mirror of
https://git.videolan.org/git/ffmpeg.git
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575 lines
18 KiB
C
575 lines
18 KiB
C
/*
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* copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* @file
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* bitstream reader API header.
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*/
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#ifndef AVCODEC_GET_BITS_H
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#define AVCODEC_GET_BITS_H
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#include <stdint.h>
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#include "libavutil/common.h"
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#include "libavutil/intreadwrite.h"
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#include "libavutil/log.h"
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#include "libavutil/avassert.h"
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#include "mathops.h"
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/*
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* Safe bitstream reading:
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* optionally, the get_bits API can check to ensure that we
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* don't read past input buffer boundaries. This is protected
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* with CONFIG_SAFE_BITSTREAM_READER at the global level, and
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* then below that with UNCHECKED_BITSTREAM_READER at the per-
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* decoder level. This means that decoders that check internally
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* can "#define UNCHECKED_BITSTREAM_READER 1" to disable
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* overread checks.
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* Boundary checking causes a minor performance penalty so for
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* applications that won't want/need this, it can be disabled
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* globally using "#define CONFIG_SAFE_BITSTREAM_READER 0".
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*/
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#ifndef UNCHECKED_BITSTREAM_READER
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#define UNCHECKED_BITSTREAM_READER !CONFIG_SAFE_BITSTREAM_READER
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#endif
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typedef struct GetBitContext {
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const uint8_t *buffer, *buffer_end;
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int index;
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int size_in_bits;
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int size_in_bits_plus8;
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} GetBitContext;
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#define VLC_TYPE int16_t
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typedef struct VLC {
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int bits;
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VLC_TYPE (*table)[2]; ///< code, bits
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int table_size, table_allocated;
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} VLC;
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typedef struct RL_VLC_ELEM {
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int16_t level;
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int8_t len;
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uint8_t run;
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} RL_VLC_ELEM;
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/* Bitstream reader API docs:
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name
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arbitrary name which is used as prefix for the internal variables
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gb
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getbitcontext
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OPEN_READER(name, gb)
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load gb into local variables
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CLOSE_READER(name, gb)
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store local vars in gb
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UPDATE_CACHE(name, gb)
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refill the internal cache from the bitstream
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after this call at least MIN_CACHE_BITS will be available,
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GET_CACHE(name, gb)
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will output the contents of the internal cache, next bit is MSB of 32 or 64 bit (FIXME 64bit)
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SHOW_UBITS(name, gb, num)
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will return the next num bits
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SHOW_SBITS(name, gb, num)
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will return the next num bits and do sign extension
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SKIP_BITS(name, gb, num)
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will skip over the next num bits
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note, this is equivalent to SKIP_CACHE; SKIP_COUNTER
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SKIP_CACHE(name, gb, num)
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will remove the next num bits from the cache (note SKIP_COUNTER MUST be called before UPDATE_CACHE / CLOSE_READER)
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SKIP_COUNTER(name, gb, num)
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will increment the internal bit counter (see SKIP_CACHE & SKIP_BITS)
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LAST_SKIP_BITS(name, gb, num)
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like SKIP_BITS, to be used if next call is UPDATE_CACHE or CLOSE_READER
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for examples see get_bits, show_bits, skip_bits, get_vlc
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*/
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#ifdef LONG_BITSTREAM_READER
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# define MIN_CACHE_BITS 32
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#else
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# define MIN_CACHE_BITS 25
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#endif
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#if UNCHECKED_BITSTREAM_READER
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#define OPEN_READER(name, gb) \
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unsigned int name##_index = (gb)->index; \
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av_unused unsigned int name##_cache
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#define HAVE_BITS_REMAINING(name, gb) 1
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#else
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#define OPEN_READER(name, gb) \
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unsigned int name##_index = (gb)->index; \
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unsigned int av_unused name##_cache = 0; \
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unsigned int av_unused name##_size_plus8 = \
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(gb)->size_in_bits_plus8
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#define HAVE_BITS_REMAINING(name, gb) \
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name##_index < name##_size_plus8
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#endif
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#define CLOSE_READER(name, gb) (gb)->index = name##_index
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#ifdef BITSTREAM_READER_LE
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# ifdef LONG_BITSTREAM_READER
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# define UPDATE_CACHE(name, gb) name##_cache = \
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AV_RL64((gb)->buffer + (name##_index >> 3)) >> (name##_index & 7)
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# else
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# define UPDATE_CACHE(name, gb) name##_cache = \
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AV_RL32((gb)->buffer + (name##_index >> 3)) >> (name##_index & 7)
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# endif
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# define SKIP_CACHE(name, gb, num) name##_cache >>= (num)
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#else
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# ifdef LONG_BITSTREAM_READER
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# define UPDATE_CACHE(name, gb) name##_cache = \
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AV_RB64((gb)->buffer + (name##_index >> 3)) >> (32 - (name##_index & 7))
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# else
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# define UPDATE_CACHE(name, gb) name##_cache = \
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AV_RB32((gb)->buffer + (name##_index >> 3)) << (name##_index & 7)
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# endif
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# define SKIP_CACHE(name, gb, num) name##_cache <<= (num)
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#endif
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#if UNCHECKED_BITSTREAM_READER
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# define SKIP_COUNTER(name, gb, num) name##_index += (num)
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#else
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# define SKIP_COUNTER(name, gb, num) \
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name##_index = FFMIN(name##_size_plus8, name##_index + (num))
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#endif
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#define SKIP_BITS(name, gb, num) do { \
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SKIP_CACHE(name, gb, num); \
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SKIP_COUNTER(name, gb, num); \
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} while (0)
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#define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)
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#ifdef BITSTREAM_READER_LE
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# define SHOW_UBITS(name, gb, num) zero_extend(name##_cache, num)
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# define SHOW_SBITS(name, gb, num) sign_extend(name##_cache, num)
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#else
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# define SHOW_UBITS(name, gb, num) NEG_USR32(name##_cache, num)
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# define SHOW_SBITS(name, gb, num) NEG_SSR32(name##_cache, num)
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#endif
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#define GET_CACHE(name, gb) ((uint32_t)name##_cache)
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static inline int get_bits_count(const GetBitContext *s)
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{
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return s->index;
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}
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static inline void skip_bits_long(GetBitContext *s, int n){
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#if UNCHECKED_BITSTREAM_READER
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s->index += n;
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#else
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s->index += av_clip(n, -s->index, s->size_in_bits_plus8 - s->index);
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#endif
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}
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/**
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* read mpeg1 dc style vlc (sign bit + mantisse with no MSB).
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* if MSB not set it is negative
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* @param n length in bits
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*/
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static inline int get_xbits(GetBitContext *s, int n)
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{
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register int sign;
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register int32_t cache;
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OPEN_READER(re, s);
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UPDATE_CACHE(re, s);
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cache = GET_CACHE(re, s);
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sign = ~cache >> 31;
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LAST_SKIP_BITS(re, s, n);
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CLOSE_READER(re, s);
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return (NEG_USR32(sign ^ cache, n) ^ sign) - sign;
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}
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static inline int get_sbits(GetBitContext *s, int n)
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{
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register int tmp;
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OPEN_READER(re, s);
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av_assert2(n>0 && n<=25);
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UPDATE_CACHE(re, s);
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tmp = SHOW_SBITS(re, s, n);
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LAST_SKIP_BITS(re, s, n);
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CLOSE_READER(re, s);
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return tmp;
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}
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/**
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* Read 1-25 bits.
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*/
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static inline unsigned int get_bits(GetBitContext *s, int n)
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{
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register int tmp;
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OPEN_READER(re, s);
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av_assert2(n>0 && n<=25);
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UPDATE_CACHE(re, s);
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tmp = SHOW_UBITS(re, s, n);
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LAST_SKIP_BITS(re, s, n);
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CLOSE_READER(re, s);
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return tmp;
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}
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/**
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* Show 1-25 bits.
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*/
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static inline unsigned int show_bits(GetBitContext *s, int n)
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{
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register int tmp;
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OPEN_READER(re, s);
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av_assert2(n>0 && n<=25);
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UPDATE_CACHE(re, s);
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tmp = SHOW_UBITS(re, s, n);
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return tmp;
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}
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static inline void skip_bits(GetBitContext *s, int n)
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{
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OPEN_READER(re, s);
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UPDATE_CACHE(re, s);
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LAST_SKIP_BITS(re, s, n);
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CLOSE_READER(re, s);
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}
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static inline unsigned int get_bits1(GetBitContext *s)
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{
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unsigned int index = s->index;
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uint8_t result = s->buffer[index>>3];
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#ifdef BITSTREAM_READER_LE
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result >>= index & 7;
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result &= 1;
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#else
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result <<= index & 7;
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result >>= 8 - 1;
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#endif
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#if !UNCHECKED_BITSTREAM_READER
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if (s->index < s->size_in_bits_plus8)
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#endif
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index++;
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s->index = index;
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return result;
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}
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static inline unsigned int show_bits1(GetBitContext *s)
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{
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return show_bits(s, 1);
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}
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static inline void skip_bits1(GetBitContext *s)
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{
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skip_bits(s, 1);
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}
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/**
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* Read 0-32 bits.
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*/
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static inline unsigned int get_bits_long(GetBitContext *s, int n)
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{
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if (n <= MIN_CACHE_BITS)
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return get_bits(s, n);
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else {
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#ifdef BITSTREAM_READER_LE
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int ret = get_bits(s, 16);
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return ret | (get_bits(s, n-16) << 16);
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#else
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int ret = get_bits(s, 16) << (n-16);
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return ret | get_bits(s, n-16);
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#endif
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}
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}
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/**
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* Read 0-32 bits as a signed integer.
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*/
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static inline int get_sbits_long(GetBitContext *s, int n)
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{
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return sign_extend(get_bits_long(s, n), n);
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}
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/**
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* Show 0-32 bits.
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*/
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static inline unsigned int show_bits_long(GetBitContext *s, int n)
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{
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if (n <= MIN_CACHE_BITS)
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return show_bits(s, n);
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else {
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GetBitContext gb = *s;
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return get_bits_long(&gb, n);
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}
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}
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static inline int check_marker(GetBitContext *s, const char *msg)
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{
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int bit = get_bits1(s);
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if (!bit)
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av_log(NULL, AV_LOG_INFO, "Marker bit missing %s\n", msg);
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return bit;
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}
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/**
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* Inititalize GetBitContext.
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* @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes larger than the actual read bits
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* because some optimized bitstream readers read 32 or 64 bit at once and could read over the end
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* @param bit_size the size of the buffer in bits
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*/
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static inline void init_get_bits(GetBitContext *s, const uint8_t *buffer,
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int bit_size)
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{
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int buffer_size = (bit_size+7)>>3;
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if (buffer_size < 0 || bit_size < 0) {
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buffer_size = bit_size = 0;
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buffer = NULL;
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}
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s->buffer = buffer;
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s->size_in_bits = bit_size;
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s->size_in_bits_plus8 = bit_size + 8;
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s->buffer_end = buffer + buffer_size;
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s->index = 0;
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}
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static inline void align_get_bits(GetBitContext *s)
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{
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int n = -get_bits_count(s) & 7;
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if (n) skip_bits(s, n);
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}
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#define init_vlc(vlc, nb_bits, nb_codes, \
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bits, bits_wrap, bits_size, \
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codes, codes_wrap, codes_size, \
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flags) \
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ff_init_vlc_sparse(vlc, nb_bits, nb_codes, \
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bits, bits_wrap, bits_size, \
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codes, codes_wrap, codes_size, \
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NULL, 0, 0, flags)
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int ff_init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
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const void *bits, int bits_wrap, int bits_size,
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const void *codes, int codes_wrap, int codes_size,
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const void *symbols, int symbols_wrap, int symbols_size,
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int flags);
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#define INIT_VLC_LE 2
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#define INIT_VLC_USE_NEW_STATIC 4
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void ff_free_vlc(VLC *vlc);
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#define INIT_VLC_STATIC(vlc, bits, a,b,c,d,e,f,g, static_size) do { \
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static VLC_TYPE table[static_size][2]; \
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(vlc)->table = table; \
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(vlc)->table_allocated = static_size; \
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init_vlc(vlc, bits, a,b,c,d,e,f,g, INIT_VLC_USE_NEW_STATIC); \
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} while (0)
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/**
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* If the vlc code is invalid and max_depth=1, then no bits will be removed.
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* If the vlc code is invalid and max_depth>1, then the number of bits removed
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* is undefined.
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*/
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#define GET_VLC(code, name, gb, table, bits, max_depth) \
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do { \
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int n, nb_bits; \
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unsigned int index; \
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\
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index = SHOW_UBITS(name, gb, bits); \
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code = table[index][0]; \
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n = table[index][1]; \
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\
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if (max_depth > 1 && n < 0) { \
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LAST_SKIP_BITS(name, gb, bits); \
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UPDATE_CACHE(name, gb); \
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\
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nb_bits = -n; \
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\
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index = SHOW_UBITS(name, gb, nb_bits) + code; \
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code = table[index][0]; \
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n = table[index][1]; \
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if (max_depth > 2 && n < 0) { \
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LAST_SKIP_BITS(name, gb, nb_bits); \
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UPDATE_CACHE(name, gb); \
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\
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nb_bits = -n; \
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\
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index = SHOW_UBITS(name, gb, nb_bits) + code; \
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code = table[index][0]; \
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n = table[index][1]; \
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} \
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} \
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SKIP_BITS(name, gb, n); \
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} while (0)
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#define GET_RL_VLC(level, run, name, gb, table, bits, max_depth, need_update) \
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do { \
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int n, nb_bits; \
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unsigned int index; \
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\
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index = SHOW_UBITS(name, gb, bits); \
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level = table[index].level; \
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n = table[index].len; \
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\
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if (max_depth > 1 && n < 0) { \
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SKIP_BITS(name, gb, bits); \
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if (need_update) { \
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UPDATE_CACHE(name, gb); \
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} \
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\
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nb_bits = -n; \
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\
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index = SHOW_UBITS(name, gb, nb_bits) + level; \
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level = table[index].level; \
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n = table[index].len; \
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} \
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run = table[index].run; \
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SKIP_BITS(name, gb, n); \
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} while (0)
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/**
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* Parse a vlc code.
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* @param bits is the number of bits which will be read at once, must be
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* identical to nb_bits in init_vlc()
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* @param max_depth is the number of times bits bits must be read to completely
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* read the longest vlc code
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* = (max_vlc_length + bits - 1) / bits
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*/
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static av_always_inline int get_vlc2(GetBitContext *s, VLC_TYPE (*table)[2],
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int bits, int max_depth)
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{
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int code;
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OPEN_READER(re, s);
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UPDATE_CACHE(re, s);
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GET_VLC(code, re, s, table, bits, max_depth);
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CLOSE_READER(re, s);
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return code;
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}
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static inline int decode012(GetBitContext *gb)
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{
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int n;
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n = get_bits1(gb);
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if (n == 0)
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return 0;
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else
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return get_bits1(gb) + 1;
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}
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static inline int decode210(GetBitContext *gb)
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{
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if (get_bits1(gb))
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return 0;
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else
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return 2 - get_bits1(gb);
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}
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static inline int get_bits_left(GetBitContext *gb)
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{
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return gb->size_in_bits - get_bits_count(gb);
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}
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//#define TRACE
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#ifdef TRACE
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static inline void print_bin(int bits, int n)
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{
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int i;
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for (i = n-1; i >= 0; i--) {
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av_log(NULL, AV_LOG_DEBUG, "%d", (bits>>i)&1);
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}
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for (i = n; i < 24; i++)
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av_log(NULL, AV_LOG_DEBUG, " ");
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}
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static inline int get_bits_trace(GetBitContext *s, int n, char *file,
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const char *func, int line)
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{
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int r = get_bits(s, n);
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print_bin(r, n);
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av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d bit @%5d in %s %s:%d\n",
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r, n, r, get_bits_count(s)-n, file, func, line);
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return r;
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}
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static inline int get_vlc_trace(GetBitContext *s, VLC_TYPE (*table)[2],
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int bits, int max_depth, char *file,
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const char *func, int line)
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|
{
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int show = show_bits(s, 24);
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int pos = get_bits_count(s);
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int r = get_vlc2(s, table, bits, max_depth);
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int len = get_bits_count(s) - pos;
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int bits2 = show >> (24-len);
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|
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print_bin(bits2, len);
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|
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av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d vlc @%5d in %s %s:%d\n",
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bits2, len, r, pos, file, func, line);
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return r;
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|
}
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static inline int get_xbits_trace(GetBitContext *s, int n, char *file,
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|
const char *func, int line)
|
|
{
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int show = show_bits(s, n);
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int r = get_xbits(s, n);
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|
|
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print_bin(show, n);
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av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d xbt @%5d in %s %s:%d\n",
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show, n, r, get_bits_count(s)-n, file, func, line);
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return r;
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}
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|
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#define get_bits(s, n) get_bits_trace(s, n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
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#define get_bits1(s) get_bits_trace(s, 1, __FILE__, __PRETTY_FUNCTION__, __LINE__)
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#define get_xbits(s, n) get_xbits_trace(s, n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
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#define get_vlc(s, vlc) get_vlc_trace(s, (vlc)->table, (vlc)->bits, 3, __FILE__, __PRETTY_FUNCTION__, __LINE__)
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#define get_vlc2(s, tab, bits, max) get_vlc_trace(s, tab, bits, max, __FILE__, __PRETTY_FUNCTION__, __LINE__)
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|
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#define tprintf(p, ...) av_log(p, AV_LOG_DEBUG, __VA_ARGS__)
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|
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#else //TRACE
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#define tprintf(p, ...) {}
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|
#endif
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#endif /* AVCODEC_GET_BITS_H */
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