aptX

A proprietary codec by CSR (Qualcomm today)
As it is not a mandatory part of the standard you need both a sender and a receiver (SouRCe and SiNK in Bluetooth lingo) supporting this protocol.

It is a lossy protocol but said to improve sound quality wise on SBC

 

An overview of devices supporting aptX

 

aptX HD

In January 2016 Qualcomm announced  aptX HD, it support 24 bits / 48 kHz LPCM audio over Bluetooth.

The big difference with APTX of course is that this is lossless audio over Bluetooth.

An overview of devices supporting aptX HD

 

Website: aptX - Qualcom