3 * Copyright (c) 2000, 2001 Fabrice Bellard
4 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
5 * Copyright (c) 2010 Loren Merritt
7 * alternative bitstream reader & writer by Michael Niedermayer <michaelni@gmx.at>
9 * This file is part of FFmpeg.
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.
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.
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
31 #include "libavutil/avassert.h"
37 const uint8_t ff_log2_run[41]={
38 0, 0, 0, 0, 1, 1, 1, 1,
39 2, 2, 2, 2, 3, 3, 3, 3,
40 4, 4, 5, 5, 6, 6, 7, 7,
41 8, 9,10,11,12,13,14,15,
42 16,17,18,19,20,21,22,23,
46 void avpriv_align_put_bits(PutBitContext *s)
48 put_bits(s, s->bit_left & 7, 0);
51 void avpriv_put_string(PutBitContext *pb, const char *string,
55 put_bits(pb, 8, *string);
62 void avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
64 int words = length >> 4;
65 int bits = length & 15;
71 if (CONFIG_SMALL || words < 16 || put_bits_count(pb) & 7) {
72 for (i = 0; i < words; i++)
73 put_bits(pb, 16, AV_RB16(src + 2 * i));
75 for (i = 0; put_bits_count(pb) & 31; i++)
76 put_bits(pb, 8, src[i]);
78 memcpy(put_bits_ptr(pb), src + i, 2 * words - i);
79 skip_put_bytes(pb, 2 * words - i);
82 put_bits(pb, bits, AV_RB16(src + 2 * words) >> (16 - bits));
87 #define GET_DATA(v, table, i, wrap, size) \
89 const uint8_t *ptr = (const uint8_t *)table + i * wrap; \
92 v = *(const uint8_t *)ptr; \
95 v = *(const uint16_t *)ptr; \
98 v = *(const uint32_t *)ptr; \
104 static int alloc_table(VLC *vlc, int size, int use_static)
106 int index = vlc->table_size;
108 vlc->table_size += size;
109 if (vlc->table_size > vlc->table_allocated) {
111 abort(); // cannot do anything, init_vlc() is used with too little memory
112 vlc->table_allocated += (1 << vlc->bits);
113 vlc->table = av_realloc_f(vlc->table, vlc->table_allocated, sizeof(VLC_TYPE) * 2);
115 return AVERROR(ENOMEM);
120 static av_always_inline uint32_t bitswap_32(uint32_t x)
122 return (uint32_t)ff_reverse[ x & 0xFF] << 24 |
123 (uint32_t)ff_reverse[(x >> 8) & 0xFF] << 16 |
124 (uint32_t)ff_reverse[(x >> 16) & 0xFF] << 8 |
125 (uint32_t)ff_reverse[ x >> 24];
131 /** codeword, with the first bit-to-be-read in the msb
132 * (even if intended for a little-endian bitstream reader) */
136 static int compare_vlcspec(const void *a, const void *b)
138 const VLCcode *sa = a, *sb = b;
139 return (sa->code >> 1) - (sb->code >> 1);
142 * Build VLC decoding tables suitable for use with get_vlc().
144 * @param vlc the context to be initted
146 * @param table_nb_bits max length of vlc codes to store directly in this table
147 * (Longer codes are delegated to subtables.)
149 * @param nb_codes number of elements in codes[]
151 * @param codes descriptions of the vlc codes
152 * These must be ordered such that codes going into the same subtable are contiguous.
153 * Sorting by VLCcode.code is sufficient, though not necessary.
155 static int build_table(VLC *vlc, int table_nb_bits, int nb_codes,
156 VLCcode *codes, int flags)
158 int table_size, table_index, index, code_prefix, symbol, subtable_bits;
159 int i, j, k, n, nb, inc;
161 VLC_TYPE (*table)[2];
163 table_size = 1 << table_nb_bits;
164 if (table_nb_bits > 30)
166 table_index = alloc_table(vlc, table_size, flags & INIT_VLC_USE_NEW_STATIC);
167 av_dlog(NULL, "new table index=%d size=%d\n", table_index, table_size);
170 table = &vlc->table[table_index];
172 for (i = 0; i < table_size; i++) {
173 table[i][1] = 0; //bits
174 table[i][0] = -1; //codes
177 /* first pass: map codes and compute auxiliary table sizes */
178 for (i = 0; i < nb_codes; i++) {
180 code = codes[i].code;
181 symbol = codes[i].symbol;
182 av_dlog(NULL, "i=%d n=%d code=0x%x\n", i, n, code);
183 if (n <= table_nb_bits) {
184 /* no need to add another table */
185 j = code >> (32 - table_nb_bits);
186 nb = 1 << (table_nb_bits - n);
188 if (flags & INIT_VLC_LE) {
189 j = bitswap_32(code);
192 for (k = 0; k < nb; k++) {
193 av_dlog(NULL, "%4x: code=%d n=%d\n", j, i, n);
194 if (table[j][1] /*bits*/ != 0) {
195 av_log(NULL, AV_LOG_ERROR, "incorrect codes\n");
196 return AVERROR_INVALIDDATA;
198 table[j][1] = n; //bits
199 table[j][0] = symbol;
203 /* fill auxiliary table recursively */
205 code_prefix = code >> (32 - table_nb_bits);
208 codes[i].code = code << table_nb_bits;
209 for (k = i+1; k < nb_codes; k++) {
210 n = codes[k].bits - table_nb_bits;
213 code = codes[k].code;
214 if (code >> (32 - table_nb_bits) != code_prefix)
217 codes[k].code = code << table_nb_bits;
218 subtable_bits = FFMAX(subtable_bits, n);
220 subtable_bits = FFMIN(subtable_bits, table_nb_bits);
221 j = (flags & INIT_VLC_LE) ? bitswap_32(code_prefix) >> (32 - table_nb_bits) : code_prefix;
222 table[j][1] = -subtable_bits;
223 av_dlog(NULL, "%4x: n=%d (subtable)\n",
224 j, codes[i].bits + table_nb_bits);
225 index = build_table(vlc, subtable_bits, k-i, codes+i, flags);
228 /* note: realloc has been done, so reload tables */
229 table = &vlc->table[table_index];
230 table[j][0] = index; //code
238 /* Build VLC decoding tables suitable for use with get_vlc().
240 'nb_bits' set thee decoding table size (2^nb_bits) entries. The
241 bigger it is, the faster is the decoding. But it should not be too
242 big to save memory and L1 cache. '9' is a good compromise.
244 'nb_codes' : number of vlcs codes
246 'bits' : table which gives the size (in bits) of each vlc code.
248 'codes' : table which gives the bit pattern of of each vlc code.
250 'symbols' : table which gives the values to be returned from get_vlc().
252 'xxx_wrap' : give the number of bytes between each entry of the
253 'bits' or 'codes' tables.
255 'xxx_size' : gives the number of bytes of each entry of the 'bits'
258 'wrap' and 'size' allows to use any memory configuration and types
259 (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.
261 'use_static' should be set to 1 for tables, which should be freed
262 with av_free_static(), 0 if ff_free_vlc() will be used.
264 int ff_init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
265 const void *bits, int bits_wrap, int bits_size,
266 const void *codes, int codes_wrap, int codes_size,
267 const void *symbols, int symbols_wrap, int symbols_size,
274 if (flags & INIT_VLC_USE_NEW_STATIC) {
280 ret = ff_init_vlc_sparse(&dyn_vlc, nb_bits, nb_codes,
281 bits, bits_wrap, bits_size,
282 codes, codes_wrap, codes_size,
283 symbols, symbols_wrap, symbols_size,
284 flags & ~INIT_VLC_USE_NEW_STATIC);
285 av_assert0(ret >= 0);
286 av_assert0(dyn_vlc.table_size <= vlc->table_allocated);
287 if (dyn_vlc.table_size < vlc->table_allocated)
288 av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n", dyn_vlc.table_size, vlc->table_allocated);
289 memcpy(vlc->table, dyn_vlc.table, dyn_vlc.table_size * sizeof(*vlc->table));
290 vlc->table_size = dyn_vlc.table_size;
291 ff_free_vlc(&dyn_vlc);
295 vlc->table_allocated = 0;
299 av_dlog(NULL, "build table nb_codes=%d\n", nb_codes);
301 buf = av_malloc((nb_codes + 1) * sizeof(VLCcode));
303 av_assert0(symbols_size <= 2 || !symbols);
305 #define COPY(condition)\
306 for (i = 0; i < nb_codes; i++) { \
307 GET_DATA(buf[j].bits, bits, i, bits_wrap, bits_size); \
310 if (buf[j].bits > 3*nb_bits || buf[j].bits>32) { \
311 av_log(NULL, AV_LOG_ERROR, "Too long VLC (%d) in init_vlc\n", buf[j].bits);\
315 GET_DATA(buf[j].code, codes, i, codes_wrap, codes_size); \
316 if (buf[j].code >= (1LL<<buf[j].bits)) { \
317 av_log(NULL, AV_LOG_ERROR, "Invalid code in init_vlc\n"); \
321 if (flags & INIT_VLC_LE) \
322 buf[j].code = bitswap_32(buf[j].code); \
324 buf[j].code <<= 32 - buf[j].bits; \
326 GET_DATA(buf[j].symbol, symbols, i, symbols_wrap, symbols_size) \
331 COPY(buf[j].bits > nb_bits);
332 // qsort is the slowest part of init_vlc, and could probably be improved or avoided
333 qsort(buf, j, sizeof(VLCcode), compare_vlcspec);
334 COPY(buf[j].bits && buf[j].bits <= nb_bits);
337 ret = build_table(vlc, nb_bits, nb_codes, buf, flags);
341 av_freep(&vlc->table);
348 void ff_free_vlc(VLC *vlc)
350 av_freep(&vlc->table);