What is a Bluetooth aptX codec, and should you care? (Sound guide)

Qualcomm, a major ARM System on a Chip (SoC) designer, invented the aptX codec (and variants) for Bluetooth sound devices.

aptX describes a series of Bluetooth Codecs as an alternative to SBC (Sub-band coding), AAC (Apple audio codec), LDAC (Sony hi-res Lossless Digital to Analog Converter), LHDC (Low Latency High-Definition Audio Codec), LLAC (Low Latency Audio Codec), and Samsung Scalable codec.

Today it is in every smartphone using a Qualcomm SoC and licensed to other OEMs to incorporate into non-Qualcomm devices.

Codecs influence how music files are compressed (encoded relates to bandwidth), transmitted, decoded and played. In this case, it is over low-bandwidth Bluetooth, but Codecs also include Dolby Atmos and many more.

Typical Bluetooth codecs

 SBCAACaptXaptX LLaptX HDaptX Adaptive
Bit depth161616162424
Sample rate44.1/4844.1/48SameSameSame+96kHz
Bit rate192-345/48kHz128-320/44.1kHz352/44.1kHz 384/48kHz384/48kHz576/24-bit/38kHz279-420 variable
Latency ms>200>20060-80<408080
Similar to AAC converts to SBC on Android devicesSBC without noise or distortionUsually requires a separate USB BT LL Dongle.LDAC and LHDC 

Bit rate (kbps) is the number of bits processed per second—a higher bit rate processes more data in the same amount of time. An MP3 is 320kbps, whereas a CD/FLAC/WAV/AIFF/ALAC is 1411kbps.

Bit depth is the number of bits of information in each sample. A higher bit depth requires more space and bandwidth and supports better sound quality.

Sample rate (kHz) is the number of audio samples recorded each second in a file.

There are other aptX variants, but the above covers the most frequently used.

CyberShack’s view – What is a Bluetooth aptX codec, and should you care

Why care? SBC and AAC are so yesterday and lose so much of the original music – once encoded (compressed), you can never get that back. It is a bit like the Vinyl versus CD debate.

aptX is better than SBC/AAC and now as popular. aptX LL is about low latency for gamers. aptX HD is about high-res music, and aptX Adaptive is probably the best overall choice.

But here is the rub. SBC, AAC (Fraunhofer FDK-AAC), and LDAC are free, so they tend to be used to avoid using Qualcomm SoC or Bluetooth chips or paying a licence.

Remember that this is only about transmitting over BT to headphones and speakers. The source content can be lossy, too – compressed MP3 to Hi-res. It’s a case of garbage in over lossy BT SBC/AAC gives garbage out.

CyberShack’s view is that aptX and its variants are desirable for better music but not essential.

BTW – you can add Qualcomm Codecs easily to your PC with Creative’s Bluetooth USB dongles.

CyberShack Bluetooth device reviews.