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avcodec/vlc: Replace mysterious max computation code in multi vlc

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Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Michael Niedermayer 2023-10-22 21:36:11 +02:00
parent 356b1ba765
commit 8516609edd
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GPG Key ID: B18E8928B3948D64
1 changed files with 8 additions and 5 deletions
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13
libavcodec/vlc.c
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@ -427,7 +427,7 @@ static void add_level(VLC_MULTI_ELEM *table, const int is16bit,
unsigned* levelcnt, VLC_MULTI_ELEM *info)
{
int max_symbols = VLC_MULTI_MAX_SYMBOLS >> is16bit;
for (int i = num-1; i > max; i--) {
for (int i = num-1; i >= max; i--) {
for (int j = 0; j < 2; j++) {
int newlimit, sym;
int t = j ? i-1 : i;
@ -466,7 +466,7 @@ static int vlc_multi_gen(VLC_MULTI_ELEM *table, const VLC *single,
const int is16bit, const int nb_codes, const int numbits,
VLCcode *buf, void *logctx)
{
int minbits, maxbits, max = nb_codes-1;
int minbits, maxbits, max;
unsigned count[VLC_MULTI_MAX_SYMBOLS-1] = { 0, };
VLC_MULTI_ELEM info = { { 0, }, 0, 0, };
int count0 = 0;
@ -487,10 +487,13 @@ static int vlc_multi_gen(VLC_MULTI_ELEM *table, const VLC *single,
}
av_assert0(maxbits <= numbits);
while (max >= nb_codes/2) {
if (buf[max].bits+minbits > maxbits)
for (max = nb_codes; max > nb_codes - count0; max--) {
// We can only add a code that fits with the shortest other code into the table
// We assume the table is sorted by bits and we skip subtables which from our
// point of view are basically random corrupted entries
// If we have not a single useable vlc we end with max = nb_codes
if (buf[max - 1].bits+minbits > numbits)
break;
max--;
}
for (int j = 0; j < 1<<numbits; j++) {