>>341479705
https://en.m.wikipedia.org/wiki/S3_Texture_Compression
>DXT1 (also known as Block Compression 1 or BC1) is the smallest variation of S3TC, storing 16 input pixels in 64 bits of output, consisting of two 16-bit RGB 5:6:5 color values c0 and c1, and a 4x4 two-bit lookup table.