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Code Issues Releases Activity

avcodec/vlc: Merge VLCElem and RL_VLC_ELEM

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It will simplify creating RL-VLCs (which until now used
a stack-based VLC as temporary buffer).

Notice that there would be another option to merge them, namely:
struct VLCElem {
    union {
        VLCBaseType sym;
        int16_t level;
    };
    int8_t len;
    uint8_t run;
};

The main difference to the current patch is that this would change
the type of the length field of VLCElem to int8_t from int16_t.
It turns out that that this would entail additional sign extensions
on ppc, see https://godbolt.org/z/behWYEYE7. I have therefore refrained
from doing so, although it would make the patch simpler.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt
2025-03-07 16:12:42 +01:00
parent 54d582e749
commit 0facdafd1e
7 changed files with 32 additions and 24 deletions
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2
libavcodec/cfhd.h
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@ -98,7 +98,7 @@ enum CFHDParam {
typedef struct CFHD_RL_VLC_ELEM {
int16_t level;
int8_t len;
int8_t len8;
uint16_t run;
} CFHD_RL_VLC_ELEM;

10
libavcodec/cfhddata.c
View File

@ -136,22 +136,22 @@ static av_cold int cfhd_init_vlc(CFHD_RL_VLC_ELEM out[], unsigned out_size,
/** Similar to dv.c, generate signed VLC tables **/
for (unsigned i = j = 0; i < table_size; i++, j++) {
tmp[j].len = table_vlc[i].len;
tmp[j].len8 = table_vlc[i].len;
tmp[j].run = table_vlc[i].run;
tmp[j].level = table_vlc[i].level;
/* Don't include the zero level nor escape bits */
if (table_vlc[i].level && table_vlc[i].run) {
tmp[j].len++;
tmp[j].len8++;
j++;
tmp[j].len = table_vlc[i].len + 1;
tmp[j].len8 = table_vlc[i].len + 1;
tmp[j].run = table_vlc[i].run;
tmp[j].level = -table_vlc[i].level;
}
}
ret = ff_vlc_init_from_lengths(&vlc, VLC_BITS, j,
&tmp[0].len, sizeof(tmp[0]),
&tmp[0].len8, sizeof(tmp[0]),
NULL, 0, 0, 0, 0, logctx);
if (ret < 0)
return ret;
@ -169,7 +169,7 @@ static av_cold int cfhd_init_vlc(CFHD_RL_VLC_ELEM out[], unsigned out_size,
run = tmp[code].run;
level = tmp[code].level;
}
out[i].len = len;
out[i].len8 = len;
out[i].level = level;
out[i].run = run;
}

12
libavcodec/dvdec.c
View File

@ -159,15 +159,15 @@ static av_cold void dv_init_static(void)
/* it's faster to include sign bit in a generic VLC parsing scheme */
for (i = 0, j = 0; i < NB_DV_VLC; i++, j++) {
tmp[j].len = ff_dv_vlc_len[i];
tmp[j].len8 = ff_dv_vlc_len[i];
tmp[j].run = ff_dv_vlc_run[i];
tmp[j].level = ff_dv_vlc_level[i];
if (ff_dv_vlc_level[i]) {
tmp[j].len++;
tmp[j].len8++;
j++;
tmp[j].len = ff_dv_vlc_len[i] + 1;
tmp[j].len8 = ff_dv_vlc_len[i] + 1;
tmp[j].run = ff_dv_vlc_run[i];
tmp[j].level = -ff_dv_vlc_level[i];
}
@ -176,7 +176,7 @@ static av_cold void dv_init_static(void)
/* NOTE: as a trick, we use the fact the no codes are unused
* to accelerate the parsing of partial codes */
ff_vlc_init_from_lengths(&dv_vlc, TEX_VLC_BITS, j,
&tmp[0].len, sizeof(tmp[0]),
&tmp[0].len8, sizeof(tmp[0]),
NULL, 0, 0, 0, VLC_INIT_USE_STATIC, NULL);
av_assert1(dv_vlc.table_size == 1664);
@ -193,7 +193,7 @@ static av_cold void dv_init_static(void)
run = tmp[code].run + 1;
level = tmp[code].level;
}
dv_rl_vlc[i].len = len;
dv_rl_vlc[i].len8 = len;
dv_rl_vlc[i].level = level;
dv_rl_vlc[i].run = run;
}
@ -301,7 +301,7 @@ static void dv_decode_ac(GetBitContext *gb, BlockInfo *mb, int16_t *block)
pos, SHOW_UBITS(re, gb, 16), re_index);
/* our own optimized GET_RL_VLC */
index = NEG_USR32(re_cache, TEX_VLC_BITS);
vlc_len = dv_rl_vlc[index].len;
vlc_len = dv_rl_vlc[index].len8;
if (vlc_len < 0) {
index = NEG_USR32((unsigned) re_cache << TEX_VLC_BITS, -vlc_len) +
dv_rl_vlc[index].level;

6
libavcodec/get_bits.h
View File

@ -594,7 +594,7 @@ static inline const uint8_t *align_get_bits(GetBitContext *s)
\
index = SHOW_UBITS(name, gb, bits); \
level = table[index].level; \
n = table[index].len; \
n = table[index].len8; \
\
if (max_depth > 1 && n < 0) { \
SKIP_BITS(name, gb, bits); \
@ -606,7 +606,7 @@ static inline const uint8_t *align_get_bits(GetBitContext *s)
\
index = SHOW_UBITS(name, gb, nb_bits) + level; \
level = table[index].level; \
n = table[index].len; \
n = table[index].len8; \
if (max_depth > 2 && n < 0) { \
LAST_SKIP_BITS(name, gb, nb_bits); \
if (need_update) { \
@ -616,7 +616,7 @@ static inline const uint8_t *align_get_bits(GetBitContext *s)
\
index = SHOW_UBITS(name, gb, nb_bits) + level; \
level = table[index].level; \
n = table[index].len; \
n = table[index].len8; \
} \
} \
run = table[index].run; \

2
libavcodec/mpeg12.c
View File

@ -119,7 +119,7 @@ av_cold void ff_init_2d_vlc_rl(const uint16_t table_vlc[][2], RL_VLC_ELEM rl_vlc
level = table_level[code];
}
}
rl_vlc[i].len = len;
rl_vlc[i].len8 = len;
rl_vlc[i].level = level;
rl_vlc[i].run = run;
}

2
libavcodec/rl.c
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@ -118,7 +118,7 @@ av_cold void ff_rl_init_vlc(RLTable *rl, unsigned static_size)
if (code >= rl->last) run += 192;
}
}
rl->rl_vlc[q][i].len = len;
rl->rl_vlc[q][i].len8 = len;
rl->rl_vlc[q][i].level = level;
rl->rl_vlc[q][i].run = run;
}

22
libavcodec/vlc.h
View File

@ -30,9 +30,23 @@
typedef int16_t VLCBaseType;
typedef struct VLCElem {
VLCBaseType sym, len;
union {
/// The struct is for use as ordinary VLC (with get_vlc2())
struct {
VLCBaseType sym;
VLCBaseType len;
};
/// This struct is for use as run-length VLC (with GET_RL_VLC)
struct {
int16_t level;
int8_t len8;
uint8_t run;
};
};
} VLCElem;
typedef VLCElem RL_VLC_ELEM;
typedef struct VLC {
int bits;
VLCElem *table;
@ -53,12 +67,6 @@ typedef struct VLC_MULTI {
int table_size, table_allocated;
} VLC_MULTI;
typedef struct RL_VLC_ELEM {
int16_t level;
int8_t len;
uint8_t run;
} RL_VLC_ELEM;
#define vlc_init(vlc, nb_bits, nb_codes, \
bits, bits_wrap, bits_size, \
codes, codes_wrap, codes_size, \