Basis Universal v2.5 with in-loop deblocking: shipping soon

We're feature complete. We're now on the downslope to shipping support for in-loop deblocking using a simple standardized reconstruction operator. The operator uses 1 tap or 5 taps (1 center, 2 up/down, 2 left/right) near ASTC block edges, and is fully compatible with mipmapping and bilinear/trilinear filtering. It can be applied in a simple GPU pixel shader or during transcoding. 

It's so simple I'm stumped why the IHV's didn't put this obvious thing directly in the sampling hardware. It makes the largest ASTC block sizes (10x8, 10x10, 12x10 and 12x12) immensely more usable in practice.

The encoder's final SCD (Stochastic Coordinate Descent) stage computes the final output taking into account the deblocking filter. The encoder simulates the exact filter the decoder will use, then optimizes the compressed data knowing the artifacts will be smoothed. This dramatically improves quality at low bitrates. 

We're shipping two full ASTC LDR encoders (an optimized version of our original one from v2.0, and a new one called "astcf") that have been modified to output 10's to 100's of block candidates for SCD. 

We're also going to optionally support the use of a slightly modified/forked version of ARM's "astcenc" library that can output candidates for use in our SCD stage. The library supports merging the output from (up to) all 3 encoders. We're supporting this because each encoder has different artifact profiles, which boosts SCD candidate diversity. Our second ASTC encoder was purposely engineered to look very different vs. our first.

With the largest ASTC/XUASTC block sizes, 80-90% of our output blocks are now created stochastically via SCD. The mutation operator can modify endpoints, partition patterns, and DCT AC/DC coefficients.

The output looks incredible at 12x12 ~0.5 bpp.