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));
86 #define GET_DATA(v, table, i, wrap, size) \
88 const uint8_t *ptr = (const uint8_t *)table + i * wrap;\
91 v = *(const uint8_t *)ptr;\
94 v = *(const uint16_t *)ptr;\
97 v = *(const uint32_t *)ptr;\
103 static int alloc_table(VLC *vlc, int size, int use_static)
106 index = vlc->table_size;
107 vlc->table_size += size;
108 if (vlc->table_size > vlc->table_allocated) {
110 abort(); //cant do anything, init_vlc() is used with too little memory
111 vlc->table_allocated += (1 << vlc->bits);
112 vlc->table = av_realloc_f(vlc->table,
113 vlc->table_allocated, sizeof(VLC_TYPE) * 2);
120 static av_always_inline uint32_t bitswap_32(uint32_t x) {
121 return (uint32_t)av_reverse[x&0xFF]<<24
122 | (uint32_t)av_reverse[(x>>8)&0xFF]<<16
123 | (uint32_t)av_reverse[(x>>16)&0xFF]<<8
124 | (uint32_t)av_reverse[x>>24];
130 /** codeword, with the first bit-to-be-read in the msb
131 * (even if intended for a little-endian bitstream reader) */
135 static int compare_vlcspec(const void *a, const void *b)
137 const VLCcode *sa=a, *sb=b;
138 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 table_index = alloc_table(vlc, table_size, flags & INIT_VLC_USE_NEW_STATIC);
165 av_dlog(NULL, "new table index=%d size=%d\n", table_index, table_size);
168 table = &vlc->table[table_index];
170 for (i = 0; i < table_size; i++) {
171 table[i][1] = 0; //bits
172 table[i][0] = -1; //codes
175 /* first pass: map codes and compute auxillary table sizes */
176 for (i = 0; i < nb_codes; i++) {
178 code = codes[i].code;
179 symbol = codes[i].symbol;
180 av_dlog(NULL, "i=%d n=%d code=0x%x\n", i, n, code);
181 if (n <= table_nb_bits) {
182 /* no need to add another table */
183 j = code >> (32 - table_nb_bits);
184 nb = 1 << (table_nb_bits - n);
186 if (flags & INIT_VLC_LE) {
187 j = bitswap_32(code);
190 for (k = 0; k < nb; k++) {
191 av_dlog(NULL, "%4x: code=%d n=%d\n", j, i, n);
192 if (table[j][1] /*bits*/ != 0) {
193 av_log(NULL, AV_LOG_ERROR, "incorrect codes\n");
196 table[j][1] = n; //bits
197 table[j][0] = symbol;
201 /* fill auxiliary table recursively */
203 code_prefix = code >> (32 - table_nb_bits);
206 codes[i].code = code << table_nb_bits;
207 for (k = i+1; k < nb_codes; k++) {
208 n = codes[k].bits - table_nb_bits;
211 code = codes[k].code;
212 if (code >> (32 - table_nb_bits) != code_prefix)
215 codes[k].code = code << table_nb_bits;
216 subtable_bits = FFMAX(subtable_bits, n);
218 subtable_bits = FFMIN(subtable_bits, table_nb_bits);
219 j = (flags & INIT_VLC_LE) ? bitswap_32(code_prefix) >> (32 - table_nb_bits) : code_prefix;
220 table[j][1] = -subtable_bits;
221 av_dlog(NULL, "%4x: n=%d (subtable)\n",
222 j, codes[i].bits + table_nb_bits);
223 index = build_table(vlc, subtable_bits, k-i, codes+i, flags);
226 /* note: realloc has been done, so reload tables */
227 table = &vlc->table[table_index];
228 table[j][0] = index; //code
236 /* Build VLC decoding tables suitable for use with get_vlc().
238 'nb_bits' set thee decoding table size (2^nb_bits) entries. The
239 bigger it is, the faster is the decoding. But it should not be too
240 big to save memory and L1 cache. '9' is a good compromise.
242 'nb_codes' : number of vlcs codes
244 'bits' : table which gives the size (in bits) of each vlc code.
246 'codes' : table which gives the bit pattern of of each vlc code.
248 'symbols' : table which gives the values to be returned from get_vlc().
250 'xxx_wrap' : give the number of bytes between each entry of the
251 'bits' or 'codes' tables.
253 'xxx_size' : gives the number of bytes of each entry of the 'bits'
256 'wrap' and 'size' allows to use any memory configuration and types
257 (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.
259 'use_static' should be set to 1 for tables, which should be freed
260 with av_free_static(), 0 if free_vlc() will be used.
262 int init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
263 const void *bits, int bits_wrap, int bits_size,
264 const void *codes, int codes_wrap, int codes_size,
265 const void *symbols, int symbols_wrap, int symbols_size,
272 if(flags & INIT_VLC_USE_NEW_STATIC){
273 if(vlc->table_size && vlc->table_size == vlc->table_allocated){
275 }else if(vlc->table_size){
276 abort(); // fatal error, we are called on a partially initialized table
280 vlc->table_allocated = 0;
284 av_dlog(NULL, "build table nb_codes=%d\n", nb_codes);
286 buf = av_malloc((nb_codes+1)*sizeof(VLCcode));
288 assert(symbols_size <= 2 || !symbols);
290 #define COPY(condition)\
291 for (i = 0; i < nb_codes; i++) {\
292 GET_DATA(buf[j].bits, bits, i, bits_wrap, bits_size);\
295 GET_DATA(buf[j].code, codes, i, codes_wrap, codes_size);\
296 if (flags & INIT_VLC_LE)\
297 buf[j].code = bitswap_32(buf[j].code);\
299 buf[j].code <<= 32 - buf[j].bits;\
301 GET_DATA(buf[j].symbol, symbols, i, symbols_wrap, symbols_size)\
306 COPY(buf[j].bits > nb_bits);
307 // qsort is the slowest part of init_vlc, and could probably be improved or avoided
308 qsort(buf, j, sizeof(VLCcode), compare_vlcspec);
309 COPY(buf[j].bits && buf[j].bits <= nb_bits);
312 ret = build_table(vlc, nb_bits, nb_codes, buf, flags);
316 av_freep(&vlc->table);
319 if((flags & INIT_VLC_USE_NEW_STATIC) && vlc->table_size != vlc->table_allocated)
320 av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n", vlc->table_size, vlc->table_allocated);
325 void free_vlc(VLC *vlc)
327 av_freep(&vlc->table);