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avcodec/mpeg4videodec: Avoid superfluous VLC structures 

For all VLCs here, the number of bits of the VLC is
write-only, because it is hardcoded at the call site.
Therefore one can replace these VLC structures with
the only thing that is actually used: The pointer
to the VLCElem table. And in some cases one can even
avoid this.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt 2023-09-24 18:35:22 +02:00
parent 8c39b2bca7
commit 5a694d62c5
1 changed files with 45 additions and 48 deletions
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93
libavcodec/mpeg4videodec.c
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@ -58,12 +58,12 @@
#define MB_TYPE_B_VLC_BITS 4
#define STUDIO_INTRA_BITS 9
static VLC dc_lum, dc_chrom;
static VLC sprite_trajectory;
static VLC mb_type_b_vlc;
static VLC studio_intra_tab[12];
static VLC studio_luma_dc;
static VLC studio_chroma_dc;
static VLCElem dc_lum[512], dc_chrom[512];
static VLCElem sprite_trajectory[128];
static VLCElem mb_type_b_vlc[16];
static const VLCElem *studio_intra_tab[12];
static VLCElem studio_luma_dc[528];
static VLCElem studio_chroma_dc[528];
static const uint8_t mpeg4_block_count[4] = { 0, 6, 8, 12 };
@ -449,14 +449,14 @@ static int mpeg4_decode_sprite_trajectory(Mpeg4DecContext *ctx, GetBitContext *g
int length;
int x = 0, y = 0;
length = get_vlc2(gb, sprite_trajectory.table, SPRITE_TRAJ_VLC_BITS, 2);
length = get_vlc2(gb, sprite_trajectory, SPRITE_TRAJ_VLC_BITS, 2);
if (length > 0)
x = get_xbits(gb, length);
if (!(ctx->divx_version == 500 && ctx->divx_build == 413))
check_marker(s->avctx, gb, "before sprite_trajectory");
length = get_vlc2(gb, sprite_trajectory.table, SPRITE_TRAJ_VLC_BITS, 2);
length = get_vlc2(gb, sprite_trajectory, SPRITE_TRAJ_VLC_BITS, 2);
if (length > 0)
y = get_xbits(gb, length);
@ -891,9 +891,9 @@ static inline int mpeg4_decode_dc(MpegEncContext *s, int n, int *dir_ptr)
int level, code;
if (n < 4)
code = get_vlc2(&s->gb, dc_lum.table, DC_VLC_BITS, 1);
code = get_vlc2(&s->gb, dc_lum, DC_VLC_BITS, 1);
else
code = get_vlc2(&s->gb, dc_chrom.table, DC_VLC_BITS, 1);
code = get_vlc2(&s->gb, dc_chrom, DC_VLC_BITS, 1);
if (code < 0 || code > 9 /* && s->nbit < 9 */) {
av_log(s->avctx, AV_LOG_ERROR, "illegal dc vlc\n");
@ -1840,7 +1840,7 @@ static int mpeg4_decode_mb(MpegEncContext *s, int16_t block[6][64])
cbp = 0;
} else {
modb2 = get_bits1(&s->gb);
mb_type = get_vlc2(&s->gb, mb_type_b_vlc.table, MB_TYPE_B_VLC_BITS, 1);
mb_type = get_vlc2(&s->gb, mb_type_b_vlc, MB_TYPE_B_VLC_BITS, 1);
if (mb_type < 0) {
av_log(s->avctx, AV_LOG_ERROR, "illegal MB_type\n");
return AVERROR_INVALIDDATA;
@ -2072,7 +2072,7 @@ static int mpeg4_decode_studio_block(MpegEncContext *s, int32_t block[64], int n
int cc, dct_dc_size, dct_diff, code, j, idx = 1, group = 0, run = 0,
additional_code_len, sign, mismatch;
const VLC *cur_vlc = &studio_intra_tab[0];
const VLCElem *cur_vlc = studio_intra_tab[0];
uint8_t *const scantable = s->intra_scantable.permutated;
const uint16_t *quant_matrix;
uint32_t flc;
@ -2086,14 +2086,14 @@ static int mpeg4_decode_studio_block(MpegEncContext *s, int32_t block[64], int n
if (n < 4) {
cc = 0;
dct_dc_size = get_vlc2(&s->gb, studio_luma_dc.table, STUDIO_INTRA_BITS, 2);
dct_dc_size = get_vlc2(&s->gb, studio_luma_dc, STUDIO_INTRA_BITS, 2);
quant_matrix = s->intra_matrix;
} else {
cc = (n & 1) + 1;
if (ctx->rgb)
dct_dc_size = get_vlc2(&s->gb, studio_luma_dc.table, STUDIO_INTRA_BITS, 2);
dct_dc_size = get_vlc2(&s->gb, studio_luma_dc, STUDIO_INTRA_BITS, 2);
else
dct_dc_size = get_vlc2(&s->gb, studio_chroma_dc.table, STUDIO_INTRA_BITS, 2);
dct_dc_size = get_vlc2(&s->gb, studio_chroma_dc, STUDIO_INTRA_BITS, 2);
quant_matrix = s->chroma_intra_matrix;
}
@ -2122,7 +2122,7 @@ static int mpeg4_decode_studio_block(MpegEncContext *s, int32_t block[64], int n
/* AC Coefficients */
while (1) {
group = get_vlc2(&s->gb, cur_vlc->table, STUDIO_INTRA_BITS, 2);
group = get_vlc2(&s->gb, cur_vlc, STUDIO_INTRA_BITS, 2);
if (group < 0) {
av_log(s->avctx, AV_LOG_ERROR, "illegal ac coefficient group vlc\n");
@ -2130,7 +2130,7 @@ static int mpeg4_decode_studio_block(MpegEncContext *s, int32_t block[64], int n
}
additional_code_len = ac_state_tab[group][0];
cur_vlc = &studio_intra_tab[ac_state_tab[group][1]];
cur_vlc = studio_intra_tab[ac_state_tab[group][1]];
if (group == 0) {
/* End of Block */
@ -3758,28 +3758,25 @@ static int mpeg4_update_thread_context_for_user(AVCodecContext *dst,
static av_cold void mpeg4_init_static(void)
{
static uint8_t mpeg4_rvlc_rl_tables[2][2][2 * MAX_RUN + MAX_LEVEL + 3];
static VLCElem vlc_buf[6498];
VLCInitState state = VLC_INIT_STATE(vlc_buf);
VLC_INIT_STATIC_FROM_LENGTHS(&studio_luma_dc, STUDIO_INTRA_BITS, 19,
&ff_mpeg4_studio_dc_luma[0][1], 2,
&ff_mpeg4_studio_dc_luma[0][0], 2, 1,
0, 0, 528);
VLC_INIT_STATIC_TABLE_FROM_LENGTHS(studio_luma_dc, STUDIO_INTRA_BITS, 19,
&ff_mpeg4_studio_dc_luma[0][1], 2,
&ff_mpeg4_studio_dc_luma[0][0], 2, 1,
0, 0);
VLC_INIT_STATIC_FROM_LENGTHS(&studio_chroma_dc, STUDIO_INTRA_BITS, 19,
&ff_mpeg4_studio_dc_chroma[0][1], 2,
&ff_mpeg4_studio_dc_chroma[0][0], 2, 1,
0, 0, 528);
VLC_INIT_STATIC_TABLE_FROM_LENGTHS(studio_chroma_dc, STUDIO_INTRA_BITS, 19,
&ff_mpeg4_studio_dc_chroma[0][1], 2,
&ff_mpeg4_studio_dc_chroma[0][0], 2, 1,
0, 0);
for (unsigned i = 0, offset = 0; i < 12; i++) {
static VLCElem vlc_buf[6498];
studio_intra_tab[i].table = &vlc_buf[offset];
studio_intra_tab[i].table_allocated = FF_ARRAY_ELEMS(vlc_buf) - offset;
ff_vlc_init_from_lengths(&studio_intra_tab[i],
STUDIO_INTRA_BITS, 24,
&ff_mpeg4_studio_intra[i][0][1], 2,
&ff_mpeg4_studio_intra[i][0][0], 2, 1,
0, VLC_INIT_STATIC_OVERLONG, NULL);
offset += studio_intra_tab[i].table_size;
for (unsigned i = 0; i < 12; i++) {
studio_intra_tab[i] =
ff_vlc_init_tables_from_lengths(&state, STUDIO_INTRA_BITS, 24,
&ff_mpeg4_studio_intra[i][0][1], 2,
&ff_mpeg4_studio_intra[i][0][0], 2, 1,
0, 0);
}
ff_mpeg4_init_rl_intra();
@ -3788,18 +3785,18 @@ static av_cold void mpeg4_init_static(void)
INIT_FIRST_VLC_RL(ff_mpeg4_rl_intra, 554);
VLC_INIT_RL(ff_rvlc_rl_inter, 1072);
INIT_FIRST_VLC_RL(ff_rvlc_rl_intra, 1072);
VLC_INIT_STATIC(&dc_lum, DC_VLC_BITS, 10 /* 13 */,
&ff_mpeg4_DCtab_lum[0][1], 2, 1,
&ff_mpeg4_DCtab_lum[0][0], 2, 1, 512);
VLC_INIT_STATIC(&dc_chrom, DC_VLC_BITS, 10 /* 13 */,
&ff_mpeg4_DCtab_chrom[0][1], 2, 1,
&ff_mpeg4_DCtab_chrom[0][0], 2, 1, 512);
VLC_INIT_STATIC_FROM_LENGTHS(&sprite_trajectory, SPRITE_TRAJ_VLC_BITS, 15,
ff_sprite_trajectory_lens, 1,
NULL, 0, 0, 0, 0, 128);
VLC_INIT_STATIC(&mb_type_b_vlc, MB_TYPE_B_VLC_BITS, 4,
&ff_mb_type_b_tab[0][1], 2, 1,
&ff_mb_type_b_tab[0][0], 2, 1, 16);
VLC_INIT_STATIC_TABLE(dc_lum, DC_VLC_BITS, 10 /* 13 */,
&ff_mpeg4_DCtab_lum[0][1], 2, 1,
&ff_mpeg4_DCtab_lum[0][0], 2, 1, 0);
VLC_INIT_STATIC_TABLE(dc_chrom, DC_VLC_BITS, 10 /* 13 */,
&ff_mpeg4_DCtab_chrom[0][1], 2, 1,
&ff_mpeg4_DCtab_chrom[0][0], 2, 1, 0);
VLC_INIT_STATIC_TABLE_FROM_LENGTHS(sprite_trajectory, SPRITE_TRAJ_VLC_BITS, 15,
ff_sprite_trajectory_lens, 1,
NULL, 0, 0, 0, 0);
VLC_INIT_STATIC_TABLE(mb_type_b_vlc, MB_TYPE_B_VLC_BITS, 4,
&ff_mb_type_b_tab[0][1], 2, 1,
&ff_mb_type_b_tab[0][0], 2, 1, 0);
}
static av_cold int decode_init(AVCodecContext *avctx)