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
35 const uint8_t ff_log2_run[41]={
36 0, 0, 0, 0, 1, 1, 1, 1,
37 2, 2, 2, 2, 3, 3, 3, 3,
38 4, 4, 5, 5, 6, 6, 7, 7,
39 8, 9,10,11,12,13,14,15,
40 16,17,18,19,20,21,22,23,
44 void align_put_bits(PutBitContext *s)
46 #ifdef ALT_BITSTREAM_WRITER
47 put_bits(s,( - s->index) & 7,0);
49 put_bits(s,s->bit_left & 7,0);
53 void ff_put_string(PutBitContext *pb, const char *string, int terminate_string)
56 put_bits(pb, 8, *string);
63 void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
71 if(CONFIG_SMALL || words < 16 || put_bits_count(pb)&7){
72 for(i=0; i<words; i++) put_bits(pb, 16, AV_RB16(src + 2*i));
74 for(i=0; put_bits_count(pb)&31; i++)
75 put_bits(pb, 8, src[i]);
77 memcpy(put_bits_ptr(pb), src+i, 2*words-i);
78 skip_put_bytes(pb, 2*words-i);
81 put_bits(pb, bits, AV_RB16(src + 2*words)>>(16-bits));
88 #define GET_DATA(v, table, i, wrap, size) \
90 const uint8_t *ptr = (const uint8_t *)table + i * wrap;\
93 v = *(const uint8_t *)ptr;\
96 v = *(const uint16_t *)ptr;\
99 v = *(const uint32_t *)ptr;\
105 static int alloc_table(VLC *vlc, int size, int use_static)
108 index = vlc->table_size;
109 vlc->table_size += size;
110 if (vlc->table_size > vlc->table_allocated) {
112 abort(); //cant do anything, init_vlc() is used with too little memory
113 vlc->table_allocated += (1 << vlc->bits);
114 vlc->table = av_realloc(vlc->table,
115 sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
122 static av_always_inline uint32_t bitswap_32(uint32_t x) {
123 return av_reverse[x&0xFF]<<24
124 | av_reverse[(x>>8)&0xFF]<<16
125 | av_reverse[(x>>16)&0xFF]<<8
132 /** codeword, with the first bit-to-be-read in the msb
133 * (even if intended for a little-endian bitstream reader) */
137 static int compare_vlcspec(const void *a, const void *b)
139 const VLCcode *sa=a, *sb=b;
140 return (sa->code >> 1) - (sb->code >> 1);
144 * Build VLC decoding tables suitable for use with get_vlc().
146 * @param vlc the context to be initted
148 * @param table_nb_bits max length of vlc codes to store directly in this table
149 * (Longer codes are delegated to subtables.)
151 * @param nb_codes number of elements in codes[]
153 * @param codes descriptions of the vlc codes
154 * These must be ordered such that codes going into the same subtable are contiguous.
155 * Sorting by VLCcode.code is sufficient, though not necessary.
157 static int build_table(VLC *vlc, int table_nb_bits, int nb_codes,
158 VLCcode *codes, int flags)
160 int table_size, table_index, index, code_prefix, symbol, subtable_bits;
161 int i, j, k, n, nb, inc;
163 VLC_TYPE (*table)[2];
165 table_size = 1 << table_nb_bits;
166 table_index = alloc_table(vlc, table_size, flags & INIT_VLC_USE_NEW_STATIC);
168 av_log(NULL,AV_LOG_DEBUG,"new table index=%d size=%d\n",
169 table_index, table_size);
173 table = &vlc->table[table_index];
175 for (i = 0; i < table_size; i++) {
176 table[i][1] = 0; //bits
177 table[i][0] = -1; //codes
180 /* first pass: map codes and compute auxillary table sizes */
181 for (i = 0; i < nb_codes; i++) {
183 code = codes[i].code;
184 symbol = codes[i].symbol;
185 #if defined(DEBUG_VLC) && 0
186 av_log(NULL,AV_LOG_DEBUG,"i=%d n=%d code=0x%x\n", i, n, code);
188 if (n <= table_nb_bits) {
189 /* no need to add another table */
190 j = code >> (32 - table_nb_bits);
191 nb = 1 << (table_nb_bits - n);
193 if (flags & INIT_VLC_LE) {
194 j = bitswap_32(code);
197 for (k = 0; k < nb; k++) {
199 av_log(NULL, AV_LOG_DEBUG, "%4x: code=%d n=%d\n",
202 if (table[j][1] /*bits*/ != 0) {
203 av_log(NULL, AV_LOG_ERROR, "incorrect codes\n");
206 table[j][1] = n; //bits
207 table[j][0] = symbol;
211 /* fill auxiliary table recursively */
213 code_prefix = code >> (32 - table_nb_bits);
216 codes[i].code = code << table_nb_bits;
217 for (k = i+1; k < nb_codes; k++) {
218 n = codes[k].bits - table_nb_bits;
221 code = codes[k].code;
222 if (code >> (32 - table_nb_bits) != code_prefix)
225 codes[k].code = code << table_nb_bits;
226 subtable_bits = FFMAX(subtable_bits, n);
228 subtable_bits = FFMIN(subtable_bits, table_nb_bits);
229 j = (flags & INIT_VLC_LE) ? bitswap_32(code_prefix) >> (32 - table_nb_bits) : code_prefix;
230 table[j][1] = -subtable_bits;
232 av_log(NULL,AV_LOG_DEBUG,"%4x: n=%d (subtable)\n",
233 j, codes[i].bits + table_nb_bits);
235 index = build_table(vlc, subtable_bits, k-i, codes+i, flags);
238 /* note: realloc has been done, so reload tables */
239 table = &vlc->table[table_index];
240 table[j][0] = index; //code
248 /* Build VLC decoding tables suitable for use with get_vlc().
250 'nb_bits' set thee decoding table size (2^nb_bits) entries. The
251 bigger it is, the faster is the decoding. But it should not be too
252 big to save memory and L1 cache. '9' is a good compromise.
254 'nb_codes' : number of vlcs codes
256 'bits' : table which gives the size (in bits) of each vlc code.
258 'codes' : table which gives the bit pattern of of each vlc code.
260 'symbols' : table which gives the values to be returned from get_vlc().
262 'xxx_wrap' : give the number of bytes between each entry of the
263 'bits' or 'codes' tables.
265 'xxx_size' : gives the number of bytes of each entry of the 'bits'
268 'wrap' and 'size' allows to use any memory configuration and types
269 (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.
271 'use_static' should be set to 1 for tables, which should be freed
272 with av_free_static(), 0 if free_vlc() will be used.
274 int init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
275 const void *bits, int bits_wrap, int bits_size,
276 const void *codes, int codes_wrap, int codes_size,
277 const void *symbols, int symbols_wrap, int symbols_size,
284 if(flags & INIT_VLC_USE_NEW_STATIC){
285 if(vlc->table_size && vlc->table_size == vlc->table_allocated){
287 }else if(vlc->table_size){
288 abort(); // fatal error, we are called on a partially initialized table
292 vlc->table_allocated = 0;
297 av_log(NULL,AV_LOG_DEBUG,"build table nb_codes=%d\n", nb_codes);
300 buf = av_malloc((nb_codes+1)*sizeof(VLCcode));
302 assert(symbols_size <= 2 || !symbols);
304 #define COPY(condition)\
305 for (i = 0; i < nb_codes; i++) {\
306 GET_DATA(buf[j].bits, bits, i, bits_wrap, bits_size);\
309 GET_DATA(buf[j].code, codes, i, codes_wrap, codes_size);\
310 if (flags & INIT_VLC_LE)\
311 buf[j].code = bitswap_32(buf[j].code);\
313 buf[j].code <<= 32 - buf[j].bits;\
315 GET_DATA(buf[j].symbol, symbols, i, symbols_wrap, symbols_size)\
320 COPY(buf[j].bits > nb_bits);
321 // qsort is the slowest part of init_vlc, and could probably be improved or avoided
322 qsort(buf, j, sizeof(VLCcode), compare_vlcspec);
323 COPY(buf[j].bits && buf[j].bits <= nb_bits);
326 ret = build_table(vlc, nb_bits, nb_codes, buf, flags);
330 av_freep(&vlc->table);
333 if((flags & INIT_VLC_USE_NEW_STATIC) && vlc->table_size != vlc->table_allocated)
334 av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n", vlc->table_size, vlc->table_allocated);
339 void free_vlc(VLC *vlc)
341 av_freep(&vlc->table);