[FFmpeg-devel] [PATCH] Fix swscale-test randomness

Stefano Sabatini stefano.sabatini-lala
Sat Jan 30 13:40:29 CET 2010

On date Friday 2010-01-29 06:16:14 -0200, Ramiro Polla encoded:
> On Fri, Jan 29, 2010 at 2:52 AM, Vitor Sessak <vitor1001 at gmail.com> wrote:
> > Stefano Sabatini wrote:
> >> this is meant to simplify the testing/debuggin work in lsws, and
> >> provide a basis for a future lswstest rule, often it happens that I
> >> need to test/debug only a particular conversion, I was using the scale
> >> lavfi filter for this but it is way easier this way.
> >>
> >> I expected the new result to be different from the old one as the
> >> random source is different,
> >
> > This is easy to work-around, just re-init LFG fo every format pair in the
> > unpatched swscale-test and it should give the same results.
> >
> >> but I noted that the new result is almost
> >> always *worse* than the old one (that is the output obtained with
> >> the old swscale-test), can someone explain?
> >
> > Have you tried running twice with exactly the same binary to see if there is
> > nothing reading uninitialized mem?
> The fast bilinear code reads unitialized memory (it always overreads
> at least one pixel).

This patch makes the swscale-test output constant, with both the
current swscale-test and and my patched

FFmpeg = Fanciful and Frenzy Most Pure Elegant Gigant
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