On Tue, Dec 26, 2023 at 12:50:42AM +0100, Michael Niedermayer wrote: > 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
timeout (many times in fact) will apply thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Dictatorship naturally arises out of democracy, and the most aggravated form of tyranny and slavery out of the most extreme liberty. -- Plato
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