Thanks for the comments and have updated the patch! -----Original Message----- From: Matt Turner [mailto:matts...@gmail.com] Sent: Wednesday, May 3, 2017 2:37 AM To: Lin, Johnson <johnson....@intel.com> Cc: mesa-dev@lists.freedesktop.org Subject: Re: [Mesa-dev] [PATCH] fix minor error in YUV2RGB matrix used in shader
On Tue, May 2, 2017 at 7:24 AM, Johnson Lin <johnson....@intel.com> wrote: > The matrix used for YCbCr to RGB is listed in Wiki > https://en.wikipedia.org/ wiki/YCbCr; There is minor error in the > matrix constant: 0.0625=16/256 should be 16.0/255,and 0.5=128.0/256 should > be 128.0/255. > Note that conversion from a 0-255 byte number to 0-1.0 float is to > divide by > 255 instead of 256. That's we get 255=1.0f. > By the constant change we can see the CSC result is bit aligned with > Wiki conversion result and FFMPeg result.Otherwise in some situation, > there will be one bit difference > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100854 > --- > src/compiler/nir/nir_lower_tex.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/src/compiler/nir/nir_lower_tex.c > b/src/compiler/nir/nir_lower_tex.c > index 352d1499bc8d..f20425e84aab 100644 > --- a/src/compiler/nir/nir_lower_tex.c > +++ b/src/compiler/nir/nir_lower_tex.c > @@ -244,9 +244,9 @@ convert_yuv_to_rgb(nir_builder *b, nir_tex_instr *tex, > nir_ssa_def *yuv = > nir_vec4(b, > nir_fmul(b, nir_imm_float(b, 1.16438356f), > - nir_fadd(b, y, nir_imm_float(b, -0.0625f))), > - nir_channel(b, nir_fadd(b, u, nir_imm_float(b, -0.5f)), 0), > - nir_channel(b, nir_fadd(b, v, nir_imm_float(b, -0.5f)), 0), > + nir_fadd(b, y, nir_imm_float(b, -16.0f/255))), > + nir_channel(b, nir_fadd(b, u, nir_imm_float(b, -128.0f/255)), > 0), > + nir_channel(b, nir_fadd(b, v, nir_imm_float(b, > + -128.0f/255)), 0), Other feedback which wasn't taken into account: spaces around operators (/), and use a floating point constant (255.0f) _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev
