[FFmpeg-devel] [PATCH] fate/pixfmt: disable dithering in the scale filter

[Michael Niedermayer]

On Sat, Nov 09, 2024 at 11:05:32AM -0300, James Almer wrote:
> On 11/8/2024 9:03 PM, Michael Niedermayer wrote:
> > On Fri, Nov 08, 2024 at 04:56:38PM -0300, James Almer wrote:
> > > On 11/8/2024 5:15 AM, Martin Storsjö wrote:
> > > > On Thu, 7 Nov 2024, James Almer wrote:
> > > > 
> > > > > Should fix fate failures across different systems.
> > > > > 
> > > > > Signed-off-by: James Almer <jamrial at gmail.com>
> > > > > ---
> > > > > This only hides the bug in the dither path for unscaled planar yuv
> > > > > 8bit to
> > > > > hbd and vice-versa.
> > > > > Someone more familiar with the code should check what exactly is
> > > > > going on.
> > > > 
> > > > LGTM, thanks! Good job in hunting this one down - it seems odd as the
> > > > exact output value seems stable on each machine (and valgrind doesn't
> > > > find any nondeterminism), but the output is different on most machines.
> > > 
> > > The only tests that fail are those using the DITHER_COPY method in
> > > planarCopyWrapper() when dither is used, and the only difference compared to
> > > the no dither path is accessing the "dithers" static const array defined in
> > > the same file.
> > > Maybe compilers are doing something weird when aligning it, or accessing it?
> > 
> > Not sure i fully understand but the brute force way to debug this is maybe
> > just add a printf() to dump every value then diff between to see where differences
> > start.
> 
> I can't even reproduce the issue locally, so...

is this a threads >1 issue ?

thx

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Good people do not need laws to tell them to act responsibly, while bad
people will find a way around the laws. -- Plato
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