dce4d0493e4c7a25a7ef8e879d69fedcb68d6de4
[libav.git] / 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 return 0;
71 }
72
73 static av_cold int escape124_decode_close(AVCodecContext *avctx)
74 {
75 unsigned i;
76 Escape124Context *s = avctx->priv_data;
77
78 for (i = 0; i < 3; i++)
79 av_free(s->codebooks[i].blocks);
80
81 if (s->frame.data[0])
82 avctx->release_buffer(avctx, &s->frame);
83
84 return 0;
85 }
86
87 static CodeBook unpack_codebook(GetBitContext* gb, unsigned depth,
88 unsigned size)
89 {
90 unsigned i, j;
91 CodeBook cb = { 0 };
92
93 if (!can_safely_read(gb, size * 34))
94 return cb;
95
96 if (size >= INT_MAX / sizeof(MacroBlock))
97 return cb;
98 cb.blocks = av_malloc(size ? size * sizeof(MacroBlock) : 1);
99 if (!cb.blocks)
100 return cb;
101
102 cb.depth = depth;
103 cb.size = size;
104 for (i = 0; i < size; i++) {
105 unsigned mask_bits = get_bits(gb, 4);
106 unsigned color0 = get_bits(gb, 15);
107 unsigned color1 = get_bits(gb, 15);
108
109 for (j = 0; j < 4; j++) {
110 if (mask_bits & (1 << j))
111 cb.blocks[i].pixels[j] = color1;
112 else
113 cb.blocks[i].pixels[j] = color0;
114 }
115 }
116 return cb;
117 }
118
119 static unsigned decode_skip_count(GetBitContext* gb)
120 {
121 unsigned value;
122 // This function reads a maximum of 23 bits,
123 // which is within the padding space
124 if (!can_safely_read(gb, 1))
125 return -1;
126 value = get_bits1(gb);
127 if (!value)
128 return value;
129
130 value += get_bits(gb, 3);
131 if (value != (1 + ((1 << 3) - 1)))
132 return value;
133
134 value += get_bits(gb, 7);
135 if (value != (1 + ((1 << 3) - 1)) + ((1 << 7) - 1))
136 return value;
137
138 return value + get_bits(gb, 12);
139 }
140
141 static MacroBlock decode_macroblock(Escape124Context* s, GetBitContext* gb,
142 int* codebook_index, int superblock_index)
143 {
144 // This function reads a maximum of 22 bits; the callers
145 // guard this function appropriately
146 unsigned block_index, depth;
147
148 if (get_bits1(gb)) {
149 static const char transitions[3][2] = { {2, 1}, {0, 2}, {1, 0} };
150 *codebook_index = transitions[*codebook_index][get_bits1(gb)];
151 }
152
153 depth = s->codebooks[*codebook_index].depth;
154
155 // depth = 0 means that this shouldn't read any bits;
156 // in theory, this is the same as get_bits(gb, 0), but
157 // that doesn't actually work.
158 block_index = depth ? get_bits(gb, depth) : 0;
159
160 if (*codebook_index == 1) {
161 block_index += superblock_index << s->codebooks[1].depth;
162 }
163
164 // This condition can occur with invalid bitstreams and
165 // *codebook_index == 2
166 if (block_index >= s->codebooks[*codebook_index].size)
167 return (MacroBlock) { { 0 } };
168
169 return s->codebooks[*codebook_index].blocks[block_index];
170 }
171
172 static void insert_mb_into_sb(SuperBlock* sb, MacroBlock mb, unsigned index) {
173 // Formula: ((index / 4) * 16 + (index % 4) * 2) / 2
174 uint32_t *dst = sb->pixels32 + index + (index & -4);
175
176 // This technically violates C99 aliasing rules, but it should be safe.
177 dst[0] = mb.pixels32[0];
178 dst[4] = mb.pixels32[1];
179 }
180
181 static void copy_superblock(uint16_t* dest, unsigned dest_stride,
182 uint16_t* src, unsigned src_stride)
183 {
184 unsigned y;
185 if (src)
186 for (y = 0; y < 8; y++)
187 memcpy(dest + y * dest_stride, src + y * src_stride,
188 sizeof(uint16_t) * 8);
189 else
190 for (y = 0; y < 8; y++)
191 memset(dest + y * dest_stride, 0, sizeof(uint16_t) * 8);
192 }
193
194 static const uint16_t mask_matrix[] = {0x1, 0x2, 0x10, 0x20,
195 0x4, 0x8, 0x40, 0x80,
196 0x100, 0x200, 0x1000, 0x2000,
197 0x400, 0x800, 0x4000, 0x8000};
198
199 static int escape124_decode_frame(AVCodecContext *avctx,
200 void *data, int *data_size,
201 AVPacket *avpkt)
202 {
203 const uint8_t *buf = avpkt->data;
204 int buf_size = avpkt->size;
205 Escape124Context *s = avctx->priv_data;
206
207 GetBitContext gb;
208 unsigned frame_flags, frame_size;
209 unsigned i;
210
211 unsigned superblock_index, cb_index = 1,
212 superblock_col_index = 0,
213 superblocks_per_row = avctx->width / 8, skip = -1;
214
215 uint16_t* old_frame_data, *new_frame_data;
216 unsigned old_stride, new_stride;
217
218 AVFrame new_frame = { { 0 } };
219
220 init_get_bits(&gb, buf, buf_size * 8);
221
222 // This call also guards the potential depth reads for the
223 // codebook unpacking.
224 if (!can_safely_read(&gb, 64))
225 return -1;
226
227 frame_flags = get_bits_long(&gb, 32);
228 frame_size = get_bits_long(&gb, 32);
229
230 // Leave last frame unchanged
231 // FIXME: Is this necessary? I haven't seen it in any real samples
232 if (!(frame_flags & 0x114) || !(frame_flags & 0x7800000)) {
233 av_log(NULL, AV_LOG_DEBUG, "Skipping frame\n");
234
235 *data_size = sizeof(AVFrame);
236 *(AVFrame*)data = s->frame;
237
238 return frame_size;
239 }
240
241 for (i = 0; i < 3; i++) {
242 if (frame_flags & (1 << (17 + i))) {
243 unsigned cb_depth, cb_size;
244 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 cb_size = get_bits_long(&gb, 20);
248 cb_depth = av_log2(cb_size - 1) + 1;
249 } else {
250 cb_depth = get_bits(&gb, 4);
251 if (i == 0) {
252 // This is the most basic codebook: pow(2,depth) entries
253 // for a depth-length key
254 cb_size = 1 << cb_depth;
255 } else {
256 // This codebook varies per superblock
257 // FIXME: I don't think this handles integer overflow
258 // properly
259 cb_size = s->num_superblocks << cb_depth;
260 }
261 }
262 av_free(s->codebooks[i].blocks);
263 s->codebooks[i] = unpack_codebook(&gb, cb_depth, cb_size);
264 if (!s->codebooks[i].blocks)
265 return -1;
266 }
267 }
268
269 new_frame.reference = 3;
270 if (ff_get_buffer(avctx, &new_frame)) {
271 av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
272 return -1;
273 }
274
275 new_frame_data = (uint16_t*)new_frame.data[0];
276 new_stride = new_frame.linesize[0] / 2;
277 old_frame_data = (uint16_t*)s->frame.data[0];
278 old_stride = s->frame.linesize[0] / 2;
279
280 for (superblock_index = 0; superblock_index < s->num_superblocks;
281 superblock_index++) {
282 MacroBlock mb;
283 SuperBlock sb;
284 unsigned multi_mask = 0;
285
286 if (skip == -1) {
287 // Note that this call will make us skip the rest of the blocks
288 // if the frame prematurely ends
289 skip = decode_skip_count(&gb);
290 }
291
292 if (skip) {
293 copy_superblock(new_frame_data, new_stride,
294 old_frame_data, old_stride);
295 } else {
296 copy_superblock(sb.pixels, 8,
297 old_frame_data, old_stride);
298
299 while (can_safely_read(&gb, 1) && !get_bits1(&gb)) {
300 unsigned mask;
301 mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
302 mask = get_bits(&gb, 16);
303 multi_mask |= mask;
304 for (i = 0; i < 16; i++) {
305 if (mask & mask_matrix[i]) {
306 insert_mb_into_sb(&sb, mb, i);
307 }
308 }
309 }
310
311 if (can_safely_read(&gb, 1) && !get_bits1(&gb)) {
312 unsigned inv_mask = get_bits(&gb, 4);
313 for (i = 0; i < 4; i++) {
314 if (inv_mask & (1 << i)) {
315 multi_mask ^= 0xF << i*4;
316 } else {
317 multi_mask ^= get_bits(&gb, 4) << i*4;
318 }
319 }
320
321 for (i = 0; i < 16; i++) {
322 if (multi_mask & mask_matrix[i]) {
323 if (!can_safely_read(&gb, 1))
324 break;
325 mb = decode_macroblock(s, &gb, &cb_index,
326 superblock_index);
327 insert_mb_into_sb(&sb, mb, i);
328 }
329 }
330 } else if (frame_flags & (1 << 16)) {
331 while (can_safely_read(&gb, 1) && !get_bits1(&gb)) {
332 mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
333 insert_mb_into_sb(&sb, mb, get_bits(&gb, 4));
334 }
335 }
336
337 copy_superblock(new_frame_data, new_stride, sb.pixels, 8);
338 }
339
340 superblock_col_index++;
341 new_frame_data += 8;
342 if (old_frame_data)
343 old_frame_data += 8;
344 if (superblock_col_index == superblocks_per_row) {
345 new_frame_data += new_stride * 8 - superblocks_per_row * 8;
346 if (old_frame_data)
347 old_frame_data += old_stride * 8 - superblocks_per_row * 8;
348 superblock_col_index = 0;
349 }
350 skip--;
351 }
352
353 av_log(NULL, AV_LOG_DEBUG,
354 "Escape sizes: %i, %i, %i\n",
355 frame_size, buf_size, get_bits_count(&gb) / 8);
356
357 if (s->frame.data[0])
358 avctx->release_buffer(avctx, &s->frame);
359
360 *(AVFrame*)data = s->frame = new_frame;
361 *data_size = sizeof(AVFrame);
362
363 return frame_size;
364 }
365
366
367 AVCodec ff_escape124_decoder = {
368 .name = "escape124",
369 .type = AVMEDIA_TYPE_VIDEO,
370 .id = AV_CODEC_ID_ESCAPE124,
371 .priv_data_size = sizeof(Escape124Context),
372 .init = escape124_decode_init,
373 .close = escape124_decode_close,
374 .decode = escape124_decode_frame,
375 .capabilities = CODEC_CAP_DR1,
376 .long_name = NULL_IF_CONFIG_SMALL("Escape 124"),
377 };