4.0.0

Status: July 2022

The 4.0.0 release introduces some major performance enhancements, and a number of larger changes to the heuristics used in the codec to find a more effective cost:quality trade off. The core compressor library is between 1.2x (4x4 blocks) and 1.6x (6x6 blocks) faster than the previous 3.7 release. The core decompressor library is 1.25x faster than the 3.7 release.

• General:
  • Change: The -array option for specifying the number of image planes for ASTC 3D volumetric block compression been renamed to -zdim.
  • Change: The build root package directory is now bin instead of astcenc, allowing the CMake install step to write binaries into
    /usr/local/bin if the user wishes to do so.
  • Feature: A new -ssw option for specifying the shader sampling swizzle has been added as convenience alternative to the -cw option. This is needed to correct error weighting during compression if not all components are read in the shader. For example, to extract and compress two components from an RGBA input image, weighting the two components equally when sampling through texture().ra in the shader, use -esw ggga -ssw ra. In this example -ssw ra is equivalent to the alternative -cw 1 0 0 1 encoding.
  • 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.
  • Feature: The core codec is now warning clean up to /W4 for both MSVC cl.exe and clangcl.exe compilers.
  • Feature: The core codec now supports arm64 for both MSVC cl.exe and clangcl.exe compilers.
  • Feature: NO_INVARIANCE builds will enable the -ffp-contract=fast option for all targets when using Clang or GCC. In addition AVX2 targets will also set the -mfma option. This reduces image quality by up to 0.2dB (normally much less), but improves performance by up to 5-20%.
  • 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 much 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: Small data tables now use in-register SIMD permutes rather than gathers (AVX2) or unrolled scalar lookups (SSE/NEON). This can be a significant optimization for paths that are load unit limited.
  • Optimization: Decompressed image block writes in the decompressor now use a vectorized approach to writing each row of texels in the block, including to ability to exploit masked stores if the target supports them.
  • 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 duplicates.
  • Optimization: Early-out the same endpoint mode color calculation if it cannot be applied.
  • Optimization: Numerous type size reductions applied to arrays to reduce both context working buffer size usage and stack usage.

Binary release sha256 checksums

7899f73ee2820b0e7d73b38fda6feb58948a30b511dd123ec4b7c89f3aae531a  astcenc-4.0.0-linux-x64.zip
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3.7

The 3.7 release contains another round of performance optimizations, including significant improvements to the command line front-end (faster PNG loader) and the arm64 build of the codec (faster NEON implementation).

Change log

General:

• Feature: The command line tool PNG loader has been switched to use the Wuffs library, which is significantly faster than the current implementation.
• Feature: Support for non-invariant builds returns. Opt-in to slightly faster, but not bit-exact, builds by setting -DNO_INVARIANCE=ON for the CMake configuration. This improves performance by around 2%.
• Optimization: Changed SIMD select() so that it matches the default NEON behavior (bitwise select), rather than the default x86-64 behavior (lane select on MSB). Specialization select_msb() added for the one case we want to select on a sign-bit, where NEON needs a different implementation. This provides a significant (>25%) performance uplift on NEON implementations.

Binary release sha256 checksums

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3.6

The 3.6 release contains another round of performance optimizations. There are no interface changes in this release, but in general the API is not designed to be binary compatible across versions. We always recommend rebuilding your client-side code using the updated astcenc.h header.

Change log

General:

• Feature: Compressor configurations no longer require the SELF_DECOMPRESS_ONLY flag to use defragmented data tables. Tables are always sorted to store active data table entries at the start of the list, with inactive entries stores at the end. If the SELF_DECOMPRESS_ONLY flag is specified the inactive entries are not created, reducing context creation time and memory footprint.
• Feature: Image quality for 4x4 -fastest compression has been improved.
• Optimization: Decimation modes are reliably excluded from processing when they are only partially selected in the compressor configuration (e.g. if used for single plane, but not dual plane modes). This is a significant performance optimization for all quality levels.
• Optimization: Fast-path block load function variant added for 2D LDR images with no swizzle. This is a moderate performance optimization for the -fast and -fastest quality levels.

Binary release sha256 checksums

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3.5

The 3.5 release contains another round of performance optimizations. There are no interface changes in this release, but in general the API is not designed to be binary compatible across versions. We always recommend rebuilding your client-side code using the updated astcenc.h header.

Change log

General:

• Feature: Compressor configurations using the SELF_DECOMPRESS_ONLY flag store compacted partition tables, which significantly improves both context creation time and compressor runtime performance.
• Feature: Bilinear infill for decimated weight grids supports a new variant for half-decimated grids which are only decimated in one axis, which gives a small performance boost across all quality levels.

Binary release sha256 checksums

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3.4

Status: Released

The 3.4 release introduces another round of optimizations, removing a number of power-user configuration options to simplify the core compressor data path. It is expected that there is some minor loss of image quality at the same compressor effort setting, but the improved performance allows a higher compressor effort level to be used for the same runtime as earlier releases.

Reminder for users of the library interface - the API is not designed to be binary compatible across versions, and this release is not compatible with earlier releases. Please update and rebuild your client-side code using the updated astcenc.h header.

• General:
  • Feature: Many memory allocations have been moved off the stack into dynamically allocated working memory. This significantly reduces the peak stack usage, allowing the compressor to run in systems with 128KB stack limits.
  • Feature: Builds now support -DBLOCK_MAX_TEXELS=<count> to allow a compressor to support a subset of block sizes. This can reduce binary size and runtime memory footprint, and improve performance.
  • Feature: The -v and -va options to set a per-texel error weight function are no longer supported.
  • Feature: The -b option to set a per-texel error weight boost for block border texels is no longer supported.
  • Feature: The -a option to set a per-texel error weight based on texel alpha value is no longer supported as an error weighting tool, but is still supported for providing sprite-sheet RDO.
  • Feature: The -mask option to set an error metric for mask map textures is still supported, but is currently a no-op in the compressor.
  • Feature: The -perceptual option to set a perceptual error metric is still supported, but is currently a no-op in the compressor for mask map and normal map textures.
  • Bug-fix: Corrected decompression of error blocks in some cases, so now returning the expected error color (magenta for LDR, NaN for HDR). Note that astcenc determines the error color to use based on the output image data type not the decoder profile.

Binary release sha256 checksums

Note: Due to a delay publishing the binaries, caused by a DevOps pipeline upgrade, these binaries have actually been built from a slightly newer git hash (c82259f) than the 3.4 tag. This includes a number of performance optimizations which didn't land in time for the 3.4 release tag, as well as a change to use ClangCL to compile the Windows builds.

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3.3

Status: Released

The 3.3 release improves image quality for normal maps, and two component textures. Normal maps are expected to compress 25% slower than the 3.2 release, although it should be noted that they are still faster to compress in 3.3 than when using the 2.5 series. This release also fixes one reported stability issue.

• General:
  • Feature: Normal map image quality has been improved.
  • Feature: Two component image quality has been improved, provided that unused components are correctly zero-weighted using e.g. -cw on the command line.
  • Bug-fix: Improved stability when trying to compress complex blocks that could not beat even the starting quality threshold. These will now always compress in to constant color blocks.

Binary release sha256 checksums

d686330476b104b94ff74eadc79b1778bf36aa42eb6f3904dca36af05a4c8c87  astcenc-3.3-linux-x64.zip
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3.2

Status: Released

The 3.2 release is the third release in the 3.x series. This release is a maintenance release, fixing two issues in the 3.1 release.

• General:
  • Bug fix: Multi-context usage of the library could result in poor quality block encodings or decompressed images if a new context was allocated while an image was being compressed or decompressed using another context.
  • Bug fix: Invalid block encodings that could not be encoded in the available bitrate are more consistently rejected during decompression.

Binary release sha256 checksums

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3.1

Status: Released

The 3.1 release is the second release in the 3.x series. This release gives another performance boost, typically between 5 and 25% faster than the 3.0 release, as well as further incremental improvements to image quality. A number of build system improvements make astcenc easier and faster to integrate into other projects as a library, including support for building universal binaries on macOS. The full change list is shown below.

Reminder for users of the library interface - the API is not designed to be binary compatible across versions, and this release is not compatible with earlier releases. Please update and rebuild your client-side code using the updated astcenc.h header.

• General:
  • Feature: RGB color data now supports -perceptual operation. The current implementation is simple, weighting color channel errors by their contribution to perceived luminance. This mimics the behavior of the human visual system, which is most sensitive to green, then red, then blue.
  • Feature: Codec supports a new low weight search mode, which is a simpler weight assignment for encodings with a low number of weights in the weight grid. The weight threshold can be overridden using the new -lowweightmodelimit command line option.
  • Feature: All platform builds now support building a native binary. Native binaries automatically select the SIMD level based on the default configuration of the compiler in use. Native binaries built on one machine may use different SIMD options than native binaries build on another.
  • Feature: macOS platform builds now support building universal binaries containing both x86_64 and arm64 target support.
  • Feature: Building the command line can be disabled when using as a library in another project. Set -DCLI=OFF during the CMake configure step.
  • Feature: A standalone minimal example of the core codec API usage has been added in the ./Utils/Example/ directory.
• Core API:
  • Feature: Config flag ASTCENC_FLG_USE_PERCEPTUAL works for color data.
  • Feature: Config option tune_low_weight_count_limit added.
  • Feature: New heuristic added which prunes dual weight plane searches if they are unlikely to help. This heuristic is not user controllable.
  • Feature: Image quality has been improved. In general we see significant improvements (up to 0.2dB) for high bitrate encodings (4x4, 5x4), and a smaller improvement (up to 0.1dB) for lower bitrate encodings.
  • Bug fix: Arm "none" SIMD builds could be invariant with other builds. This fix has also been back-ported to the 2.x LTS branch.

Performance:

This release includes further performance optimizations which improve performance vs the 3.0 release by between 5% and 25%, depending on image and quality search preset used. High bitrate (e.g. 4x4) block sizes benefit the most for -fast searches, medium bitrate (e.g. 6x6) block sizes benefit the most for -medium and -thorough searches.

Image quality:

There are small image quality improvements of between 0.05-0.1dB for most bit rates, but larger improvements of up to 0.2 dB for high-bitrate encodings (eg. 4x4) for -fast and -medium searches.

Binary release sha256 checksums

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3.0

Status: Released

The 3.0 release is the first in a series of updates to the compressor that are making more radical changes than we felt we could make with the 2.x series. The primary goals of the 3.x series are to keep the image quality the same or better compared to the 2.5 release, but continue to improve performance.

Reminder for users of the library interface - the API is not designed to be binary compatible across versions, and this release is not compatible with earlier releases. Please update and rebuild your client-side code using the updated astcenc.h header.

• General:
  • Feature: The code has been significantly cleaned up, with improved comments, API documentation, function naming, and variable naming.
• Core API:
  • API Change: The core APIs for astcenc_compress_image() and for astcenc_decompress_image() now accept swizzle structures by const pointer, instead of pass-by-value.
  • API Change: Calling the astcenc_compress_reset() and the astcenc_decompress_reset() functions between images is no longer required f the context was created for use by a single thread.
  • Feature: New heuristics have been added for controlling when to search beyond 2 partitions and 1 plane, and when to search beyond 3 partitions and 1 plane. The previous tune_partition_early_out_limit config option has been removed, and replaced with two new options tune_2_partition_early_out_limit_factor and tune_3_partition_early_out_limit_factor. See command line help for more detailed documentation.
  • Feature: New heuristics have been added for controlling when to use dual weight planes. The previous tune_two_plane_early_out_limit has been renamed totune_2_plane_early_out_limit_correlation. See command line help for more detailed documentation.
  • Feature: Support for using dual weight planes has been restricted to single partition blocks; it rarely helps blocks with 2 or more partitions and takes considerable compression search time.

Performance:

This release includes further performance optimizations which improve performance vs the 2.5 release by between 25% and 75%, depending on image and quality search preset used. Smaller block sizes and higher search qualities benefit the most.

Image quality:

The -medium and -fast presets have been tuned to give measurably better image quality. Despite this they are still faster than the equivalent in the 2.5 release.

Binary release sha256 checksums

663f67a2eb85c4eb539857534f32d828aecff770dfb2fe35f2355996cbdf2bdd  astcenc-3.0-linux-x64.zip
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2.5

Status: Released

The 2.5 release is the last major release in the 2.x series. After this release a 2.x branch will provide stable long-term support, and the main branch will switch to focusing on more radical changes for the 3.x series.

Reminder for users of the library interface - the API is not designed to be stable across versions, and this release is not compatible with earlier 2.x releases. Please update and rebuild your client-side code using the updated astcenc.h header.

General:

• Feature: The ISA_INVARIANCE build option is no longer supported, as there is no longer any performance benefit from the variant paths. All builds are now using the equivalent of the ISA_INVARIANCE=ON setting, and all builds (except Armv7) are now believed to be invariant across operating systems, compilers, CPU architectures, and SIMD instruction sets.
• Feature: Armv8 32-bit builds with NEON are now supported, with out-of-the-box support for Arm Linux soft-float and hard-float ABIs. There are no pre-built binaries for these targets; support is included for library users targeting older 32-bit Android and iOS devices.
• Feature: A compressor mode for encoding HDR textures that have been encoded into LDR RGBM wrapper format is now supported. Note that this encoding has some strong recommendations for how the RGBM encoding is implemented to avoid block artifacts in the compressed image.

Core API:

• API Change: The core API has been changed to be a pure C API, making it easier to wrap the codec in a stable shared library ABI. Some entry points that used to accept references now expect pointers.
• API Change: The decompression functionality in the core API has been changed to allow use of multiple threads. The design pattern matches the compression functionality, requiring the caller to create the threads, synchronize them between images, and to call the new astcenc_decompress_reset() function between images.
• API Feature: Defines to support exporting public API entry point symbols from a shared object are provided, but not exposed off-the-shelf by the CMake provided by the project.
• API Feature: New astcenc_get_block_info() function added to the core API to allow users to perform high level analysis of compressed data. This API is not implemented in decompressor-only builds.
• API Feature: Codec configuration structure has been extended to expose the new RGBM compression mode. See the API header for details.

Performance:

This release includes further performance optimizations which improve performance vs the 2.4 release by between 15 and 25%, depending on image and quality search preset used.

Image quality:

The -fast and -fastest presets have been retuned to give measurably better image quality. Despite this they are still faster than the equivalent in the 2.4 release.

Binary release sha256 checksums

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