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avcodec/get_bits: add cached bitstream reader 

Signed-off-by: Paul B Mahol <onemda@gmail.com>
tags/n4.1
Paul B Mahol 8 years ago
parent
a3c6b7ff59
commit
ca079b0954
2 changed files with 367 additions and 2 deletions
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  1. +216
    -2
      libavcodec/get_bits.h
  2. +151
    -0
      libavcodec/golomb.h

+ 216
- 2
libavcodec/get_bits.h View File

@@ -1,5 +1,6 @@
/*
* copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
* Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
* Copyright (c) 2016 Alexandra Hájková
*
* This file is part of FFmpeg.
*
@@ -55,11 +56,19 @@

typedef struct GetBitContext {
const uint8_t *buffer, *buffer_end;
#ifdef CACHED_BITSTREAM_READER
uint64_t cache;
unsigned bits_left;
#endif
int index;
int size_in_bits;
int size_in_bits_plus8;
} GetBitContext;

static inline unsigned int get_bits(GetBitContext *s, int n);
static inline void skip_bits(GetBitContext *s, int n);
static inline unsigned int show_bits(GetBitContext *s, int n);

/* Bitstream reader API docs:
* name
* arbitrary name which is used as prefix for the internal variables
@@ -107,12 +116,16 @@ typedef struct GetBitContext {
* For examples see get_bits, show_bits, skip_bits, get_vlc.
*/

#ifdef LONG_BITSTREAM_READER
#ifdef CACHED_BITSTREAM_READER
# define MIN_CACHE_BITS 64
#elif defined LONG_BITSTREAM_READER
# define MIN_CACHE_BITS 32
#else
# define MIN_CACHE_BITS 25
#endif

#ifndef CACHED_BITSTREAM_READER

#define OPEN_READER_NOSIZE(name, gb) \
unsigned int name ## _index = (gb)->index; \
unsigned int av_unused name ## _cache
@@ -197,11 +210,75 @@ typedef struct GetBitContext {

#define GET_CACHE(name, gb) ((uint32_t) name ## _cache)

#endif

static inline int get_bits_count(const GetBitContext *s)
{
#ifdef CACHED_BITSTREAM_READER
return s->index - s->bits_left;
#else
return s->index;
#endif
}

#ifdef CACHED_BITSTREAM_READER
static inline void refill_32(GetBitContext *s)
{
#if !UNCHECKED_BITSTREAM_READER
if (s->index >> 3 >= s->buffer_end - s->buffer)
return;
#endif

#ifdef BITSTREAM_READER_LE
s->cache = (uint64_t)AV_RL32(s->buffer + (s->index >> 3)) << s->bits_left | s->cache;
#else
s->cache = s->cache | (uint64_t)AV_RB32(s->buffer + (s->index >> 3)) << (32 - s->bits_left);
#endif
s->index += 32;
s->bits_left += 32;
}

static inline void refill_64(GetBitContext *s)
{
#if !UNCHECKED_BITSTREAM_READER
if (s->index >> 3 >= s->buffer_end - s->buffer)
return;
#endif

#ifdef BITSTREAM_READER_LE
s->cache = AV_RL64(s->buffer + (s->index >> 3));
#else
s->cache = AV_RB64(s->buffer + (s->index >> 3));
#endif
s->index += 64;
s->bits_left = 64;
}

static inline uint64_t get_val(GetBitContext *s, unsigned n, int is_le)
{
uint64_t ret;
av_assert2(n>0 && n<=63);
if (is_le) {
ret = s->cache & ((UINT64_C(1) << n) - 1);
s->cache >>= n;
} else {
ret = s->cache >> (64 - n);
s->cache <<= n;
}
s->bits_left -= n;
return ret;
}

static inline unsigned show_val(const GetBitContext *s, unsigned n)
{
#ifdef BITSTREAM_READER_LE
return s->cache & ((UINT64_C(1) << n) - 1);
#else
return s->cache >> (64 - n);
#endif
}
#endif

/**
* Skips the specified number of bits.
* @param n the number of bits to skip,
@@ -211,13 +288,29 @@ static inline int get_bits_count(const GetBitContext *s)
*/
static inline void skip_bits_long(GetBitContext *s, int n)
{
#ifdef CACHED_BITSTREAM_READER
skip_bits(s, n);
#else
#if UNCHECKED_BITSTREAM_READER
s->index += n;
#else
s->index += av_clip(n, -s->index, s->size_in_bits_plus8 - s->index);
#endif
#endif
}

#ifdef CACHED_BITSTREAM_READER
static inline void skip_remaining(GetBitContext *s, unsigned n)
{
#ifdef BITSTREAM_READER_LE
s->cache >>= n;
#else
s->cache <<= n;
#endif
s->bits_left -= n;
}
#endif

/**
* Read MPEG-1 dc-style VLC (sign bit + mantissa with no MSB).
* if MSB not set it is negative
@@ -225,6 +318,13 @@ static inline void skip_bits_long(GetBitContext *s, int n)
*/
static inline int get_xbits(GetBitContext *s, int n)
{
#ifdef CACHED_BITSTREAM_READER
int32_t cache = show_bits(s, 32);
int sign = ~cache >> 31;
skip_remaining(s, n);

return ((((uint32_t)(sign ^ cache)) >> (32 - n)) ^ sign) - sign;
#else
register int sign;
register int32_t cache;
OPEN_READER(re, s);
@@ -235,8 +335,10 @@ static inline int get_xbits(GetBitContext *s, int n)
LAST_SKIP_BITS(re, s, n);
CLOSE_READER(re, s);
return (NEG_USR32(sign ^ cache, n) ^ sign) - sign;
#endif
}

#ifndef CACHED_BITSTREAM_READER
static inline int get_xbits_le(GetBitContext *s, int n)
{
register int sign;
@@ -250,16 +352,22 @@ static inline int get_xbits_le(GetBitContext *s, int n)
CLOSE_READER(re, s);
return (zero_extend(sign ^ cache, n) ^ sign) - sign;
}
#endif

static inline int get_sbits(GetBitContext *s, int n)
{
register int tmp;
#ifdef CACHED_BITSTREAM_READER
av_assert2(n>0 && n<=25);
tmp = sign_extend(get_bits(s, n), n);
#else
OPEN_READER(re, s);
av_assert2(n>0 && n<=25);
UPDATE_CACHE(re, s);
tmp = SHOW_SBITS(re, s, n);
LAST_SKIP_BITS(re, s, n);
CLOSE_READER(re, s);
#endif
return tmp;
}

@@ -269,12 +377,28 @@ static inline int get_sbits(GetBitContext *s, int n)
static inline unsigned int get_bits(GetBitContext *s, int n)
{
register int tmp;
#ifdef CACHED_BITSTREAM_READER

av_assert2(n>0 && n<=32);
if (n > s->bits_left) {
refill_32(s);
if (s->bits_left < 32)
s->bits_left = n;
}

#ifdef BITSTREAM_READER_LE
tmp = get_val(s, n, 1);
#else
tmp = get_val(s, n, 0);
#endif
#else
OPEN_READER(re, s);
av_assert2(n>0 && n<=25);
UPDATE_CACHE(re, s);
tmp = SHOW_UBITS(re, s, n);
LAST_SKIP_BITS(re, s, n);
CLOSE_READER(re, s);
#endif
return tmp;
}

@@ -288,6 +412,16 @@ static av_always_inline int get_bitsz(GetBitContext *s, int n)

static inline unsigned int get_bits_le(GetBitContext *s, int n)
{
#ifdef CACHED_BITSTREAM_READER
av_assert2(n>0 && n<=32);
if (n > s->bits_left) {
refill_32(s);
if (s->bits_left < 32)
s->bits_left = n;
}

return get_val(s, n, 1);
#else
register int tmp;
OPEN_READER(re, s);
av_assert2(n>0 && n<=25);
@@ -296,6 +430,7 @@ static inline unsigned int get_bits_le(GetBitContext *s, int n)
LAST_SKIP_BITS(re, s, n);
CLOSE_READER(re, s);
return tmp;
#endif
}

/**
@@ -304,22 +439,59 @@ static inline unsigned int get_bits_le(GetBitContext *s, int n)
static inline unsigned int show_bits(GetBitContext *s, int n)
{
register int tmp;
#ifdef CACHED_BITSTREAM_READER
if (n > s->bits_left)
refill_32(s);

tmp = show_val(s, n);
#else
OPEN_READER_NOSIZE(re, s);
av_assert2(n>0 && n<=25);
UPDATE_CACHE(re, s);
tmp = SHOW_UBITS(re, s, n);
#endif
return tmp;
}

static inline void skip_bits(GetBitContext *s, int n)
{
#ifdef CACHED_BITSTREAM_READER
if (n < s->bits_left)
skip_remaining(s, n);
else {
n -= s->bits_left;
s->cache = 0;
s->bits_left = 0;

if (n >= 64) {
unsigned skip = (n / 8) * 8;

n -= skip;
s->index += skip;
}
refill_64(s);
if (n)
skip_remaining(s, n);
}
#else
OPEN_READER(re, s);
LAST_SKIP_BITS(re, s, n);
CLOSE_READER(re, s);
#endif
}

static inline unsigned int get_bits1(GetBitContext *s)
{
#ifdef CACHED_BITSTREAM_READER
if (!s->bits_left)
refill_64(s);

#ifdef BITSTREAM_READER_LE
return get_val(s, 1, 1);
#else
return get_val(s, 1, 0);
#endif
#else
unsigned int index = s->index;
uint8_t result = s->buffer[index >> 3];
#ifdef BITSTREAM_READER_LE
@@ -336,6 +508,7 @@ static inline unsigned int get_bits1(GetBitContext *s)
s->index = index;

return result;
#endif
}

static inline unsigned int show_bits1(GetBitContext *s)
@@ -356,6 +529,10 @@ static inline unsigned int get_bits_long(GetBitContext *s, int n)
av_assert2(n>=0 && n<=32);
if (!n) {
return 0;
#ifdef CACHED_BITSTREAM_READER
}
return get_bits(s, n);
#else
} else if (n <= MIN_CACHE_BITS) {
return get_bits(s, n);
} else {
@@ -367,6 +544,7 @@ static inline unsigned int get_bits_long(GetBitContext *s, int n)
return ret | get_bits(s, n - 16);
#endif
}
#endif
}

/**
@@ -450,6 +628,10 @@ static inline int init_get_bits(GetBitContext *s, const uint8_t *buffer,
s->buffer_end = buffer + buffer_size;
s->index = 0;

#ifdef CACHED_BITSTREAM_READER
refill_64(s);
#endif

return ret;
}

@@ -551,6 +733,19 @@ static inline const uint8_t *align_get_bits(GetBitContext *s)
SKIP_BITS(name, gb, n); \
} while (0)

/* Return the LUT element for the given bitstream configuration. */
static inline int set_idx(GetBitContext *s, int code, int *n, int *nb_bits,
VLC_TYPE (*table)[2])
{
unsigned idx;

*nb_bits = -*n;
idx = show_bits(s, *nb_bits) + code;
*n = table[idx][1];

return table[idx][0];
}

/**
* Parse a vlc code.
* @param bits is the number of bits which will be read at once, must be
@@ -563,6 +758,24 @@ static inline const uint8_t *align_get_bits(GetBitContext *s)
static av_always_inline int get_vlc2(GetBitContext *s, VLC_TYPE (*table)[2],
int bits, int max_depth)
{
#ifdef CACHED_BITSTREAM_READER
int nb_bits;
unsigned idx = show_bits(s, bits);
int code = table[idx][0];
int n = table[idx][1];

if (max_depth > 1 && n < 0) {
skip_remaining(s, bits);
code = set_idx(s, code, &n, &nb_bits, table);
if (max_depth > 2 && n < 0) {
skip_remaining(s, nb_bits);
code = set_idx(s, code, &n, &nb_bits, table);
}
}
skip_remaining(s, n);

return code;
#else
int code;

OPEN_READER(re, s);
@@ -573,6 +786,7 @@ static av_always_inline int get_vlc2(GetBitContext *s, VLC_TYPE (*table)[2],
CLOSE_READER(re, s);

return code;
#endif
}

static inline int decode012(GetBitContext *gb)


+ 151
- 0
libavcodec/golomb.h View File

@@ -54,6 +54,23 @@ static inline int get_ue_golomb(GetBitContext *gb)
{
unsigned int buf;

#ifdef CACHED_BITSTREAM_READER
buf = show_bits_long(gb, 32);

if (buf >= (1 << 27)) {
buf >>= 32 - 9;
skip_bits_long(gb, ff_golomb_vlc_len[buf]);

return ff_ue_golomb_vlc_code[buf];
} else {
int log = 2 * av_log2(buf) - 31;
buf >>= log;
buf--;
skip_bits_long(gb, 32 - log);

return buf;
}
#else
OPEN_READER(re, gb);
UPDATE_CACHE(re, gb);
buf = GET_CACHE(re, gb);
@@ -77,6 +94,7 @@ static inline int get_ue_golomb(GetBitContext *gb)

return buf;
}
#endif
}

/**
@@ -101,6 +119,13 @@ static inline int get_ue_golomb_31(GetBitContext *gb)
{
unsigned int buf;

#ifdef CACHED_BITSTREAM_READER
buf = show_bits_long(gb, 32);

buf >>= 32 - 9;
skip_bits_long(gb, ff_golomb_vlc_len[buf]);
#else

OPEN_READER(re, gb);
UPDATE_CACHE(re, gb);
buf = GET_CACHE(re, gb);
@@ -108,6 +133,7 @@ static inline int get_ue_golomb_31(GetBitContext *gb)
buf >>= 32 - 9;
LAST_SKIP_BITS(re, gb, ff_golomb_vlc_len[buf]);
CLOSE_READER(re, gb);
#endif

return ff_ue_golomb_vlc_code[buf];
}
@@ -116,6 +142,33 @@ static inline unsigned get_interleaved_ue_golomb(GetBitContext *gb)
{
uint32_t buf;

#ifdef CACHED_BITSTREAM_READER
buf = show_bits_long(gb, 32);

if (buf & 0xAA800000) {
buf >>= 32 - 8;
skip_bits_long(gb, ff_interleaved_golomb_vlc_len[buf]);

return ff_interleaved_ue_golomb_vlc_code[buf];
} else {
unsigned ret = 1;

do {
buf >>= 32 - 8;
skip_bits_long(gb, FFMIN(ff_interleaved_golomb_vlc_len[buf], 8));

if (ff_interleaved_golomb_vlc_len[buf] != 9) {
ret <<= (ff_interleaved_golomb_vlc_len[buf] - 1) >> 1;
ret |= ff_interleaved_dirac_golomb_vlc_code[buf];
break;
}
ret = (ret << 4) | ff_interleaved_dirac_golomb_vlc_code[buf];
buf = show_bits_long(gb, 32);
} while (get_bits_left(gb) > 0);

return ret - 1;
}
#else
OPEN_READER(re, gb);
UPDATE_CACHE(re, gb);
buf = GET_CACHE(re, gb);
@@ -147,6 +200,7 @@ static inline unsigned get_interleaved_ue_golomb(GetBitContext *gb)
CLOSE_READER(re, gb);
return ret - 1;
}
#endif
}

/**
@@ -184,6 +238,28 @@ static inline int get_se_golomb(GetBitContext *gb)
{
unsigned int buf;

#ifdef CACHED_BITSTREAM_READER
buf = show_bits_long(gb, 32);

if (buf >= (1 << 27)) {
buf >>= 32 - 9;
skip_bits_long(gb, ff_golomb_vlc_len[buf]);

return ff_se_golomb_vlc_code[buf];
} else {
int log = 2 * av_log2(buf) - 31;
buf >>= log;

skip_bits_long(gb, 32 - log);

if (buf & 1)
buf = -(buf >> 1);
else
buf = (buf >> 1);

return buf;
}
#else
OPEN_READER(re, gb);
UPDATE_CACHE(re, gb);
buf = GET_CACHE(re, gb);
@@ -210,6 +286,7 @@ static inline int get_se_golomb(GetBitContext *gb)

return buf;
}
#endif
}

static inline int get_se_golomb_long(GetBitContext *gb)
@@ -223,6 +300,30 @@ static inline int get_interleaved_se_golomb(GetBitContext *gb)
{
unsigned int buf;

#ifdef CACHED_BITSTREAM_READER
buf = show_bits_long(gb, 32);

if (buf & 0xAA800000) {
buf >>= 32 - 8;
skip_bits_long(gb, ff_interleaved_golomb_vlc_len[buf]);

return ff_interleaved_se_golomb_vlc_code[buf];
} else {
int log;
skip_bits(gb, 8);
buf |= 1 | show_bits_long(gb, 24);

if ((buf & 0xAAAAAAAA) == 0)
return INVALID_VLC;

for (log = 31; (buf & 0x80000000) == 0; log--)
buf = (buf << 2) - ((buf << log) >> (log - 1)) + (buf >> 30);

skip_bits_long(gb, 63 - 2 * log - 8);

return (signed) (((((buf << log) >> log) - 1) ^ -(buf & 0x1)) + 1) >> 1;
}
#else
OPEN_READER(re, gb);
UPDATE_CACHE(re, gb);
buf = GET_CACHE(re, gb);
@@ -250,6 +351,7 @@ static inline int get_interleaved_se_golomb(GetBitContext *gb)

return (signed) (((((buf << log) >> log) - 1) ^ -(buf & 0x1)) + 1) >> 1;
}
#endif
}

static inline int dirac_get_se_golomb(GetBitContext *gb)
@@ -273,6 +375,24 @@ static inline int get_ur_golomb(GetBitContext *gb, int k, int limit,
unsigned int buf;
int log;

#ifdef CACHED_BITSTREAM_READER
buf = show_bits_long(gb, 32);

log = av_log2(buf);

if (log > 31 - limit) {
buf >>= log - k;
buf += (30 - log) << k;
skip_bits_long(gb, 32 + k - log);

return buf;
} else {
skip_bits_long(gb, limit);
buf = get_bits_long(gb, esc_len);

return buf + limit - 1;
}
#else
OPEN_READER(re, gb);
UPDATE_CACHE(re, gb);
buf = GET_CACHE(re, gb);
@@ -297,6 +417,7 @@ static inline int get_ur_golomb(GetBitContext *gb, int k, int limit,

return buf + limit - 1;
}
#endif
}

/**
@@ -308,6 +429,35 @@ static inline int get_ur_golomb_jpegls(GetBitContext *gb, int k, int limit,
unsigned int buf;
int log;

#ifdef CACHED_BITSTREAM_READER
buf = show_bits_long(gb, 32);

log = av_log2(buf);

if (log - k >= 1 && 32 - log < limit) {
buf >>= log - k;
buf += (30 - log) << k;
skip_bits_long(gb, 32 + k - log);

return buf;
} else {
int i;
for (i = 0;
i < limit && get_bits1(gb) == 0 && get_bits_left(gb) > 0;
i++);

if (i < limit - 1) {
buf = get_bits_long(gb, k);

return buf + (i << k);
} else if (i == limit - 1) {
buf = get_bits_long(gb, esc_len);

return buf + 1;
} else
return -1;
}
#else
OPEN_READER(re, gb);
UPDATE_CACHE(re, gb);
buf = GET_CACHE(re, gb);
@@ -364,6 +514,7 @@ static inline int get_ur_golomb_jpegls(GetBitContext *gb, int k, int limit,
CLOSE_READER(re, gb);
return buf;
}
#endif
}

/**


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