[Mesa-dev] S2TC - yet another attempt to solve the "S3TC issue"

Ian Romanick idr at freedesktop.org
Tue Aug 9 15:26:38 PDT 2011

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On 08/09/2011 04:10 AM, Rudolf Polzer wrote:
> As for compression: the compressed format is basically "each 4x4 block is a
> 2-color optimum palette image". Similar schemes have existed way before S3TC
> (e.g. in some video codecs used by DOS games - see ffmpeg for implementations
> of these), and even way before Apple's RPZA, which I still see as obvious prior
> art that should render any S3TC related patents invalid (which is apparently
> exactly what Apple now is trying to achieve in court). Whether my specific
> algorithms for choosing the 2 colors, or for finding the nearest color of the
> two for each pixel, violate any patents, I cannot say, but these two things are
> quite interchangable. Too bad the standard color reduction algorithm "Median
> cut" does not work well if the target is just two colors, as it would have been
> a VERY safe choice.

Yes.  Getting some legal confirmation that the patents are invalid and
that we can just do the right thing is the way forward here.
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