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

Rudolf Polzer divverent at xonotic.org
Wed Aug 10 05:00:46 PDT 2011

On Wed, Aug 10, 2011 at 04:32:20AM -0700, Jose Fonseca wrote:
> ----- Original Message -----
> > On Tue, Aug 09, 2011 at 03:25:05AM -0700, Jose Fonseca wrote:
> > > How should you brought this? You should have assumed that we have
> > > our reasons
> > > -- after all we've been living under the frustration of these
> > > patents,
> > > walking on a mine field, for a decade --, instead of assuming we
> > > have NIH
> > > syndrome.
> > 
> > So I should never try to do anything new, as likely someone else may
> > have
> > already done it and rejected it.
> We must be talking different things. I was answering on how you should have
> approached this subject on the mailing list _after_ doing S2TC work.
> Essentially you started to wrongly accuse the developers of already doing
> illegal things, when your proposal was refused, which totally pissed me off.
> We strive to keep legal risk under check, and you were trying to tip the
> scale.

I did not. It was "proof by contradiction", or "reductio ad absurdum", a common
mathematical method of proof. I was saying, your claim that uploading texture
data to a S3TC decoding sircuit is a reason against S2TC must be void, because
Mesa does the same already, and thus your interpretation must be wrong.

It was not meant as an accusation that Mesa is breaking any law. But rather as
a "proof" that in this specific aspect, S2TC is not.

> If you are talking of what you should have done before doing the S2TC work,
> then my opinion is that you should have:
> - a) read all threads about S3TC on mesa3d-dev mailing list -- if you had
> done so you would have noticed that several times now people have proposed to
> develop a variant of the S3TC GL extension that would not require any
> software (de)compression (therefore completely avoiding the software side of
> the issue), but that it was always abandoned, because the hardware licensing
> terms were potentially too narrow -- the intuitive idea that "if I bought the
> hardware I must have the license" simply is not true in the general case.
> The recent Apple/S3 lawsuit corroborates that.

I never understood that part, and still do not. But if US law is that insane,
it is. If only voters had any actual power to get rid of such nonsense... and
apparently, US law forbids public explanations of such issues, so it is
impossible to learn about it. Not my fault though.

> b) contacted the developers before doing the work -- they would have told you
> the same.

Before doing the work, it likely would have been shot down because of potential
quality issues. Without actually trying it out, it is not obvious at all that
S2TC still yields sufficient quality.

Plus, my only contact to the mesa developers IS this list.

> Either would have saved everybody grief. That said, I still think that S2TC
> work is interesting for software rendererers (although that may not be your
> intention), or even if one day the IHVs do get a S3TC license for Mesa/Linux,
> we can use it to solve the software compression issue. But the hardware use,
> is and always has been in the IHV/S3 hands.

Supposedly, by some post elsewhere in this thread, nvidia has the sufficient
license, and thus nouveau could use it.

For other but sufficiently new chipsets, it was suggested to implement S2TC
decoding via shader. No idea how that would work though, and what performance
impact it would have.

> (Furthermore b) applies not only to patent issues but any contribution to any
> open source project. The only way to ensure one does not waste time is to get
> the maintainers' buy in for the general concept beforehand.)

In this case, that clearly is not possible without having an implementation
already, as a quality comparison was necessary.

Best regards,

Rudolf Polzer

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