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"
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,
47 void avpriv_align_put_bits(PutBitContext *s)
49 put_bits(s,s->bit_left & 7,0);
52 void avpriv_put_string(PutBitContext *pb, const char *string, int terminate_string)
55 put_bits(pb, 8, *string);
62 void avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
70 if(CONFIG_SMALL || words < 16 || put_bits_count(pb)&7){
71 for(i=0; i<words; i++) put_bits(pb, 16, AV_RB16(src + 2*i));
73 for(i=0; put_bits_count(pb)&31; i++)
74 put_bits(pb, 8, src[i]);
76 memcpy(put_bits_ptr(pb), src+i, 2*words-i);
77 skip_put_bytes(pb, 2*words-i);
80 put_bits(pb, bits, AV_RB16(src + 2*words)>>(16-bits));
85 #define GET_DATA(v, table, i, wrap, size) \
87 const uint8_t *ptr = (const uint8_t *)table + i * wrap;\
90 v = *(const uint8_t *)ptr;\
93 v = *(const uint16_t *)ptr;\
96 v = *(const uint32_t *)ptr;\
102 static int alloc_table(VLC *vlc, int size, int use_static)
105 index = vlc->table_size;
106 vlc->table_size += size;
107 if (vlc->table_size > vlc->table_allocated) {
109 abort(); // cannot do anything, init_vlc() is used with too little memory
110 vlc->table_allocated += (1 << vlc->bits);
111 vlc->table = av_realloc_f(vlc->table,
112 vlc->table_allocated, sizeof(VLC_TYPE) * 2);
119 static av_always_inline uint32_t bitswap_32(uint32_t x) {
120 return (uint32_t)ff_reverse[x&0xFF]<<24
121 | (uint32_t)ff_reverse[(x>>8)&0xFF]<<16
122 | (uint32_t)ff_reverse[(x>>16)&0xFF]<<8
123 | (uint32_t)ff_reverse[x>>24];
129 /** codeword, with the first bit-to-be-read in the msb
130 * (even if intended for a little-endian bitstream reader) */
134 static int compare_vlcspec(const void *a, const void *b)
136 const VLCcode *sa=a, *sb=b;
137 return (sa->code >> 1) - (sb->code >> 1);
141 * Build VLC decoding tables suitable for use with get_vlc().
143 * @param vlc the context to be initted
145 * @param table_nb_bits max length of vlc codes to store directly in this table
146 * (Longer codes are delegated to subtables.)
148 * @param nb_codes number of elements in codes[]
150 * @param codes descriptions of the vlc codes
151 * These must be ordered such that codes going into the same subtable are contiguous.
152 * Sorting by VLCcode.code is sufficient, though not necessary.
154 static int build_table(VLC *vlc, int table_nb_bits, int nb_codes,
155 VLCcode *codes, int flags)
157 int table_size, table_index, index, code_prefix, symbol, subtable_bits;
158 int i, j, k, n, nb, inc;
160 VLC_TYPE (*table)[2];
162 table_size = 1 << table_nb_bits;
163 if (table_nb_bits > 30)
165 table_index = alloc_table(vlc, table_size, flags & INIT_VLC_USE_NEW_STATIC);
166 av_dlog(NULL, "new table index=%d size=%d\n", table_index, table_size);
169 table = &vlc->table[table_index];
171 for (i = 0; i < table_size; i++) {
172 table[i][1] = 0; //bits
173 table[i][0] = -1; //codes
176 /* first pass: map codes and compute auxillary table sizes */
177 for (i = 0; i < nb_codes; i++) {
179 code = codes[i].code;
180 symbol = codes[i].symbol;
181 av_dlog(NULL, "i=%d n=%d code=0x%x\n", i, n, code);
182 if (n <= table_nb_bits) {
183 /* no need to add another table */
184 j = code >> (32 - table_nb_bits);
185 nb = 1 << (table_nb_bits - n);
187 if (flags & INIT_VLC_LE) {
188 j = bitswap_32(code);
191 for (k = 0; k < nb; k++) {
192 av_dlog(NULL, "%4x: code=%d n=%d\n", j, i, n);
193 if (table[j][1] /*bits*/ != 0) {
194 av_log(NULL, AV_LOG_ERROR, "incorrect codes\n");
197 table[j][1] = n; //bits
198 table[j][0] = symbol;
202 /* fill auxiliary table recursively */
204 code_prefix = code >> (32 - table_nb_bits);
207 codes[i].code = code << table_nb_bits;
208 for (k = i+1; k < nb_codes; k++) {
209 n = codes[k].bits - table_nb_bits;
212 code = codes[k].code;
213 if (code >> (32 - table_nb_bits) != code_prefix)
216 codes[k].code = code << table_nb_bits;
217 subtable_bits = FFMAX(subtable_bits, n);
219 subtable_bits = FFMIN(subtable_bits, table_nb_bits);
220 j = (flags & INIT_VLC_LE) ? bitswap_32(code_prefix) >> (32 - table_nb_bits) : code_prefix;
221 table[j][1] = -subtable_bits;
222 av_dlog(NULL, "%4x: n=%d (subtable)\n",
223 j, codes[i].bits + table_nb_bits);
224 index = build_table(vlc, subtable_bits, k-i, codes+i, flags);
227 /* note: realloc has been done, so reload tables */
228 table = &vlc->table[table_index];
229 table[j][0] = index; //code
237 /* Build VLC decoding tables suitable for use with get_vlc().
239 'nb_bits' set thee decoding table size (2^nb_bits) entries. The
240 bigger it is, the faster is the decoding. But it should not be too
241 big to save memory and L1 cache. '9' is a good compromise.
243 'nb_codes' : number of vlcs codes
245 'bits' : table which gives the size (in bits) of each vlc code.
247 'codes' : table which gives the bit pattern of of each vlc code.
249 'symbols' : table which gives the values to be returned from get_vlc().
251 'xxx_wrap' : give the number of bytes between each entry of the
252 'bits' or 'codes' tables.
254 'xxx_size' : gives the number of bytes of each entry of the 'bits'
257 'wrap' and 'size' allows to use any memory configuration and types
258 (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.
260 'use_static' should be set to 1 for tables, which should be freed
261 with av_free_static(), 0 if ff_free_vlc() will be used.
263 int ff_init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
264 const void *bits, int bits_wrap, int bits_size,
265 const void *codes, int codes_wrap, int codes_size,
266 const void *symbols, int symbols_wrap, int symbols_size,
273 if(flags & INIT_VLC_USE_NEW_STATIC){
274 if(vlc->table_size && vlc->table_size == vlc->table_allocated){
276 }else if(vlc->table_size){
277 abort(); // fatal error, we are called on a partially initialized table
279 av_assert0(ff_avcodec_locked);
282 vlc->table_allocated = 0;
286 av_dlog(NULL, "build table nb_codes=%d\n", nb_codes);
288 buf = av_malloc((nb_codes+1)*sizeof(VLCcode));
290 av_assert0(symbols_size <= 2 || !symbols);
292 #define COPY(condition)\
293 for (i = 0; i < nb_codes; i++) {\
294 GET_DATA(buf[j].bits, bits, i, bits_wrap, bits_size);\
297 GET_DATA(buf[j].code, codes, i, codes_wrap, codes_size);\
298 if (flags & INIT_VLC_LE)\
299 buf[j].code = bitswap_32(buf[j].code);\
301 buf[j].code <<= 32 - buf[j].bits;\
303 GET_DATA(buf[j].symbol, symbols, i, symbols_wrap, symbols_size)\
308 COPY(buf[j].bits > nb_bits);
309 // qsort is the slowest part of init_vlc, and could probably be improved or avoided
310 qsort(buf, j, sizeof(VLCcode), compare_vlcspec);
311 COPY(buf[j].bits && buf[j].bits <= nb_bits);
314 ret = build_table(vlc, nb_bits, nb_codes, buf, flags);
318 av_freep(&vlc->table);
321 if((flags & INIT_VLC_USE_NEW_STATIC) && vlc->table_size != vlc->table_allocated)
322 av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n", vlc->table_size, vlc->table_allocated);
327 void ff_free_vlc(VLC *vlc)
329 av_freep(&vlc->table);