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a1e98f198e
FFmpeg/libavcodec/get_bits.h
Mans Rullgard a1e98f198e get_bits: remove A32 variant 
The A32 bitstream reader variant is only used on ARMv5 and for
Prores due to the larger bit cache this decoder requires.

In benchmarks on ARMv5 (Marvell Sheeva) with gcc 4.6, the only
statistically significant difference between ALT and A32 is
a 4% advantage for ALT in FLAC decoding.  There is thus no (longer)
any reason to keep the A32 reader from this point of view.

This patch adds an option to the ALT reader increasing the bit
cache to 32 bits as required by the Prores decoder.  Benchmarking
shows no significant change in speed on Intel i7.  Again, the
A32 reader fails to justify its existence.

Signed-off-by: Mans Rullgard <mans@mansr.com>
2011-12-16 21:21:48 +00:00

518 lines
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/*
* 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"
/* 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;
int index;
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)
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_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 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 ALT_BITSTREAM_READER_LE
# ifdef LONG_BITSTREAM_READER
# define UPDATE_CACHE(name, gb) \
name##_cache = AV_RL64((gb)->buffer+(name##_index>>3)) >> (name##_index&0x07)
# else
# define UPDATE_CACHE(name, gb) \
name##_cache = AV_RL32((gb)->buffer+(name##_index>>3)) >> (name##_index&0x07)
# 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 & 0x07))
# else
# define UPDATE_CACHE(name, gb) \
name##_cache = AV_RB32((gb)->buffer+(name##_index>>3)) << (name##_index&0x07)
# endif
# 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;
}
/**
* 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;
}
/**
* 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){
//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){
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;
}
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 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
}
}
/**
* 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
*
* 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;
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, 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 */
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