4.8.0

Status: May 2024

The 4.8.0 release is a minor maintenance release.

Reminder - the codec library API is not designed to be binary compatible across versions. We always recommend rebuilding your client-side code using the updated astcenc.h header.

• General:
  • Bug fix: Native builds on macOS will now correctly build for arm64 when run outside of Rosetta on an Apple silicon device.
  • Bug fix: Multiple small improvements to remove use of undefined language behavior, to improve support for deployment using Emscripten.
  • Feature: Builds using Clang can now build with undefined behavior sanitizer by setting -DASTCENC_UBSAN=ON on the CMake configure line.
  • Feature: Updated to Wuffs library 0.3.4, which ignores tRNS alpha chunks for type 4 (LA) and 6 (RGBA) PNGs, to improve compatibility with libpng.

Binary release sha256 checksums

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26b82cac7a41c99c4a5789df5025d1bc42a02067be4670a5f4639e176083cee2  astcenc-4.8.0-macos-universal.zip
cdf073b42c86e766959e0c363b84b16ca4908b0d1a6304eafa6ae8d32b2dd393  astcenc-4.8.0-windows-arm64.zip
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4.7.0

Status: January 2024

The 4.7.0 release is a major maintenance release, fixing rounding behavior in the decompressor to match the Khronos specification. This fix includes the addition of explicit support for optimizing for decode_unorm8 rounding.

Reminder - the codec library API is not designed to be binary compatible across versions. We always recommend rebuilding your client-side code using the updated astcenc.h header.

• General:
  • Bug fix: sRGB LDR decompression now uses the correct endpoint expansion method to create the 16-bit RGB endpoint colors, and removes the previous correction code from the interpolation function. This bug could result in LSB bit flips relative to the standard specification.
  • Bug fix: Decompressing to an 8-bit per component output image now matches the decode_unorm8 extension rounding rules. This bug could result in LSB bit flips relative to the standard specification.
  • Bug fix: Code now avoids using alignas() in the reference C implementation, as the default alignas(16) is narrower than the native minimum alignment requirement on some CPU architectures.
  • Feature: Library configuration supports a new flag, ASTCENC_FLG_USE_DECODE_UNORM8. This flag indicates that the image will be used with the decode_unorm8 decode mode. When set during compression this allows the compressor to use the correct rounding when determining the best encoding.
  • Feature: Command line tool supports a new option, -decode_unorm8. This option indicates that the image will be used with the decode_unorm8 decode mode. This option will automatically be set for decompression (-d*) and trial (-t*) tool operation if the decompressed output image is stored to an 8-bit per component file format. This option must be set manually for compression (-c*) tool operation, as the desired decode mode cannot be reliably determined.
  • Feature: Library configuration supports a new optional progress reporting callback to be specified. This is called during compression to to allow interactive tooling use cases to display incremental progress. The command line tool uses this feature to show compression progress unless -silent is used.
  • Feature: Prebuilt Linux binary releases updated to use Clang 14 (previously Clang 9) which gives a small performance improvement.

Binary release sha256 checksums

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4.6.1

Status: November 2023

The 4.6.1 release is a minor maintenance release to fix a performance scaling issue on large core count Windows systems. No other performance or image changes are expected for this release.

• General:
  • Optimization: Windows builds of the astcenc command line tool can now use more than 64 cores on large core count systems. This change doubles command line performance for -exhastive compression when testing on an 96 core/192 thread system.
  • Feature: Windows Arm64 native builds of the astcenc command line tool are now included in the prebuilt release binaries.

Binary release sha256 checksums

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4.6.0

Status: November 2023

The 4.6.0 release is a minor release with a few code quality improvements, and a small performance boost.

Reminder - the codec library API is not designed to be binary compatible across versions. We always recommend rebuilding your client-side code using the updated astcenc.h header.

• General:
  • Bug-fix: Fixed context allocation for contexts allocated with the ASTCENC_FLG_DECOMPRESS_ONLY flag.
  • Bug-fix: Reduced use of reinterpret_cast in the core codec to avoid strict aliasing violations.
  • Optimization: -medium search quality no longer tests 4 partition encodings for block sizes between 25 and 83 texels (inclusive). This improves performance for a tiny drop in image quality.
  • Optimization: -thorough and higher search qualities no longer test the mode0 first search for block sizes between 25 and 83 texels (inclusive). This improves performance for a tiny drop in image quality.
  • Optimization: TUNE_MAX_PARTITIONING_CANDIDATES reduced from 32 to 8 to reduce the size of stack allocated data structures. This causes a tiny drop in image quality for the -verythorough and -exhaustive presets.

Binary release sha256 checksums

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4.5.0

Status: June 2023

The 4.5.0 release is a minor release with minor image quality improvements, and multiple build system quality-of-life improvements.

• General:
  • Bug-fix: Improved handling compiler arguments in CMake, including consistent use of MSVC-style command line arguments for ClangCL.
  • Bug-fix: Invariant Clang builds now use -ffp-model=precise with -ffp-contract=off which is needed to restore invariance due to recent changes in compiler defaults.
  • Change: macOS binary releases are now distributed as a single universal binary for all platforms.
  • Change: Windows binary releases are now compiled with VS2022.
  • Change: Invariant MSVC builds for VS2022 now use /fp:precise instead of /fp:strict, which is is now possible because precise no longer implies contraction. This should improve performance for MSVC builds.
  • Change: Non-invariant Clang builds now use -ffp-model=precise with -ffp-contract=on. This should improve performance on older Clang versions which defaulted to no contraction.
  • Change: Non-invariant MSVC builds for VS2022 now use /fp:precise with /fp:contract. This should improve performance for MSVC builds.
  • Change: CMake config variables now use an ASTCENC_ prefix to add a namespace and group options when the library is used in a larger project.
  • Change: CMake config ASTCENC_UNIVERSAL_BUILD for building macOS universal binaries has been improved to include the x86_64h slice for AVX2 builds. Universal builds are now on by default for macOS, and always include NEON (arm64), SSE4.1 (x86_64), and AVX2 (x86_64h) variants.
  • Change: CMake config ASTCENC_NO_INVARIANCE has been inverted to remove the negated option, and is now ASTCENC_INVARIANCE with a default of ON. Disabling this option can substantially improve performance, but images can different across platforms and compilers.
  • Optimization: Color quantization and packing for LDR RGB and RGBA has been vectorized to improve performance.
  • Change: Color quantization for LDR RGB and RGBA endpoints will now try multiple quantization packing methods, and pick the one with the lowest endpoint encoding error. This gives a minor image quality improvement, for no significant performance impact when combined with the vectorization optimizations.

Binary release sha256 checksums

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4.4.0

Status: March 2023

The 4.4.0 release is a minor release with image quality improvements, a small performance boost, a few new quality-of-life features, and a few minor fixes for uncommon build configurations.

• General:
  • Change: Core library no longer checks availability of required instruction set extensions, such as SSE4.1 or AVX2. Checking compatibility
    is now the responsibility of the caller. See astcenccli_entry.cpp for an example of code performing this check.
  • Change: Core library can be built as a shared object by setting the -DSHAREDLIB=ON CMake option, resulting in e.g. libastcenc-avx2-shared.so. Note that the command line tool is always statically linked.
  • Change: Decompressed 3D images will now write one output file per slice, if the target format is a 2D image format, rather than just writing slice zero.
  • Change: Command line tool errors print to stderr instead of stdout.
  • Change: Color encoding uses new quantization tables, that now factor in floating-point rounding if a distance tie is found when using the integer quant256 value. This improves image quality for 4x4 and 5x5 block sizes.
  • Optimization: Partition selection uses a simplified line calculation with a faster approximation. This improves performance for all block sizes.
  • Bug-fix: Fixed missing symbol error in dead code for decompressor-only builds.
  • Bug-fix: Fixed infinity handling in debug trace JSON files.

Binary release sha256 checksums

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4.3.1

Status: January 2023

The 4.3.1 release is a minor maintenance release. No performance or image quality changes are expected.

• General:
  • Bug-fix: Fixed typo in -2/3/4partitioncandidatelimit CLI options.
  • Bug-fix: Fixed handling for -3/4partitionindexlimit CLI options.
  • Bug-fix: Updated to stb_image.h v2.28, which includes multiple fixes for image loading.

Binary release sha256 checksums

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4.3.0

Status: January 2023

The 4.3.0 release is an optimization release. There are minor performance improvements, minor image quality improvements, significant memory footprint improvements, and library interface changes in this release.

Reminder - the codec library API is not designed to be binary compatible across versions. We always recommend rebuilding your client-side code using the updated astcenc.h header.

• General:
  • Bug-fix: Use lower case windows.h include for MinGW compatibility.
  • Change: The -mask command line option, ASTCENC_FLG_MAP_MASK in the library API, has been removed.
  • Optimization: Always skip blue-contraction for QUANT_256 encodings. This gives a small image quality improvement for images using the 4x4 block size.
  • Optimization: Always skip RGBO vector calculation for LDR encodings.
  • Optimization: Defer color packing and scrambling to physical layer.
  • Optimization: Remove folded decimation_info lookup tables. This significantly reduces compressor memory footprint and improves context creation time. Impact increases with block size.
  • Optimization: Increased trial and refinement pruning by using stricter target errors when determining whether to skip iterations.

Binary release sha256 checksums

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4.2.0

Status: November 2022

The 4.2.0 release is an optimization release. There are significant performance improvements, minor image quality improvements, and library interface changes in this release.

Reminder - the codec library API is not designed to be binary compatible across versions. We always recommend rebuilding your client-side code using the updated astcenc.h header.

• General:
  • Bug-fix: Compression for RGB and RGBA base+offset encodings no longer generate endpoints with the incorrect blue-contract behavior.
  • Bug-fix: Lowest channel correlation calculation now correctly ignores constant color channels for the purposes of filtering 2 plane encodings.
  • Bug-fix: ISA compatibility now checked in config_init() as well as in context_alloc().
  • Change: Removed the low-weight count optimization, as more recent changes had significantly reduced its performance benefit. Option removed from both command line and configuration structure.
  • Feature: The -exhaustive mode now runs full trials on more partitioning candidates and block candidates. This improves image quality by 0.1 to 0.25 dB, but slows down compression by 3x. The -verythorough and -thorough modes also test more candidates.
  • Feature: A new preset, -verythorough, has been introduced to provide a standard performance point between -thorough and the re-tuned -exhaustive mode. This new mode is faster and higher quality than the -exhaustive preset in the 4.1 release.
  • Feature: The compressor can now independently vary the number of partitionings considered for error estimation for 2/3/4 partitions. This allows heuristics to put more effort into 2 partitions, and less in to 3 and 4 partitions.
  • Feature: The compressor can now run trials on a variable number of candidate partitionings, allowing high quality modes to explore more of the search space at the expense of slower compression. The number of trials is independently configurable for 2/3/4 partition cases.
  • Optimization: Introduce early-out threshold for 2/3/4 partition searches based on the results after 1 of 2 trials. This significantly
    improves performance for -medium and -thorough searches, for a minor loss in image quality.
  • Optimization: Reduce early-out threshold for 3/4 partition searches based on 2/3 partition results. This significantly improves performance, especially for -thorough searches, for a minor loss in image quality.
  • Optimization: Use direct vector compare to create a SIMD mask instead of a scalar compare that is broadcast to a vector mask.
  • Optimization: Remove obsolete partition validity masks from the partition selection algorithm.
  • Optimization: Removed obsolete channel scaling from partition avgs_and_dirs() calculations.

Binary release sha256 checksums

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4.1.0

Status: August 2022

The 4.1.0 release is a maintenance release. There is no performance or image quality change in this release.

• General:
  • Change: Command line decompressor no longer uses the legacy GL_LUMINANCE or GL_LUMINANCE_ALPHA format enums when writing KTX output files. Luminance textures now use the GL_RED format and luminance_alpha textures now use the GL_RG format.
  • Change: Command line tool gains a new -dimage option to generate diagnostic images showing aspects of the compression encoding. The output file name with its extension stripped is used as the stem of the diagnostic image file names.
  • Bug-fix: Library decompressor builds for SSE no longer use masked store maskmovdqu, as they can generate faults on masked lanes.
  • Bug-fix: Command line decompressor now correctly uses sized type enums for the internal format when writing output KTX files.
  • Bug-fix: Command line compressor now correctly loads 16 and 32-bit per component input KTX files.
  • Bug-fix: Fixed GCC9 compiler warnings on Arm aarch64.

Binary release sha256 checksums

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