Status: June 2026

The 5.5.0 release is a minor maintenance release, fixing minor functional issues and improving robustness when processing invalid images.

• Codec library updates:
  • Bug fix: Correct vfloat8 NaN inequality comparisons for AVX2 builds, so that decompressing an invalid encoding returns the correct max magenta error color for UNORM output formats instead of black.
  • Bug fix: Add overflow detection so that the API returns errors for cases when input image size would result in integer overflow in
    calculations of total texel count, total block count, or compressed image byte size.
  • Bug fix: Fix bad offset calculation in compute_averages() when using 3D block sizes.
  • Bug fix: Add missing low-clamp when storing decompressed HDR data into a UNORM8 image. Prior to this fix, output colors would be incorrect if a HDR void-extent block contained a negative FP16 constant color component.
  • Improvement: Return standard error color when decompression requires an unavailable partitioning when using an ASTCENC_FLG_SELF_DECOMPRESS_ONLY context. Note that this is still not allowed API usage and may trigger asserts in a debug build.
• Command line tool updates:
  • Update: Update stb_image to v2.30.
  • Update: Update Wuffs to v0.3.4.
  • Update: Update TinyEXR to v1.0.13.
  • Bug fix: Use C++ RAII to manage resource lifetime, removing resource leaks when an error condition is encountered.
  • Bug fix: Report errors for .astc, .dds, and .ktx input image sizes that would result in integer overflow in calculations of total block count or data size.
  • Bug fix: Avoid undefined behavior on NaN to int conversion triggered by atan2() calls when both inputs are zero.
  • Bug fix: Avoid undefined behavior on left shift of negative integer, that is triggered for some HDR encodings in hdr_alpha_unpack().
  • Bug fix: Redirect error logging for failed .dds and .ktx input image loading to stderr, and improve message consistency.

Binary release sha256 checksums

aee2efe79fa07ab5b341200f45b2a613b540490e64047107fbbc9bdbb3f4b179 astcenc-5.5.0-linux-arm64.zip
ecf4c6bc858ce6a3b7ac49af800c5d1268410cebaed35bc998e6eeb8b547ceca astcenc-5.5.0-linux-x64.zip
52b7c3380ac1e6afa1565c4fc86f571c510fed67f38d6e80c2f3cc3f23ae3059 astcenc-5.5.0-macos-universal.zip
e342902eed198011ef88267f081695905ad6586be25fd923a5a9e039f2dab083 astcenc-5.5.0-windows-arm64.zip
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Status: May 2026

The 5.4.0 release is a minor feature release.

This release includes changes to the public interface in the astcenc.h header. We always recommend rebuilding your client-side code using the header from the same release to avoid compatibility issues.

Thank you to the community contributors for this release cycle, who contributed the changes for astcenc.h C compliance, RISC-V backend support, and new fuzzers that significantly increase our OSS Fuzz code coverage.

• General:
  • Improvement: The interface header astcenc.h is now C compliant to make it usable from C programs.
  • Improvement: Contexts using the same configuration can now share read-only data tables. This can significantly reduce the amount of memory needed for applications that parallelize by processing multiple images in parallel instead of slicing a single image in parallel.
  • Improvement: Decompressor (astcdec) builds, which lack compression support, now use a smaller block_size_descriptor by omitting fields that are only needed for compression. This reduces the size of a decompressor context by more than 10MB!
  • Optimization: A SIMD backend for the RISC-V Vector extensions has been added, and is auto-selected when configured with ASTCENC_ISA_NONE and a core with a 256-bit vector width. See Building.md for details.
  • Bug fix: Avoid using an undefined quant_weight value if all one partition trials return an error block.
  • Bug fix: Remove remaining instances of type aliasing through unions.
  • Bug fix: Avoid compiler double definition warning for NOMINMAX when compiling with MinGW.
  • Bug fix: Avoid compiler floating point model override warning when compiling with Clang 20.

Binary release sha256 checksums

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4d02d5cad4a026e026b60f0e8dd02064858637f6f96e942d986a9e96003bf6f3 astcenc-5.4.0-macos-universal.zip
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Status: March 2025

The 5.3.0 release is a minor maintenance release.

• General:
  • Feature: Reference C builds (ASTCENC_ISA_NONE) support compiling for big-endian CPUs. Compile with -DASTCENC_BIG_ENDIAN=ON when compiling for a big-endian target; it is not auto-detected.
  • Improvement: Builds using GCC now specify -flto=auto to allow parallel link steps and remove the log warnings about not setting a CPU count parameter value.
  • Bug fix: Builds using MSVC cl.exe that do not specify an explicit ISA using the preprocessor configuration defines will now correctly default to the SSE2 backend on x86-64 and the NEON backend on Arm64. Previously they would have defaulted to the reference C implementation, which is around 3.25 times slower.

Binary release sha256 checksums

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495b2f0cf0357ae05728a727e3d0e81d6e7f27b242c21cb5ef6254dd56dba5ff astcenc-5.3.0-linux-x64.zip
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Status: February 2025

The 5.2.0 release is a minor maintenance release.

• General:
  • Change: Changed sRGB alpha channel endpoint expansion to match the revised Khronos Data Format Specification (v1.4.0), which reverts an unintended specification change. Compared to previous releases, this change can cause LSB bit differences in the alpha channel of compressed sRGB images.
  • Feature: Arm64 builds for Linux added to the GitHub Actions builds, and Arm64 binaries for NEON, 128-bit SVE, and 256-bit SVE added to release builds.
  • Feature: Added a new codec API, astcenc_compress_cancel(), which can be used to cancel an in-flight compression. This is designed to help make it easier to integrate the codec into an interactive user interface that can respond to user events with low latency.
  • Bug fix: Removed incorrect static variable qualifier, which could result in an incorrect tune_mse_overshoot heuristic threshold being used if a user ran multiple concurrent compressions with different settings.

Binary release sha256 checksums

9c46d5e493d000fb2334b02bb16b862bb983c7471b157ba6f99d320a2e78d359 astcenc-5.2.0-linux-arm64.zip
b8c805b3c4a32680287ad5e5fc2a8b5ddf78c80f24cc0ec7ed1e4eb03c6cc5d2 astcenc-5.2.0-linux-x64.zip
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Status: November 2024

The 5.1.0 release is an optimization release, giving moderate performance improvements on all platforms. There are no image quality differences.

• General:
  • Feature: Added a new CMake build option to control use of native gathers, as they can be slower than scalar loads on some common x86 microarchitectures. Build with -DASTCENC_X86_GATHERS=OFF to disable use of native gathers in AVX2 builds.
  • Optimization: Added new gather() abstraction for gathers using byte indices, allowing implementations without gather hardware to skip the byte-to-int index conversion.
  • Optimization: Optimized compute_lowest_and_highest_weight() to pre-compute min/max outside of the main loop.
  • Optimization: Added improved intrinsics sequence for SSE and AVX2 integer hmin() and hmax().
  • Optimization: Added improved intrinsics sequence for vint4(uint8_t*) on systems implementing Arm SVE.

Binary release sha256 checksums

a9f61f954f8c6f75675b9b8187454a3b1328c172cb62747715a30937bb8fe7bb astcenc-5.1.0-linux-x64.zip
4ecb330104e05a35febfc0d83b0c128ee2f51b671577e9952ca4278b5455197b astcenc-5.1.0-macos-universal.zip
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Status: November 2024

The 5.0.0 release is the first stable release in the 5.x series. The main new feature over the 4.x series is support for the Arm Scalable Vector Extensions (SVE) SIMD instruction set, with both 128-bit and 256-bit backends provided. This gives up to 60% performance improvement on Neoverse V2 with its 256-bit SVE implementation.

• General:
  • Bug fix: Fixed incorrect return type in "None" vector library reference implementation.
  • Bug fix: Fixed sincos table index under/overflow.
  • Feature: Changed ASTCENC_ISA_NATIVE builds to use -march=native and -mcpu=native.
  • Feature: Added backend for Arm SVE fixed-width 256-bit builds. These can only run on hardware implementing 256-bit SVE.
  • Feature: Added backend for Arm SVE 128-bit builds. These are portable builds and can run on hardware implementing any SVE vector length, but the explicit SVE use is augmented NEON and will only use the bottom 128-bits of each SVE vector.
  • Feature: Optimized NEON mask any() and all() functions.
  • Feature: Migrated build and test to GitHub Actions pipelines.

Binary release sha256 checksums

70183c4346f9fc0f55cd8e3ca5b326cbb4675233b026c02df60657e344c44cc0 astcenc-5.0.0-linux-x64.zip
b8e450250932f07765d868318709964da2a36d41be0538f5c018d8fc72a41e70 astcenc-5.0.0-macos-universal.zip
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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

dfd7fb8056aeb1c9fa19d8c101f9a6a710ffa2000e62d5a536d4a7ca06c81c8d astcenc-4.8.0-linux-x64.zip
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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

4f596546808c58f2b7e0271302d05df40159cdc7c47645cc96f331229d22ab66 astcenc-4.7.0-linux-x64.zip
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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

e360aeabf3b5aeda6a7cfabddc49af8b204e28befa04ab8e8942c85620ba071a astcenc-4.6.1-linux-x64.zip
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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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