On Wed, Feb 18, 2015 at 04:09:39PM -0800, Chris Kennedy wrote: > On Wed, Feb 18, 2015 at 2:34 PM, Clément Bœsch <u...@pkh.me> wrote: > > > On Wed, Feb 18, 2015 at 02:22:53PM -0800, Chris Kennedy wrote: > > > This is a pretty obvious bug we caught in the thumbnail filter that is > > very > > > subtle and hardly ever shows issues except for certain videos. Yet it > > can > > > be seen how it is blatantly going out of bounds by basing the width > > > increment off of i*3 that resulted in odd crashes in rare cases. > > > > > > > > > Thanks, > > > Chris > > > -- > > > --- > > > Chris Kennedy > > > Video Engineer > > > CrunchyRoll - http://www.crunchyroll.com > > > > > diff --git a/libavfilter/vf_thumbnail.c b/libavfilter/vf_thumbnail.c > > > index 1883154..a1272a0 100644 > > > --- a/libavfilter/vf_thumbnail.c > > > +++ b/libavfilter/vf_thumbnail.c > > > @@ -142,7 +142,8 @@ static int filter_frame(AVFilterLink *inlink, > > AVFrame *frame) > > > > > > // update current frame RGB histogram > > > for (j = 0; j < inlink->h; j++) { > > > - for (i = 0; i < inlink->w; i++) { > > > + // last third of image, walk every 3 bytes/pixels reading RGB > > > + for (i = 0; i < inlink->w/3; i++) { > > > > width is expressed in pixels, not bytes. > > > > Right, this part seems tricky, yet it doesn't make sense to walk the entire > width with var i and then walk it by 3's up to the very last increment. >
well it's width x 3 components, so I'm not sure I get your problem. > > > > > How to reproduce the issue or crash? > > > > > hist[0*256 + p[i*3 ]]++; > > > hist[1*256 + p[i*3 + 1]]++; > > > hist[2*256 + p[i*3 + 2]]++; > > > > > > > > The source is copyrighted, and it happens on certain types of encodings it > seems, and only 1 out of every 250 or some really low number. I will work > on getting a reproducible case. > valgrind doesn't give you hints? Or you can't get a coredump & backtrace? [...] -- Clément B.
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