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 Libav.
11 * Libav 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 * Libav 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 Libav; if not, write to the Free Software
23 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
36 const uint8_t ff_log2_run[41]={
37 0, 0, 0, 0, 1, 1, 1, 1,
38 2, 2, 2, 2, 3, 3, 3, 3,
39 4, 4, 5, 5, 6, 6, 7, 7,
40 8, 9,10,11,12,13,14,15,
41 16,17,18,19,20,21,22,23,
45 void avpriv_align_put_bits(PutBitContext *s)
47 put_bits(s,s->bit_left & 7,0);
50 void avpriv_put_string(PutBitContext *pb, const char *string, int terminate_string)
53 put_bits(pb, 8, *string);
60 void avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
68 if(CONFIG_SMALL || words < 16 || put_bits_count(pb)&7){
69 for(i=0; i<words; i++) put_bits(pb, 16, AV_RB16(src + 2*i));
71 for(i=0; put_bits_count(pb)&31; i++)
72 put_bits(pb, 8, src[i]);
74 memcpy(put_bits_ptr(pb), src+i, 2*words-i);
75 skip_put_bytes(pb, 2*words-i);
78 put_bits(pb, bits, AV_RB16(src + 2*words)>>(16-bits));
83 #define GET_DATA(v, table, i, wrap, size) \
85 const uint8_t *ptr = (const uint8_t *)table + i * wrap;\
88 v = *(const uint8_t *)ptr;\
91 v = *(const uint16_t *)ptr;\
94 v = *(const uint32_t *)ptr;\
100 static int alloc_table(VLC *vlc, int size, int use_static)
103 index = vlc->table_size;
104 vlc->table_size += size;
105 if (vlc->table_size > vlc->table_allocated) {
107 abort(); // cannot do anything, init_vlc() is used with too little memory
108 vlc->table_allocated += (1 << vlc->bits);
109 vlc->table = av_realloc(vlc->table,
110 sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
117 static av_always_inline uint32_t bitswap_32(uint32_t x) {
118 return (uint32_t)ff_reverse[x&0xFF]<<24
119 | (uint32_t)ff_reverse[(x>>8)&0xFF]<<16
120 | (uint32_t)ff_reverse[(x>>16)&0xFF]<<8
121 | (uint32_t)ff_reverse[x>>24];
127 /** codeword, with the first bit-to-be-read in the msb
128 * (even if intended for a little-endian bitstream reader) */
132 static int compare_vlcspec(const void *a, const void *b)
134 const VLCcode *sa=a, *sb=b;
135 return (sa->code >> 1) - (sb->code >> 1);
139 * Build VLC decoding tables suitable for use with get_vlc().
141 * @param vlc the context to be initted
143 * @param table_nb_bits max length of vlc codes to store directly in this table
144 * (Longer codes are delegated to subtables.)
146 * @param nb_codes number of elements in codes[]
148 * @param codes descriptions of the vlc codes
149 * These must be ordered such that codes going into the same subtable are contiguous.
150 * Sorting by VLCcode.code is sufficient, though not necessary.
152 static int build_table(VLC *vlc, int table_nb_bits, int nb_codes,
153 VLCcode *codes, int flags)
155 int table_size, table_index, index, code_prefix, symbol, subtable_bits;
156 int i, j, k, n, nb, inc;
158 VLC_TYPE (*table)[2];
160 table_size = 1 << table_nb_bits;
161 table_index = alloc_table(vlc, table_size, flags & INIT_VLC_USE_NEW_STATIC);
162 av_dlog(NULL, "new table index=%d size=%d\n", table_index, table_size);
165 table = &vlc->table[table_index];
167 for (i = 0; i < table_size; i++) {
168 table[i][1] = 0; //bits
169 table[i][0] = -1; //codes
172 /* first pass: map codes and compute auxiliary table sizes */
173 for (i = 0; i < nb_codes; i++) {
175 code = codes[i].code;
176 symbol = codes[i].symbol;
177 av_dlog(NULL, "i=%d n=%d code=0x%x\n", i, n, code);
178 if (n <= table_nb_bits) {
179 /* no need to add another table */
180 j = code >> (32 - table_nb_bits);
181 nb = 1 << (table_nb_bits - n);
183 if (flags & INIT_VLC_LE) {
184 j = bitswap_32(code);
187 for (k = 0; k < nb; k++) {
188 av_dlog(NULL, "%4x: code=%d n=%d\n", j, i, n);
189 if (table[j][1] /*bits*/ != 0) {
190 av_log(NULL, AV_LOG_ERROR, "incorrect codes\n");
193 table[j][1] = n; //bits
194 table[j][0] = symbol;
198 /* fill auxiliary table recursively */
200 code_prefix = code >> (32 - table_nb_bits);
203 codes[i].code = code << table_nb_bits;
204 for (k = i+1; k < nb_codes; k++) {
205 n = codes[k].bits - table_nb_bits;
208 code = codes[k].code;
209 if (code >> (32 - table_nb_bits) != code_prefix)
212 codes[k].code = code << table_nb_bits;
213 subtable_bits = FFMAX(subtable_bits, n);
215 subtable_bits = FFMIN(subtable_bits, table_nb_bits);
216 j = (flags & INIT_VLC_LE) ? bitswap_32(code_prefix) >> (32 - table_nb_bits) : code_prefix;
217 table[j][1] = -subtable_bits;
218 av_dlog(NULL, "%4x: n=%d (subtable)\n",
219 j, codes[i].bits + table_nb_bits);
220 index = build_table(vlc, subtable_bits, k-i, codes+i, flags);
223 /* note: realloc has been done, so reload tables */
224 table = &vlc->table[table_index];
225 table[j][0] = index; //code
233 /* Build VLC decoding tables suitable for use with get_vlc().
235 'nb_bits' set thee decoding table size (2^nb_bits) entries. The
236 bigger it is, the faster is the decoding. But it should not be too
237 big to save memory and L1 cache. '9' is a good compromise.
239 'nb_codes' : number of vlcs codes
241 'bits' : table which gives the size (in bits) of each vlc code.
243 'codes' : table which gives the bit pattern of of each vlc code.
245 'symbols' : table which gives the values to be returned from get_vlc().
247 'xxx_wrap' : give the number of bytes between each entry of the
248 'bits' or 'codes' tables.
250 'xxx_size' : gives the number of bytes of each entry of the 'bits'
253 'wrap' and 'size' allows to use any memory configuration and types
254 (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.
256 'use_static' should be set to 1 for tables, which should be freed
257 with av_free_static(), 0 if ff_free_vlc() will be used.
259 int ff_init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
260 const void *bits, int bits_wrap, int bits_size,
261 const void *codes, int codes_wrap, int codes_size,
262 const void *symbols, int symbols_wrap, int symbols_size,
269 if(flags & INIT_VLC_USE_NEW_STATIC){
270 if(vlc->table_size && vlc->table_size == vlc->table_allocated){
272 }else if(vlc->table_size){
273 abort(); // fatal error, we are called on a partially initialized table
277 vlc->table_allocated = 0;
281 av_dlog(NULL, "build table nb_codes=%d\n", nb_codes);
283 buf = av_malloc((nb_codes+1)*sizeof(VLCcode));
285 assert(symbols_size <= 2 || !symbols);
287 #define COPY(condition)\
288 for (i = 0; i < nb_codes; i++) {\
289 GET_DATA(buf[j].bits, bits, i, bits_wrap, bits_size);\
292 GET_DATA(buf[j].code, codes, i, codes_wrap, codes_size);\
293 if (flags & INIT_VLC_LE)\
294 buf[j].code = bitswap_32(buf[j].code);\
296 buf[j].code <<= 32 - buf[j].bits;\
298 GET_DATA(buf[j].symbol, symbols, i, symbols_wrap, symbols_size)\
303 COPY(buf[j].bits > nb_bits);
304 // qsort is the slowest part of init_vlc, and could probably be improved or avoided
305 qsort(buf, j, sizeof(VLCcode), compare_vlcspec);
306 COPY(buf[j].bits && buf[j].bits <= nb_bits);
309 ret = build_table(vlc, nb_bits, nb_codes, buf, flags);
313 av_freep(&vlc->table);
316 if((flags & INIT_VLC_USE_NEW_STATIC) && vlc->table_size != vlc->table_allocated)
317 av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n", vlc->table_size, vlc->table_allocated);
322 void ff_free_vlc(VLC *vlc)
324 av_freep(&vlc->table);