Use bitstream_init8() where appropriate
[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 #define BITSTREAM_READER_LE
23 #include "avcodec.h"
24 #include "bitstream.h"
25 #include "internal.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
51 static int can_safely_read(BitstreamContext *bc, int bits)
52 {
53 return bitstream_bits_left(bc) >= 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(BitstreamContext *bc, unsigned depth,
91 unsigned size)
92 {
93 unsigned i, j;
94 CodeBook cb = { 0 };
95
96 if (!can_safely_read(bc, 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 = bitstream_read(bc, 4);
109 unsigned color0 = bitstream_read(bc, 15);
110 unsigned color1 = bitstream_read(bc, 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(BitstreamContext *bc)
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(bc, 1))
128 return -1;
129 value = bitstream_read_bit(bc);
130 if (!value)
131 return value;
132
133 value += bitstream_read(bc, 3);
134 if (value != (1 + ((1 << 3) - 1)))
135 return value;
136
137 value += bitstream_read(bc, 7);
138 if (value != (1 + ((1 << 3) - 1)) + ((1 << 7) - 1))
139 return value;
140
141 return value + bitstream_read(bc, 12);
142 }
143
144 static MacroBlock decode_macroblock(Escape124Context *s, BitstreamContext *bc,
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 = bitstream_read_bit(bc);
151 if (value) {
152 static const char transitions[3][2] = { {2, 1}, {0, 2}, {1, 0} };
153 value = bitstream_read_bit(bc);
154 *codebook_index = transitions[*codebook_index][value];
155 }
156
157 depth = s->codebooks[*codebook_index].depth;
158 block_index = bitstream_read(bc, depth);
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 *got_frame,
201 AVPacket *avpkt)
202 {
203 const uint8_t *buf = avpkt->data;
204 int buf_size = avpkt->size;
205 Escape124Context *s = avctx->priv_data;
206 AVFrame *frame = data;
207
208 BitstreamContext bc;
209 unsigned frame_flags, frame_size;
210 unsigned i;
211
212 unsigned superblock_index, cb_index = 1,
213 superblock_col_index = 0,
214 superblocks_per_row = avctx->width / 8, skip = -1;
215
216 uint16_t* old_frame_data, *new_frame_data;
217 unsigned old_stride, new_stride;
218 int ret;
219
220 bitstream_init8(&bc, buf, buf_size);
221
222 // This call also guards the potential depth reads for the
223 // codebook unpacking.
224 if (!can_safely_read(&bc, 64))
225 return -1;
226
227 frame_flags = bitstream_read(&bc, 32);
228 frame_size = bitstream_read(&bc, 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 if (!s->frame->data[0])
234 return AVERROR_INVALIDDATA;
235
236 av_log(NULL, AV_LOG_DEBUG, "Skipping frame\n");
237
238 *got_frame = 1;
239 if ((ret = av_frame_ref(frame, s->frame)) < 0)
240 return ret;
241
242 return frame_size;
243 }
244
245 for (i = 0; i < 3; i++) {
246 if (frame_flags & (1 << (17 + i))) {
247 unsigned cb_depth, cb_size;
248 if (i == 2) {
249 // This codebook can be cut off at places other than
250 // powers of 2, leaving some of the entries undefined.
251 cb_size = bitstream_read(&bc, 20);
252 cb_depth = av_log2(cb_size - 1) + 1;
253 } else {
254 cb_depth = bitstream_read(&bc, 4);
255 if (i == 0) {
256 // This is the most basic codebook: pow(2,depth) entries
257 // for a depth-length key
258 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 cb_size = s->num_superblocks << cb_depth;
264 }
265 }
266 av_free(s->codebooks[i].blocks);
267 s->codebooks[i] = unpack_codebook(&bc, cb_depth, cb_size);
268 if (!s->codebooks[i].blocks)
269 return -1;
270 }
271 }
272
273 if ((ret = ff_get_buffer(avctx, frame, AV_GET_BUFFER_FLAG_REF)) < 0) {
274 av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
275 return ret;
276 }
277
278 new_frame_data = (uint16_t*)frame->data[0];
279 new_stride = frame->linesize[0] / 2;
280 old_frame_data = (uint16_t*)s->frame->data[0];
281 old_stride = s->frame->linesize[0] / 2;
282
283 for (superblock_index = 0; superblock_index < s->num_superblocks;
284 superblock_index++) {
285 MacroBlock mb;
286 SuperBlock sb;
287 unsigned multi_mask = 0;
288
289 if (skip == -1) {
290 // Note that this call will make us skip the rest of the blocks
291 // if the frame prematurely ends
292 skip = decode_skip_count(&bc);
293 }
294
295 if (skip) {
296 copy_superblock(new_frame_data, new_stride,
297 old_frame_data, old_stride);
298 } else {
299 copy_superblock(sb.pixels, 8,
300 old_frame_data, old_stride);
301
302 while (can_safely_read(&bc, 1) && !bitstream_read_bit(&bc)) {
303 unsigned mask;
304 mb = decode_macroblock(s, &bc, &cb_index, superblock_index);
305 mask = bitstream_read(&bc, 16);
306 multi_mask |= mask;
307 for (i = 0; i < 16; i++) {
308 if (mask & mask_matrix[i]) {
309 insert_mb_into_sb(&sb, mb, i);
310 }
311 }
312 }
313
314 if (can_safely_read(&bc, 1) && !bitstream_read_bit(&bc)) {
315 unsigned inv_mask = bitstream_read(&bc, 4);
316 for (i = 0; i < 4; i++) {
317 if (inv_mask & (1 << i)) {
318 multi_mask ^= 0xF << i*4;
319 } else {
320 multi_mask ^= bitstream_read(&bc, 4) << i * 4;
321 }
322 }
323
324 for (i = 0; i < 16; i++) {
325 if (multi_mask & mask_matrix[i]) {
326 if (!can_safely_read(&bc, 1))
327 break;
328 mb = decode_macroblock(s, &bc, &cb_index,
329 superblock_index);
330 insert_mb_into_sb(&sb, mb, i);
331 }
332 }
333 } else if (frame_flags & (1 << 16)) {
334 while (can_safely_read(&bc, 1) && !bitstream_read_bit(&bc)) {
335 mb = decode_macroblock(s, &bc, &cb_index, superblock_index);
336 insert_mb_into_sb(&sb, mb, bitstream_read(&bc, 4));
337 }
338 }
339
340 copy_superblock(new_frame_data, new_stride, sb.pixels, 8);
341 }
342
343 superblock_col_index++;
344 new_frame_data += 8;
345 if (old_frame_data)
346 old_frame_data += 8;
347 if (superblock_col_index == superblocks_per_row) {
348 new_frame_data += new_stride * 8 - superblocks_per_row * 8;
349 if (old_frame_data)
350 old_frame_data += old_stride * 8 - superblocks_per_row * 8;
351 superblock_col_index = 0;
352 }
353 skip--;
354 }
355
356 av_log(NULL, AV_LOG_DEBUG,
357 "Escape sizes: %i, %i, %i\n",
358 frame_size, buf_size, bitstream_tell(&bc) / 8);
359
360 av_frame_unref(s->frame);
361 if ((ret = av_frame_ref(s->frame, frame)) < 0)
362 return ret;
363
364 *got_frame = 1;
365
366 return frame_size;
367 }
368
369
370 AVCodec ff_escape124_decoder = {
371 .name = "escape124",
372 .long_name = NULL_IF_CONFIG_SMALL("Escape 124"),
373 .type = AVMEDIA_TYPE_VIDEO,
374 .id = AV_CODEC_ID_ESCAPE124,
375 .priv_data_size = sizeof(Escape124Context),
376 .init = escape124_decode_init,
377 .close = escape124_decode_close,
378 .decode = escape124_decode_frame,
379 .capabilities = AV_CODEC_CAP_DR1,
380 };