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@@ -71,39 +71,39 @@ UASTC HDR 4x4, ASTC HDR 6x6, and UASTC HDR 6x6 files can be transcoded to:
Supported Texture Compression/Supercompression Modes
----------------------------------------------------
1. [ETC1S](https://github.com/BinomialLLC/basis_universal/wiki/.basis-File-Format-and-ETC1S-Texture-Video-Specification): A roughly .3-3bpp low to medium quality supercompressed mode based off a subset of [ETC1](https://en.wikipedia.org/wiki/Ericsson_Texture_Compression) called "ETC1S". This mode supports variable quality vs. file size levels (like JPEG), alpha channels, built-in compression, and texture arrays optionally compressed as a video sequence using skip blocks ([Conditional Replenishment](https://en.wikipedia.org/wiki/MPEG-1)). This mode can be rapidly transcoded to all of the supported LDR texture formats.
1. **[ETC1S](https://github.com/BinomialLLC/basis_universal/wiki/.basis-File-Format-and-ETC1S-Texture-Video-Specification)**: A roughly .3-3bpp low to medium quality supercompressed mode based off a subset of [ETC1](https://en.wikipedia.org/wiki/Ericsson_Texture_Compression) called "ETC1S". This mode supports variable quality vs. file size levels (like JPEG), alpha channels, built-in compression, and texture arrays optionally compressed as a video sequence using skip blocks ([Conditional Replenishment](https://en.wikipedia.org/wiki/MPEG-1)). This mode can be rapidly transcoded to all of the supported LDR texture formats.
2. [UASTC LDR 4x4](https://github.com/BinomialLLC/basis_universal/wiki/UASTC-LDR-4x4-Texture-Specification): An 8 bits/pixel LDR high quality mode. UASTC LDR is a 19 mode subset of the standard [ASTC LDR](https://en.wikipedia.org/wiki/Adaptive_scalable_texture_compression) 4x4 (8bpp) texture format, but with a custom block format containing transcoding hints. Transcoding UASTC LDR to ASTC LDR and BC7 are particularly fast and simple, because UASTC LDR is a common subset of both BC7 and ASTC. The transcoders for the other texture formats are accelerated by several format-specific hint bits present in each UASTC LDR block.
2. **[UASTC LDR 4x4](https://github.com/BinomialLLC/basis_universal/wiki/UASTC-LDR-4x4-Texture-Specification)**: An 8 bits/pixel LDR high quality mode. UASTC LDR is a 19 mode subset of the standard [ASTC LDR](https://en.wikipedia.org/wiki/Adaptive_scalable_texture_compression) 4x4 (8bpp) texture format, but with a custom block format containing transcoding hints. Transcoding UASTC LDR to ASTC LDR and BC7 are particularly fast and simple, because UASTC LDR is a common subset of both BC7 and ASTC. The transcoders for the other texture formats are accelerated by several format-specific hint bits present in each UASTC LDR block.
This mode supports an optional [Rate-Distortion Optimizated (RDO)](https://en.wikipedia.org/wiki/Rate%E2%80%93distortion_optimization) post-process stage that conditions the encoded UASTC LDR texture data in the .KTX2/.basis file so it can be more effectively LZ compressed. More details [here](https://github.com/BinomialLLC/basis_universal/wiki/UASTC-implementation-details).
Here is the [UASTC LDR 4x4 specification document](https://github.com/BinomialLLC/basis_universal/wiki/UASTC-LDR-4x4-Texture-Specification).
3. [UASTC HDR 4x4](https://github.com/BinomialLLC/basis_universal/wiki/UASTC-HDR-4x4-Texture-Specification-v1.0): An 8 bits/pixel HDR high quality mode. This is a 24 mode subset of the standard [ASTC HDR](https://en.wikipedia.org/wiki/Adaptive_scalable_texture_compression) 4x4 (8bpp) texture format. It's designed to be high quality, supporting the 27 partition patterns in common between BC6H and ASTC, and fast to transcode with very little loss (typically a fraction of a dB PSNR) to the BC6H HDR texture format. Notably, **UASTC HDR 4x4 data is 100% standard ASTC texture data**, so no transcoding at all is required on devices or API's supporting ASTC HDR. This mode can also be transcoded to various 32-64bpp uncompressed HDR texture/image formats.
3. **[UASTC HDR 4x4](https://github.com/BinomialLLC/basis_universal/wiki/UASTC-HDR-4x4-Texture-Specification-v1.0)**: An 8 bits/pixel HDR high quality mode. This is a 24 mode subset of the standard [ASTC HDR](https://en.wikipedia.org/wiki/Adaptive_scalable_texture_compression) 4x4 (8bpp) texture format. It's designed to be high quality, supporting the 27 partition patterns in common between BC6H and ASTC, and fast to transcode with very little loss (typically a fraction of a dB PSNR) to the BC6H HDR texture format. Notably, **UASTC HDR 4x4 data is 100% standard ASTC texture data**, so no transcoding at all is required on devices or API's supporting ASTC HDR. This mode can also be transcoded to various 32-64bpp uncompressed HDR texture/image formats.
Here is the [UASTC HDR 4x4 specification document](https://github.com/BinomialLLC/basis_universal/wiki/UASTC-HDR-4x4-Texture-Specification-v1.0), and here are some compressed [example images](https://github.com/BinomialLLC/basis_universal/wiki/UASTC-HDR-Examples).
4. ASTC HDR 6x6 or RDO ASTC HDR 6x6: A 3.56 bits/pixel (or less with RDO+Zstd) HDR high quality mode. Just like mode #3, **ASTC HDR 6x6 data is 100% standard ASTC texture data**. Here's a [page with details](https://github.com/BinomialLLC/basis_universal/wiki/UASTC-HDR-6x6-Support-Notes). The current encoder supports weight grid upsampling, 1-3 subsets, single or dual planes, CEM's 7 and 11, and all unique ASTC partition patterns.
4. **ASTC HDR 6x6 or RDO ASTC HDR 6x6**: A 3.56 bits/pixel (or less with RDO+Zstd) HDR high quality mode. Just like mode #3, **ASTC HDR 6x6 data is 100% standard ASTC texture data**. Here's a [page with details](https://github.com/BinomialLLC/basis_universal/wiki/UASTC-HDR-6x6-Support-Notes). The current encoder supports weight grid upsampling, 1-3 subsets, single or dual planes, CEM's 7 and 11, and all unique ASTC partition patterns.
The ASTC HDR decoder, used in the transcoder module, supports the entire ASTC HDR format.
5. UASTC HDR 6x6 Intermediate ("GPU Photo"): A custom compressed intermediate format that can be rapidly transcoded to ASTC HDR 6x6, BC6H, and various uncompressed HDR formats. The custom compressed file format is [described here](https://github.com/BinomialLLC/basis_universal/wiki/UASTC-HDR-6x6-Intermediate-File-Format-(Basis-GPU-Photo-6x6)). The format supports 75 unique ASTC configurations, weight grid upsampling, 1-3 subsets, single or dual planes, CEM's 7 and 11, and all unique ASTC partition patterns.
5. **UASTC HDR 6x6 Intermediate ("GPU Photo")**: A custom compressed intermediate format that can be rapidly transcoded to ASTC HDR 6x6, BC6H, and various uncompressed HDR formats. The custom compressed file format is [described here](https://github.com/BinomialLLC/basis_universal/wiki/UASTC-HDR-6x6-Intermediate-File-Format-(Basis-GPU-Photo-6x6)). The format supports 75 unique ASTC configurations, weight grid upsampling, 1-3 subsets, single or dual planes, CEM's 7 and 11, and all unique ASTC partition patterns.
6. Standard ASTC LDR-4x4-12x12. Supports all 14 ASTC block sizes. Transcodable to any other supported LDR texture format.
6. **Standard ASTC LDR-4x4-12x12**. Supports all 14 ASTC block sizes. Transcodable to any other supported LDR texture format.
The ASTC LDR decoder, used in the transcoder module, supports the entire standard ASTC LDR format.
7. XUASTC LDR 4x4-12x12: Supercompressed ASTC with weight grid DCT. Bitrate ranges between approximately .3-5.7bpp, depending on profile, block size, and weight grid DCT quality settings. Supports context-based range/arithmetic coding (for higher ratios), Zstd (for faster transcoding), or a hybrid profile using both. Supports all 14 ASTC block sizes. Transcodable to all other supported LDR texture formats. Certain common block sizes (4x4, 6x6, and 8x6) have specializations for particularly fast transcoding directly to BC7.
7. **XUASTC LDR 4x4-12x12**: Supercompressed ASTC with weight grid DCT. Bitrate ranges between approximately .3-5.7bpp, depending on profile, block size, and weight grid DCT quality settings. Supports context-based range/arithmetic coding (for higher ratios), Zstd (for faster transcoding), or a hybrid profile using both. Supports all 14 ASTC block sizes. Transcodable to all other supported LDR texture formats. Certain common block sizes (4x4, 6x6, and 8x6) have specializations for particularly fast transcoding directly to BC7.
Supported ASTC configurations: L/LA/RGB/RGBA CEM's, base+scale or RGB/RGBA direct, base+ofs CEM's, Blue Contraction encoding, 1-3 subsets, all partition patterns, single or dual plane.
Here is the [XUASTC LDR specification](https://github.com/BinomialLLC/basis_universal/wiki/XUASTC-LDR-Specification-v1.0).
Notes:
- Modes #3 (UASTC HDR 4x4) and #4 (plain or RDO ASTC HDR 6x6) output 100% standard or plain ASTC texture data (with or without RDO), like any other ASTC encoder. The .KTX2 files are just plain textures.
- The other modes (#1, #2, #5) output compressed data in various custom formats, which our transcoder library can convert in real-time to various GPU texture or pixel formats.
- Modes #4 and #5 internally use the same unified ASTC HDR 6x6 encoder.
- Modes #6 and #7 internally use the same unified ASTC LDR ASTC encoder.
- Modes #3 (UASTC HDR 4x4) and #4 (RDO ASTC HDR 6x6), and #6 (ASTC LDR 4x4-12x12) output 100% standard or plain ASTC texture data (with or without RDO), like any other ASTC encoder. The .KTX2 files are just plain textures.
- The other modes (#1, #2, #5) output compressed data in various custom supercompressed formats, which our transcoder library can convert in real-time to various GPU texture or pixel formats.
- Modes #4 (ASTC HDR 6x6) and #5 (UASTC HDR 6x6) internally use the same unified ASTC HDR 6x6 encoder.
- Modes #6 (ASTC LDR 4x4-12x12) and #7 (XUASTC LDR 4x4-12x12) internally use the same unified ASTC LDR ASTC encoder.
### Other Features