Hi On Sun, Oct 22, 2023 at 07:35:52PM +0100, Mark Thompson wrote: > The spec allows at least thirty-two zero bits followed by a one to mean > 2^32-1, with no constraint on the number of zeroes. The libaom > reference decoder does not match this, instead reading thirty-two zeroes > but not the following one to mean 2^32-1. These two interpretations are > incompatible and other implementations may follow one or the other. > Therefore reject thirty-two zeroes because the intended behaviour is not > clear. > --- > libaom, dav1d and SVT-AV1 all have the same nonstandard behaviour of stopping > at thirty-two zeroes and not reading the one. gav1 just rejects thirty-two > zeroes. > > This is also a source of arbitrarily large single syntax elements to hit > <https://lists.ffmpeg.org/pipermail/ffmpeg-devel/2023-October/315973.html>. > > libavcodec/cbs_av1.c | 18 +++++++++++++----- > 1 file changed, 13 insertions(+), 5 deletions(-) > > diff --git a/libavcodec/cbs_av1.c b/libavcodec/cbs_av1.c > index 1d9ac5ab44..13c749a25b 100644 > --- a/libavcodec/cbs_av1.c > +++ b/libavcodec/cbs_av1.c > @@ -36,7 +36,7 @@ static int cbs_av1_read_uvlc(CodedBitstreamContext *ctx, > GetBitContext *gbc, > CBS_TRACE_READ_START(); > > zeroes = 0; > - while (1) { > + while (zeroes < 32) {
what happened with this patch ? the git master code still aborts thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB The worst form of inequality is to try to make unequal things equal. -- Aristotle
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