On Sun, Apr 23, 2017 at 06:00:06PM +0200, Martin Vignali wrote: > Hello, > > In attach a patch who fix this sample : > https://we.tl/HWgF0SFEll > > This sample contain negative value in the red channel. > > Before this patch, negative red float are converted to max red > instead of zero. > > The previous hack doesn't seems to work for float to uint > so i add an explicit sign check > > but i'm not familiar with float binary manipulation, > so maybe there is a better way to fix the problem > > Comments welcome > > Martin > Jokyo Images
> exr.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > 99febb919a36ca28f2fd2500cd820f5ec75ebeb0 > 0002-libavcodec-exr-fix-float-to-uint16-conversion-for-ne.patch > From 5385ed8d8d258e68474e3ff24b601fd9ae595677 Mon Sep 17 00:00:00 2001 > From: Martin Vignali <martin.vign...@gmail.com> > Date: Sun, 23 Apr 2017 17:57:53 +0200 > Subject: [PATCH 2/2] libavcodec/exr : fix float to uint16 conversion for > negative value > > the previous hack doesn't seems to work > so add an explicit sign check > --- > libavcodec/exr.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/libavcodec/exr.c b/libavcodec/exr.c > index 7194640..0e69a8d 100644 > --- a/libavcodec/exr.c > +++ b/libavcodec/exr.c > @@ -223,9 +223,9 @@ static union av_intfloat32 exr_half2float(uint16_t hf) > static inline uint16_t exr_flt2uint(uint32_t v) > { > unsigned int exp = v >> 23; > - // "HACK": negative values result in exp< 0, so clipping them to 0 > - // is also handled by this condition, avoids explicit check for sign bit. > - if (exp <= 127 + 7 - 24) // we would shift out all bits anyway > + if (v >> 31 == 1)/* clamp negative value to 0*/ > + return 0; > + if (exp <= 127 + 7 - 24) > return 0; did you try to make exp int32_t to avoid the 2nd check ? [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Those who are too smart to engage in politics are punished by being governed by those who are dumber. -- Plato
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