XUASTC's next step: Intra-prediction of weight grids

Binomial has shown that image compression and GPU texture compression aren't separate fields. They're the same field, and the tools from one transfer directly to the other.

XUASTC is currently using JPEG-style DCT (from 1992) on ASTC weight grids:

https://github.com/BinomialLLC/basis_universal/wiki/XUASTC-LDR-Weight-Grid-DCT

We ported JPEG-style coding into ASTC, even preserving how libjpeg-style [1-100] Q factors are used to calculate quantization tables. (Our quantization table is the standard luminance JPEG table, with simple adaptive quantization added on top.)

This works, but it means the DCT has to carry the entire weight signal (just like JPEG). At the very lowest quality factors (Q levels 1-25 or so), the lowest spatial frequencies suffer (again, just like JPEG).

The next step is to port WebP-style intra-prediction into the weight grid domain. We can easily predict weight grids from nearby blocks, then code the weight residuals using DCT. It's the logical next step, and it'll push our bitrates even lower. While seemingly everyone is distracted by neural techniques, we're targeting billions of already shipped, hyper-efficient hardware decoders.

First XUASTC LDR 4x4 rate-distortion graphs

ASTC GPU texture blocks form a latent image space where JPEG techniques still work. (So does BC7.)

Here's a XUASTC LDR 4x4 (arithmetic vs. Zstd profile) bit rate vs. distortion graph across 151 test textures/images (the same test corpus we used to create bc7e.ispc). Distortion was measured using PSNR-HVS-M. 

XUASTC LDR 4x4 transcodes to standard ASTC LDR 4x4 in memory/VRAM (8.0 bpp). It supports all 14 standard ASTC block sizes up to 12x12.

Multiple block sizes, effort 9, arithmetic profile. It took ~10k invocations of the compressor-transcoder to make this graph.

ETC1S - effort 2:

Open Geospatial Consortium membership

I'm now a member of the OGC:

https://www.ogc.org/

Basis Universal v2.1 library wiki mirror

It's been automatically converted to HTML and mirrored outside of GitHub here: Home.

A static mirror of the GitHub repo is here.

The KTX-Software repo has been forked

Binomial LLC has forked the Khronos Group's KTX-Software repo, to use as a staging ground for next-generation GPU texture compression technology:

https://github.com/BinomialLLC/KTX-Software-Binomial-Fork/

Degenerate but valid ASTC configs: suboptimal CEM encodings

See: 

https://github.com/BinomialLLC/basis_universal/wiki/List-of-Available-Software-ASTC-Decoders#degenerate-but-valid-astc-configs-suboptimal-cem-encoding

Updated: "ASTC GPU Texture Decoding: Software Decoders, Spec Issues, and ARM Errata"

ASTC's complexity has created an ecosystem where correctness is an ongoing research problem rather than a fully solved one. See:

https://github.com/BinomialLLC/basis_universal/wiki/List-of-Available-Software-ASTC-Decoders