On Fri, Jan 13, 2017 at 02:09:00PM -0800, Brion Vibber wrote: > Patch fixes an issue with broken Ogg Theora videos containing bogus > negative granulepos on some packets: libavformat was reporting huge > positive dts timestamps for these packets, causing downstream problems for > ffmpeg2theora at Wikimedia Commons (near-infinite loop during transcoding). > > Bug report: https://trac.ffmpeg.org/ticket/6080 > Downstream issue: https://phabricator.wikimedia.org/T155247 > > Patch for libavformat attached. Returns AV_NOPTS_VALUE instead of bogus > value for the dts, which downstream ffmpeg2theora can already understand > and handle. > > Thanks! > > -- brion
> oggparsetheora.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > 42fc64f023a47d8faccf2428a2ef13c0b4d5ac26 > 0001-Fix-for-dts-on-Ogg-Theora-packets-with-bad-granulepo.patch > From 8eed58d3f6c2d591e9e179248ff53518270a5363 Mon Sep 17 00:00:00 2001 > From: Brion Vibber <bvib...@wikimedia.org> > Date: Fri, 13 Jan 2017 13:53:38 -0800 > Subject: [PATCH] Fix for dts on Ogg Theora packets with bad granulepos > > At Wikimedia Commons we found some Ogg Theora video files that had > packets with bad granulepos (set to -2). This was causing a reported > dts in the billions of seconds, which triggered further problems > transcoding with downstream ffmpeg2theora such as recording billions > of duplicate frames to pad out the time until the bad dts. > > This patch checks for a bad granulepos in theora, similarly to how > vorbis audio is checked, and returns AV_NOPTS_VALUE for the dts for > affected packets. That fixes ffmpeg2theora's behavior which was based > on the dts reported from ffmpeg/libav. > > Downstream bug at Wikimedia: https://phabricator.wikimedia.org/T155247 > --- > libavformat/oggparsetheora.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/libavformat/oggparsetheora.c b/libavformat/oggparsetheora.c > index b14f9f0669..d0dbe3f2c7 100644 > --- a/libavformat/oggparsetheora.c > +++ b/libavformat/oggparsetheora.c > @@ -153,6 +153,10 @@ static uint64_t theora_gptopts(AVFormatContext *ctx, int > idx, uint64_t gp, > if (!thp) > return AV_NOPTS_VALUE; > > + // Fix for broken files; negative granulepos is invalid. Please add a reference to the spec and section that says this is this documented in some specification about ogg or theora ? I cannot find any definite statment that granulepos is a signed field, just that -1 as in twos compliment is a special value for it. and that its interpretation is left to the codec, but i knew that already. is something declaring the highest bit to be 0 for all frames of all codecs in ogg ? orthogonal to this, timestamps half as large would still cause problems if software has problems with huge timestamps We should reject invalid granulepos, if this is invalid but i think this is not a sufficient fix if the problem is frame duplication from large timestamp differences [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB No snowflake in an avalanche ever feels responsible. -- Voltaire
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