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4.x series change log

This page summarizes the major functional and performance changes in each release of the 4.x series.

All performance data on this page is measured on an Intel Core i5-9600K clocked at 4.2 GHz, running astcenc using AVX2 and 6 threads.

4.0

Status: In development

The 4.0 release introduces some major performance enhancement, and a number of larger changes to the heuristics used in the codec to find a more effective cost:quality trade off.

  • General:
    • Feature: The -a alpha weighting option has been re-enabled in the backend, and now again applies alpha scaling to the RGB error metrics when encoding. This is based on the maximum alpha in each block, not the individual texel alpha values used in the earlier implementation.
    • Feature: The command line tool now has -repeats <count> for testing, which will iterate around compression and decompression count times. Reported performance metrics also now separate compression and decompression scores.
    • Optimization: Angular endpoint min/max weight selection is restricted to weight QUANT_11 or lower. Higher quantization levels assume default 0-1 range, which is less accurate but must faster.
    • Optimization: Maximum weight quantization for later trials is selected based on the weight quantization of the best encoding from the 1 plane 1 partition trial. This significantly reduces the search space for the later trials with more planes or partitions.
    • Optimization: Weight scrambling has been moved into the physical layer; the rest of the codec now uses linear order weights.
    • Optimization: Weight packing has been moved into the physical layer; the rest of the codec now uses unpacked weights in the 0-64 range.
    • Optimization: Consistently vectorize the creation of unquantized weight grids when they are needed.
    • Optimization: Remove redundant per-decimation mode copies of endpoint and weight structures, which were really read-only.
    • Optimization: Early-out the same endpoint mode color calculation if it cannot be applied.

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