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avcodec/mpeg4videodec: Bail out earlier when parsing

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The scantables are unused for the parser (and in fact
the IDCT permutation used has not been initialized at all).

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt
2025-03-02 23:09:39 +01:00
parent f5f2c37a52
commit c050269eda
1 changed files with 6 additions and 6 deletions
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12
libavcodec/mpeg4videodec.c
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@ -3250,6 +3250,12 @@ static int decode_vop_header(Mpeg4DecContext *ctx, GetBitContext *gb,
} else
s->alternate_scan = 0;
}
/* Skip at this point when only parsing since the remaining
* data is not useful for a parser and requires the
* sprite_trajectory VLC to be initialized. */
if (parse_only)
goto end;
if (s->alternate_scan) {
ff_init_scantable(s->idsp.idct_permutation, &s->intra_scantable, ff_alternate_vertical_scan);
ff_permute_scantable(s->permutated_intra_h_scantable, ff_alternate_vertical_scan,
@ -3262,12 +3268,6 @@ static int decode_vop_header(Mpeg4DecContext *ctx, GetBitContext *gb,
ff_permute_scantable(s->permutated_intra_v_scantable, ff_alternate_vertical_scan,
s->idsp.idct_permutation);
/* Skip at this point when only parsing since the remaining
* data is not useful for a parser and requires the
* sprite_trajectory VLC to be initialized. */
if (parse_only)
goto end;
if (s->pict_type == AV_PICTURE_TYPE_S) {
if((ctx->vol_sprite_usage == STATIC_SPRITE ||
ctx->vol_sprite_usage == GMC_SPRITE)) {