aptX

A proprietary Bluetooth codec developed 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.

Although many think so, aptX is not lossless. It is an alternative for the standard SBC codec.

It has a fixed compression ration of 4:1 and a data rate of 352kbps.

aptX HD

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

Compression remains at a ratio of 4:1, with a bit rate of 576kbps.

Although the data rate is substantially higher compared with aptX, it is and remains a lossy codec.

aptX LL

Bluetooth latency is a bit high.
If you are sensitive to it, lip sync will be a problem.
Values are in the 200 ms range.
Aptx Low Latency cuts this down to 40 ms.

 

There are other proprietary codecs today offering an even higher bit-rate.

Bluetooth is covered in more detail here.

 

 

aptX - Qualcom