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escape124.c
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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 #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;
42 } CodeBook;
43 
44 typedef struct Escape124Context {
46 
47  unsigned num_superblocks;
48 
51 
52 /**
53  * Initialize the decoder
54  * @param avctx decoder context
55  * @return 0 success, negative on error
56  */
58 {
59  Escape124Context *s = avctx->priv_data;
60 
61  avctx->pix_fmt = AV_PIX_FMT_RGB555;
62 
63  s->num_superblocks = ((unsigned)avctx->width / 8) *
64  ((unsigned)avctx->height / 8);
65 
66  s->frame = av_frame_alloc();
67  if (!s->frame)
68  return AVERROR(ENOMEM);
69 
70  return 0;
71 }
72 
74 {
75  unsigned i;
76  Escape124Context *s = avctx->priv_data;
77 
78  for (i = 0; i < 3; i++)
79  av_freep(&s->codebooks[i].blocks);
80 
81  av_frame_free(&s->frame);
82 
83  return 0;
84 }
85 
87  unsigned size)
88 {
89  unsigned i, j;
90  CodeBook cb = { 0 };
91 
92  if (size >= INT_MAX / 34 || get_bits_left(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 
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 (get_bits_left(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 
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 
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 
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 
199  void *data, int *got_frame,
200  AVPacket *avpkt)
201 {
202  int buf_size = avpkt->size;
203  Escape124Context *s = avctx->priv_data;
204  AVFrame *frame = data;
205 
206  GetBitContext gb;
207  unsigned frame_flags, frame_size;
208  unsigned i;
209 
210  unsigned superblock_index, cb_index = 1,
211  superblock_col_index = 0,
212  superblocks_per_row = avctx->width / 8, skip = -1;
213 
214  uint16_t* old_frame_data, *new_frame_data;
215  unsigned old_stride, new_stride;
216 
217  int ret;
218 
219  if ((ret = init_get_bits8(&gb, avpkt->data, avpkt->size)) < 0)
220  return ret;
221 
222  // This call also guards the potential depth reads for the
223  // codebook unpacking.
224  if (get_bits_left(&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  if (!s->frame->data[0])
234  return AVERROR_INVALIDDATA;
235 
236  av_log(avctx, 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 = get_bits_long(&gb, 20);
252  cb_depth = av_log2(cb_size - 1) + 1;
253  } else {
254  cb_depth = get_bits(&gb, 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_freep(&s->codebooks[i].blocks);
267  s->codebooks[i] = unpack_codebook(&gb, 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  return ret;
275 
276  new_frame_data = (uint16_t*)frame->data[0];
277  new_stride = frame->linesize[0] / 2;
278  old_frame_data = (uint16_t*)s->frame->data[0];
279  old_stride = s->frame->linesize[0] / 2;
280 
281  for (superblock_index = 0; superblock_index < s->num_superblocks;
282  superblock_index++) {
283  MacroBlock mb;
284  SuperBlock sb;
285  unsigned multi_mask = 0;
286 
287  if (skip == -1) {
288  // Note that this call will make us skip the rest of the blocks
289  // if the frame prematurely ends
290  skip = decode_skip_count(&gb);
291  }
292 
293  if (skip) {
294  copy_superblock(new_frame_data, new_stride,
295  old_frame_data, old_stride);
296  } else {
297  copy_superblock(sb.pixels, 8,
298  old_frame_data, old_stride);
299 
300  while (get_bits_left(&gb) >= 1 && !get_bits1(&gb)) {
301  unsigned mask;
302  mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
303  mask = get_bits(&gb, 16);
304  multi_mask |= mask;
305  for (i = 0; i < 16; i++) {
306  if (mask & mask_matrix[i]) {
307  insert_mb_into_sb(&sb, mb, i);
308  }
309  }
310  }
311 
312  if (!get_bits1(&gb)) {
313  unsigned inv_mask = get_bits(&gb, 4);
314  for (i = 0; i < 4; i++) {
315  if (inv_mask & (1 << i)) {
316  multi_mask ^= 0xF << i*4;
317  } else {
318  multi_mask ^= get_bits(&gb, 4) << i*4;
319  }
320  }
321 
322  for (i = 0; i < 16; i++) {
323  if (multi_mask & mask_matrix[i]) {
324  mb = decode_macroblock(s, &gb, &cb_index,
325  superblock_index);
326  insert_mb_into_sb(&sb, mb, i);
327  }
328  }
329  } else if (frame_flags & (1 << 16)) {
330  while (get_bits_left(&gb) >= 1 && !get_bits1(&gb)) {
331  mb = decode_macroblock(s, &gb, &cb_index, superblock_index);
332  insert_mb_into_sb(&sb, mb, get_bits(&gb, 4));
333  }
334  }
335 
336  copy_superblock(new_frame_data, new_stride, sb.pixels, 8);
337  }
338 
339  superblock_col_index++;
340  new_frame_data += 8;
341  if (old_frame_data)
342  old_frame_data += 8;
343  if (superblock_col_index == superblocks_per_row) {
344  new_frame_data += new_stride * 8 - superblocks_per_row * 8;
345  if (old_frame_data)
346  old_frame_data += old_stride * 8 - superblocks_per_row * 8;
347  superblock_col_index = 0;
348  }
349  skip--;
350  }
351 
352  av_log(avctx, AV_LOG_DEBUG,
353  "Escape sizes: %i, %i, %i\n",
354  frame_size, buf_size, get_bits_count(&gb) / 8);
355 
356  av_frame_unref(s->frame);
357  if ((ret = av_frame_ref(s->frame, frame)) < 0)
358  return ret;
359 
360  *got_frame = 1;
361 
362  return frame_size;
363 }
364 
365 
367  .name = "escape124",
368  .long_name = NULL_IF_CONFIG_SMALL("Escape 124"),
369  .type = AVMEDIA_TYPE_VIDEO,
370  .id = AV_CODEC_ID_ESCAPE124,
371  .priv_data_size = sizeof(Escape124Context),
375  .capabilities = CODEC_CAP_DR1,
376 };