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https://git.ffmpeg.org/ffmpeg.git
synced 2025-12-08 06:09:50 +00:00
avcodec/get_bits: add cached bitstream reader
Signed-off-by: Paul B Mahol <onemda@gmail.com>
This commit is contained in:
Paul B Mahol
parent
a3c6b7ff59
commit
ca079b0954
2 changed files with 367 additions and 2 deletions
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@ -1,5 +1,6 @@
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/*
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* copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
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* Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
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* Copyright (c) 2016 Alexandra Hájková
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*
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* This file is part of FFmpeg.
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*
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@ -55,11 +56,19 @@
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typedef struct GetBitContext {
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const uint8_t *buffer, *buffer_end;
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#ifdef CACHED_BITSTREAM_READER
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uint64_t cache;
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unsigned bits_left;
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#endif
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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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static inline unsigned int get_bits(GetBitContext *s, int n);
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static inline void skip_bits(GetBitContext *s, int n);
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static inline unsigned int show_bits(GetBitContext *s, int n);
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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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@ -107,12 +116,16 @@ typedef struct GetBitContext {
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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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#ifdef CACHED_BITSTREAM_READER
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# define MIN_CACHE_BITS 64
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#elif defined 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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#ifndef CACHED_BITSTREAM_READER
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#define OPEN_READER_NOSIZE(name, gb) \
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unsigned int name ## _index = (gb)->index; \
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unsigned int av_unused name ## _cache
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@ -197,11 +210,75 @@ typedef struct GetBitContext {
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#define GET_CACHE(name, gb) ((uint32_t) name ## _cache)
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#endif
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static inline int get_bits_count(const GetBitContext *s)
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{
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#ifdef CACHED_BITSTREAM_READER
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return s->index - s->bits_left;
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#else
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return s->index;
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#endif
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}
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#ifdef CACHED_BITSTREAM_READER
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static inline void refill_32(GetBitContext *s)
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{
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#if !UNCHECKED_BITSTREAM_READER
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if (s->index >> 3 >= s->buffer_end - s->buffer)
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return;
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#endif
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#ifdef BITSTREAM_READER_LE
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s->cache = (uint64_t)AV_RL32(s->buffer + (s->index >> 3)) << s->bits_left | s->cache;
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#else
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s->cache = s->cache | (uint64_t)AV_RB32(s->buffer + (s->index >> 3)) << (32 - s->bits_left);
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#endif
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s->index += 32;
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s->bits_left += 32;
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}
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static inline void refill_64(GetBitContext *s)
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{
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#if !UNCHECKED_BITSTREAM_READER
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if (s->index >> 3 >= s->buffer_end - s->buffer)
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return;
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#endif
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#ifdef BITSTREAM_READER_LE
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s->cache = AV_RL64(s->buffer + (s->index >> 3));
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#else
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s->cache = AV_RB64(s->buffer + (s->index >> 3));
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#endif
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s->index += 64;
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s->bits_left = 64;
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}
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static inline uint64_t get_val(GetBitContext *s, unsigned n, int is_le)
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{
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uint64_t ret;
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av_assert2(n>0 && n<=63);
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if (is_le) {
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ret = s->cache & ((UINT64_C(1) << n) - 1);
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s->cache >>= n;
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} else {
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ret = s->cache >> (64 - n);
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s->cache <<= n;
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}
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s->bits_left -= n;
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return ret;
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}
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static inline unsigned show_val(const GetBitContext *s, unsigned n)
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{
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#ifdef BITSTREAM_READER_LE
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return s->cache & ((UINT64_C(1) << n) - 1);
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#else
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return s->cache >> (64 - n);
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#endif
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}
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#endif
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/**
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* Skips the specified number of bits.
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* @param n the number of bits to skip,
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@ -211,13 +288,29 @@ static inline int get_bits_count(const GetBitContext *s)
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*/
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static inline void skip_bits_long(GetBitContext *s, int n)
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{
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#ifdef CACHED_BITSTREAM_READER
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skip_bits(s, n);
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#else
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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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#endif
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}
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#ifdef CACHED_BITSTREAM_READER
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static inline void skip_remaining(GetBitContext *s, unsigned n)
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{
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#ifdef BITSTREAM_READER_LE
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s->cache >>= n;
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#else
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s->cache <<= n;
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#endif
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s->bits_left -= n;
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}
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#endif
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/**
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* Read MPEG-1 dc-style VLC (sign bit + mantissa with no MSB).
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* if MSB not set it is negative
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@ -225,6 +318,13 @@ static inline void skip_bits_long(GetBitContext *s, int n)
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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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#ifdef CACHED_BITSTREAM_READER
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int32_t cache = show_bits(s, 32);
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int sign = ~cache >> 31;
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skip_remaining(s, n);
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return ((((uint32_t)(sign ^ cache)) >> (32 - n)) ^ sign) - sign;
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#else
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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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@ -235,8 +335,10 @@ static inline int get_xbits(GetBitContext *s, int n)
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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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#endif
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}
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#ifndef CACHED_BITSTREAM_READER
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static inline int get_xbits_le(GetBitContext *s, int n)
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{
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register int sign;
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@ -250,16 +352,22 @@ static inline int get_xbits_le(GetBitContext *s, int n)
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CLOSE_READER(re, s);
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return (zero_extend(sign ^ cache, n) ^ sign) - sign;
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}
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#endif
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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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#ifdef CACHED_BITSTREAM_READER
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av_assert2(n>0 && n<=25);
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tmp = sign_extend(get_bits(s, n), n);
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#else
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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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#endif
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return tmp;
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}
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@ -269,12 +377,28 @@ static inline int get_sbits(GetBitContext *s, int n)
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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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#ifdef CACHED_BITSTREAM_READER
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av_assert2(n>0 && n<=32);
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if (n > s->bits_left) {
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refill_32(s);
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if (s->bits_left < 32)
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s->bits_left = n;
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}
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#ifdef BITSTREAM_READER_LE
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tmp = get_val(s, n, 1);
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#else
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tmp = get_val(s, n, 0);
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#endif
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#else
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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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#endif
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return tmp;
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}
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@ -288,6 +412,16 @@ static av_always_inline int get_bitsz(GetBitContext *s, int n)
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static inline unsigned int get_bits_le(GetBitContext *s, int n)
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{
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#ifdef CACHED_BITSTREAM_READER
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av_assert2(n>0 && n<=32);
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if (n > s->bits_left) {
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refill_32(s);
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if (s->bits_left < 32)
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s->bits_left = n;
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}
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return get_val(s, n, 1);
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#else
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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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@ -296,6 +430,7 @@ static inline unsigned int get_bits_le(GetBitContext *s, int 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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#endif
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}
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/**
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@ -304,22 +439,59 @@ static inline unsigned int get_bits_le(GetBitContext *s, int n)
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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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#ifdef CACHED_BITSTREAM_READER
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if (n > s->bits_left)
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refill_32(s);
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tmp = show_val(s, n);
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#else
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OPEN_READER_NOSIZE(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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#endif
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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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#ifdef CACHED_BITSTREAM_READER
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if (n < s->bits_left)
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skip_remaining(s, n);
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else {
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n -= s->bits_left;
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s->cache = 0;
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s->bits_left = 0;
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if (n >= 64) {
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unsigned skip = (n / 8) * 8;
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n -= skip;
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s->index += skip;
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}
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refill_64(s);
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if (n)
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skip_remaining(s, n);
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}
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#else
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OPEN_READER(re, s);
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LAST_SKIP_BITS(re, s, n);
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CLOSE_READER(re, s);
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#endif
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}
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static inline unsigned int get_bits1(GetBitContext *s)
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{
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#ifdef CACHED_BITSTREAM_READER
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if (!s->bits_left)
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refill_64(s);
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#ifdef BITSTREAM_READER_LE
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return get_val(s, 1, 1);
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#else
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return get_val(s, 1, 0);
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#endif
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#else
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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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@ -336,6 +508,7 @@ static inline unsigned int get_bits1(GetBitContext *s)
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s->index = index;
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return result;
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#endif
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}
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static inline unsigned int show_bits1(GetBitContext *s)
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@ -356,6 +529,10 @@ static inline unsigned int get_bits_long(GetBitContext *s, int n)
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av_assert2(n>=0 && n<=32);
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if (!n) {
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return 0;
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#ifdef CACHED_BITSTREAM_READER
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}
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return get_bits(s, n);
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#else
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} else if (n <= MIN_CACHE_BITS) {
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return get_bits(s, n);
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} else {
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@ -367,6 +544,7 @@ static inline unsigned int get_bits_long(GetBitContext *s, int n)
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return ret | get_bits(s, n - 16);
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#endif
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}
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#endif
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}
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/**
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@ -450,6 +628,10 @@ static inline int init_get_bits(GetBitContext *s, const uint8_t *buffer,
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s->buffer_end = buffer + buffer_size;
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s->index = 0;
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#ifdef CACHED_BITSTREAM_READER
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refill_64(s);
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#endif
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return ret;
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}
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@ -551,6 +733,19 @@ static inline const uint8_t *align_get_bits(GetBitContext *s)
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SKIP_BITS(name, gb, n); \
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} while (0)
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/* Return the LUT element for the given bitstream configuration. */
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static inline int set_idx(GetBitContext *s, int code, int *n, int *nb_bits,
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VLC_TYPE (*table)[2])
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{
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unsigned idx;
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*nb_bits = -*n;
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idx = show_bits(s, *nb_bits) + code;
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*n = table[idx][1];
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return table[idx][0];
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}
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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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@ -563,6 +758,24 @@ static inline const uint8_t *align_get_bits(GetBitContext *s)
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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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#ifdef CACHED_BITSTREAM_READER
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int nb_bits;
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unsigned idx = show_bits(s, bits);
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int code = table[idx][0];
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int n = table[idx][1];
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if (max_depth > 1 && n < 0) {
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skip_remaining(s, bits);
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code = set_idx(s, code, &n, &nb_bits, table);
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if (max_depth > 2 && n < 0) {
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skip_remaining(s, nb_bits);
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code = set_idx(s, code, &n, &nb_bits, table);
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}
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}
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skip_remaining(s, n);
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return code;
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#else
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int code;
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OPEN_READER(re, s);
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@ -573,6 +786,7 @@ static av_always_inline int get_vlc2(GetBitContext *s, VLC_TYPE (*table)[2],
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CLOSE_READER(re, s);
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return code;
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#endif
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}
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static inline int decode012(GetBitContext *gb)
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