Rich Geldreich outlines the planning and current state of XBC7, an open source GPU texture compression format. XBC7 v1 is complete and supports lossless or lossy weight encoding via DPCM or DCT, near-lossless ASTC LDR 4x4 transcoding, threaded decoding, and legacy format support (ETC, PVRTC1, BC1). The encoder has significant headroom including potential Lagrangian RDO. XBC7 v2 plans include material stack support for 2-3 BC7 textures encoded simultaneously, exploiting inter-texture correlations for lower bpp on PBR textures. Future work includes CUDA tile decoding and an eventual HLSL decoder port. Geldreich notes that image/video codec specialists find the use of DCT/DST transforms for GPU textures obvious, questioning why the GPU texture community hasn't adopted these techniques sooner.
