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Bluetooth Codecs Decoded: LDAC, aptX, AAC, and more

Bluetooth Codecs

Bluetooth codecs: Everything you need to know about in a nutshell

You keep hearing in headphone testing that the model doesn't support AptX or LDAC, and you're not sure what that implies. Then you've arrived at the perfect spot!

Since its introduction, Bluetooth technology has progressed significantly. Today, you have a variety of codecs to pick from that will vastly improve your audio experience. We'll go over what Bluetooth codecs are, how they work, and the various Bluetooth audio codecs in this guide.

Bluetooth Codecs

How Do They Work? What Are Their Functions?

A Bluetooth codec is a piece of software or algorithm that allows audio to be sent wirelessly between a source and a receiver. It takes your data (music), compresses it to reduce file size, and encodes it in a transmission-friendly manner. We'll need the same codec to decode the encoded data so we can listen to our music.

Simply put, it's a channel that allows audio from your phone to reach your Bluetooth headphones. The goal is to transmit audio with minimal data loss and latency, simulating the quality of wired audio.

However, lowering file size while retaining audio data fidelity is a difficult issue. The codec ignores concealed information in the music, information that can be deleted without a significant loss in quality, thanks to psychoacoustic study and analysis.

Each Bluetooth audio codec uses a different compression process and transmits data at a different pace. This has an impact on the latency and fidelity of wireless audio.

Audio Terminology for Beginners:

We must first recognize and understand some basic audio terminologies before diving into codecs and their properties.

Sample rate (Hz): Snapshots, or samples, of the incoming signal are captured at a certain rate, or sampling rate, in order to capture, store, and replicate a signal precisely. Two samples are required to accurately capture a given frequency. This indicates that audio is sampled at twice the human hearing limit (about 20Hz). 96kHz or higher is used for high-resolution formats.

Bit depth (-bit): The resolution of a file is determined by the number of bits per audio sample. CDs have a 16-bit resolution, whereas DVDs and Blu-ray discs may have a 24-bit resolution. A higher bit-depth, like a higher sampling rate, results in larger files.

Bit rate (kbps): The bit rate is a measurement of how quickly data is transported from one location to another. Bits per second is the unit of measurement (bps). We usually record this in kilobits per second (kbps) or megabits per second (Mbps). The sample rate x bit-depth x channels formula is used to compute the bit rate. The term bitrate is often used to define the fidelity of audio files.

The following are some of the most often used codecs:

1. SBC - Low Complexity Sub-band Coding

It's the first audio-transfer Bluetooth codec. It's part of the Advanced Audio Distribution Profile (A2DP), which is a collection of standard Bluetooth specifications for audio transmission.

SBC has a poor reputation among Bluetooth audio codecs because of its high lossy compression method, which results in lower audio quality overall. SBC, on the other hand, is a very adaptable codec. It has a sampling rate of up to 48 kHz and a bit depth of 16 bits. It can also transmit data at speeds of up to 345kbps.

SBC will work great if you don't care about HD audio and are using lossless files, but it can cause latency difficulties when used for gaming or watching streams.

2. aptX - Audio Processing Technology

Qualcomm is the owner of the aptX codec family. aptX was introduced as a replacement for SBC in order to address issues with SBC's implementation and sound quality.

Different aptX codecs are supported by Qualcomm: aptX, aptX Low Latency (LL), and aptX HD.

The standard Bluetooth codec in the music industry is aptX, which is noted for its minimal latency and outstanding audio quality. Despite the availability of various specialized variations, aptX remains a popular choice among professionals and laypeople alike.

3. aptX HD – High Definition

aptX HD was created to emulate high-resolution audio over Bluetooth. To send high-quality audio, you'll need to send larger audio files with less compression. Due to the restricted bandwidth of Bluetooth connections, this increases latency. Despite this, aptX HD is able to provide HD audio with low latency.

4. aptX LL – Low Latency

The aptX LL, like the aptX HD, is not a stand-alone codec. Low latency is abbreviated as LL. It provides lossless audio, unlike other aptX variations, as long as the signal strength is sufficient. This is a rare gift for audiophiles, as few codecs can match this level of fidelity.

Latency: The delay induced by audio processing is known as latency. It's the time it takes for data to be encoded, transferred, and received, and it'll make an appearance in gaming and dialogue sync in movies and TV shows.

5. AAC - Advanced Audio Codec

It is the lossy digital audio compression standard. It's also YouTube's license-free standard, as well as Apple's preferred method of data delivery. The hi-res playback of AAC, which peaks out at 250kbps, is especially beneficial to iPhone owners.

This is because AAC's file transport is based on psychoacoustic models, which consider what people can hear at the moment of compression. AAC gives higher sound quality on the iPhone because it demands more processing power and power management differs between Android and iOS.

6. LDAC 

You should pay attention to the Bluetooth LDAC codec if you wish to cut losses even more when streaming music wirelessly. LDAC comes in three different speeds: 990kbps, 660kbps, and 330kbps. Above 20Hz, the two highest bit rates lose fidelity, and both aptX and SBC surpass LDAC (330kbps).

Headphones that enable LDAC are hard to come by and often come with a hefty price tag.

7. LHDC – Low-Latency High-Definition Codec

The High-res Wireless Audio (HWA) Union and Savitech collaborated to create it. This codec is supported by all Android smartphones running Android 10 or higher, but not by iOS devices. It provides excellent audio quality while maintaining a minimal latency. Its key advantage is that it allows three times the amount of data transfer than SBC allows, and it offers a maximum bitrate of 900kbps and a maximum sample rate of 96kHz.

8. LC3 - Low Complexity Communication Codec

It's a brand-new codec created by Fraunhofer IIS and Ericsson to enable Bluetooth functionality in hearing aids. For one thing, the LC3 will help the deaf and hard-of-hearing community by enhancing Bluetooth capabilities, allowing a single source to broadcast to many Bluetooth devices. This means that hearing aids with Bluetooth will be able to broadcast audio (for example, train departure information) while keeping users aware of their surroundings.

9. SSC - Samsung Scalable Codec

This is a Samsung-developed proprietary codec for its Galaxy Buds True Wireless earbuds. This codec is solely supported by Samsung devices, as expected. The Samsung Scalable Codec is unique in that it can accommodate a wide range of bitrates. It can switch bitrate adaptively based on the stability of the Bluetooth connection to keep the connection stable and reduce choppy sounds.

What Is the Best Bluetooth Codec?

There isn't a single codec that excels in all circumstances. Due to the fact that Bluetooth codec technology is still in its early stages of development, audio quality and latency will always be a trade-off.

LDAC is a wonderful option if you want to listen to a premium streaming service with as little loss as possible. The Aptx or AptX HD is seen to be a decent compromise between distribution and compression, but the Apple faithful are once again left out. As a result, iPhone users should look into headphones that support SBC and AAC.

So, the next time you're searching for Bluetooth headphones, double-check the codecs they support and their specifications to ensure you get the most out of them.