aboutsummaryrefslogtreecommitdiffstats
path: root/libavcodec/get_bits.h
blob: d2ae3453156218533e330d29d9f2437a41bd54db (plain) (blame)
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
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
/*
 * copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
 *
 * This file is part of Libav.
 *
 * Libav 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.
 *
 * Libav 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 Libav; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file
 * bitstream reader API header.
 */

#ifndef AVCODEC_GET_BITS_H
#define AVCODEC_GET_BITS_H

#include <stdint.h>
#include <stdlib.h>
#include <assert.h>
#include "libavutil/bswap.h"
#include "libavutil/common.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/log.h"
#include "mathops.h"

#if defined(ALT_BITSTREAM_READER_LE) && !defined(ALT_BITSTREAM_READER)
#   define ALT_BITSTREAM_READER
#endif

#if !defined(A32_BITSTREAM_READER) && !defined(ALT_BITSTREAM_READER)
#   if ARCH_ARM && !HAVE_FAST_UNALIGNED
#       define A32_BITSTREAM_READER
#   else
#       define ALT_BITSTREAM_READER
//#define A32_BITSTREAM_READER
#   endif
#endif

/* bit input */
/* buffer, buffer_end and size_in_bits must be present and used by every reader */
typedef struct GetBitContext {
    const uint8_t *buffer, *buffer_end;
#ifdef ALT_BITSTREAM_READER
    int index;
#elif defined A32_BITSTREAM_READER
    uint32_t *buffer_ptr;
    uint32_t cache0;
    uint32_t cache1;
    int bit_count;
#endif
    int size_in_bits;
} GetBitContext;

#define VLC_TYPE int16_t

typedef struct VLC {
    int bits;
    VLC_TYPE (*table)[2]; ///< code, bits
    int table_size, table_allocated;
} VLC;

typedef struct RL_VLC_ELEM {
    int16_t level;
    int8_t len;
    uint8_t run;
} RL_VLC_ELEM;

/* Bitstream reader API docs:
name
    arbitrary name which is used as prefix for the internal variables

gb
    getbitcontext

OPEN_READER(name, gb)
    loads gb into local variables

CLOSE_READER(name, gb)
    stores local vars in gb

UPDATE_CACHE(name, gb)
    refills the internal cache from the bitstream
    after this call at least MIN_CACHE_BITS will be available,

GET_CACHE(name, gb)
    will output the contents of the internal cache, next bit is MSB of 32 or 64 bit (FIXME 64bit)

SHOW_UBITS(name, gb, num)
    will return the next num bits

SHOW_SBITS(name, gb, num)
    will return the next num bits and do sign extension

SKIP_BITS(name, gb, num)
    will skip over the next num bits
    note, this is equivalent to SKIP_CACHE; SKIP_COUNTER

SKIP_CACHE(name, gb, num)
    will remove the next num bits from the cache (note SKIP_COUNTER MUST be called before UPDATE_CACHE / CLOSE_READER)

SKIP_COUNTER(name, gb, num)
    will increment the internal bit counter (see SKIP_CACHE & SKIP_BITS)

LAST_SKIP_CACHE(name, gb, num)
    will remove the next num bits from the cache if it is needed for UPDATE_CACHE otherwise it will do nothing

LAST_SKIP_BITS(name, gb, num)
    is equivalent to LAST_SKIP_CACHE; SKIP_COUNTER

for examples see get_bits, show_bits, skip_bits, get_vlc
*/

#ifdef ALT_BITSTREAM_READER
#   define MIN_CACHE_BITS 25

#   define OPEN_READER(name, gb)                \
    unsigned int name##_index = (gb)->index;    \
    unsigned int av_unused name##_cache = 0

#   define CLOSE_READER(name, gb) (gb)->index = name##_index

# ifdef ALT_BITSTREAM_READER_LE
#   define UPDATE_CACHE(name, gb) \
    name##_cache = AV_RL32(((const uint8_t *)(gb)->buffer)+(name##_index>>3)) >> (name##_index&0x07)

#   define SKIP_CACHE(name, gb, num) name##_cache >>= (num)
# else
#   define UPDATE_CACHE(name, gb) \
    name##_cache = AV_RB32(((const uint8_t *)(gb)->buffer)+(name##_index>>3)) << (name##_index&0x07)

#   define SKIP_CACHE(name, gb, num) name##_cache <<= (num)
# endif

// FIXME name?
#   define SKIP_COUNTER(name, gb, num) name##_index += (num)

#   define SKIP_BITS(name, gb, num) do {        \
        SKIP_CACHE(name, gb, num);              \
        SKIP_COUNTER(name, gb, num);            \
    } while (0)

#   define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)
#   define LAST_SKIP_CACHE(name, gb, num)

# ifdef ALT_BITSTREAM_READER_LE
#   define SHOW_UBITS(name, gb, num) zero_extend(name##_cache, num)

#   define SHOW_SBITS(name, gb, num) sign_extend(name##_cache, num)
# else
#   define SHOW_UBITS(name, gb, num) NEG_USR32(name##_cache, num)

#   define SHOW_SBITS(name, gb, num) NEG_SSR32(name##_cache, num)
# endif

#   define GET_CACHE(name, gb) ((uint32_t)name##_cache)

static inline int get_bits_count(const GetBitContext *s){
    return s->index;
}

static inline void skip_bits_long(GetBitContext *s, int n){
    s->index += n;
}

#elif defined A32_BITSTREAM_READER

#   define MIN_CACHE_BITS 32

#   define OPEN_READER(name, gb)                        \
    int name##_bit_count        = (gb)->bit_count;      \
    uint32_t name##_cache0      = (gb)->cache0;         \
    uint32_t name##_cache1      = (gb)->cache1;         \
    uint32_t *name##_buffer_ptr = (gb)->buffer_ptr

#   define CLOSE_READER(name, gb) do {          \
        (gb)->bit_count  = name##_bit_count;    \
        (gb)->cache0     = name##_cache0;       \
        (gb)->cache1     = name##_cache1;       \
        (gb)->buffer_ptr = name##_buffer_ptr;   \
    } while (0)

#   define UPDATE_CACHE(name, gb) do {                                  \
        if(name##_bit_count > 0){                                       \
            const uint32_t next = av_be2ne32(*name##_buffer_ptr);       \
            name##_cache0 |= NEG_USR32(next, name##_bit_count);         \
            name##_cache1 |= next << name##_bit_count;                  \
            name##_buffer_ptr++;                                        \
            name##_bit_count -= 32;                                     \
        }                                                               \
    } while (0)

#   define SKIP_CACHE(name, gb, num) do {               \
        name##_cache0 <<= (num);                        \
        name##_cache0 |= NEG_USR32(name##_cache1,num);  \
        name##_cache1 <<= (num);                        \
    } while (0)

#   define SKIP_COUNTER(name, gb, num) name##_bit_count += (num)

#   define SKIP_BITS(name, gb, num) do {        \
        SKIP_CACHE(name, gb, num);              \
        SKIP_COUNTER(name, gb, num);            \
    } while (0)

#   define LAST_SKIP_BITS(name, gb, num)  SKIP_BITS(name, gb, num)
#   define LAST_SKIP_CACHE(name, gb, num) SKIP_CACHE(name, gb, num)

#   define SHOW_UBITS(name, gb, num) NEG_USR32(name##_cache0, num)

#   define SHOW_SBITS(name, gb, num) NEG_SSR32(name##_cache0, num)

#   define GET_CACHE(name, gb) name##_cache0

static inline int get_bits_count(const GetBitContext *s) {
    return ((uint8_t*)s->buffer_ptr - s->buffer)*8 - 32 + s->bit_count;
}

static inline void skip_bits_long(GetBitContext *s, int n){
    OPEN_READER(re, s);
    re_bit_count += n;
    re_buffer_ptr += re_bit_count>>5;
    re_bit_count &= 31;
    re_cache0 = av_be2ne32(re_buffer_ptr[-1]) << re_bit_count;
    re_cache1 = 0;
    UPDATE_CACHE(re, s);
    CLOSE_READER(re, s);
}

#endif

/**
 * read mpeg1 dc style vlc (sign bit + mantisse with no MSB).
 * if MSB not set it is negative
 * @param n length in bits
 * @author BERO
 */
static inline int get_xbits(GetBitContext *s, int n){
    register int sign;
    register int32_t cache;
    OPEN_READER(re, s);
    UPDATE_CACHE(re, s);
    cache = GET_CACHE(re, s);
    sign = ~cache >> 31;
    LAST_SKIP_BITS(re, s, n);
    CLOSE_READER(re, s);
    return (NEG_USR32(sign ^ cache, n) ^ sign) - sign;
}

static inline int get_sbits(GetBitContext *s, int n){
    register int tmp;
    OPEN_READER(re, s);
    UPDATE_CACHE(re, s);
    tmp = SHOW_SBITS(re, s, n);
    LAST_SKIP_BITS(re, s, n);
    CLOSE_READER(re, s);
    return tmp;
}

/**
 * Read 1-25 bits.
 */
static inline unsigned int get_bits(GetBitContext *s, int n){
    register int tmp;
    OPEN_READER(re, s);
    UPDATE_CACHE(re, s);
    tmp = SHOW_UBITS(re, s, n);
    LAST_SKIP_BITS(re, s, n);
    CLOSE_READER(re, s);
    return tmp;
}

/**
 * Shows 1-25 bits.
 */
static inline unsigned int show_bits(GetBitContext *s, int n){
    register int tmp;
    OPEN_READER(re, s);
    UPDATE_CACHE(re, s);
    tmp = SHOW_UBITS(re, s, n);
    return tmp;
}

static inline void skip_bits(GetBitContext *s, int n){
 //Note gcc seems to optimize this to s->index+=n for the ALT_READER :))
    OPEN_READER(re, s);
    UPDATE_CACHE(re, s);
    LAST_SKIP_BITS(re, s, n);
    CLOSE_READER(re, s);
}

static inline unsigned int get_bits1(GetBitContext *s){
#ifdef ALT_BITSTREAM_READER
    unsigned int index = s->index;
    uint8_t result = s->buffer[index>>3];
#ifdef ALT_BITSTREAM_READER_LE
    result >>= index & 7;
    result &= 1;
#else
    result <<= index & 7;
    result >>= 8 - 1;
#endif
    index++;
    s->index = index;

    return result;
#else
    return get_bits(s, 1);
#endif
}

static inline unsigned int show_bits1(GetBitContext *s){
    return show_bits(s, 1);
}

static inline void skip_bits1(GetBitContext *s){
    skip_bits(s, 1);
}

/**
 * reads 0-32 bits.
 */
static inline unsigned int get_bits_long(GetBitContext *s, int n){
    if (n <= MIN_CACHE_BITS) return get_bits(s, n);
    else {
#ifdef ALT_BITSTREAM_READER_LE
        int ret = get_bits(s, 16);
        return ret | (get_bits(s, n-16) << 16);
#else
        int ret = get_bits(s, 16) << (n-16);
        return ret | get_bits(s, n-16);
#endif
    }
}

/**
 * reads 0-32 bits as a signed integer.
 */
static inline int get_sbits_long(GetBitContext *s, int n) {
    return sign_extend(get_bits_long(s, n), n);
}

/**
 * shows 0-32 bits.
 */
static inline unsigned int show_bits_long(GetBitContext *s, int n){
    if (n <= MIN_CACHE_BITS) return show_bits(s, n);
    else {
        GetBitContext gb = *s;
        return get_bits_long(&gb, n);
    }
}

static inline int check_marker(GetBitContext *s, const char *msg)
{
    int bit = get_bits1(s);
    if (!bit)
        av_log(NULL, AV_LOG_INFO, "Marker bit missing %s\n", msg);

    return bit;
}

/**
 * init GetBitContext.
 * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes larger than the actual read bits
 * because some optimized bitstream readers read 32 or 64 bit at once and could read over the end
 * @param bit_size the size of the buffer in bits
 *
 * While GetBitContext stores the buffer size, for performance reasons you are
 * responsible for checking for the buffer end yourself (take advantage of the padding)!
 */
static inline void init_get_bits(GetBitContext *s,
                   const uint8_t *buffer, int bit_size)
{
    int buffer_size = (bit_size+7)>>3;
    if (buffer_size < 0 || bit_size < 0) {
        buffer_size = bit_size = 0;
        buffer = NULL;
    }

    s->buffer       = buffer;
    s->size_in_bits = bit_size;
    s->buffer_end   = buffer + buffer_size;
#ifdef ALT_BITSTREAM_READER
    s->index        = 0;
#elif defined A32_BITSTREAM_READER
    s->buffer_ptr   = (uint32_t*)((intptr_t)buffer & ~3);
    s->bit_count    = 32 +     8*((intptr_t)buffer &  3);
    skip_bits_long(s, 0);
#endif
}

static inline void align_get_bits(GetBitContext *s)
{
    int n = -get_bits_count(s) & 7;
    if (n) skip_bits(s, n);
}

#define init_vlc(vlc, nb_bits, nb_codes,                \
                 bits, bits_wrap, bits_size,            \
                 codes, codes_wrap, codes_size,         \
                 flags)                                 \
        init_vlc_sparse(vlc, nb_bits, nb_codes,         \
                        bits, bits_wrap, bits_size,     \
                        codes, codes_wrap, codes_size,  \
                        NULL, 0, 0, flags)

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);
#define INIT_VLC_LE         2
#define INIT_VLC_USE_NEW_STATIC 4
void free_vlc(VLC *vlc);

#define INIT_VLC_STATIC(vlc, bits, a,b,c,d,e,f,g, static_size) do {     \
        static VLC_TYPE table[static_size][2];                          \
        (vlc)->table = table;                                           \
        (vlc)->table_allocated = static_size;                           \
        init_vlc(vlc, bits, a,b,c,d,e,f,g, INIT_VLC_USE_NEW_STATIC);    \
    } while (0)


/**
 *
 * If the vlc code is invalid and max_depth=1, then no bits will be removed.
 * If the vlc code is invalid and max_depth>1, then the number of bits removed
 * is undefined.
 */
#define GET_VLC(code, name, gb, table, bits, max_depth) do {    \
        int n, nb_bits;                                         \
        unsigned int index;                                     \
                                                                \
        index = SHOW_UBITS(name, gb, bits);                     \
        code  = table[index][0];                                \
        n     = table[index][1];                                \
                                                                \
        if (max_depth > 1 && n < 0) {                           \
            LAST_SKIP_BITS(name, gb, bits);                     \
            UPDATE_CACHE(name, gb);                             \
                                                                \
            nb_bits = -n;                                       \
                                                                \
            index = SHOW_UBITS(name, gb, nb_bits) + code;       \
            code  = table[index][0];                            \
            n     = table[index][1];                            \
            if (max_depth > 2 && n < 0) {                       \
                LAST_SKIP_BITS(name, gb, nb_bits);              \
                UPDATE_CACHE(name, gb);                         \
                                                                \
                nb_bits = -n;                                   \
                                                                \
                index = SHOW_UBITS(name, gb, nb_bits) + code;   \
                code  = table[index][0];                        \
                n     = table[index][1];                        \
            }                                                   \
        }                                                       \
        SKIP_BITS(name, gb, n);                                 \
    } while (0)

#define GET_RL_VLC(level, run, name, gb, table, bits, max_depth, need_update) do { \
        int n, nb_bits;                                                 \
        unsigned int index;                                             \
                                                                        \
        index = SHOW_UBITS(name, gb, bits);                             \
        level = table[index].level;                                     \
        n     = table[index].len;                                       \
                                                                        \
        if (max_depth > 1 && n < 0) {                                   \
            SKIP_BITS(name, gb, bits);                                  \
            if (need_update) {                                          \
                UPDATE_CACHE(name, gb);                                 \
            }                                                           \
                                                                        \
            nb_bits = -n;                                               \
                                                                        \
            index = SHOW_UBITS(name, gb, nb_bits) + level;              \
            level = table[index].level;                                 \
            n     = table[index].len;                                   \
        }                                                               \
        run = table[index].run;                                         \
        SKIP_BITS(name, gb, n);                                         \
    } while (0)


/**
 * parses a vlc code, faster than get_vlc()
 * @param bits is the number of bits which will be read at once, must be
 *             identical to nb_bits in init_vlc()
 * @param max_depth is the number of times bits bits must be read to completely
 *                  read the longest vlc code
 *                  = (max_vlc_length + bits - 1) / bits
 */
static av_always_inline int get_vlc2(GetBitContext *s, VLC_TYPE (*table)[2],
                                  int bits, int max_depth)
{
    int code;

    OPEN_READER(re, s);
    UPDATE_CACHE(re, s);

    GET_VLC(code, re, s, table, bits, max_depth);

    CLOSE_READER(re, s);
    return code;
}

static inline int decode012(GetBitContext *gb){
    int n;
    n = get_bits1(gb);
    if (n == 0)
        return 0;
    else
        return get_bits1(gb) + 1;
}

static inline int decode210(GetBitContext *gb){
    if (get_bits1(gb))
        return 0;
    else
        return 2 - get_bits1(gb);
}

static inline int get_bits_left(GetBitContext *gb)
{
    return gb->size_in_bits - get_bits_count(gb);
}

//#define TRACE

#ifdef TRACE
static inline void print_bin(int bits, int n){
    int i;

    for (i = n-1; i >= 0; i--) {
        av_log(NULL, AV_LOG_DEBUG, "%d", (bits>>i)&1);
    }
    for (i = n; i < 24; i++)
        av_log(NULL, AV_LOG_DEBUG, " ");
}

static inline int get_bits_trace(GetBitContext *s, int n, char *file,
                                 const char *func, int line){
    int r = get_bits(s, n);

    print_bin(r, n);
    av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d bit @%5d in %s %s:%d\n",
           r, n, r, get_bits_count(s)-n, file, func, line);
    return r;
}
static inline int get_vlc_trace(GetBitContext *s, VLC_TYPE (*table)[2],
                                int bits, int max_depth, char *file,
                                const char *func, int line){
    int show  = show_bits(s, 24);
    int pos   = get_bits_count(s);
    int r     = get_vlc2(s, table, bits, max_depth);
    int len   = get_bits_count(s) - pos;
    int bits2 = show >> (24-len);

    print_bin(bits2, len);

    av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d vlc @%5d in %s %s:%d\n",
           bits2, len, r, pos, file, func, line);
    return r;
}
static inline int get_xbits_trace(GetBitContext *s, int n, char *file,
                                  const char *func, int line){
    int show = show_bits(s, n);
    int r    = get_xbits(s, n);

    print_bin(show, n);
    av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d xbt @%5d in %s %s:%d\n",
           show, n, r, get_bits_count(s)-n, file, func, line);
    return r;
}

#define get_bits(s, n)  get_bits_trace(s, n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
#define get_bits1(s)    get_bits_trace(s, 1, __FILE__, __PRETTY_FUNCTION__, __LINE__)
#define get_xbits(s, n) get_xbits_trace(s, n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
#define get_vlc(s, vlc)            get_vlc_trace(s, (vlc)->table, (vlc)->bits, 3, __FILE__, __PRETTY_FUNCTION__, __LINE__)
#define get_vlc2(s, tab, bits, max) get_vlc_trace(s, tab, bits, max, __FILE__, __PRETTY_FUNCTION__, __LINE__)

#define tprintf(p, ...) av_log(p, AV_LOG_DEBUG, __VA_ARGS__)

#else //TRACE
#define tprintf(p, ...) {}
#endif

#endif /* AVCODEC_GET_BITS_H */