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1/*
2 * Common bit i/o utils
3 * Copyright (c) 2000, 2001 Fabrice Bellard
4 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
5 * Copyright (c) 2010 Loren Merritt
6 *
7 * alternative bitstream reader & writer by Michael Niedermayer <michaelni@gmx.at>
8 *
9 * This file is part of FFmpeg.
10 *
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.
15 *
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.
20 *
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
24 */
25
26/**
27 * @file
28 * bitstream api.
29 */
30
31#include "libavutil/avassert.h"
32#include "libavutil/qsort.h"
33#include "avcodec.h"
34#include "internal.h"
35#include "mathops.h"
36#include "put_bits.h"
37#include "vlc.h"
38
39const uint8_t ff_log2_run[41]={
40 0, 0, 0, 0, 1, 1, 1, 1,
41 2, 2, 2, 2, 3, 3, 3, 3,
42 4, 4, 5, 5, 6, 6, 7, 7,
43 8, 9,10,11,12,13,14,15,
4416,17,18,19,20,21,22,23,
4524,
46};
47
48void avpriv_align_put_bits(PutBitContext *s)
49{
50 put_bits(s, s->bit_left & 7, 0);
51}
52
53void avpriv_put_string(PutBitContext *pb, const char *string,
54 int terminate_string)
55{
56 while (*string) {
57 put_bits(pb, 8, *string);
58 string++;
59 }
60 if (terminate_string)
61 put_bits(pb, 8, 0);
62}
63
64void avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
65{
66 int words = length >> 4;
67 int bits = length & 15;
68 int i;
69
70 if (length == 0)
71 return;
72
73 av_assert0(length <= put_bits_left(pb));
74
75 if (CONFIG_SMALL || words < 16 || put_bits_count(pb) & 7) {
76 for (i = 0; i < words; i++)
77 put_bits(pb, 16, AV_RB16(src + 2 * i));
78 } else {
79 for (i = 0; put_bits_count(pb) & 31; i++)
80 put_bits(pb, 8, src[i]);
81 flush_put_bits(pb);
82 memcpy(put_bits_ptr(pb), src + i, 2 * words - i);
83 skip_put_bytes(pb, 2 * words - i);
84 }
85
86 put_bits(pb, bits, AV_RB16(src + 2 * words) >> (16 - bits));
87}
88
89/* VLC decoding */
90
91#define GET_DATA(v, table, i, wrap, size) \
92{ \
93 const uint8_t *ptr = (const uint8_t *)table + i * wrap; \
94 switch(size) { \
95 case 1: \
96 v = *(const uint8_t *)ptr; \
97 break; \
98 case 2: \
99 v = *(const uint16_t *)ptr; \
100 break; \
101 case 4: \
102 v = *(const uint32_t *)ptr; \
103 break; \
104 default: \
105 av_assert1(0); \
106 } \
107}
108
109
110static int alloc_table(VLC *vlc, int size, int use_static)
111{
112 int index = vlc->table_size;
113
114 vlc->table_size += size;
115 if (vlc->table_size > vlc->table_allocated) {
116 if (use_static)
117 abort(); // cannot do anything, init_vlc() is used with too little memory
118 vlc->table_allocated += (1 << vlc->bits);
119 vlc->table = av_realloc_f(vlc->table, vlc->table_allocated, sizeof(VLC_TYPE) * 2);
120 if (!vlc->table) {
121 vlc->table_allocated = 0;
122 vlc->table_size = 0;
123 return AVERROR(ENOMEM);
124 }
125 memset(vlc->table + vlc->table_allocated - (1 << vlc->bits), 0, sizeof(VLC_TYPE) * 2 << vlc->bits);
126 }
127 return index;
128}
129
130typedef struct VLCcode {
131 uint8_t bits;
132 uint16_t symbol;
133 /** codeword, with the first bit-to-be-read in the msb
134 * (even if intended for a little-endian bitstream reader) */
135 uint32_t code;
136} VLCcode;
137
138static int compare_vlcspec(const void *a, const void *b)
139{
140 const VLCcode *sa = a, *sb = b;
141 return (sa->code >> 1) - (sb->code >> 1);
142}
143/**
144 * Build VLC decoding tables suitable for use with get_vlc().
145 *
146 * @param vlc the context to be initialized
147 *
148 * @param table_nb_bits max length of vlc codes to store directly in this table
149 * (Longer codes are delegated to subtables.)
150 *
151 * @param nb_codes number of elements in codes[]
152 *
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.
156 */
157static int build_table(VLC *vlc, int table_nb_bits, int nb_codes,
158 VLCcode *codes, int flags)
159{
160 int table_size, table_index, index, code_prefix, symbol, subtable_bits;
161 int i, j, k, n, nb, inc;
162 uint32_t code;
163 volatile VLC_TYPE (* volatile table)[2]; // the double volatile is needed to prevent an internal compiler error in gcc 4.2
164
165 table_size = 1 << table_nb_bits;
166 if (table_nb_bits > 30)
167 return -1;
168 table_index = alloc_table(vlc, table_size, flags & INIT_VLC_USE_NEW_STATIC);
169 ff_dlog(NULL, "new table index=%d size=%d\n", table_index, table_size);
170 if (table_index < 0)
171 return table_index;
172 table = (volatile VLC_TYPE (*)[2])&vlc->table[table_index];
173
174 /* first pass: map codes and compute auxiliary table sizes */
175 for (i = 0; i < nb_codes; i++) {
176 n = codes[i].bits;
177 code = codes[i].code;
178 symbol = codes[i].symbol;
179 ff_dlog(NULL, "i=%d n=%d code=0x%"PRIx32"\n", i, n, code);
180 if (n <= table_nb_bits) {
181 /* no need to add another table */
182 j = code >> (32 - table_nb_bits);
183 nb = 1 << (table_nb_bits - n);
184 inc = 1;
185 if (flags & INIT_VLC_LE) {
186 j = bitswap_32(code);
187 inc = 1 << n;
188 }
189 for (k = 0; k < nb; k++) {
190 int bits = table[j][1];
191 ff_dlog(NULL, "%4x: code=%d n=%d\n", j, i, n);
192 if (bits != 0 && bits != n) {
193 av_log(NULL, AV_LOG_ERROR, "incorrect codes\n");
194 return AVERROR_INVALIDDATA;
195 }
196 table[j][1] = n; //bits
197 table[j][0] = symbol;
198 j += inc;
199 }
200 } else {
201 /* fill auxiliary table recursively */
202 n -= table_nb_bits;
203 code_prefix = code >> (32 - table_nb_bits);
204 subtable_bits = n;
205 codes[i].bits = n;
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;
209 if (n <= 0)
210 break;
211 code = codes[k].code;
212 if (code >> (32 - table_nb_bits) != code_prefix)
213 break;
214 codes[k].bits = n;
215 codes[k].code = code << table_nb_bits;
216 subtable_bits = FFMAX(subtable_bits, n);
217 }
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 ff_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);
224 if (index < 0)
225 return index;
226 /* note: realloc has been done, so reload tables */
227 table = (volatile VLC_TYPE (*)[2])&vlc->table[table_index];
228 table[j][0] = index; //code
229 i = k-1;
230 }
231 }
232
233 for (i = 0; i < table_size; i++) {
234 if (table[i][1] == 0) //bits
235 table[i][0] = -1; //codes
236 }
237
238 return table_index;
239}
240
241
242/* Build VLC decoding tables suitable for use with get_vlc().
243
244 'nb_bits' sets the decoding table size (2^nb_bits) entries. The
245 bigger it is, the faster is the decoding. But it should not be too
246 big to save memory and L1 cache. '9' is a good compromise.
247
248 'nb_codes' : number of vlcs codes
249
250 'bits' : table which gives the size (in bits) of each vlc code.
251
252 'codes' : table which gives the bit pattern of of each vlc code.
253
254 'symbols' : table which gives the values to be returned from get_vlc().
255
256 'xxx_wrap' : give the number of bytes between each entry of the
257 'bits' or 'codes' tables.
258
259 'xxx_size' : gives the number of bytes of each entry of the 'bits'
260 or 'codes' tables. Currently 1,2 and 4 are supported.
261
262 'wrap' and 'size' make it possible to use any memory configuration and types
263 (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.
264
265 'use_static' should be set to 1 for tables, which should be freed
266 with av_free_static(), 0 if ff_free_vlc() will be used.
267*/
268int ff_init_vlc_sparse(VLC *vlc_arg, int nb_bits, int nb_codes,
269 const void *bits, int bits_wrap, int bits_size,
270 const void *codes, int codes_wrap, int codes_size,
271 const void *symbols, int symbols_wrap, int symbols_size,
272 int flags)
273{
274 VLCcode *buf;
275 int i, j, ret;
276 VLCcode localbuf[1500]; // the maximum currently needed is 1296 by rv34
277 VLC localvlc, *vlc;
278
279 vlc = vlc_arg;
280 vlc->bits = nb_bits;
281 if (flags & INIT_VLC_USE_NEW_STATIC) {
282 av_assert0(nb_codes + 1 <= FF_ARRAY_ELEMS(localbuf));
283 buf = localbuf;
284 localvlc = *vlc_arg;
285 vlc = &localvlc;
286 vlc->table_size = 0;
287 } else {
288 vlc->table = NULL;
289 vlc->table_allocated = 0;
290 vlc->table_size = 0;
291
292 buf = av_malloc_array((nb_codes + 1), sizeof(VLCcode));
293 if (!buf)
294 return AVERROR(ENOMEM);
295 }
296
297
298 av_assert0(symbols_size <= 2 || !symbols);
299 j = 0;
300#define COPY(condition)\
301 for (i = 0; i < nb_codes; i++) { \
302 GET_DATA(buf[j].bits, bits, i, bits_wrap, bits_size); \
303 if (!(condition)) \
304 continue; \
305 if (buf[j].bits > 3*nb_bits || buf[j].bits>32) { \
306 av_log(NULL, AV_LOG_ERROR, "Too long VLC (%d) in init_vlc\n", buf[j].bits);\
307 if (!(flags & INIT_VLC_USE_NEW_STATIC)) \
308 av_free(buf); \
309 return -1; \
310 } \
311 GET_DATA(buf[j].code, codes, i, codes_wrap, codes_size); \
312 if (buf[j].code >= (1LL<<buf[j].bits)) { \
313 av_log(NULL, AV_LOG_ERROR, "Invalid code %"PRIx32" for %d in " \
314 "init_vlc\n", buf[j].code, i); \
315 if (!(flags & INIT_VLC_USE_NEW_STATIC)) \
316 av_free(buf); \
317 return -1; \
318 } \
319 if (flags & INIT_VLC_LE) \
320 buf[j].code = bitswap_32(buf[j].code); \
321 else \
322 buf[j].code <<= 32 - buf[j].bits; \
323 if (symbols) \
324 GET_DATA(buf[j].symbol, symbols, i, symbols_wrap, symbols_size) \
325 else \
326 buf[j].symbol = i; \
327 j++; \
328 }
329 COPY(buf[j].bits > nb_bits);
330 // qsort is the slowest part of init_vlc, and could probably be improved or avoided
331 AV_QSORT(buf, j, struct VLCcode, compare_vlcspec);
332 COPY(buf[j].bits && buf[j].bits <= nb_bits);
333 nb_codes = j;
334
335 ret = build_table(vlc, nb_bits, nb_codes, buf, flags);
336
337 if (flags & INIT_VLC_USE_NEW_STATIC) {
338 if(vlc->table_size != vlc->table_allocated)
339 av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n", vlc->table_size, vlc->table_allocated);
340
341 av_assert0(ret >= 0);
342 *vlc_arg = *vlc;
343 } else {
344 av_free(buf);
345 if (ret < 0) {
346 av_freep(&vlc->table);
347 return ret;
348 }
349 }
350 return 0;
351}
352
353
354void ff_free_vlc(VLC *vlc)
355{
356 av_freep(&vlc->table);
357}
358
generated by cgit at 2024-05-17 01:45:35 (GMT)