Understanding Bluetooth Codecs

Matthew Cox | June 19, 2021 10:55 am

Before we jump into a discussion about Bluetooth codecs, what they are, and why they matter, we need to do a quick review of how Bluetooth works. Feel free to check out our detailed Bluetooth guide if you want to know more.

How does Bluetooth Work?

Bluetooth operates using what we refer to as Ultra High Frequencies (UHF for short). This frequency range is situated in the range of 300 MegaHertz (MHz) to 3 GigaHertz (GHz). This frequency band is known as the Decimetre Band as the waveforms range from 1 meter to 1/10th of a meter.

We can compare Bluetooth and how it works by looking at how other wireless technologies work, such as televisions, radios, or the internet. Waves of signal are transmitted through the air by a source device – this can be your WIFI router, TV station satellite, or radio tower. These waves are made up of many frequencies, each carrying specific information – such as a certain radio station’s feed. By tuning in or connecting on your receiving device (car radio, mobile phone, laptop, etc.), we can access this media that appears to be floating in the air.

Bluetooth works remarkably similarly; however, it cannot operate over such a large range compared to radio signals or the internet. Again, this is dependent on the Bluetooth version you are using to connect two or more devices. Bluetooth commonly operates over short distances of around 30f; this is plenty of space to work with when performing simple tasks such as:

  • Connecting a wireless mouse or keyboard to your computer
  • Sending and receiving audio, photo, video, or documents between devices
  • Streaming audio from a cell phone or computer to a wireless sound system
  • Or mirroring the screen on one device in real-time onto a television or computer.

So, Bluetooth effectively sends and receives data using the abovementioned radio waves across a band of 79 different frequencies or channels, situated around 2.45 GigaHertz. This frequency band is separate from radios, television, cellphones, and other frequencies reserved by industrial, military, scientific, or medical technology. 

When you link two devices via Bluetooth, they pick a random channel of the 79 options and switch frequencies thousands of times per second to minimize the risk of interfering with other electrical devices and improve security. This is known as Spread Spectrum Frequency Hopping. When multiple devices share information, a computer forms a network-like system known as a Piconet. Multiple Piconet’s joined together to make up a Scatternet.

Bluetooth Codecs

Bluetooth Audio Codecs

A Bluetooth Audio Codec is a concept necessary to understand to gain a better-informed idea of how your device will operate with other pieces of technology.

A codec determines how Bluetooth will be transmitted from the source device to the Bluetooth speaker or receiving device.

As one can imagine, the name is derived from encoding and decoding the transferred media. Without getting too involved, we need to understand how different codecs affect the signal in question differently – some provide stronger connection strength, while some provide improved audio quality. The various Bluetooth codec options are as follows:

  • SBC Codec: This codec’s full name is Low Complexity Sub Band Codec and was the codec in which Bluetooth was first used. It can be described as the simplest of Bluetooth codecs, as it is the minimum requirement for any wireless audio streaming capable device. While this codec fits within Bluetooth’s frequency band and has the necessary processing power to allow multiple devices to communicate, it does, however, cause some data loss, which can be in the form of reduced dynamic range and frequency response.  Factors that can severely degrade the audio fidelity you’re sending through the network.
  • Qualcomm Codec: Qualcomm hosts a range of higher-quality wireless audio codecs; this family of codecs comprises AptX, aptX HD, aptX Adaptive, and aptX LL.
  • aptX: The most basic of the modern codec varieties. This codec supports streaming at a sample rate of 48kHz and a bit depth of 16-bits. This is similar to CD-quality audio. 
  • aptX HD: The HD variant of aptX is further improved, supporting 48kHz sampling rates at 24-bit bit depths. This leads to an improved dynamic range. 
  • aptX LL: This is the Low Latency version of aptX, which means a faster response time between the communicating devices in use. aptX Adaptive is a soon-to-be-released codec format that will replace aptX Low Latency mode. It is important to note that while they are significantly superior to the basic SBC codec, the codecs mentioned above can still inflict some data loss. 
  • Sont LDAC: Sont LDAC is a codec developed by Sony Technology that can operate in three separate streaming rate settings. While some of the options are superior to SBC and aptX, most mobile phones will default to the lowest mode, which essentially functions on the same settings as SBC, and unless you’re a computer programmer, you can’t really adjust these modes.

There are a few other Bluetooth codecs on the market; however, these are specifically for certain manufacturers and aren’t too important to know when it comes to the context of this article. Different Bluetooth codecs also operate along with different wireless ranges. Typically, a more modernized and advanced codec can securely connect to another Bluetooth device over a longer physical distance.

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Author: Matthew Cox

A sound engineering student and musician, Matthew enjoys writing and performing music, working in the studio, and geeking out over anything audio-related.

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