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

Rudolf Polzer divverent at xonotic.org
Tue Aug 9 10:49:08 PDT 2011

On Tue, Aug 09, 2011 at 10:46:12AM -0700, Corbin Simpson wrote:
> I should point out something not immediately obvious about S3TC: It's
> believed that the patents cover any complete pipeline which
> decompresses S3TC textures according to the S3TC algorithm. It's
> stupidly broad that way.

Sure is, which is why S2TC is not able to decode full S3TC, but has a weird
"fallback" handling that does not make use of inferred colors.

If only it weren't for the glaring similarity to RPZA's 0xC0 opcode... which is
VERY similar to S3TC's encoding scheme, and was invented 8 years earlier. That
can get very interesting, as I assume that Apple tries to defend against the
S3TC patent exactly by pointing out the similarity to RPZA (the Quicktime 1

Best regards,

Rudolf Polzer

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