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
can_safely_read(GetBitContext * gb,int bits)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 */
escape124_decode_init(AVCodecContext * avctx)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
escape124_decode_close(AVCodecContext * avctx)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
unpack_codebook(GetBitContext * gb,unsigned depth,unsigned size)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
decode_skip_count(GetBitContext * gb)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
decode_macroblock(Escape124Context * s,GetBitContext * gb,int * codebook_index,int superblock_index)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
insert_mb_into_sb(SuperBlock * sb,MacroBlock mb,unsigned index)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
copy_superblock(uint16_t * dest,unsigned dest_stride,uint16_t * src,unsigned src_stride)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 */
escape124_decode_frame(AVCodecContext * avctx,void * data,int * data_size,const uint8_t * buf,int buf_size)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 = "Escape 124",
384 };
385
386