https://www.khronos.org/opengl/wiki/ASTC_Texture_Compression

https://www.khronos.org/opengl/wiki/Image_Format

ASTC Texture Compression (KHR_texture_compression_astc_hdr only) is a block compression encoding scheme that allows for a variable block size. 

It supports both floating-point and normalized integer formats, as well as sRGB encoding for normalized integers. It can even compress different channels separately, like RGTC formats.