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[libav.git] / libavcodec / bitstream.c
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 libavcodec/bitstream.c
28 * bitstream api.
29 */
30
31 #include "avcodec.h"
32 #include "get_bits.h"
33 #include "put_bits.h"
34
35 const uint8_t ff_log2_run[32]={
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 };
41
42 void align_put_bits(PutBitContext *s)
43 {
44 #ifdef ALT_BITSTREAM_WRITER
45 put_bits(s,( - s->index) & 7,0);
46 #else
47 put_bits(s,s->bit_left & 7,0);
48 #endif
49 }
50
51 void ff_put_string(PutBitContext *pb, const char *string, int terminate_string)
52 {
53 while(*string){
54 put_bits(pb, 8, *string);
55 string++;
56 }
57 if(terminate_string)
58 put_bits(pb, 8, 0);
59 }
60
61 void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
62 {
63 int words= length>>4;
64 int bits= length&15;
65 int i;
66
67 if(length==0) return;
68
69 if(CONFIG_SMALL || words < 16 || put_bits_count(pb)&7){
70 for(i=0; i<words; i++) put_bits(pb, 16, AV_RB16(src + 2*i));
71 }else{
72 for(i=0; put_bits_count(pb)&31; i++)
73 put_bits(pb, 8, src[i]);
74 flush_put_bits(pb);
75 memcpy(put_bits_ptr(pb), src+i, 2*words-i);
76 skip_put_bytes(pb, 2*words-i);
77 }
78
79 put_bits(pb, bits, AV_RB16(src + 2*words)>>(16-bits));
80 }
81
82 /* VLC decoding */
83
84 //#define DEBUG_VLC
85
86 #define GET_DATA(v, table, i, wrap, size) \
87 {\
88 const uint8_t *ptr = (const uint8_t *)table + i * wrap;\
89 switch(size) {\
90 case 1:\
91 v = *(const uint8_t *)ptr;\
92 break;\
93 case 2:\
94 v = *(const uint16_t *)ptr;\
95 break;\
96 default:\
97 v = *(const uint32_t *)ptr;\
98 break;\
99 }\
100 }
101
102
103 static int alloc_table(VLC *vlc, int size, int use_static)
104 {
105 int index;
106 index = vlc->table_size;
107 vlc->table_size += size;
108 if (vlc->table_size > vlc->table_allocated) {
109 if(use_static)
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(vlc->table,
113 sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
114 if (!vlc->table)
115 return -1;
116 }
117 return index;
118 }
119
120 static av_always_inline uint32_t bitswap_32(uint32_t x) {
121 return av_reverse[x&0xFF]<<24
122 | av_reverse[(x>>8)&0xFF]<<16
123 | av_reverse[(x>>16)&0xFF]<<8
124 | av_reverse[x>>24];
125 }
126
127 typedef struct {
128 uint8_t bits;
129 uint16_t symbol;
130 /** codeword, with the first bit-to-be-read in the msb
131 * (even if intended for a little-endian bitstream reader) */
132 uint32_t code;
133 } VLCcode;
134
135 static int compare_vlcspec(const void *a, const void *b)
136 {
137 const VLCcode *sa=a, *sb=b;
138 return (sa->code >> 1) - (sb->code >> 1);
139 }
140
141 /**
142 * Build VLC decoding tables suitable for use with get_vlc().
143 *
144 * @param vlc the context to be initted
145 *
146 * @param table_nb_bits max length of vlc codes to store directly in this table
147 * (Longer codes are delegated to subtables.)
148 *
149 * @param nb_codes number of elements in codes[]
150 *
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.
154 */
155 static int build_table(VLC *vlc, int table_nb_bits, int nb_codes,
156 VLCcode *codes, int flags)
157 {
158 int table_size, table_index, index, code_prefix, symbol, subtable_bits;
159 int i, j, k, n, nb, inc;
160 uint32_t code;
161 VLC_TYPE (*table)[2];
162
163 table_size = 1 << table_nb_bits;
164 table_index = alloc_table(vlc, table_size, flags & INIT_VLC_USE_NEW_STATIC);
165 #ifdef DEBUG_VLC
166 av_log(NULL,AV_LOG_DEBUG,"new table index=%d size=%d\n",
167 table_index, table_size);
168 #endif
169 if (table_index < 0)
170 return -1;
171 table = &vlc->table[table_index];
172
173 for (i = 0; i < table_size; i++) {
174 table[i][1] = 0; //bits
175 table[i][0] = -1; //codes
176 }
177
178 /* first pass: map codes and compute auxillary table sizes */
179 for (i = 0; i < nb_codes; i++) {
180 n = codes[i].bits;
181 code = codes[i].code;
182 symbol = codes[i].symbol;
183 #if defined(DEBUG_VLC) && 0
184 av_log(NULL,AV_LOG_DEBUG,"i=%d n=%d code=0x%x\n", i, n, code);
185 #endif
186 if (n <= table_nb_bits) {
187 /* no need to add another table */
188 j = code >> (32 - table_nb_bits);
189 nb = 1 << (table_nb_bits - n);
190 inc = 1;
191 if (flags & INIT_VLC_LE) {
192 j = bitswap_32(code);
193 inc = 1 << n;
194 }
195 for (k = 0; k < nb; k++) {
196 #ifdef DEBUG_VLC
197 av_log(NULL, AV_LOG_DEBUG, "%4x: code=%d n=%d\n",
198 j, i, n);
199 #endif
200 if (table[j][1] /*bits*/ != 0) {
201 av_log(NULL, AV_LOG_ERROR, "incorrect codes\n");
202 return -1;
203 }
204 table[j][1] = n; //bits
205 table[j][0] = symbol;
206 j += inc;
207 }
208 } else {
209 /* fill auxiliary table recursively */
210 n -= table_nb_bits;
211 code_prefix = code >> (32 - table_nb_bits);
212 subtable_bits = n;
213 codes[i].bits = n;
214 codes[i].code = code << table_nb_bits;
215 for (k = i+1; k < nb_codes; k++) {
216 n = codes[k].bits - table_nb_bits;
217 if (n <= 0)
218 break;
219 code = codes[k].code;
220 if (code >> (32 - table_nb_bits) != code_prefix)
221 break;
222 codes[k].bits = n;
223 codes[k].code = code << table_nb_bits;
224 subtable_bits = FFMAX(subtable_bits, n);
225 }
226 subtable_bits = FFMIN(subtable_bits, table_nb_bits);
227 j = (flags & INIT_VLC_LE) ? bitswap_32(code_prefix) >> (32 - table_nb_bits) : code_prefix;
228 table[j][1] = -subtable_bits;
229 #ifdef DEBUG_VLC
230 av_log(NULL,AV_LOG_DEBUG,"%4x: n=%d (subtable)\n",
231 j, codes[i].bits + table_nb_bits);
232 #endif
233 index = build_table(vlc, subtable_bits, k-i, codes+i, flags);
234 if (index < 0)
235 return -1;
236 /* note: realloc has been done, so reload tables */
237 table = &vlc->table[table_index];
238 table[j][0] = index; //code
239 i = k-1;
240 }
241 }
242 return table_index;
243 }
244
245
246 /* Build VLC decoding tables suitable for use with get_vlc().
247
248 'nb_bits' set thee decoding table size (2^nb_bits) entries. The
249 bigger it is, the faster is the decoding. But it should not be too
250 big to save memory and L1 cache. '9' is a good compromise.
251
252 'nb_codes' : number of vlcs codes
253
254 'bits' : table which gives the size (in bits) of each vlc code.
255
256 'codes' : table which gives the bit pattern of of each vlc code.
257
258 'symbols' : table which gives the values to be returned from get_vlc().
259
260 'xxx_wrap' : give the number of bytes between each entry of the
261 'bits' or 'codes' tables.
262
263 'xxx_size' : gives the number of bytes of each entry of the 'bits'
264 or 'codes' tables.
265
266 'wrap' and 'size' allows to use any memory configuration and types
267 (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.
268
269 'use_static' should be set to 1 for tables, which should be freed
270 with av_free_static(), 0 if free_vlc() will be used.
271 */
272 int init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
273 const void *bits, int bits_wrap, int bits_size,
274 const void *codes, int codes_wrap, int codes_size,
275 const void *symbols, int symbols_wrap, int symbols_size,
276 int flags)
277 {
278 VLCcode buf[nb_codes];
279 int i, j;
280
281 vlc->bits = nb_bits;
282 if(flags & INIT_VLC_USE_NEW_STATIC){
283 if(vlc->table_size && vlc->table_size == vlc->table_allocated){
284 return 0;
285 }else if(vlc->table_size){
286 abort(); // fatal error, we are called on a partially initialized table
287 }
288 }else {
289 vlc->table = NULL;
290 vlc->table_allocated = 0;
291 vlc->table_size = 0;
292 }
293
294 #ifdef DEBUG_VLC
295 av_log(NULL,AV_LOG_DEBUG,"build table nb_codes=%d\n", nb_codes);
296 #endif
297
298 assert(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 GET_DATA(buf[j].code, codes, i, codes_wrap, codes_size);\
306 if (flags & INIT_VLC_LE)\
307 buf[j].code = bitswap_32(buf[j].code);\
308 else\
309 buf[j].code <<= 32 - buf[j].bits;\
310 if (symbols)\
311 GET_DATA(buf[j].symbol, symbols, i, symbols_wrap, symbols_size)\
312 else\
313 buf[j].symbol = i;\
314 j++;\
315 }
316 COPY(buf[j].bits > nb_bits);
317 // qsort is the slowest part of init_vlc, and could probably be improved or avoided
318 qsort(buf, j, sizeof(VLCcode), compare_vlcspec);
319 COPY(buf[j].bits && buf[j].bits <= nb_bits);
320 nb_codes = j;
321
322 if (build_table(vlc, nb_bits, nb_codes, buf, flags) < 0) {
323 av_freep(&vlc->table);
324 return -1;
325 }
326 if((flags & INIT_VLC_USE_NEW_STATIC) && vlc->table_size != vlc->table_allocated)
327 av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n", vlc->table_size, vlc->table_allocated);
328 return 0;
329 }
330
331
332 void free_vlc(VLC *vlc)
333 {
334 av_freep(&vlc->table);
335 }
336