Mailinglist Archive: radeonhd (365 mails)

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Re: [radeonhd] [PATCH] Fix blurry Xv image
  • From: Alex Deucher <alexdeucher@xxxxxxxxx>
  • Date: Wed, 4 Mar 2009 10:27:58 -0500
  • Message-id: <a728f9f90903040727u387cd085yadbcaceef9b194a@xxxxxxxxxxxxxx>
On Wed, Mar 4, 2009 at 10:18 AM, Matthias Hopf <mhopf@xxxxxxx> wrote:
On Mar 03, 09 18:03:22 -0800, Yang Zhao wrote:
The attached patch fixes the issue of blurry images under Xv, compared
to unaccelerated rendering.

The texture sampler for CbCr used to be configured to use bilinear
interpolation when upscaling. This results in a smoothing of the
chroma channels, and is perceived as being blurry when a lot of sharp
changes in colour is present. Simply flip the bits to use
nearest-point interpolation instead.

Yang, I wouldn't change that. AFAIU color subsampling in the normal
YCb'Cr' color spaces is defined to be interpolative. If it does look to
blurry, there could be a different bug. Also, with nearest-neighbor
interpolation at least I always stumble over hard edges at smooth
surfaces, especially if they are red.

BTW - I already tried to use bicubic filters once, and I couldn't get
them to work. Apparently they need a little extra love (read:
coefficients) to actually work.
Of course one can always emulate bicubic filters by manually fetching
the necessary samples.

I looked into the bicubic stuff and it has a fairly complex kernel
setup, and, unfortunately, it was dropped on r7xx hardware. All in
all, it's probably easier to implement it in shaders. The relevant
shader code already exists for r3xx-r5xx hardware.

Alex
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