2 * copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
4 * This file is part of FFmpeg.
6 * FFmpeg is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
11 * FFmpeg is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with FFmpeg; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
23 * bitstream reader API header.
26 #ifndef AVCODEC_GET_BITS_H
27 #define AVCODEC_GET_BITS_H
32 #include "libavutil/bswap.h"
33 #include "libavutil/common.h"
34 #include "libavutil/intreadwrite.h"
35 #include "libavutil/log.h"
38 #if defined(ALT_BITSTREAM_READER_LE) && !defined(ALT_BITSTREAM_READER)
39 # define ALT_BITSTREAM_READER
42 #if !defined(A32_BITSTREAM_READER) && !defined(ALT_BITSTREAM_READER)
43 # if ARCH_ARM && !HAVE_FAST_UNALIGNED
44 # define A32_BITSTREAM_READER
46 # define ALT_BITSTREAM_READER
47 //#define A32_BITSTREAM_READER
52 /* buffer, buffer_end and size_in_bits must be present and used by every reader */
53 typedef struct GetBitContext {
54 const uint8_t *buffer, *buffer_end;
55 #ifdef ALT_BITSTREAM_READER
57 #elif defined A32_BITSTREAM_READER
66 #define VLC_TYPE int16_t
70 VLC_TYPE (*table)[2]; ///< code, bits
71 int table_size, table_allocated;
74 typedef struct RL_VLC_ELEM {
80 /* Bitstream reader API docs:
82 arbitrary name which is used as prefix for the internal variables
88 loads gb into local variables
90 CLOSE_READER(name, gb)
91 stores local vars in gb
93 UPDATE_CACHE(name, gb)
94 refills the internal cache from the bitstream
95 after this call at least MIN_CACHE_BITS will be available,
98 will output the contents of the internal cache, next bit is MSB of 32 or 64 bit (FIXME 64bit)
100 SHOW_UBITS(name, gb, num)
101 will return the next num bits
103 SHOW_SBITS(name, gb, num)
104 will return the next num bits and do sign extension
106 SKIP_BITS(name, gb, num)
107 will skip over the next num bits
108 note, this is equivalent to SKIP_CACHE; SKIP_COUNTER
110 SKIP_CACHE(name, gb, num)
111 will remove the next num bits from the cache (note SKIP_COUNTER MUST be called before UPDATE_CACHE / CLOSE_READER)
113 SKIP_COUNTER(name, gb, num)
114 will increment the internal bit counter (see SKIP_CACHE & SKIP_BITS)
116 LAST_SKIP_CACHE(name, gb, num)
117 will remove the next num bits from the cache if it is needed for UPDATE_CACHE otherwise it will do nothing
119 LAST_SKIP_BITS(name, gb, num)
120 is equivalent to LAST_SKIP_CACHE; SKIP_COUNTER
122 for examples see get_bits, show_bits, skip_bits, get_vlc
125 #ifdef ALT_BITSTREAM_READER
126 # define MIN_CACHE_BITS 25
128 # define OPEN_READER(name, gb) \
129 unsigned int name##_index = (gb)->index; \
130 av_unused unsigned int name##_cache
132 # define CLOSE_READER(name, gb) (gb)->index = name##_index
134 # ifdef ALT_BITSTREAM_READER_LE
135 # define UPDATE_CACHE(name, gb) \
136 name##_cache = AV_RL32(((const uint8_t *)(gb)->buffer)+(name##_index>>3)) >> (name##_index&0x07)
138 # define SKIP_CACHE(name, gb, num) name##_cache >>= (num)
140 # define UPDATE_CACHE(name, gb) \
141 name##_cache = AV_RB32(((const uint8_t *)(gb)->buffer)+(name##_index>>3)) << (name##_index&0x07)
143 # define SKIP_CACHE(name, gb, num) name##_cache <<= (num)
147 # define SKIP_COUNTER(name, gb, num) name##_index += (num)
149 # define SKIP_BITS(name, gb, num) do { \
150 SKIP_CACHE(name, gb, num); \
151 SKIP_COUNTER(name, gb, num); \
154 # define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)
155 # define LAST_SKIP_CACHE(name, gb, num)
157 # ifdef ALT_BITSTREAM_READER_LE
158 # define SHOW_UBITS(name, gb, num) zero_extend(name##_cache, num)
160 # define SHOW_SBITS(name, gb, num) sign_extend(name##_cache, num)
162 # define SHOW_UBITS(name, gb, num) NEG_USR32(name##_cache, num)
164 # define SHOW_SBITS(name, gb, num) NEG_SSR32(name##_cache, num)
167 # define GET_CACHE(name, gb) ((uint32_t)name##_cache)
169 static inline int get_bits_count(const GetBitContext *s){
173 static inline void skip_bits_long(GetBitContext *s, int n){
177 #elif defined A32_BITSTREAM_READER
179 # define MIN_CACHE_BITS 32
181 # define OPEN_READER(name, gb) \
182 int name##_bit_count = (gb)->bit_count; \
183 uint32_t name##_cache0 = (gb)->cache0; \
184 uint32_t name##_cache1 = (gb)->cache1; \
185 uint32_t *name##_buffer_ptr = (gb)->buffer_ptr
187 # define CLOSE_READER(name, gb) do { \
188 (gb)->bit_count = name##_bit_count; \
189 (gb)->cache0 = name##_cache0; \
190 (gb)->cache1 = name##_cache1; \
191 (gb)->buffer_ptr = name##_buffer_ptr; \
194 # define UPDATE_CACHE(name, gb) do { \
195 if(name##_bit_count > 0){ \
196 const uint32_t next = av_be2ne32(*name##_buffer_ptr); \
197 name##_cache0 |= NEG_USR32(next, name##_bit_count); \
198 name##_cache1 |= next << name##_bit_count; \
199 name##_buffer_ptr++; \
200 name##_bit_count -= 32; \
205 # define SKIP_CACHE(name, gb, num) \
206 __asm__("shldl %2, %1, %0 \n\t" \
208 : "+r" (name##_cache0), "+r" (name##_cache1) \
209 : "Ic" ((uint8_t)(num)))
211 # define SKIP_CACHE(name, gb, num) do { \
212 name##_cache0 <<= (num); \
213 name##_cache0 |= NEG_USR32(name##_cache1,num); \
214 name##_cache1 <<= (num); \
218 # define SKIP_COUNTER(name, gb, num) name##_bit_count += (num)
220 # define SKIP_BITS(name, gb, num) do { \
221 SKIP_CACHE(name, gb, num); \
222 SKIP_COUNTER(name, gb, num); \
225 # define LAST_SKIP_BITS(name, gb, num) SKIP_BITS(name, gb, num)
226 # define LAST_SKIP_CACHE(name, gb, num) SKIP_CACHE(name, gb, num)
228 # define SHOW_UBITS(name, gb, num) NEG_USR32(name##_cache0, num)
230 # define SHOW_SBITS(name, gb, num) NEG_SSR32(name##_cache0, num)
232 # define GET_CACHE(name, gb) name##_cache0
234 static inline int get_bits_count(const GetBitContext *s) {
235 return ((uint8_t*)s->buffer_ptr - s->buffer)*8 - 32 + s->bit_count;
238 static inline void skip_bits_long(GetBitContext *s, int n){
241 re_buffer_ptr += re_bit_count>>5;
243 re_cache0 = av_be2ne32(re_buffer_ptr[-1]) << re_bit_count;
252 * read mpeg1 dc style vlc (sign bit + mantisse with no MSB).
253 * if MSB not set it is negative
254 * @param n length in bits
257 static inline int get_xbits(GetBitContext *s, int n){
259 register int32_t cache;
262 cache = GET_CACHE(re, s);
264 LAST_SKIP_BITS(re, s, n);
266 return (NEG_USR32(sign ^ cache, n) ^ sign) - sign;
269 static inline int get_sbits(GetBitContext *s, int n){
273 tmp = SHOW_SBITS(re, s, n);
274 LAST_SKIP_BITS(re, s, n);
282 static inline unsigned int get_bits(GetBitContext *s, int n){
286 tmp = SHOW_UBITS(re, s, n);
287 LAST_SKIP_BITS(re, s, n);
295 static inline unsigned int show_bits(GetBitContext *s, int n){
299 tmp = SHOW_UBITS(re, s, n);
303 static inline void skip_bits(GetBitContext *s, int n){
304 //Note gcc seems to optimize this to s->index+=n for the ALT_READER :))
307 LAST_SKIP_BITS(re, s, n);
311 static inline unsigned int get_bits1(GetBitContext *s){
312 #ifdef ALT_BITSTREAM_READER
313 unsigned int index = s->index;
314 uint8_t result = s->buffer[index>>3];
315 #ifdef ALT_BITSTREAM_READER_LE
316 result >>= index & 7;
319 result <<= index & 7;
327 return get_bits(s, 1);
331 static inline unsigned int show_bits1(GetBitContext *s){
332 return show_bits(s, 1);
335 static inline void skip_bits1(GetBitContext *s){
342 static inline unsigned int get_bits_long(GetBitContext *s, int n){
343 if (n <= MIN_CACHE_BITS) return get_bits(s, n);
345 #ifdef ALT_BITSTREAM_READER_LE
346 int ret = get_bits(s, 16);
347 return ret | (get_bits(s, n-16) << 16);
349 int ret = get_bits(s, 16) << (n-16);
350 return ret | get_bits(s, n-16);
356 * reads 0-32 bits as a signed integer.
358 static inline int get_sbits_long(GetBitContext *s, int n) {
359 return sign_extend(get_bits_long(s, n), n);
365 static inline unsigned int show_bits_long(GetBitContext *s, int n){
366 if (n <= MIN_CACHE_BITS) return show_bits(s, n);
368 GetBitContext gb = *s;
369 return get_bits_long(&gb, n);
373 static inline int check_marker(GetBitContext *s, const char *msg)
375 int bit = get_bits1(s);
377 av_log(NULL, AV_LOG_INFO, "Marker bit missing %s\n", msg);
383 * init GetBitContext.
384 * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes larger then the actual read bits
385 * because some optimized bitstream readers read 32 or 64 bit at once and could read over the end
386 * @param bit_size the size of the buffer in bits
388 * While GetBitContext stores the buffer size, for performance reasons you are
389 * responsible for checking for the buffer end yourself (take advantage of the padding)!
391 static inline void init_get_bits(GetBitContext *s,
392 const uint8_t *buffer, int bit_size)
394 int buffer_size = (bit_size+7)>>3;
395 if (buffer_size < 0 || bit_size < 0) {
396 buffer_size = bit_size = 0;
401 s->size_in_bits = bit_size;
402 s->buffer_end = buffer + buffer_size;
403 #ifdef ALT_BITSTREAM_READER
405 #elif defined A32_BITSTREAM_READER
406 s->buffer_ptr = (uint32_t*)((intptr_t)buffer & ~3);
407 s->bit_count = 32 + 8*((intptr_t)buffer & 3);
408 skip_bits_long(s, 0);
412 static inline void align_get_bits(GetBitContext *s)
414 int n = -get_bits_count(s) & 7;
415 if (n) skip_bits(s, n);
418 #define init_vlc(vlc, nb_bits, nb_codes, \
419 bits, bits_wrap, bits_size, \
420 codes, codes_wrap, codes_size, \
422 init_vlc_sparse(vlc, nb_bits, nb_codes, \
423 bits, bits_wrap, bits_size, \
424 codes, codes_wrap, codes_size, \
427 int init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
428 const void *bits, int bits_wrap, int bits_size,
429 const void *codes, int codes_wrap, int codes_size,
430 const void *symbols, int symbols_wrap, int symbols_size,
432 #define INIT_VLC_LE 2
433 #define INIT_VLC_USE_NEW_STATIC 4
434 void free_vlc(VLC *vlc);
436 #define INIT_VLC_STATIC(vlc, bits, a,b,c,d,e,f,g, static_size) do { \
437 static VLC_TYPE table[static_size][2]; \
438 (vlc)->table = table; \
439 (vlc)->table_allocated = static_size; \
440 init_vlc(vlc, bits, a,b,c,d,e,f,g, INIT_VLC_USE_NEW_STATIC); \
446 * If the vlc code is invalid and max_depth=1, then no bits will be removed.
447 * If the vlc code is invalid and max_depth>1, then the number of bits removed
450 #define GET_VLC(code, name, gb, table, bits, max_depth) do { \
452 unsigned int index; \
454 index = SHOW_UBITS(name, gb, bits); \
455 code = table[index][0]; \
456 n = table[index][1]; \
458 if (max_depth > 1 && n < 0) { \
459 LAST_SKIP_BITS(name, gb, bits); \
460 UPDATE_CACHE(name, gb); \
464 index = SHOW_UBITS(name, gb, nb_bits) + code; \
465 code = table[index][0]; \
466 n = table[index][1]; \
467 if (max_depth > 2 && n < 0) { \
468 LAST_SKIP_BITS(name, gb, nb_bits); \
469 UPDATE_CACHE(name, gb); \
473 index = SHOW_UBITS(name, gb, nb_bits) + code; \
474 code = table[index][0]; \
475 n = table[index][1]; \
478 SKIP_BITS(name, gb, n); \
481 #define GET_RL_VLC(level, run, name, gb, table, bits, max_depth, need_update) do { \
483 unsigned int index; \
485 index = SHOW_UBITS(name, gb, bits); \
486 level = table[index].level; \
487 n = table[index].len; \
489 if (max_depth > 1 && n < 0) { \
490 SKIP_BITS(name, gb, bits); \
492 UPDATE_CACHE(name, gb); \
497 index = SHOW_UBITS(name, gb, nb_bits) + level; \
498 level = table[index].level; \
499 n = table[index].len; \
501 run = table[index].run; \
502 SKIP_BITS(name, gb, n); \
507 * parses a vlc code, faster then get_vlc()
508 * @param bits is the number of bits which will be read at once, must be
509 * identical to nb_bits in init_vlc()
510 * @param max_depth is the number of times bits bits must be read to completely
511 * read the longest vlc code
512 * = (max_vlc_length + bits - 1) / bits
514 static av_always_inline int get_vlc2(GetBitContext *s, VLC_TYPE (*table)[2],
515 int bits, int max_depth)
522 GET_VLC(code, re, s, table, bits, max_depth);
528 static inline int decode012(GetBitContext *gb){
534 return get_bits1(gb) + 1;
537 static inline int decode210(GetBitContext *gb){
541 return 2 - get_bits1(gb);
544 static inline int get_bits_left(GetBitContext *gb)
546 return gb->size_in_bits - get_bits_count(gb);
552 static inline void print_bin(int bits, int n){
555 for (i = n-1; i >= 0; i--) {
556 av_log(NULL, AV_LOG_DEBUG, "%d", (bits>>i)&1);
558 for (i = n; i < 24; i++)
559 av_log(NULL, AV_LOG_DEBUG, " ");
562 static inline int get_bits_trace(GetBitContext *s, int n, char *file,
563 const char *func, int line){
564 int r = get_bits(s, n);
567 av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d bit @%5d in %s %s:%d\n",
568 r, n, r, get_bits_count(s)-n, file, func, line);
571 static inline int get_vlc_trace(GetBitContext *s, VLC_TYPE (*table)[2],
572 int bits, int max_depth, char *file,
573 const char *func, int line){
574 int show = show_bits(s, 24);
575 int pos = get_bits_count(s);
576 int r = get_vlc2(s, table, bits, max_depth);
577 int len = get_bits_count(s) - pos;
578 int bits2 = show >> (24-len);
580 print_bin(bits2, len);
582 av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d vlc @%5d in %s %s:%d\n",
583 bits2, len, r, pos, file, func, line);
586 static inline int get_xbits_trace(GetBitContext *s, int n, char *file,
587 const char *func, int line){
588 int show = show_bits(s, n);
589 int r = get_xbits(s, n);
592 av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d xbt @%5d in %s %s:%d\n",
593 show, n, r, get_bits_count(s)-n, file, func, line);
597 #define get_bits(s, n) get_bits_trace(s, n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
598 #define get_bits1(s) get_bits_trace(s, 1, __FILE__, __PRETTY_FUNCTION__, __LINE__)
599 #define get_xbits(s, n) get_xbits_trace(s, n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
600 #define get_vlc(s, vlc) get_vlc_trace(s, (vlc)->table, (vlc)->bits, 3, __FILE__, __PRETTY_FUNCTION__, __LINE__)
601 #define get_vlc2(s, tab, bits, max) get_vlc_trace(s, tab, bits, max, __FILE__, __PRETTY_FUNCTION__, __LINE__)
603 #define tprintf(p, ...) av_log(p, AV_LOG_DEBUG, __VA_ARGS__)
606 #define tprintf(p, ...) {}
609 #endif /* AVCODEC_GET_BITS_H */