aaf47bcde7
The prefix is a historic remnant that probably meant "alternative". Now that the A32 bitstream reader has been dropped it makes no sense anymore.
562 lines
17 KiB
C
562 lines
17 KiB
C
/*
|
|
* 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 "libavutil/common.h"
|
|
#include "libavutil/intreadwrite.h"
|
|
#include "libavutil/log.h"
|
|
#include "mathops.h"
|
|
|
|
/*
|
|
* Safe bitstream reading:
|
|
* optionally, the get_bits API can check to ensure that we
|
|
* don't read past input buffer boundaries. This is protected
|
|
* with CONFIG_SAFE_BITSTREAM_READER at the global level, and
|
|
* then below that with UNCHECKED_BITSTREAM_READER at the per-
|
|
* decoder level. This means that decoders that check internally
|
|
* can "#define UNCHECKED_BITSTREAM_READER 1" to disable
|
|
* overread checks.
|
|
* Boundary checking causes a minor performance penalty so for
|
|
* applications that won't want/need this, it can be disabled
|
|
* globally using "#define CONFIG_SAFE_BITSTREAM_READER 0".
|
|
*/
|
|
#ifndef UNCHECKED_BITSTREAM_READER
|
|
#define UNCHECKED_BITSTREAM_READER !CONFIG_SAFE_BITSTREAM_READER
|
|
#endif
|
|
|
|
typedef struct GetBitContext {
|
|
const uint8_t *buffer, *buffer_end;
|
|
int index;
|
|
int size_in_bits;
|
|
#if !UNCHECKED_BITSTREAM_READER
|
|
int size_in_bits_plus8;
|
|
#endif
|
|
} 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)
|
|
load gb into local variables
|
|
|
|
CLOSE_READER(name, gb)
|
|
store local vars in gb
|
|
|
|
UPDATE_CACHE(name, gb)
|
|
refill 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_BITS(name, gb, num)
|
|
like SKIP_BITS, to be used if next call is UPDATE_CACHE or CLOSE_READER
|
|
|
|
for examples see get_bits, show_bits, skip_bits, get_vlc
|
|
*/
|
|
|
|
#ifdef LONG_BITSTREAM_READER
|
|
# define MIN_CACHE_BITS 32
|
|
#else
|
|
# define MIN_CACHE_BITS 25
|
|
#endif
|
|
|
|
#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 BITSTREAM_READER_LE
|
|
|
|
# ifdef LONG_BITSTREAM_READER
|
|
# define UPDATE_CACHE(name, gb) name##_cache = \
|
|
AV_RL64((gb)->buffer + (name##_index >> 3)) >> (name##_index & 7)
|
|
# else
|
|
# define UPDATE_CACHE(name, gb) name##_cache = \
|
|
AV_RL32((gb)->buffer + (name##_index >> 3)) >> (name##_index & 7)
|
|
# endif
|
|
|
|
# define SKIP_CACHE(name, gb, num) name##_cache >>= (num)
|
|
|
|
#else
|
|
|
|
# ifdef LONG_BITSTREAM_READER
|
|
# define UPDATE_CACHE(name, gb) name##_cache = \
|
|
AV_RB64((gb)->buffer + (name##_index >> 3)) >> (32 - (name##_index & 7))
|
|
# else
|
|
# define UPDATE_CACHE(name, gb) name##_cache = \
|
|
AV_RB32((gb)->buffer + (name##_index >> 3)) << (name##_index & 7)
|
|
# endif
|
|
|
|
# define SKIP_CACHE(name, gb, num) name##_cache <<= (num)
|
|
|
|
#endif
|
|
|
|
#if UNCHECKED_BITSTREAM_READER
|
|
# define SKIP_COUNTER(name, gb, num) name##_index += (num)
|
|
#else
|
|
# define SKIP_COUNTER(name, gb, num) \
|
|
name##_index = FFMIN((gb)->size_in_bits_plus8, name##_index + (num))
|
|
#endif
|
|
|
|
#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)
|
|
|
|
#ifdef 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){
|
|
#if UNCHECKED_BITSTREAM_READER
|
|
s->index += n;
|
|
#else
|
|
s->index += av_clip(n, -s->index, s->size_in_bits_plus8 - s->index);
|
|
#endif
|
|
}
|
|
|
|
/**
|
|
* read mpeg1 dc style vlc (sign bit + mantisse with no MSB).
|
|
* if MSB not set it is negative
|
|
* @param n length in bits
|
|
*/
|
|
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;
|
|
}
|
|
|
|
/**
|
|
* Show 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)
|
|
{
|
|
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)
|
|
{
|
|
unsigned int index = s->index;
|
|
uint8_t result = s->buffer[index>>3];
|
|
#ifdef BITSTREAM_READER_LE
|
|
result >>= index & 7;
|
|
result &= 1;
|
|
#else
|
|
result <<= index & 7;
|
|
result >>= 8 - 1;
|
|
#endif
|
|
#if !UNCHECKED_BITSTREAM_READER
|
|
if (s->index < s->size_in_bits_plus8)
|
|
#endif
|
|
index++;
|
|
s->index = index;
|
|
|
|
return result;
|
|
}
|
|
|
|
static inline unsigned int show_bits1(GetBitContext *s)
|
|
{
|
|
return show_bits(s, 1);
|
|
}
|
|
|
|
static inline void skip_bits1(GetBitContext *s)
|
|
{
|
|
skip_bits(s, 1);
|
|
}
|
|
|
|
/**
|
|
* Read 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 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
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Read 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);
|
|
}
|
|
|
|
/**
|
|
* Show 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;
|
|
}
|
|
|
|
/**
|
|
* Inititalize 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
|
|
*/
|
|
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;
|
|
#if !UNCHECKED_BITSTREAM_READER
|
|
s->size_in_bits_plus8 = bit_size + 8;
|
|
#endif
|
|
s->buffer_end = buffer + buffer_size;
|
|
s->index = 0;
|
|
}
|
|
|
|
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)
|
|
|
|
|
|
/**
|
|
* Parse a vlc code.
|
|
* @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 */
|