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| author | Michael Niedermayer <michael@niedermayer.cc> | 2023-10-22 21:36:11 +0200 |
|---|---|---|
| committer | Michael Niedermayer <michael@niedermayer.cc> | 2023-11-01 16:40:21 +0100 |
| commit | 8516609edde98391017fb145b4f492c01b360a03 (patch) | |
| tree | 0f446555a20abf0186571a8248c1a04e94de176b | |
| parent | 356b1ba765623ec1640a366e587232f1631800f8 (diff) | |
| download | ffmpeg-8516609edde98391017fb145b4f492c01b360a03.tar.gz | |
avcodec/vlc: Replace mysterious max computation code in multi vlc
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
| -rw-r--r-- | libavcodec/vlc.c | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/libavcodec/vlc.c b/libavcodec/vlc.c index f1c638e304..07a4f019a2 100644 --- a/libavcodec/vlc.c +++ b/libavcodec/vlc.c @@ -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++) { |