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

[Ian Romanick]

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On 08/03/2011 12:11 PM, Bryan Cain wrote:
> On 08/03/2011 01:58 PM, Ian Romanick wrote:
>> I think this solves the issue for the compressor and for the software
>> decompressor.  I don't think this solves the problem for the
>> decompressor for hardware drivers, so that may still pose a problem for
>> Linux distros.
> 
> Pardon my ignorance, but why do hardware drivers need a decompressor?

To quote the EXT_texture_compression_s3tc spec:

    WARNING:  Vendors able to support S3TC texture compression in Direct3D
    drivers do not necessarily have the right to use the same
functionality in
    OpenGL.

This is the same issue that Linux distros have with ARB_texture_float
being enabled in hardware drivers.  The hardware may implement the
functionality, and the hardware vendor may have some license for the
patent, but that license may not cover making the functionality
available in Mesa.  That S3 has sued Apple is some indication that these
licenses may have very narrow scope.
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