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Code Issues Releases Activity

avcodec/mpeg12dec: Put mb_skip_run on the stack

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Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt
2025-06-20 12:09:01 +02:00
parent 9f42725d75
commit d5fa282936
1 changed files with 11 additions and 12 deletions
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23
libavcodec/mpeg12dec.c
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@ -402,7 +402,7 @@ static inline int get_dmv(Mpeg12SliceContext *const s)
#define MT_16X8 2
#define MT_DMV 3
static int mpeg_decode_mb(Mpeg12SliceContext *const s)
static int mpeg_decode_mb(Mpeg12SliceContext *const s, int *mb_skip_run)
{
int i, j, k, cbp, val, mb_type, motion_type;
const int mb_block_count = 4 + (1 << s->c.chroma_format);
@ -412,7 +412,7 @@ static int mpeg_decode_mb(Mpeg12SliceContext *const s)
av_assert2(s->c.mb_skipped == 0);
if (s->c.mb_skip_run-- != 0) {
if ((*mb_skip_run)-- != 0) {
if (s->c.pict_type == AV_PICTURE_TYPE_P) {
s->c.mb_skipped = 1;
s->c.cur_pic.mb_type[s->c.mb_x + s->c.mb_y * s->c.mb_stride] =
@ -1432,7 +1432,6 @@ static int mpeg_decode_slice(Mpeg12SliceContext *const s, int mb_y,
s->c.resync_mb_x = s->c.mb_x;
s->c.resync_mb_y = s->c.mb_y = mb_y;
s->c.mb_skip_run = 0;
ff_init_block_index(&s->c);
if (s->c.mb_y == 0 && s->c.mb_x == 0 && (s->c.first_field || s->c.picture_structure == PICT_FRAME)) {
@ -1456,8 +1455,8 @@ static int mpeg_decode_slice(Mpeg12SliceContext *const s, int mb_y,
}
}
for (;;) {
ret = mpeg_decode_mb(s);
for (int mb_skip_run = 0;;) {
ret = mpeg_decode_mb(s, &mb_skip_run);
if (ret < 0)
return ret;
@ -1552,7 +1551,7 @@ static int mpeg_decode_slice(Mpeg12SliceContext *const s, int mb_y,
!s->c.progressive_sequence &&
left <= 25 &&
left >= 0 &&
s->c.mb_skip_run == -1 &&
mb_skip_run == -1 &&
(!left || show_bits(&s->gb, left) == 0))
goto eos;
@ -1560,9 +1559,9 @@ static int mpeg_decode_slice(Mpeg12SliceContext *const s, int mb_y,
}
/* skip mb handling */
if (s->c.mb_skip_run == -1) {
if (mb_skip_run == -1) {
/* read increment again */
s->c.mb_skip_run = 0;
mb_skip_run = 0;
for (;;) {
int code = get_vlc2(&s->gb, ff_mbincr_vlc,
MBINCR_VLC_BITS, 2);
@ -1572,9 +1571,9 @@ static int mpeg_decode_slice(Mpeg12SliceContext *const s, int mb_y,
}
if (code >= 33) {
if (code == 33) {
s->c.mb_skip_run += 33;
mb_skip_run += 33;
} else if (code == 35) {
if (s->c.mb_skip_run != 0 || show_bits(&s->gb, 15) != 0) {
if (mb_skip_run != 0 || show_bits(&s->gb, 15) != 0) {
av_log(s->c.avctx, AV_LOG_ERROR, "slice mismatch\n");
return AVERROR_INVALIDDATA;
}
@ -1582,11 +1581,11 @@ static int mpeg_decode_slice(Mpeg12SliceContext *const s, int mb_y,
}
/* otherwise, stuffing, nothing to do */
} else {
s->c.mb_skip_run += code;
mb_skip_run += code;
break;
}
}
if (s->c.mb_skip_run) {
if (mb_skip_run) {
int i;
if (s->c.pict_type == AV_PICTURE_TYPE_I) {
av_log(s->c.avctx, AV_LOG_ERROR,