Mailinglist Archive: radeonhd (365 mails)

[Matthias Hopf <mhopf@xxxxxxx>]

On Mar 05, 09 09:34:56 -0800, Yang Zhao wrote:
> > I haven't found a spec for how the values have to be reconstructed. But
> > the original sample positions would influence that very much.
>
> From page 93:
> "To interpolate the missing chroma samples prior to conversion back to
> R'G'B', low-end systems simply replicate the subsampled Cb and Cr
> values throughout the 2x2 quad. This technique is ubiquitous in
> JPEG/JFIF... and is used in M-JPEG, H.261, and MPEG-1"
>
> This seems to imply that stored chroma is upscaled using nearest-point
> interpolation by standard, or at least that's the common way for
> renderers to operate. This is the same conclusion I arrived at after
> comments of blurriness prompted me to investigate how the up-sampling
> is done.

I rather read this as: the simple way is to use nearest neighbor, more
elaborate versions do interpolation.

> That's one of the more useful sites I did manage to find, but I didn't
> give it much thought since it seemed to be geared toward how to encode
> the stills such that artifacts as a result of nearest-neighbour
> decoding doesn't end up producing crappy results. Looking over it
> again, it seems to have some hints for decoders as well. I'll give it
> a better read through.

Same to me.

Matthias

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