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/atomic.h"
32 #include "libavutil/avassert.h"
33 #include "libavutil/qsort.h"
40 const uint8_t ff_log2_run[41]={
41 0, 0, 0, 0, 1, 1, 1, 1,
42 2, 2, 2, 2, 3, 3, 3, 3,
43 4, 4, 5, 5, 6, 6, 7, 7,
44 8, 9,10,11,12,13,14,15,
45 16,17,18,19,20,21,22,23,
49 void avpriv_align_put_bits(PutBitContext *s)
51 put_bits(s, s->bit_left & 7, 0);
54 void avpriv_put_string(PutBitContext *pb, const char *string,
58 put_bits(pb, 8, *string);
65 void avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
67 int words = length >> 4;
68 int bits = length & 15;
74 av_assert0(length <= put_bits_left(pb));
76 if (CONFIG_SMALL || words < 16 || put_bits_count(pb) & 7) {
77 for (i = 0; i < words; i++)
78 put_bits(pb, 16, AV_RB16(src + 2 * i));
80 for (i = 0; put_bits_count(pb) & 31; i++)
81 put_bits(pb, 8, src[i]);
83 memcpy(put_bits_ptr(pb), src + i, 2 * words - i);
84 skip_put_bytes(pb, 2 * words - i);
87 put_bits(pb, bits, AV_RB16(src + 2 * words) >> (16 - bits));
92 #define GET_DATA(v, table, i, wrap, size) \
94 const uint8_t *ptr = (const uint8_t *)table + i * wrap; \
97 v = *(const uint8_t *)ptr; \
100 v = *(const uint16_t *)ptr; \
103 v = *(const uint32_t *)ptr; \
109 static int alloc_table(VLC *vlc, int size, int use_static)
111 int index = vlc->table_size;
113 vlc->table_size += size;
114 if (vlc->table_size > vlc->table_allocated) {
116 abort(); // cannot do anything, init_vlc() is used with too little memory
117 vlc->table_allocated += (1 << vlc->bits);
118 vlc->table = av_realloc_f(vlc->table, vlc->table_allocated, sizeof(VLC_TYPE) * 2);
120 vlc->table_allocated = 0;
122 return AVERROR(ENOMEM);
124 memset(vlc->table + vlc->table_allocated - (1 << vlc->bits), 0, sizeof(VLC_TYPE) * 2 << vlc->bits);
129 static av_always_inline uint32_t bitswap_32(uint32_t x)
131 return (uint32_t)ff_reverse[ x & 0xFF] << 24 |
132 (uint32_t)ff_reverse[(x >> 8) & 0xFF] << 16 |
133 (uint32_t)ff_reverse[(x >> 16) & 0xFF] << 8 |
134 (uint32_t)ff_reverse[ x >> 24];
137 typedef struct VLCcode {
140 /** codeword, with the first bit-to-be-read in the msb
141 * (even if intended for a little-endian bitstream reader) */
145 static int compare_vlcspec(const void *a, const void *b)
147 const VLCcode *sa = a, *sb = b;
148 return (sa->code >> 1) - (sb->code >> 1);
151 * Build VLC decoding tables suitable for use with get_vlc().
153 * @param vlc the context to be initted
155 * @param table_nb_bits max length of vlc codes to store directly in this table
156 * (Longer codes are delegated to subtables.)
158 * @param nb_codes number of elements in codes[]
160 * @param codes descriptions of the vlc codes
161 * These must be ordered such that codes going into the same subtable are contiguous.
162 * Sorting by VLCcode.code is sufficient, though not necessary.
164 static int build_table(VLC *vlc, int table_nb_bits, int nb_codes,
165 VLCcode *codes, int flags)
167 int table_size, table_index, index, code_prefix, symbol, subtable_bits;
168 int i, j, k, n, nb, inc;
170 volatile VLC_TYPE (* volatile table)[2]; // the double volatile is needed to prevent an internal compiler error in gcc 4.2
172 table_size = 1 << table_nb_bits;
173 if (table_nb_bits > 30)
175 table_index = alloc_table(vlc, table_size, flags & INIT_VLC_USE_NEW_STATIC);
176 ff_dlog(NULL, "new table index=%d size=%d\n", table_index, table_size);
179 table = (volatile VLC_TYPE (*)[2])&vlc->table[table_index];
181 /* first pass: map codes and compute auxiliary table sizes */
182 for (i = 0; i < nb_codes; i++) {
184 code = codes[i].code;
185 symbol = codes[i].symbol;
186 ff_dlog(NULL, "i=%d n=%d code=0x%x\n", i, n, code);
187 if (n <= table_nb_bits) {
188 /* no need to add another table */
189 j = code >> (32 - table_nb_bits);
190 nb = 1 << (table_nb_bits - n);
192 if (flags & INIT_VLC_LE) {
193 j = bitswap_32(code);
196 for (k = 0; k < nb; k++) {
197 int bits = table[j][1];
198 ff_dlog(NULL, "%4x: code=%d n=%d\n", j, i, n);
199 if (bits != 0 && bits != n) {
200 av_log(NULL, AV_LOG_ERROR, "incorrect codes\n");
201 return AVERROR_INVALIDDATA;
203 table[j][1] = n; //bits
204 table[j][0] = symbol;
208 /* fill auxiliary table recursively */
210 code_prefix = code >> (32 - table_nb_bits);
213 codes[i].code = code << table_nb_bits;
214 for (k = i+1; k < nb_codes; k++) {
215 n = codes[k].bits - table_nb_bits;
218 code = codes[k].code;
219 if (code >> (32 - table_nb_bits) != code_prefix)
222 codes[k].code = code << table_nb_bits;
223 subtable_bits = FFMAX(subtable_bits, n);
225 subtable_bits = FFMIN(subtable_bits, table_nb_bits);
226 j = (flags & INIT_VLC_LE) ? bitswap_32(code_prefix) >> (32 - table_nb_bits) : code_prefix;
227 table[j][1] = -subtable_bits;
228 ff_dlog(NULL, "%4x: n=%d (subtable)\n",
229 j, codes[i].bits + table_nb_bits);
230 index = build_table(vlc, subtable_bits, k-i, codes+i, flags);
233 /* note: realloc has been done, so reload tables */
234 table = (volatile VLC_TYPE (*)[2])&vlc->table[table_index];
235 table[j][0] = index; //code
240 for (i = 0; i < table_size; i++) {
241 if (table[i][1] == 0) //bits
242 table[i][0] = -1; //codes
249 /* Build VLC decoding tables suitable for use with get_vlc().
251 'nb_bits' set the decoding table size (2^nb_bits) entries. The
252 bigger it is, the faster is the decoding. But it should not be too
253 big to save memory and L1 cache. '9' is a good compromise.
255 'nb_codes' : number of vlcs codes
257 'bits' : table which gives the size (in bits) of each vlc code.
259 'codes' : table which gives the bit pattern of of each vlc code.
261 'symbols' : table which gives the values to be returned from get_vlc().
263 'xxx_wrap' : give the number of bytes between each entry of the
264 'bits' or 'codes' tables.
266 'xxx_size' : gives the number of bytes of each entry of the 'bits'
269 'wrap' and 'size' make it possible to use any memory configuration and types
270 (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.
272 'use_static' should be set to 1 for tables, which should be freed
273 with av_free_static(), 0 if ff_free_vlc() will be used.
275 int ff_init_vlc_sparse(VLC *vlc_arg, int nb_bits, int nb_codes,
276 const void *bits, int bits_wrap, int bits_size,
277 const void *codes, int codes_wrap, int codes_size,
278 const void *symbols, int symbols_wrap, int symbols_size,
283 VLCcode localbuf[1500]; // the maximum currently needed is 1296 by rv34
288 if (flags & INIT_VLC_USE_NEW_STATIC) {
289 av_assert0(nb_codes + 1 <= FF_ARRAY_ELEMS(localbuf));
296 vlc->table_allocated = 0;
299 buf = av_malloc_array((nb_codes + 1), sizeof(VLCcode));
301 return AVERROR(ENOMEM);
305 av_assert0(symbols_size <= 2 || !symbols);
307 #define COPY(condition)\
308 for (i = 0; i < nb_codes; i++) { \
309 GET_DATA(buf[j].bits, bits, i, bits_wrap, bits_size); \
312 if (buf[j].bits > 3*nb_bits || buf[j].bits>32) { \
313 av_log(NULL, AV_LOG_ERROR, "Too long VLC (%d) in init_vlc\n", buf[j].bits);\
314 if (!(flags & INIT_VLC_USE_NEW_STATIC)) \
318 GET_DATA(buf[j].code, codes, i, codes_wrap, codes_size); \
319 if (buf[j].code >= (1LL<<buf[j].bits)) { \
320 av_log(NULL, AV_LOG_ERROR, "Invalid code %x for %d in init_vlc\n", buf[j].code, i);\
321 if (!(flags & INIT_VLC_USE_NEW_STATIC)) \
325 if (flags & INIT_VLC_LE) \
326 buf[j].code = bitswap_32(buf[j].code); \
328 buf[j].code <<= 32 - buf[j].bits; \
330 GET_DATA(buf[j].symbol, symbols, i, symbols_wrap, symbols_size) \
335 COPY(buf[j].bits > nb_bits);
336 // qsort is the slowest part of init_vlc, and could probably be improved or avoided
337 AV_QSORT(buf, j, struct VLCcode, compare_vlcspec);
338 COPY(buf[j].bits && buf[j].bits <= nb_bits);
341 ret = build_table(vlc, nb_bits, nb_codes, buf, flags);
343 if (flags & INIT_VLC_USE_NEW_STATIC) {
344 if(vlc->table_size != vlc->table_allocated)
345 av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n", vlc->table_size, vlc->table_allocated);
347 av_assert0(ret >= 0);
352 av_freep(&vlc->table);
360 void ff_free_vlc(VLC *vlc)
362 av_freep(&vlc->table);