[FFmpeg-cvslog] avcodec/get_bits: add cached bitstream reader
Paul B Mahol
git at videolan.org
Thu Aug 30 13:05:18 EEST 2018
ffmpeg | branch: master | Paul B Mahol <onemda at gmail.com> | Fri Jul 7 16:56:10 2017 +0200| [ca079b0954997affe4df8cf3120197875f75f3d7] | committer: Paul B Mahol
avcodec/get_bits: add cached bitstream reader
Signed-off-by: Paul B Mahol <onemda at gmail.com>
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=ca079b0954997affe4df8cf3120197875f75f3d7
---
libavcodec/get_bits.h | 218 +++++++++++++++++++++++++++++++++++++++++++++++++-
libavcodec/golomb.h | 151 ++++++++++++++++++++++++++++++++++
2 files changed, 367 insertions(+), 2 deletions(-)
diff --git a/libavcodec/get_bits.h b/libavcodec/get_bits.h
index 56ef5f0cbe..58ebb64656 100644
--- a/libavcodec/get_bits.h
+++ b/libavcodec/get_bits.h
@@ -1,5 +1,6 @@
/*
- * copyright (c) 2004 Michael Niedermayer <michaelni at gmx.at>
+ * Copyright (c) 2004 Michael Niedermayer <michaelni at 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)
diff --git a/libavcodec/golomb.h b/libavcodec/golomb.h
index efb1eff8aa..e66675b292 100644
--- a/libavcodec/golomb.h
+++ b/libavcodec/golomb.h
@@ -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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