3 * Copyright (c) 2000, 2001 Fabrice Bellard.
4 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
6 * This file is part of FFmpeg.
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22 * alternative bitstream reader & writer by Michael Niedermayer <michaelni@gmx.at>
31 #include "bitstream.h"
34 * Same as av_mallocz_static(), but does a realloc.
36 * @param[in] ptr The block of memory to reallocate.
37 * @param[in] size The requested size.
38 * @return Block of memory of requested size.
40 void *ff_realloc_static(void *ptr, unsigned int size);
42 void align_put_bits(PutBitContext *s)
44 #ifdef ALT_BITSTREAM_WRITER
45 put_bits(s,( - s->index) & 7,0);
47 put_bits(s,s->bit_left & 7,0);
51 void ff_put_string(PutBitContext * pbc, char *s, int put_zero)
65 #define GET_DATA(v, table, i, wrap, size) \
67 const uint8_t *ptr = (const uint8_t *)table + i * wrap;\
70 v = *(const uint8_t *)ptr;\
73 v = *(const uint16_t *)ptr;\
76 v = *(const uint32_t *)ptr;\
82 static int alloc_table(VLC *vlc, int size, int use_static)
85 index = vlc->table_size;
86 vlc->table_size += size;
87 if (vlc->table_size > vlc->table_allocated) {
88 vlc->table_allocated += (1 << vlc->bits);
90 vlc->table = ff_realloc_static(vlc->table,
91 sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
93 vlc->table = av_realloc(vlc->table,
94 sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
101 static int build_table(VLC *vlc, int table_nb_bits,
103 const void *bits, int bits_wrap, int bits_size,
104 const void *codes, int codes_wrap, int codes_size,
105 uint32_t code_prefix, int n_prefix, int flags)
107 int i, j, k, n, table_size, table_index, nb, n1, index, code_prefix2;
109 VLC_TYPE (*table)[2];
111 table_size = 1 << table_nb_bits;
112 table_index = alloc_table(vlc, table_size, flags & INIT_VLC_USE_STATIC);
114 printf("new table index=%d size=%d code_prefix=%x n=%d\n",
115 table_index, table_size, code_prefix, n_prefix);
119 table = &vlc->table[table_index];
121 for(i=0;i<table_size;i++) {
122 table[i][1] = 0; //bits
123 table[i][0] = -1; //codes
126 /* first pass: map codes and compute auxillary table sizes */
127 for(i=0;i<nb_codes;i++) {
128 GET_DATA(n, bits, i, bits_wrap, bits_size);
129 GET_DATA(code, codes, i, codes_wrap, codes_size);
130 /* we accept tables with holes */
133 #if defined(DEBUG_VLC) && 0
134 printf("i=%d n=%d code=0x%x\n", i, n, code);
136 /* if code matches the prefix, it is in the table */
138 if(flags & INIT_VLC_LE)
139 code_prefix2= code & (n_prefix>=32 ? 0xffffffff : (1 << n_prefix)-1);
141 code_prefix2= code >> n;
142 if (n > 0 && code_prefix2 == code_prefix) {
143 if (n <= table_nb_bits) {
144 /* no need to add another table */
145 j = (code << (table_nb_bits - n)) & (table_size - 1);
146 nb = 1 << (table_nb_bits - n);
148 if(flags & INIT_VLC_LE)
149 j = (code >> n_prefix) + (k<<n);
151 av_log(NULL, AV_LOG_DEBUG, "%4x: code=%d n=%d\n",
154 if (table[j][1] /*bits*/ != 0) {
155 av_log(NULL, AV_LOG_ERROR, "incorrect codes\n");
158 table[j][1] = n; //bits
159 table[j][0] = i; //code
164 j = (code >> ((flags & INIT_VLC_LE) ? n_prefix : n)) & ((1 << table_nb_bits) - 1);
166 printf("%4x: n=%d (subtable)\n",
169 /* compute table size */
170 n1 = -table[j][1]; //bits
173 table[j][1] = -n1; //bits
178 /* second pass : fill auxillary tables recursively */
179 for(i=0;i<table_size;i++) {
180 n = table[i][1]; //bits
183 if (n > table_nb_bits) {
185 table[i][1] = -n; //bits
187 index = build_table(vlc, n, nb_codes,
188 bits, bits_wrap, bits_size,
189 codes, codes_wrap, codes_size,
190 (flags & INIT_VLC_LE) ? (code_prefix | (i << n_prefix)) : ((code_prefix << table_nb_bits) | i),
191 n_prefix + table_nb_bits, flags);
194 /* note: realloc has been done, so reload tables */
195 table = &vlc->table[table_index];
196 table[i][0] = index; //code
203 /* Build VLC decoding tables suitable for use with get_vlc().
205 'nb_bits' set thee decoding table size (2^nb_bits) entries. The
206 bigger it is, the faster is the decoding. But it should not be too
207 big to save memory and L1 cache. '9' is a good compromise.
209 'nb_codes' : number of vlcs codes
211 'bits' : table which gives the size (in bits) of each vlc code.
213 'codes' : table which gives the bit pattern of of each vlc code.
215 'xxx_wrap' : give the number of bytes between each entry of the
216 'bits' or 'codes' tables.
218 'xxx_size' : gives the number of bytes of each entry of the 'bits'
221 'wrap' and 'size' allows to use any memory configuration and types
222 (byte/word/long) to store the 'bits' and 'codes' tables.
224 'use_static' should be set to 1 for tables, which should be freed
225 with av_free_static(), 0 if free_vlc() will be used.
227 int init_vlc(VLC *vlc, int nb_bits, int nb_codes,
228 const void *bits, int bits_wrap, int bits_size,
229 const void *codes, int codes_wrap, int codes_size,
235 vlc->table_allocated = 0;
238 /* Static tables are initially always NULL, return
239 if vlc->table != NULL to avoid double allocation */
245 printf("build table nb_codes=%d\n", nb_codes);
248 if (build_table(vlc, nb_bits, nb_codes,
249 bits, bits_wrap, bits_size,
250 codes, codes_wrap, codes_size,
251 0, 0, use_static) < 0) {
259 void free_vlc(VLC *vlc)