summaryrefslogtreecommitdiff
path: root/libavcodec/bitstream.c
blob: 7de6bba5cd1d2052ef0603dd271b19b5e67a188d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
/*
 * Common bit i/o utils
 * Copyright (c) 2000, 2001 Fabrice Bellard
 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
 *
 * alternative bitstream reader & writer by Michael Niedermayer <michaelni@gmx.at>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file bitstream.c
 * bitstream api.
 */

#include "avcodec.h"
#include "bitstream.h"

const uint8_t ff_log2_run[32]={
 0, 0, 0, 0, 1, 1, 1, 1,
 2, 2, 2, 2, 3, 3, 3, 3,
 4, 4, 5, 5, 6, 6, 7, 7,
 8, 9,10,11,12,13,14,15
};

/**
 * Same as av_mallocz_static(), but does a realloc.
 *
 * @param[in] ptr The block of memory to reallocate.
 * @param[in] size The requested size.
 * @return Block of memory of requested size.
 * @deprecated. Code which uses ff_realloc_static is broken/misdesigned
 * and should correctly use static arrays
 */
attribute_deprecated av_alloc_size(2)
static void *ff_realloc_static(void *ptr, unsigned int size);

static void *ff_realloc_static(void *ptr, unsigned int size)
{
    return av_realloc(ptr, size);
}

void align_put_bits(PutBitContext *s)
{
#ifdef ALT_BITSTREAM_WRITER
    put_bits(s,(  - s->index) & 7,0);
#else
    put_bits(s,s->bit_left & 7,0);
#endif
}

void ff_put_string(PutBitContext * pbc, const char *s, int put_zero)
{
    while(*s){
        put_bits(pbc, 8, *s);
        s++;
    }
    if(put_zero)
        put_bits(pbc, 8, 0);
}

void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
{
    const uint16_t *srcw= (const uint16_t*)src;
    int words= length>>4;
    int bits= length&15;
    int i;

    if(length==0) return;

    if(CONFIG_SMALL || words < 16 || put_bits_count(pb)&7){
        for(i=0; i<words; i++) put_bits(pb, 16, be2me_16(srcw[i]));
    }else{
        for(i=0; put_bits_count(pb)&31; i++)
            put_bits(pb, 8, src[i]);
        flush_put_bits(pb);
        memcpy(pbBufPtr(pb), src+i, 2*words-i);
        skip_put_bytes(pb, 2*words-i);
    }

    put_bits(pb, bits, be2me_16(srcw[words])>>(16-bits));
}

/* VLC decoding */

//#define DEBUG_VLC

#define GET_DATA(v, table, i, wrap, size) \
{\
    const uint8_t *ptr = (const uint8_t *)table + i * wrap;\
    switch(size) {\
    case 1:\
        v = *(const uint8_t *)ptr;\
        break;\
    case 2:\
        v = *(const uint16_t *)ptr;\
        break;\
    default:\
        v = *(const uint32_t *)ptr;\
        break;\
    }\
}


static int alloc_table(VLC *vlc, int size, int use_static)
{
    int index;
    index = vlc->table_size;
    vlc->table_size += size;
    if (vlc->table_size > vlc->table_allocated) {
        if(use_static>1)
            abort(); //cant do anything, init_vlc() is used with too little memory
        vlc->table_allocated += (1 << vlc->bits);
        if(use_static)
            vlc->table = ff_realloc_static(vlc->table,
                                           sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
        else
            vlc->table = av_realloc(vlc->table,
                                    sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
        if (!vlc->table)
            return -1;
    }
    return index;
}

static int build_table(VLC *vlc, int table_nb_bits,
                       int nb_codes,
                       const void *bits, int bits_wrap, int bits_size,
                       const void *codes, int codes_wrap, int codes_size,
                       const void *symbols, int symbols_wrap, int symbols_size,
                       uint32_t code_prefix, int n_prefix, int flags)
{
    int i, j, k, n, table_size, table_index, nb, n1, index, code_prefix2, symbol;
    uint32_t code;
    VLC_TYPE (*table)[2];

    table_size = 1 << table_nb_bits;
    table_index = alloc_table(vlc, table_size, flags & (INIT_VLC_USE_STATIC|INIT_VLC_USE_NEW_STATIC));
#ifdef DEBUG_VLC
    av_log(NULL,AV_LOG_DEBUG,"new table index=%d size=%d code_prefix=%x n=%d\n",
           table_index, table_size, code_prefix, n_prefix);
#endif
    if (table_index < 0)
        return -1;
    table = &vlc->table[table_index];

    for(i=0;i<table_size;i++) {
        table[i][1] = 0; //bits
        table[i][0] = -1; //codes
    }

    /* first pass: map codes and compute auxillary table sizes */
    for(i=0;i<nb_codes;i++) {
        GET_DATA(n, bits, i, bits_wrap, bits_size);
        GET_DATA(code, codes, i, codes_wrap, codes_size);
        /* we accept tables with holes */
        if (n <= 0)
            continue;
        if (!symbols)
            symbol = i;
        else
            GET_DATA(symbol, symbols, i, symbols_wrap, symbols_size);
#if defined(DEBUG_VLC) && 0
        av_log(NULL,AV_LOG_DEBUG,"i=%d n=%d code=0x%x\n", i, n, code);
#endif
        /* if code matches the prefix, it is in the table */
        n -= n_prefix;
        if(flags & INIT_VLC_LE)
            code_prefix2= code & (n_prefix>=32 ? 0xffffffff : (1 << n_prefix)-1);
        else
            code_prefix2= code >> n;
        if (n > 0 && code_prefix2 == code_prefix) {
            if (n <= table_nb_bits) {
                /* no need to add another table */
                j = (code << (table_nb_bits - n)) & (table_size - 1);
                nb = 1 << (table_nb_bits - n);
                for(k=0;k<nb;k++) {
                    if(flags & INIT_VLC_LE)
                        j = (code >> n_prefix) + (k<<n);
#ifdef DEBUG_VLC
                    av_log(NULL, AV_LOG_DEBUG, "%4x: code=%d n=%d\n",
                           j, i, n);
#endif
                    if (table[j][1] /*bits*/ != 0) {
                        av_log(NULL, AV_LOG_ERROR, "incorrect codes\n");
                        return -1;
                    }
                    table[j][1] = n; //bits
                    table[j][0] = symbol;
                    j++;
                }
            } else {
                n -= table_nb_bits;
                j = (code >> ((flags & INIT_VLC_LE) ? n_prefix : n)) & ((1 << table_nb_bits) - 1);
#ifdef DEBUG_VLC
                av_log(NULL,AV_LOG_DEBUG,"%4x: n=%d (subtable)\n",
                       j, n);
#endif
                /* compute table size */
                n1 = -table[j][1]; //bits
                if (n > n1)
                    n1 = n;
                table[j][1] = -n1; //bits
            }
        }
    }

    /* second pass : fill auxillary tables recursively */
    for(i=0;i<table_size;i++) {
        n = table[i][1]; //bits
        if (n < 0) {
            n = -n;
            if (n > table_nb_bits) {
                n = table_nb_bits;
                table[i][1] = -n; //bits
            }
            index = build_table(vlc, n, nb_codes,
                                bits, bits_wrap, bits_size,
                                codes, codes_wrap, codes_size,
                                symbols, symbols_wrap, symbols_size,
                                (flags & INIT_VLC_LE) ? (code_prefix | (i << n_prefix)) : ((code_prefix << table_nb_bits) | i),
                                n_prefix + table_nb_bits, flags);
            if (index < 0)
                return -1;
            /* note: realloc has been done, so reload tables */
            table = &vlc->table[table_index];
            table[i][0] = index; //code
        }
    }
    return table_index;
}


/* Build VLC decoding tables suitable for use with get_vlc().

   'nb_bits' set thee decoding table size (2^nb_bits) entries. The
   bigger it is, the faster is the decoding. But it should not be too
   big to save memory and L1 cache. '9' is a good compromise.

   'nb_codes' : number of vlcs codes

   'bits' : table which gives the size (in bits) of each vlc code.

   'codes' : table which gives the bit pattern of of each vlc code.

   'symbols' : table which gives the values to be returned from get_vlc().

   'xxx_wrap' : give the number of bytes between each entry of the
   'bits' or 'codes' tables.

   'xxx_size' : gives the number of bytes of each entry of the 'bits'
   or 'codes' tables.

   'wrap' and 'size' allows to use any memory configuration and types
   (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.

   'use_static' should be set to 1 for tables, which should be freed
   with av_free_static(), 0 if free_vlc() will be used.
*/
int init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
             const void *bits, int bits_wrap, int bits_size,
             const void *codes, int codes_wrap, int codes_size,
             const void *symbols, int symbols_wrap, int symbols_size,
             int flags)
{
    vlc->bits = nb_bits;
    if(flags & INIT_VLC_USE_NEW_STATIC){
        if(vlc->table_size && vlc->table_size == vlc->table_allocated){
            return 0;
        }else if(vlc->table_size){
            abort(); // fatal error, we are called on a partially initialized table
        }
    }else if(!(flags & INIT_VLC_USE_STATIC)) {
        vlc->table = NULL;
        vlc->table_allocated = 0;
        vlc->table_size = 0;
    } else {
        /* Static tables are initially always NULL, return
           if vlc->table != NULL to avoid double allocation */
        if(vlc->table)
            return 0;
    }

#ifdef DEBUG_VLC
    av_log(NULL,AV_LOG_DEBUG,"build table nb_codes=%d\n", nb_codes);
#endif

    if (build_table(vlc, nb_bits, nb_codes,
                    bits, bits_wrap, bits_size,
                    codes, codes_wrap, codes_size,
                    symbols, symbols_wrap, symbols_size,
                    0, 0, flags) < 0) {
        av_freep(&vlc->table);
        return -1;
    }
    if((flags & INIT_VLC_USE_NEW_STATIC) && vlc->table_size != vlc->table_allocated)
        av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n", vlc->table_size, vlc->table_allocated);
    return 0;
}


void free_vlc(VLC *vlc)
{
    av_freep(&vlc->table);
}