[FFmpeg-devel] [PATCH] Fix swscale-test randomness
Sat Jan 30 13:49:05 CET 2010
On Sat, Jan 30, 2010 at 01:40:29PM +0100, Stefano Sabatini wrote:
> 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
> swscale-test.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
> 5015d3a1a95f9408dc59e6d7a47302c795e7734a fix-swscale-test-randomness.patch
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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