On 02/27/2013 03:41 PM, Kristian Høgsberg wrote:
On Wed, Feb 27, 2013 at 2:32 AM, Pohjolainen, Topi
<topi.pohjolai...@intel.com> wrote:
On Tue, Feb 26, 2013 at 12:28:14PM -0500, Kristian H?gsberg wrote:
On Tue, Feb 26, 2013 at 8:19 AM, Topi Pohjolainen
<topi.pohjolai...@intel.com> wrote:
Namely YUV420, YVU420 (YV12) and NV12. Here one extends the shader
program with instructions that sample the separate Y- and U/V-planes
and convert the YUV to RGB as specified by ITU-R BT.601. Packed
formats are handled through the normal paths.
I didn't read the entire patch series yet, but this doesn't sound
right. You can't handle packed (YUYV) buffers through normal
sampling. If you're filtering, you end up blending the wrong
components. If you're sampling the buffer as 32 bpp, you'll blend Y
components not with their neighboring pixel but the pixel one over, as
each sample has two Y components. If you sample the texture as 16bpp,
you end up blending the U and V components as you sample. The trick
is to set up two textures for the same buffer and sample Y using a 16
bpp texture and sample the U and V components using a 32 bpp buffer.
Here the first two (YUV420, YVU420) have all the components in different planes
and I'm giving each plane its own sampling surface, and hence sampling them
separately as R8_UNORM. The packed UV-plane of NV12 I'm treating in turn as
having two channels (sampling using R8G8_UNORM). Does that make sense? I haven't
written support for anything more complex yet, but it is good to know your trick
if the need arises.
Right, that works for thos formats. The trick of using two samplers
on the same buffer applies to YUYV buffers, ie packed format where
each 32bit word contains two Y samples, one U and one V sample and
corresponds to two pixels.
We have surface formats, BRW_SURFACEFORMAT_YCRCB_*, for those kinds of
packed formats. We use that (or used to use that) to support
GL_MESA_ycbcr_texture. On GEN4+ it just doesn't do the color space
conversion.
I do like your trick, though. :)
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