FFmpeg: libavcodec/bitstream.c Source File

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libavcodec

bitstream.c

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1 /*

2 * Common bit i/o utils

6 *

7 * alternative bitstream reader & writer by Michael Niedermayer <michaelni@gmx.at>

8 *

9 * This file is part of FFmpeg.

10 *

11 * FFmpeg is free software; you can redistribute it and/or

12 * modify it under the terms of the GNU Lesser General Public

13 * License as published by the Free Software Foundation; either

14 * version 2.1 of the License, or (at your option) any later version.

15 *

16 * FFmpeg is distributed in the hope that it will be useful,

17 * but WITHOUT ANY WARRANTY; without even the implied warranty of

18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

19 * Lesser General Public License for more details.

20 *

21 * You should have received a copy of the GNU Lesser General Public

22 * License along with FFmpeg; if not, write to the Free Software

23 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

24 */

26 /**

27 * @file

28 * bitstream api.

29 */

31 #include "libavutil/atomic.h"

32 #include "libavutil/avassert.h"

33 #include "avcodec.h"

34 #include "mathops.h"

35 #include "get_bits.h"

36 #include "put_bits.h"

38 const uint8_t ff_log2_run[41]={

39 0, 0, 0, 0, 1, 1, 1, 1,

40 2, 2, 2, 2, 3, 3, 3, 3,

41 4, 4, 5, 5, 6, 6, 7, 7,

42 8, 9,10,11,12,13,14,15,

43 16,17,18,19,20,21,22,23,

44 24,

45 };

47 void avpriv_align_put_bits(PutBitContext *s)

48 {

49 put_bits(s, s->bit_left & 7, 0);

50 }

52 void avpriv_put_string(PutBitContext *pb, const char *string,

53 int terminate_string)

54 {

55 while (*string) {

56 put_bits(pb, 8, *string);

57 string++;

58 }

59 if (terminate_string)

60 put_bits(pb, 8, 0);

61 }

63 void avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length)

64 {

65 int words = length >> 4;

66 int bits = length & 15;

67 int i;

69 if (length == 0)

70 return;

72 if (CONFIG_SMALL || words < 16 || put_bits_count(pb) & 7) {

73 for (i = 0; i < words; i++)

74 put_bits(pb, 16, AV_RB16(src + 2 * i));

75 } else {

76 for (i = 0; put_bits_count(pb) & 31; i++)

77 put_bits(pb, 8, src[i]);

78 flush_put_bits(pb);

79 memcpy(put_bits_ptr(pb), src + i, 2 * words - i);

80 skip_put_bytes(pb, 2 * words - i);

81 }

83 put_bits(pb, bits, AV_RB16(src + 2 * words) >> (16 - bits));

84 }

86 /* VLC decoding */

88 #define GET_DATA(v, table, i, wrap, size) \

89 { \

90 const uint8_t *ptr = (const uint8_t *)table + i * wrap; \

91 switch(size) { \

92 case 1: \

93 v = *(const uint8_t *)ptr; \

94 break; \

95 case 2: \

96 v = *(const uint16_t *)ptr; \

97 break; \

98 default: \

99 v = *(const uint32_t *)ptr; \

100 break; \

101 } \

102 }

103

104

105 static int alloc_table(VLC *vlc, int size, int use_static)

106 {

107 int index = vlc->table_size;

108

109 vlc->table_size += size;

110 if (vlc->table_size > vlc->table_allocated) {

111 if (use_static)

112 abort(); // cannot do anything, init_vlc() is used with too little memory

113 vlc->table_allocated += (1 << vlc->bits);

114 vlc->table = av_realloc_f(vlc->table, vlc->table_allocated, sizeof(VLC_TYPE) * 2);

115 if (!vlc->table)

116 return AVERROR(ENOMEM);

117 }

118 return index;

119 }

120

121 static av_always_inline uint32_t bitswap_32(uint32_t x)

122 {

123 return (uint32_t)ff_reverse[ x & 0xFF] << 24 |

124 (uint32_t)ff_reverse[(x >> 8) & 0xFF] << 16 |

125 (uint32_t)ff_reverse[(x >> 16) & 0xFF] << 8 |

126 (uint32_t)ff_reverse[ x >> 24];

127 }

128

129 typedef struct {

130 uint8_t bits;

131 uint16_t symbol;

132 /** codeword, with the first bit-to-be-read in the msb

133 * (even if intended for a little-endian bitstream reader) */

134 uint32_t code;

135 } VLCcode;

136

137 static int compare_vlcspec(const void *a, const void *b)

138 {

139 const VLCcode *sa = a, *sb = b;

140 return (sa->code >> 1) - (sb->code >> 1);

141 }

142 /**

143 * Build VLC decoding tables suitable for use with get_vlc().

144 *

145 * @param vlc the context to be initted

146 *

147 * @param table_nb_bits max length of vlc codes to store directly in this table

148 * (Longer codes are delegated to subtables.)

149 *

150 * @param nb_codes number of elements in codes[]

151 *

152 * @param codes descriptions of the vlc codes

153 * These must be ordered such that codes going into the same subtable are contiguous.

154 * Sorting by VLCcode.code is sufficient, though not necessary.

155 */

156 static int build_table(VLC *vlc, int table_nb_bits, int nb_codes,

157 VLCcode *codes, int flags)

158 {

159 int table_size, table_index, index, code_prefix, symbol, subtable_bits;

160 int i, j, k, n, nb, inc;

161 uint32_t code;

162 VLC_TYPE (*table)[2];

163

164 table_size = 1 << table_nb_bits;

165 if (table_nb_bits > 30)

166 return -1;

167 table_index = alloc_table(vlc, table_size, flags & INIT_VLC_USE_NEW_STATIC);

168 av_dlog(NULL, "new table index=%d size=%d\n", table_index, table_size);

169 if (table_index < 0)

170 return table_index;

171 table = &vlc->table[table_index];

172

173 for (i = 0; i < table_size; i++) {

174 table[i][1] = 0; //bits

175 table[i][0] = -1; //codes

176 }

177

178 /* first pass: map codes and compute auxiliary table sizes */

179 for (i = 0; i < nb_codes; i++) {

180 n = codes[i].bits;

181 code = codes[i].code;

182 symbol = codes[i].symbol;

183 av_dlog(NULL, "i=%d n=%d code=0x%x\n", i, n, code);

184 if (n <= table_nb_bits) {

185 /* no need to add another table */

186 j = code >> (32 - table_nb_bits);

187 nb = 1 << (table_nb_bits - n);

188 inc = 1;

189 if (flags & INIT_VLC_LE) {

190 j = bitswap_32(code);

191 inc = 1 << n;

192 }

193 for (k = 0; k < nb; k++) {

194 av_dlog(NULL, "%4x: code=%d n=%d\n", j, i, n);

195 if (table[j][1] /*bits*/ != 0) {

196 av_log(NULL, AV_LOG_ERROR, "incorrect codes\n");

197 return AVERROR_INVALIDDATA;

198 }

199 table[j][1] = n; //bits

200 table[j][0] = symbol;

201 j += inc;

202 }

203 } else {

204 /* fill auxiliary table recursively */

205 n -= table_nb_bits;

206 code_prefix = code >> (32 - table_nb_bits);

207 subtable_bits = n;

208 codes[i].bits = n;

209 codes[i].code = code << table_nb_bits;

210 for (k = i+1; k < nb_codes; k++) {

211 n = codes[k].bits - table_nb_bits;

212 if (n <= 0)

213 break;

214 code = codes[k].code;

215 if (code >> (32 - table_nb_bits) != code_prefix)

216 break;

217 codes[k].bits = n;

218 codes[k].code = code << table_nb_bits;

219 subtable_bits = FFMAX(subtable_bits, n);

220 }

221 subtable_bits = FFMIN(subtable_bits, table_nb_bits);

222 j = (flags & INIT_VLC_LE) ? bitswap_32(code_prefix) >> (32 - table_nb_bits) : code_prefix;

223 table[j][1] = -subtable_bits;

224 av_dlog(NULL, "%4x: n=%d (subtable)\n",

225 j, codes[i].bits + table_nb_bits);

226 index = build_table(vlc, subtable_bits, k-i, codes+i, flags);

227 if (index < 0)

228 return index;

229 /* note: realloc has been done, so reload tables */

230 table = &vlc->table[table_index];

231 table[j][0] = index; //code

232 i = k-1;

233 }

234 }

235 return table_index;

236 }

237

238

239 /* Build VLC decoding tables suitable for use with get_vlc().

240

241 'nb_bits' set thee decoding table size (2^nb_bits) entries. The

242 bigger it is, the faster is the decoding. But it should not be too

243 big to save memory and L1 cache. '9' is a good compromise.

244

245 'nb_codes' : number of vlcs codes

246

247 'bits' : table which gives the size (in bits) of each vlc code.

248

249 'codes' : table which gives the bit pattern of of each vlc code.

250

251 'symbols' : table which gives the values to be returned from get_vlc().

252

253 'xxx_wrap' : give the number of bytes between each entry of the

254 'bits' or 'codes' tables.

255

256 'xxx_size' : gives the number of bytes of each entry of the 'bits'

257 or 'codes' tables.

258

259 'wrap' and 'size' allows to use any memory configuration and types

260 (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.

261

262 'use_static' should be set to 1 for tables, which should be freed

263 with av_free_static(), 0 if ff_free_vlc() will be used.

264 */

265 int ff_init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,

266 const void *bits, int bits_wrap, int bits_size,

267 const void *codes, int codes_wrap, int codes_size,

268 const void *symbols, int symbols_wrap, int symbols_size,

269 int flags)

270 {

271 VLCcode *buf;

272 int i, j, ret;

273 VLCcode localbuf[1500]; // the maximum currently needed is 1296 by rv34

274 void *state;

275

276 vlc->bits = nb_bits;

277 if (flags & INIT_VLC_USE_NEW_STATIC) {

278 while (state = avpriv_atomic_ptr_cas(&vlc->init_state, NULL, vlc)) {

279 if (state == vlc + 1) {

280 av_assert0(vlc->table_size && vlc->table_size == vlc->table_allocated);

281 return 0;

282 }

283 }

284 av_assert0(!vlc->table_size);

285 av_assert0(nb_codes + 1 <= FF_ARRAY_ELEMS(localbuf));

286 buf = localbuf;

287 } else {

288 vlc->table = NULL;

289 vlc->table_allocated = 0;

290 vlc->table_size = 0;

291

292 buf = av_malloc((nb_codes + 1) * sizeof(VLCcode));

293 if (!buf)

294 return AVERROR(ENOMEM);

295 }

296

297

298 av_assert0(symbols_size <= 2 || !symbols);

299 j = 0;

300 #define COPY(condition)\

301 for (i = 0; i < nb_codes; i++) { \

302 GET_DATA(buf[j].bits, bits, i, bits_wrap, bits_size); \

303 if (!(condition)) \

304 continue; \

305 if (buf[j].bits > 3*nb_bits || buf[j].bits>32) { \

306 av_log(NULL, AV_LOG_ERROR, "Too long VLC (%d) in init_vlc\n", buf[j].bits);\

307 if (!(flags & INIT_VLC_USE_NEW_STATIC)) \

308 av_free(buf); \

309 return -1; \

310 } \

311 GET_DATA(buf[j].code, codes, i, codes_wrap, codes_size); \

312 if (buf[j].code >= (1LL<<buf[j].bits)) { \

313 av_log(NULL, AV_LOG_ERROR, "Invalid code in init_vlc\n"); \

314 if (!(flags & INIT_VLC_USE_NEW_STATIC)) \

315 av_free(buf); \

316 return -1; \

317 } \

318 if (flags & INIT_VLC_LE) \

319 buf[j].code = bitswap_32(buf[j].code); \

320 else \

321 buf[j].code <<= 32 - buf[j].bits; \

322 if (symbols) \

323 GET_DATA(buf[j].symbol, symbols, i, symbols_wrap, symbols_size) \

324 else \

325 buf[j].symbol = i; \

326 j++; \

327 }

328 COPY(buf[j].bits > nb_bits);

329 // qsort is the slowest part of init_vlc, and could probably be improved or avoided

330 qsort(buf, j, sizeof(VLCcode), compare_vlcspec);

331 COPY(buf[j].bits && buf[j].bits <= nb_bits);

332 nb_codes = j;

333

334 ret = build_table(vlc, nb_bits, nb_codes, buf, flags);

335

336 if (flags & INIT_VLC_USE_NEW_STATIC) {

337 if(vlc->table_size != vlc->table_allocated)

338 av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n", vlc->table_size, vlc->table_allocated);

339 state = avpriv_atomic_ptr_cas(&vlc->init_state, vlc, vlc+1);

340 av_assert0(state == vlc);

341 av_assert0(ret >= 0);

342 } else {

343 av_free(buf);

344 if (ret < 0) {

345 av_freep(&vlc->table);

346 return ret;

347 }

348 }

349 return 0;

350 }

351

352

353 void ff_free_vlc(VLC *vlc)

354 {

355 av_freep(&vlc->table);

356 }

Generated on Sat Jan 25 2014 19:51:45 for FFmpeg by doxygen 1.8.2