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avcodec/vlc: Skip subtable entries in multi VLC 

These entries do not correspond to VLC symbols that can be used
they do corrupt various variables like min/max bits

This also no longer assumes that there is a single non subtable
entry
Probably fixes some infinite loops too

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2023-10-22 21:20:25 +02:00
parent c2f2bf82c1
commit 356b1ba765
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GPG Key ID: B18E8928B3948D64
1 changed files with 12 additions and 4 deletions
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16
libavcodec/vlc.c
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@ -469,15 +469,23 @@ static int vlc_multi_gen(VLC_MULTI_ELEM *table, const VLC *single,
int minbits, maxbits, max = nb_codes-1;
unsigned count[VLC_MULTI_MAX_SYMBOLS-1] = { 0, };
VLC_MULTI_ELEM info = { { 0, }, 0, 0, };
int count0 = 0;
minbits = buf[0].bits;
maxbits = buf[0].bits;
for (int j = 0; j < 1<<numbits; j++) {
if (single->table[j].len > 0) {
count0 ++;
j += (1 << (numbits - single->table[j].len)) - 1;
}
}
for (int n = 1; n < nb_codes; n++) {
minbits = 32;
maxbits = 0;
for (int n = nb_codes - count0; n < nb_codes; n++) {
minbits = FFMIN(minbits, buf[n].bits);
maxbits = FFMAX(maxbits, buf[n].bits);
}
maxbits = FFMIN(maxbits, numbits);
av_assert0(maxbits <= numbits);
while (max >= nb_codes/2) {
if (buf[max].bits+minbits > maxbits)