Bluetooth is a blessing to the world because the technology is pushing the world towards wireless connectivity of electronic devices. Bluetooth connectivity is now a regular thing in music devices such as headphones. The constant development of Bluetooth versions, as well as audio compression codecs, makes it possible to send the audio signal without losing the quality of the method.
In recent times, many audio codecs have flooded the market. While buying a Bluetooth audio device, the choice of audio codec is very important. This is because it literally determines the audio quality you can expect from the device. We’ll explain everything you need to know about Bluetooth audio codecs from technical terminology to different audio codecs.
What is Bluetooth Codec?
A codec is a technology that compresses and decompresses data for faster and easier transmission. A codec has two components – an encoder to compress the data and a decoder to decompress the data. A Bluetooth codec decides how data is sent from the source, such as your smartphone, to the destination, such as your headphones via Bluetooth technology.
The main goal of a Bluetooth codec is to send a high-fidelity audio signal at a minimum bit rate. This helps in transmitting audio signals with minimum bandwidth and therefore, at a faster speed. Similarly, the storage space and memory required for playback is also less.
Note: A lower bit rate ensures greater compression with reduced audio quality. Conversely, a high bit rate ensures less compression with better audio quality.
Why Do You Need a Codec In Bluetooth Audio Transmission?
In Bluetooth connection, you need a transmitter and a receiver. In this case, the Bluetooth audio transmitter is your smartphone, and the Bluetooth audio receiver is your headphones. The job of the transmitter is not just to send the audio file to the receiver. This is because sending the audio file in its raw form wirelessly will exceed the bandwidth of the Bluetooth connection.
Depending on the quality of the recorded audio, the file size is determined. High quality audio can be a large file size. On top of that, popular lossless audio file formats like WAV and AIFF will ensure that the file size remains large. Since the Bluetooth connection has a limited bandwidth, the audio connection established through Bluetooth will begin to stutter, and the audio quality will suffer. So there is a need for encoding and decoding, and that’s where a codec comes into play.
How Does Bluetooth Wireless Audio Transmission Work?
A Bluetooth transmitter can reduce the size of the audio file using an algorithm, and the audio file becomes a compressed file. This process is called encoding and is done by an encoder in the codec. The compressed file is sent to the Bluetooth receiver.
The compressed file is not a viable audio file, and therefore, it must be decompressed. This decompression action is performed by a codec decoder. After decompression, the audio file will be playable.
A codec is an algorithm that takes audio data, compresses it to reduce size, encodes it in a format for transmission. The same codec decodes the receiver format and makes the data playable for the user.
Each codec has a unique algorithm for compressing audio data. Compression involves reducing the audio data without reducing the quality significantly. That is why there are various Bluetooth audio codecs available in the market. We will discuss them in detail in the following sections.
Terminology For Bluetooth Audio Codec
Before going to the different Bluetooth audio codecs, we need to discuss the related terminology for your better understanding.
1. Sample Rate
It refers to the number of data points contained in an audio file per second. In simple words, it refers to the frequency of the analog signal being transmitted. It is measured in Hz.
2. Bit Depth
This refers to the number of bits per audio sample. This is a measurement of audio resolution and quality. It is represented in bits. You’ll find DVDs provide 24-bit while CDs provide 16-bit.
3. Bit Rate
It refers to the number of bits processed per second. It is represented in kilobits per second (kbps) or megabits per second (mbps).
4. Data Rate
This refers to the data sent per second.
5. Sampling Depth
This refers to the resolution of the audio data in the file.
This refers to the lag between the transmission and reception of the audio signal.
Different Types of Bluetooth Audio Codecs
1. SBC (Sub-Band Codec)
This is the most common codec that you will find in almost all wireless headphones. However, its compression leads to severe loss of audio quality. Its bit rate reaches a maximum of 345 kbps while its sample rate reaches a maximum of 45KHz.
The reason for the wide use of SBC is that it is suitable for transmitting good enough audio quality at a medium bit rate. So, there are no streaming issues, and the transfer rates are easily manageable. The reason is that if a headphone has only SBC, the audio quality is not superior.
2. AAC (Advanced Audio Codec)
You can find this codec on iPhones and iPads. It is also compatible with Android. The codec supports 320 kbps bit rate at 24-bit depth and 96Khz sample rate. It uses a psychoacoustic model in its compression algorithm.
iOS device owners are recommended to purchase headphones that support AAC for the best audio quality. The popular Bose Noise Canceling Headphones 720 has this advanced audio codec and you know how powerful and high quality audio output it produces.
3. AptX (Audio Processing Technology)
The codec is designed by Qualcomm, and it ensures better audio quality. You can find it under different labels like AptX, AptX HD, AptX LL. They have different bit rates, sample rates, and bit depths.
In AptX HD, the maximum bit rate is 567 kbps with a sample rate of 48 Khz and a bit depth of 24-bit. In AptX, the maximum bit rate is 384 kbps with a sample rate of 48 Khz and a bit depth of 16-bit. However, they both have a latency of 170 and 270 milliseconds, respectively.
This latency problem is solved with AptX LL where the latency is reduced to only 40 milliseconds. If you opt for a gaming headset, you should have low latency and therefore, AptX LL is a better codec choice. However, Apple does not support AptX LL.
4. AptX Lossless
AptX Lossless is one of the latest codecs designed by Qualcomm. It was released in the second half of 2021. It offers a sample rate of 44.1KHz at 16-bit depth. It is perfectly suitable for premium audio streaming as the audio quality loss is minimal. However, both the source and the destination must support the codec for it to work properly.
5. AptX Adaptive
AptX Adaptive came out as the successor of AptX, but it did not reach the popularity as expected. You can see the codec on selected headphones only. It is better than AptX, and you have different advantages over other versions of AptX.
The latency is relatively low, and therefore, it is suitable for gamers and movie watchers. It can achieve a maximum bit rate of 420 kbps, and the latency is about 80 milliseconds. The codec has backward compatibility as well.
6. LDAC (Lossless Digital to Analog Converter)
The codec was designed by Sony, and they are a pioneer in the audio device industry. The codec focuses on reducing audio quality loss during transmission and streaming. The maximum bit rate is 990 kbps with a sample rate of 48KHz and a bit depth of 16 bits.
There are many devices that support the LDAC codec, and you get true HD audio quality. However, if you use it on an Apple device, you won’t notice the quality differences because the bit rate is automatically lowered.
There are three different modes available – 990 kbps, 660 kbps, and 330 kbps. By default, smartphones use 330 kbps, but you can upgrade it to two other options. You need to use high-end headphones to get the best LDAC.
7. LHDC (Low-Latency and High-Definition Audio Codec)
This codec is available in some high-end headphones, such as the OnePlus Buds Pro. The maximum bit rate is 900 kbps with a sample rate of 96KHz and a bit depth of 24 bits. Although it has very low latency, it has not yet developed a widespread application outside of flagship headphones.
The latest version of Bluetooth has the LC3 codec, which ensures better audio quality at a lower sample rate. This is a dream come true codec for audio geeks. You can consider it the newest Bluetooth audio codec on the market.
The codec delivers audio to people using Bluetooth-enabled hearing aids. They can stream any audio and still be aware of their surroundings. You can stream audio to multiple Bluetooth devices from one source.
Comparison Between Different Codecs
|Codec||Max Bitrate||Bit depth||Sample Rate||Indicated Year|
|SBC||320 kbps||16 little||48.0 kHz||2003|
|AAC||264 kbps||16 little||44.1 kHz||2015|
|aptX||352 kbps||16 little||48.0 kHz||2009|
|aptX HD||576 kbps||24 little||48.0 kHz||2016|
|aptX LL||352 kbps||16 little||44.1 kHz||2016|
|LDAC||990 kbps||24 little||96.0 kHz||2015|
Buying a Bluetooth-enabled audio device with the latest codec may not always be the right choice. This is because compatibility is important, and the source device should not automatically lower the audio parameters. Therefore, you should always aim for the best audio quality with less important parameters for your understanding and quick decision making.