 multi_mask ^= 0xF << i*4;
327 } else {
328 73058 multi_mask ^= get_bits(&gb, 4) << i*4;
329 }
330 }
331
332
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 503285 for (i = 0; i < 16; i++) {
333
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 473680 if (multi_mask & mask_matrix[i]) {
334 251422 mb = decode_macroblock(s, &gb, &cb_index,
335 superblock_index);
336 251422 insert_mb_into_sb(&sb, mb, i);
337 }
338 }
339
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 39421 } else if (frame_flags & (1 << 16)) {
340
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 95638 while (get_bits_left(&gb) >= 1 && !get_bits1(&gb)) {
341 56217 mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
342 56217 insert_mb_into_sb(&sb, mb, get_bits(&gb, 4));
343 }
344 }
345
346 69026 copy_superblock(new_frame_data, new_stride, sb.pixels, 8);
347 }
348
349 120000 superblock_col_index++;
350 120000 new_frame_data += 8;
351
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 120000 if (old_frame_data)
352 118800 old_frame_data += 8;
353
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 120000 if (superblock_col_index == superblocks_per_row) {
354 3000 new_frame_data += new_stride * 8 - superblocks_per_row * 8;
355
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 3000 if (old_frame_data)
356 2970 old_frame_data += old_stride * 8 - superblocks_per_row * 8;
357 3000 superblock_col_index = 0;
358 }
359 120000 skip--;
360 }
361
362 100 av_log(avctx, AV_LOG_DEBUG,
363 "Escape sizes: %i, %i, %i\n",
364 100 frame_size, buf_size, get_bits_count(&gb) / 8);
365
366
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 100 if ((ret = av_frame_replace(s->frame, frame)) < 0)
367 ✗ return ret;
368
369 100 *got_frame = 1;
370
371 100 return 0;
372 }
373
374
375 const FFCodec ff_escape124_decoder = {
376 .p.name = "escape124",
377 CODEC_LONG_NAME("Escape 124"),
378 .p.type = AVMEDIA_TYPE_VIDEO,
379 .p.id = AV_CODEC_ID_ESCAPE124,
380 .priv_data_size = sizeof(Escape124Context),
381 .init = escape124_decode_init,
382 .close = escape124_decode_close,
383 FF_CODEC_DECODE_CB(escape124_decode_frame),
384 .p.capabilities = AV_CODEC_CAP_DR1,
385 };
386