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
| SBC | AAC | aptX | aptX LL | aptX HD | aptX Adaptive | |
| Bit depth | 16 | 16 | 16 | 16 | 24 | 24 |
| Sample rate | 44.1/48 | 44.1/48 | Same | Same | Same | +96kHz |
| Bit rate | 192-345/48kHz | 128-320/44.1kHz | 352/44.1kHz 384/48kHz | 384/48kHz | 576/24-bit/38kHz | 279-420 variable |
| Latency ms | >200 | >200 | 60-80 | <40 | 80 | 80 |
| Compression | Lossy | Lossy | 4:1 | Lossy | Lossless | Lossless |
| Similar to | AAC converts to SBC on Android devices | SBC without noise or distortion | Usually 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.
