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avcodec: add multi vlc reader

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Heavily based and inspired by Christophe's cache branches.

Co-Authored-by: Christophe Gisquet
This commit is contained in:
Paul B Mahol 2023-08-27 21:18:46 +02:00
parent 3a5be28857
commit 29b9fca4b3
5 changed files with 231 additions and 0 deletions
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2
libavcodec/bitstream.h
View File

@ -102,6 +102,7 @@
# define bits_decode210 bits_decode210_le
# define bits_apply_sign bits_apply_sign_le
# define bits_read_vlc bits_read_vlc_le
# define bits_read_vlc_multi bits_read_vlc_multi_le
#elif defined(BITS_DEFAULT_BE)
@ -130,6 +131,7 @@
# define bits_decode210 bits_decode210_be
# define bits_apply_sign bits_apply_sign_be
# define bits_read_vlc bits_read_vlc_be
# define bits_read_vlc_multi bits_read_vlc_multi_be
#endif

29
libavcodec/bitstream_template.h
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@ -520,6 +520,35 @@ static inline int BS_FUNC(read_vlc)(BSCTX *bc, const VLCElem *table,
return code;
}
static inline int BS_FUNC(read_vlc_multi)(BSCTX *bc, uint8_t *dst,
const VLC_MULTI_ELEM *const Jtable,
const VLCElem *const table,
const int bits, const int max_depth)
{
unsigned idx = BS_FUNC(peek)(bc, bits);
int ret, nb_bits, code, n = Jtable[idx].len;
if (Jtable[idx].num) {
AV_COPY64U(dst, Jtable[idx].val);
ret = Jtable[idx].num;
} else {
code = table[idx].sym;
n = table[idx].len;
if (max_depth > 1 && n < 0) {
BS_FUNC(priv_skip_remaining)(bc, bits);
code = BS_FUNC(priv_set_idx)(bc, code, &n, &nb_bits, table);
if (max_depth > 2 && n < 0) {
BS_FUNC(priv_skip_remaining)(bc, nb_bits);
code = BS_FUNC(priv_set_idx)(bc, code, &n, &nb_bits, table);
}
}
AV_WN16(dst, code);
ret = n > 0;
}
BS_FUNC(priv_skip_remaining)(bc, n);
return ret;
}
#undef BSCTX
#undef BS_FUNC
#undef BS_JOIN3

10
libavcodec/get_bits.h
View File

@ -93,6 +93,7 @@ typedef BitstreamContext GetBitContext;
#define init_get_bits8 bits_init8
#define align_get_bits bits_align
#define get_vlc2 bits_read_vlc
#define get_vlc_multi bits_read_vlc_multi
#define init_get_bits8_le(s, buffer, byte_size) bits_init8_le((BitstreamContextLE*)s, buffer, byte_size)
#define get_bits_le(s, n) bits_read_le((BitstreamContextLE*)s, n)
@ -643,6 +644,15 @@ static av_always_inline int get_vlc2(GetBitContext *s, const VLCElem *table,
return code;
}
static inline int get_vlc_multi(GetBitContext *s, uint8_t *dst,
const VLC_MULTI_ELEM *const Jtable,
const VLCElem *const table,
const int bits, const int max_depth)
{
dst[0] = get_vlc2(s, table, bits, max_depth);
return 1;
}
static inline int decode012(GetBitContext *gb)
{
int n;

137
libavcodec/vlc.c
View File

@ -30,6 +30,7 @@
#include "libavutil/avassert.h"
#include "libavutil/error.h"
#include "libavutil/internal.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/log.h"
#include "libavutil/macros.h"
#include "libavutil/mem.h"
@ -372,6 +373,142 @@ fail:
return AVERROR_INVALIDDATA;
}
static void add_level(VLC_MULTI_ELEM *table, const int nb_elems,
const int num, const int numbits,
const VLCcode *buf,
uint32_t curcode, int curlen,
int curlimit, int curlevel,
const int minlen, const int max,
unsigned* levelcnt, VLC_MULTI_ELEM *info)
{
if (nb_elems > 256 && curlevel > 2)
return; // No room
for (int i = num-1; i > max; i--) {
for (int j = 0; j < 2; j++) {
int newlimit, sym;
int t = j ? i-1 : i;
int l = buf[t].bits;
uint32_t code;
sym = buf[t].symbol;
if (l > curlimit)
return;
code = curcode + (buf[t].code >> curlen);
newlimit = curlimit - l;
l += curlen;
if (nb_elems>256) AV_WN16(info->val+2*curlevel, sym);
else info->val[curlevel] = sym&0xFF;
if (curlevel) { // let's not add single entries
uint32_t val = code >> (32 - numbits);
uint32_t nb = val + (1U << (numbits - l));
info->len = l;
info->num = curlevel+1;
for (; val < nb; val++)
AV_COPY64(table+val, info);
levelcnt[curlevel-1]++;
}
if (curlevel+1 < VLC_MULTI_MAX_SYMBOLS && newlimit >= minlen) {
add_level(table, nb_elems, num, numbits, buf,
code, l, newlimit, curlevel+1,
minlen, max, levelcnt, info);
}
}
}
}
static int vlc_multi_gen(VLC_MULTI_ELEM *table, const VLC *single,
const int nb_elems, const int nb_codes, const int numbits,
VLCcode *buf, void *logctx)
{
int minbits, maxbits, max = nb_codes-1;
unsigned count[VLC_MULTI_MAX_SYMBOLS-1] = { 0, };
VLC_MULTI_ELEM info = { { 0, }, 0, };
minbits = buf[nb_codes-1].bits;
maxbits = FFMIN(buf[0].bits, numbits);
while (max >= nb_codes/2) {
if (buf[max].bits+minbits > maxbits)
break;
max--;
}
for (int j = 0; j < 1<<numbits; j++) {
table[j].len = single->table[j].len;
table[j].num = single->table[j].len > 0 ? 1 : 0;
AV_WN16(table[j].val, single->table[j].sym);
}
add_level(table, nb_elems, nb_codes, numbits, buf,
0, 0, numbits, 0, minbits, max, count, &info);
av_log(NULL, AV_LOG_DEBUG, "Joint: %d/%d/%d/%d/%d codes min=%ubits max=%u\n",
count[0], count[1], count[2], count[3], count[4], minbits, max);
return 0;
}
int ff_init_vlc_multi_from_lengths(VLC *vlc, VLC_MULTI *multi, int nb_bits, int nb_elems,
int nb_codes, const int8_t *lens, int lens_wrap,
const void *symbols, int symbols_wrap, int symbols_size,
int offset, int flags, void *logctx)
{
VLCcode localbuf[LOCALBUF_ELEMS], *buf = localbuf;
uint64_t code;
int ret, j, len_max = FFMIN(32, 3 * nb_bits);
ret = vlc_common_init(vlc, nb_bits, nb_codes, &buf, flags);
if (ret < 0)
return ret;
multi->table = av_malloc(sizeof(*multi->table) << nb_bits);
if (!multi->table)
return AVERROR(ENOMEM);
j = code = 0;
for (int i = 0; i < nb_codes; i++, lens += lens_wrap) {
int len = *lens;
if (len > 0) {
unsigned sym;
buf[j].bits = len;
if (symbols)
GET_DATA(sym, symbols, i, symbols_wrap, symbols_size)
else
sym = i;
buf[j].symbol = sym + offset;
buf[j++].code = code;
} else if (len < 0) {
len = -len;
} else
continue;
if (len > len_max || code & ((1U << (32 - len)) - 1)) {
av_log(logctx, AV_LOG_ERROR, "Invalid VLC (length %u)\n", len);
goto fail;
}
code += 1U << (32 - len);
if (code > UINT32_MAX + 1ULL) {
av_log(logctx, AV_LOG_ERROR, "Overdetermined VLC tree\n");
goto fail;
}
}
ret = vlc_common_end(vlc, nb_bits, j, buf, flags, localbuf);
if (ret < 0)
goto fail;
return vlc_multi_gen(multi->table, vlc, nb_elems, j, nb_bits, buf, logctx);
fail:
if (buf != localbuf)
av_free(buf);
return AVERROR_INVALIDDATA;
}
void ff_free_vlc_multi(VLC_MULTI *vlc)
{
av_freep(&vlc->table);
}
void ff_free_vlc(VLC *vlc)
{
av_freep(&vlc->table);

53
libavcodec/vlc.h
View File

@ -21,6 +21,8 @@
#include <stdint.h>
#define VLC_MULTI_MAX_SYMBOLS 6
// When changing this, be sure to also update tableprint_vlc.h accordingly.
typedef int16_t VLCBaseType;
@ -34,6 +36,17 @@ typedef struct VLC {
int table_size, table_allocated;
} VLC;
typedef struct VLC_MULTI_ELEM {
uint8_t val[VLC_MULTI_MAX_SYMBOLS];
int8_t len; // -31,32
uint8_t num;
} VLC_MULTI_ELEM;
typedef struct VLC_MULTI {
VLC_MULTI_ELEM *table;
int table_size, table_allocated;
} VLC_MULTI;
typedef struct RL_VLC_ELEM {
int16_t level;
int8_t len;
@ -89,6 +102,46 @@ int ff_init_vlc_from_lengths(VLC *vlc, int nb_bits, int nb_codes,
const void *symbols, int symbols_wrap, int symbols_size,
int offset, int flags, void *logctx);
/**
* Build VLC decoding tables suitable for use with get_vlc_multi()
*
* This function takes lengths and symbols and calculates the codes from them.
* For this the input lengths and symbols have to be sorted according to "left
* nodes in the corresponding tree first".
*
* @param[in,out] vlc The VLC to be initialized; table and table_allocated
* must have been set when initializing a static VLC,
* otherwise this will be treated as uninitialized.
* @param[in,out] multi The VLC_MULTI to be initialized; table and table_allocated
* must have been set when initializing a static VLC,
* otherwise this will be treated as uninitialized.
* @param[in] nb_bits The number of bits to use for the VLC table;
* higher values take up more memory and cache, but
* allow to read codes with fewer reads.
* @param[in] nb_elems The max possible number of elements.
* @param[in] nb_codes The number of provided length and (if supplied) symbol
* entries.
* @param[in] lens The lengths of the codes. Entries > 0 correspond to
* valid codes; entries == 0 will be skipped and entries
* with len < 0 indicate that the tree is incomplete and
* has an open end of length -len at this position.
* @param[in] lens_wrap Stride (in bytes) of the lengths.
* @param[in] symbols The symbols, i.e. what is returned from get_vlc2()
* when the corresponding code is encountered.
* May be NULL, then 0, 1, 2, 3, 4,... will be used.
* @param[in] symbols_wrap Stride (in bytes) of the symbols.
* @param[in] symbols_size Size of the symbols. 1 and 2 are supported.
* @param[in] offset An offset to apply to all the valid symbols.
* @param[in] flags A combination of the INIT_VLC_* flags; notice that
* INIT_VLC_INPUT_LE is pointless and ignored.
*/
int ff_init_vlc_multi_from_lengths(VLC *vlc, VLC_MULTI *multi, int nb_bits, int nb_elems,
int nb_codes, const int8_t *lens, int lens_wrap,
const void *symbols, int symbols_wrap, int symbols_size,
int offset, int flags, void *logctx);
void ff_free_vlc_multi(VLC_MULTI *vlc);
void ff_free_vlc(VLC *vlc);
/* If INIT_VLC_INPUT_LE is set, the LSB bit of the codes used to