FFmpeg: libavcodec/escape124.c Source File

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libavcodec

escape124.c

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1 /*

2 * Escape 124 Video Decoder

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 */

22 #include "avcodec.h"

23 #include "internal.h"

25 #define BITSTREAM_READER_LE

26 #include "get_bits.h"

28 typedef union MacroBlock {

29 uint16_t pixels[4];

30 uint32_t pixels32[2];

31 } MacroBlock;

33 typedef union SuperBlock {

34 uint16_t pixels[64];

35 uint32_t pixels32[32];

36 } SuperBlock;

38 typedef struct CodeBook {

39 unsigned depth;

40 unsigned size;

41 MacroBlock* blocks;

42 } CodeBook;

44 typedef struct Escape124Context {

45 AVFrame frame;

47 unsigned num_superblocks;

49 CodeBook codebooks[3];

50 } Escape124Context;

52 static int can_safely_read(GetBitContext* gb, uint64_t bits) {

53 return get_bits_left(gb) >= bits;

54 }

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;

65 avcodec_get_frame_defaults(&s->frame);

66 avctx->pix_fmt = AV_PIX_FMT_RGB555;

68 s->num_superblocks = ((unsigned)avctx->width / 8) *

69 ((unsigned)avctx->height / 8);

71 return 0;

72 }

74 static av_cold int escape124_decode_close(AVCodecContext *avctx)

75 {

76 unsigned i;

77 Escape124Context *s = avctx->priv_data;

79 for (i = 0; i < 3; i++)

80 av_free(s->codebooks[i].blocks);

82 av_frame_unref(&s->frame);

84 return 0;

85 }

87 static CodeBook unpack_codebook(GetBitContext* gb, unsigned depth,

88 unsigned size)

89 {

90 unsigned i, j;

91 CodeBook cb = { 0 };

93 if (!can_safely_read(gb, (uint64_t)size * 34))

94 return cb;

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 *got_frame,

201 AVPacket *avpkt)

202 {

203 int buf_size = avpkt->size;

204 Escape124Context *s = avctx->priv_data;

205 AVFrame *frame = 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 int ret;

219

220 if ((ret = init_get_bits8(&gb, avpkt->data, avpkt->size)) < 0)

221 return ret;

222

223 // This call also guards the potential depth reads for the

224 // codebook unpacking.

225 if (!can_safely_read(&gb, 64))

226 return -1;

227

228 frame_flags = get_bits_long(&gb, 32);

229 frame_size = get_bits_long(&gb, 32);

230

231 // Leave last frame unchanged

232 // FIXME: Is this necessary? I haven't seen it in any real samples

233 if (!(frame_flags & 0x114) || !(frame_flags & 0x7800000)) {

234 if (!s->frame.data[0])

235 return AVERROR_INVALIDDATA;

236

237 av_log(avctx, AV_LOG_DEBUG, "Skipping frame\n");

238

239 *got_frame = 1;

240 if ((ret = av_frame_ref(frame, &s->frame)) < 0)

241 return ret;

242

243 return frame_size;

244 }

245

246 for (i = 0; i < 3; i++) {

247 if (frame_flags & (1 << (17 + i))) {

248 unsigned cb_depth, cb_size;

249 if (i == 2) {

250 // This codebook can be cut off at places other than

251 // powers of 2, leaving some of the entries undefined.

252 cb_size = get_bits_long(&gb, 20);

253 cb_depth = av_log2(cb_size - 1) + 1;

254 } else {

255 cb_depth = get_bits(&gb, 4);

256 if (i == 0) {

257 // This is the most basic codebook: pow(2,depth) entries

258 // for a depth-length key

259 cb_size = 1 << cb_depth;

260 } else {

261 // This codebook varies per superblock

262 // FIXME: I don't think this handles integer overflow

263 // properly

264 cb_size = s->num_superblocks << cb_depth;

265 }

266 }

267 av_free(s->codebooks[i].blocks);

268 s->codebooks[i] = unpack_codebook(&gb, cb_depth, cb_size);

269 if (!s->codebooks[i].blocks)

270 return -1;

271 }

272 }

273

274 if ((ret = ff_get_buffer(avctx, frame, AV_GET_BUFFER_FLAG_REF)) < 0)

275 return ret;

276

277 new_frame_data = (uint16_t*)frame->data[0];

278 new_stride = frame->linesize[0] / 2;

279 old_frame_data = (uint16_t*)s->frame.data[0];

280 old_stride = s->frame.linesize[0] / 2;

281

282 for (superblock_index = 0; superblock_index < s->num_superblocks;

283 superblock_index++) {

284 MacroBlock mb;

285 SuperBlock sb;

286 unsigned multi_mask = 0;

287

288 if (skip == -1) {

289 // Note that this call will make us skip the rest of the blocks

290 // if the frame prematurely ends

291 skip = decode_skip_count(&gb);

292 }

293

294 if (skip) {

295 copy_superblock(new_frame_data, new_stride,

296 old_frame_data, old_stride);

297 } else {

298 copy_superblock(sb.pixels, 8,

299 old_frame_data, old_stride);

300

301 while (can_safely_read(&gb, 1) && !get_bits1(&gb)) {

302 unsigned mask;

303 mb = decode_macroblock(s, &gb, &cb_index, superblock_index);

304 mask = get_bits(&gb, 16);

305 multi_mask |= mask;

306 for (i = 0; i < 16; i++) {

307 if (mask & mask_matrix[i]) {

308 insert_mb_into_sb(&sb, mb, i);

309 }

310 }

311 }

312

313 if (can_safely_read(&gb, 1) && !get_bits1(&gb)) {

314 unsigned inv_mask = get_bits(&gb, 4);

315 for (i = 0; i < 4; i++) {

316 if (inv_mask & (1 << i)) {

317 multi_mask ^= 0xF << i*4;

318 } else {

319 multi_mask ^= get_bits(&gb, 4) << i*4;

320 }

321 }

322

323 for (i = 0; i < 16; i++) {

324 if (multi_mask & mask_matrix[i]) {

325 if (!can_safely_read(&gb, 1))

326 break;

327 mb = decode_macroblock(s, &gb, &cb_index,

328 superblock_index);

329 insert_mb_into_sb(&sb, mb, i);

330 }

331 }

332 } else if (frame_flags & (1 << 16)) {

333 while (can_safely_read(&gb, 1) && !get_bits1(&gb)) {

334 mb = decode_macroblock(s, &gb, &cb_index, superblock_index);

335 insert_mb_into_sb(&sb, mb, get_bits(&gb, 4));

336 }

337 }

338

339 copy_superblock(new_frame_data, new_stride, sb.pixels, 8);

340 }

341

342 superblock_col_index++;

343 new_frame_data += 8;

344 if (old_frame_data)

345 old_frame_data += 8;

346 if (superblock_col_index == superblocks_per_row) {

347 new_frame_data += new_stride * 8 - superblocks_per_row * 8;

348 if (old_frame_data)

349 old_frame_data += old_stride * 8 - superblocks_per_row * 8;

350 superblock_col_index = 0;

351 }

352 skip--;

353 }

354

355 av_log(avctx, AV_LOG_DEBUG,

356 "Escape sizes: %i, %i, %i\n",

357 frame_size, buf_size, get_bits_count(&gb) / 8);

358

359 av_frame_unref(&s->frame);

360 if ((ret = av_frame_ref(&s->frame, frame)) < 0)

361 return ret;

362

363 *got_frame = 1;

364

365 return frame_size;

366 }

367

368

369 AVCodec ff_escape124_decoder = {

370 .name = "escape124",

371 .type = AVMEDIA_TYPE_VIDEO,

372 .id = AV_CODEC_ID_ESCAPE124,

373 .priv_data_size = sizeof(Escape124Context),

374 .init = escape124_decode_init,

375 .close = escape124_decode_close,

376 .decode = escape124_decode_frame,

377 .capabilities = CODEC_CAP_DR1,

378 .long_name = NULL_IF_CONFIG_SMALL("Escape 124"),

379 };

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