Windows / Direct3D 11 port of the shader_deblocking_glfw OpenGL sample: same assets, same behavior, same controls, same shader logic — only the graphics API layer changes. The primary deliverable is bin/deblock.hlsl, which contains the deblocking operator as a reusable DeblockSample() function that engine integrators can lift verbatim.

Two facts to understand before using the shader:

This is an in-loop filter. The Basis Universal encoder factors this exact deblocking operator into its rate/quality decisions — it is the decoder half of the codec, not an optional post-process. When a KTX2 file's DeblockingFilterIndex == 1, viewers should enable the GPU deblock shader by default, and the CPU transcoder must be passed cDecodeFlagsNoDeblockFiltering so the image is not deblocked twice.
The filter block size is a property of the encoded SOURCE, not the GPU format. On desktop D3D there is no ASTC support, so textures transcode to BC7 — but transcoding changes the container, not the artifact lattice. An 8x8 XUASTC source transcoded to BC7 still carries seams on the 8x8 source grid, and the shader must deblock at 8x8. The block size passed to the shader comes from the KTX2 header (get_block_width()/get_block_height()), never from the chosen GPU format.

Building

cmake -B build -S .
cmake --build build --config Release

No dependencies beyond the C runtime, Win32, D3D11, and D3DCompiler. The Basis Universal transcoder is compiled in directly. The executable is written to bin/, next to deblock.hlsl and the test .ktx2 files, and loads the shader from the working directory at runtime (edit deblock.hlsl and press R to reload).

Running

cd bin
deblock_d3d11 kodim26_12x12.ktx2            (12x12 XUASTC; deblock auto-enables)
deblock_d3d11 t8x8.ktx2                     (8x8 test texture)
deblock_d3d11 <file.ktx2> [--bc7|--rgba32] [--nomips]

GPU format selection: BC7 when the base mip is 4-aligned (or the texture is single-level, in which case the dims are rounded up to the 4x4 block grid — the padding is encoder-duplicated edge texels); otherwise uncompressed RGBA8. See the GPU-format-selection comment in load_ktx2_texture in main.cpp. LDR textures only.

Controls

Arrows move, W/S zoom, A/D yaw, Q/E pitch, Shift slow, C cube/quad, P/B/T point/bilinear/trilinear, 1 deblock on/off, 2 block-edge weight visualization, 3-8 spare constant toggles, R reload shader, Space reset, Esc quit.