3.x series change log

This page summarizes the major functional and performance changes in each release of the 3.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.

3.3

Status: November 2021

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 a constant color blocks.

3.2

Status: August 2021

The 3.2 release is a bugfix release; no significant image quality or performance differences are expected.

• General:
  • Bug-fix: Improved stability when new contexts were created while other contexts were compressing or decompressing an image.
  • Bug-fix: Improved stability when decompressing blocks with invalid block encodings.

3.1

Status: July 2021

The 3.1 release is the second release in the 3.x series. This release gives another performance boost, typically between 5 and 20% 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. 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:

Key for charts:

• Color = block size (see legend).
• Letter = image format (N = normal map, G = greyscale, L = LDR, H = HDR).

Relative performance vs 3.0 release:

3.0

Status: June 2021

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 ~static 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 if 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:

Key for charts:

• Color = block size (see legend).
• Letter = image format (N = normal map, G = greyscale, L = LDR, H = HDR).

Absolute performance vs 2.5 release:

Relative performance vs 2.5 release: