Re: [Mesa3d-dev] Status of s3tc patent in respect to open-source drivers and workarounds

[Ian R. <id...@fr...>]

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Philipp Klaus Krause wrote:
> Corbin Simpson schrieb:
>> After re-reading ARB_texture_compression, it does seem like it is
>> legal for extensions such as EXT_texture_compression_s3tc to fall
>> back, using a basic mechanism: glGetTexLevelParameter can return
>> GL_FALSE for GL_TEXTURE_COMPRESSED_ARB (now GL_TEXTURE_COMPRESSED) if
>> the texture could not successfully be compressed. Issue (10) of
>> ARB_texture_compression deals with this explicitly:
> 
> Yes, ARB_texture_compression allows to support decompression only. That
> could probably be used to have decompression support for the S3TC
> formats in Mesa. However, this does mean that
> EXT_texture_compression_s3tc would be supported, since
> EXT_texture_compression_s3tc does require support for encoding and the
> wording in ARB_texture_compression does not change that.

EXT_texture_compression_s3tc is layered on top of
ARB_texture_compression.  I don't see anything in the spec that adds
this requirement.  In fact, I don't see *anything* in that spec that
mentions TexImage2D.  Am I just overlooking some wording in
EXT_texture_compression_s3tc that adds this?
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