PVRTC
PVRTC (PowerVR Texture Compression) and PVRTC2 are a family of lossy, fixed-rate texture compression formats used in PowerVR's MBX (PVRTC only), SGX and Rogue technologies. The PVRTC algorithm is documented in Simon Fenney's paper "Texture Compression using Low-Frequency Signal Modulation" that was presented (slides) at Graphics Hardware 2003.