Bluetooth Audio Codecs Explained

Having fewer wire clutters to deal with is a relief and luckily some smartphone companies are bringing back the headphone jack. Bluetooth’s presence is literally more prominent than ever because of the trend for wireless audio gear.

Bluetooth Audio Codecs come in very handy in this situation. In this article, you will understand what Bluetooth codecs are, audio quality variations, different codecs and levels of stability.

Bluetooth audio codecs explained – GIZMOTRIBE

Basic Terminologies of Bluetooth Codecs

Sample Rate (Hz): Sample rate is the number of samples taken from a set of signals per unit time. Audio is sampled at 40 Hz i.e two times the limit of human hearing (20 Hz). So, to capture a frequency accurately, two samples are to be captured. Pulse code modulation is used to store audio signals.

Incoming signals are captured, stored, and reproduced – they are taken at a sampling rate measured in hertz. The minimum sampling rate needed to produce a full spectrum of audio signals is 44,100 samples per second i.e. 44100Hz or 44.1KHz.

For consumer use, 44.1KHz is acceptable but you can see higher sample rates for music like 48KHz even 192KHz. One reason why 44.1KHz is used as a sample rate for consumer use is it allows accurate reproduction of frequencies up to 22,020Hz. Lower sample rates can be used with audio, like speech as critical listening is not required.

Bit-depth: is the amount of information present in a single audio data. It dictates a file’s resolution. The bit depths used for music are 16 bit and 24 bit. Bit depth corresponds to the resolution of an audio sample. It is similar to the dynamic range.

Dynamic range is the resolution and distance between the silent and the loudest sounds in audio data. 16 bits are commonly used on CDs, while Blu-ray and DVDs discs support a bit depth of 24-bit. Hi-res audio currently supports the use of 24bit, so consumers can buy lossless music formats with high bit depths.

From MasteringTheMix

Bitrate: measured in bits per second (bps), kilobits per second (kbps), and megabits per second (Mbps). Bitrate is the number of data carried in bits transferred per unit time. Bitrate can be used to describe the fidelity of audio files.

Here’s how: Let’s say an MP3 file is compressed at 350kbps, it will have a better sound quality and dynamic range compared to the one compressed at 120kpbs. The higher the bitrate, the higher the sample rate and the depth that is sent wirelessly and in turn improving the quality of the audio. But audio files with high bitrate tend to have a high bandwidth used in transmission. Bitrate can be calculated using this formula:

Bitrate formula = Bit depth x Sample rate x No of channels

Bluetooth codecs can change the rate at which audio data is being transmitted, thereby affecting audio quality.

HD Audio: More users are getting more accustomed to lossless file formats, as they are one of the best ways to distribute music. Streaming platforms like Tidal and Qobuz are some of the companies utilizing lossless files to deliver their services.

Audiophiles and music collectors are moving away from CDs and all physical mediums- most enjoy digital HD formats like ALAC, AIFF, WAV, and FLAC. For users of HD audio, it is important to choose equipment that will deliver the best results.

What is a Bluetooth Codec?

A codec encodes and decodes audio data into a different format. It determines how Bluetooth is transmitted from a source to your headphones.The source can be your tablets, smartphone, or computer. Bluetooth codecs transmit high-quality audio signals at the smallest bit rate thereby reducing bandwidth and space requirements of the playback.

As we stated earlier, a high bitrate leads to great audio quality and less compression while a lower bitrate leads to low audio quality and high compression. One of the greatest hindrances of Bluetooth is limited bandwidth – it can result in connection problems.

But, there are situations where a low bitrate comes very useful. For example, in an area with heavy traffic, a low bit rate makes the connection strength more stable. The Bluetooth connection is stable but the sound quality produced is low.

Bluetooth Transfer rates

It is very vital to note that Bluetooth data transfer rates are inconsistent. When a company claims a specific transfer rate for its codec, it is not likely the only transfer rate. It is within the range of the value provided. No matter how smooth the connection of the Bluetooth is, your streaming speed may never reach that amount.

This phenomenon was demonstrated by SoundGuys regarding Androids encoding of AAC and Sony LDAC with their latency issues. If you use wireless earbuds and subscribe to lossless music from streaming services like Apple Music, Amazon Music HD, you will not enjoy the full benefits of high-resolution playback.

Some of the audio data cannot be transmitted from a smartphone to Bluetooth Earphones, due to the fact that Bluetooth transmits lossy audio. There is a limitation to the wired playback when you use Airpods Max that has lighting to 3.5mm cable. This is because data is lost during the re-digitization process. To get a normal/ high bit rate and sample rate, a direct TRRS connection will do the trick.

Most Bluetooth devices have a connectivity range, this is usually three meters from the headphones or earbuds. The farther you move away from your source, the interference the signal has to remove increases. This interference might be air, people, walls, and other frequencies too like Wi-Fi signals and radio waves.

The way humans process sound (psychoacoustics) can be related to digital media. In fact, it’s a very important term to be aware of. It shows the data points that need to be deleted or compressed without degradation to the sound quality.

From SoundGuys

Types of Bluetooth Codecs

1. SBC

2. QUALCOMM’S APTX Codecs

3. AAC

4. SONY LDAC

5. LHDAC AND LLAC Codecs

6. SAMSUNG SCALABLE Codecs

7. BLUETOOTH LE AUDIO LC3 Codecs

SBC (Low Complexity Subband Codec)

SBC is the first Bluetooth codec introduced to transfer audio data. It is integrated to work with a set of default Bluetooth specifications to stream audio over Bluetooth ( Audio Distribution Profile). Every Bluetooth device is compatible and communicates easily with this codec because of its A2DP characteristics. SBC is public domain, so it is used by a lot of Bluetooth equipment manufacturers.

However, most users do not like using this codec because it has a high lossy compression algorithm thereby producing low audio quality. Putting the low audio quality aside, SBC is very easy-to-use. It supports up to 48KHz sample rate and 16-bit bit depth. It can also transfer data at high rates as 256 kbps. Manufacturers don’t stretch the SBC features to the max due to improved device performances. A high bitrate of 256 kbps is equal to the quality of an MP3 recording.

When using this codec to play games or stream music, you will experience latency issues. But, this issue is not unique to SBC alone. The thing is, SBC will be a great fit for you if you’re not concerned about HD audio. It is efficient and consumes less battery. Even in noisy situations like a subway or when you’re using low-quality earbuds, you won’t notice the difference between SBC and the other discussed in the upcoming paragraphs.

Highlights

  • Low power consumption
  • Supports 16-bit/48KHz files
  • Bit rates up to 256kbps
  • Universal compatibility

QUALCOMM APTX Codecs

All APTX codecs are owned by Qualcomm. It was introduced as an improvement to SBC, addressing all the complaints about SBC’s sound quality and implementation. The data compression used in the APTX codec is different from the one used in SBC.

Instead of psychoacoustic analysis and masking to delete or compress unnecessary files, it coded them in another way to reduce the bandwidth. Qualcomm is not public domain, they charge manufacturers a fee to use it. Manufacturers have to pay a one-time payment fee of $6,000 and $1 per device to use the APTX codec.

Key features of QUALCOMM’s APTX Codecs

  • Supported on Windows desktop
  • Supports bit rates of up to 384kbps
  • Supports 16-bit/48KHz audio files
  • No iOS support

APTX HD

APTX HD is an improved encoding profile. It is not a standalone audio codec and it supports high bit rates and bit depths. APTX produces better sound, less noise with more dynamic range. It offers high-quality audio that can literally be the same as the original file. However, this codec is not widely used by manufacturers.

Highlights

  • Supports high bit rates of up tp 576kbps
  • Supports 24-bit/48KHz audio files
  • Doesn’t support IOs
  • Can be used in Android 8+
  • An improved APTX encoding profile

APTX LL

Like the APTX HD, the LL is not standalone. LL represents low latency. This codec works on improving latency issues. Latency lag experienced due to audio processing. It is the time delay between the data being processed and received.

It is the cause of the delay in dialogue sync or gameplay in films and TV. For most codecs, the most common issue is Latency. When listening to music, you may not experience it at all. But for playing games or watching films, the latency gets obvious and you see the non-sync problem.

It is important to make APTX LLC a requirement if you want to get wireless headphones for watching films or gaming. Be sure to check if your audio source supports the same codec as your headphones. If not, they might change back to their default codec settings. APTX LLC can be used on a Windows desktop, but it can’t be used on a smartphone currently.

Highlights

  • Zero smartphone support
  • Latency as low as ~32ms
  • Supports high bit rates
  • Supports 16-bit/44.1 kHz audio files

AAC (Advanced Audio Coding)

Compared to SBC, AAC is a complex audio codec. It uses a lot of computing powers causing high power consumption. It produces better results than SBC when it works on lossy compression files. AAC produces an improved audio quality than MP3 even though they have similar compression settings (kbps).

This improvement can be a bit expensive and power-consuming. Unlike SBC, AAC is not free for public use, manufacturers have to pay patent holders to use in their creations. If the company has less than 15 employees, the manufacturer has to pay $1,000 and another $0.98 per 500,000 devices.

Most users might think Apple owns AAC because it is the default codec used in their devices. It’s not the case. AAC is built well, but the most important thing is how each manufacturer implements it in their devices.

Looking at how Apple implemented AAC in their devices produces a great audio quality that is far better than Android devices. Some AAC specifications might be similar to SBC but AAC is a more advanced codec.

Highlights

  • Consumes a lot of battery power
  • Supports Android 8+
  • Great lossy compression algorithm than SBC
  • Supports high bit rates
  • Supports 24-bit/44.1 kHz audio files

SONY LDAC

The LDAC codec was developed by Sony. It provides a very good lossless audio quality. To ensure that you get the most of Sony LDAC, make sure your receiving and transmitting device must support the codec. Because most default codecs might not be able to support the large data bandwidth that will be transferred.

LDAC codec worked with very good signal strength, it plays an important role when using the codec. LDAC uses more data and a slight signal interference might reduce the bandwidth. A drop in bandwidth obviously will reduce the audio quality and the benefits of LDAC will not be enjoyed as expected. The devices that support LDAC are sony headphones due to licensing issues.

Highlights

  • Limited to Sony headphones
  • Supports Android 8+
  • Supports high bit rates of 990kbps
  • Supports 24-bit/94KHz

SAMSUNG SCALABLE Codecs

Samsung scalable codecs work similarly to APTX codec, the only difference is it works with only some Samsung devices particularly Samsung Galaxy S20 and Samsung Galaxy Buds Plus.

Samsung scalable codecs work by changing the bitrate dynamically ( 88kbps and 512kbps) and analyzing the radio frequency environment thereby preventing audio chopping. It also supports a wide range of bitrates.

It can maintain a stable connection by switching the bitrate depending on how stable the Bluetooth connection is. One fascinating thing about this codec is that it increases the compression ratio by lowering the bitrate as the strength of the Bluetooth connection decreases. This action might lower the audio quality but the connection will be maintained.

Bluetooth LE  AUDIO L3 Codec

LC3 is a transparent codec. The L3 delivers aid to the deaf and hard-of-hearing patients by making a single source of Bluetooth stream to multiple Bluetooth passes. With LC3 codec, Bluetooth hearing aids can be able to stream audio (train departure information) while keeping the user aware of their surroundings.

Therefore, different broadcasts can be transmitted to a single pair of wireless earbuds. LC3 audio breaks up a single 160kbps stream into 80kbps each. This works great if you and a friend want to share a pair of earbuds.

Lets say, you’re at a pub watching a game with friends, you can use the left earbuds to switch to your preferred announcer and your friend can use the other earbuds to switch to the preferred announcer.

Some technical properties of the Bluetooth LE Audio L3 codecs include:

  • Supports a wide range of usable bitrates
  • Supports bit depths of 16, 24 and 32 bits per audio sample
  • Supports a frame interval of 7.5ms to 10ms
  • Supports a large number of audio channels

What Difference Do Bluetooth Codecs make?

Bluetooth Codecs make a difference and sometimes they don’t. If you’re listening to audio from a very noisy environment, you will not have the ability to know the difference between AAC, SBC and APTX.

However, there are more benefits to Bluetooth than audio quality. Bluetooth codecs are very responsive, you might have noticed that if you skip a track through your headphones onboard controls, you have to wait seconds before the next song comes up. This is because your headphone is streaming over SBC.

It is more noticeable in situations like a video playback where late-night show host jokes are marred by an audio-visual lag caused by SBC streaming. Even though there is support to keep the video and audio in sync, it doesn’t eliminate the frequent lags that occur.

APTX and APTX HD headphones are very good for Android users while AAC-supported headphones work best for iPhone users.

Conclusion

One important thing to note is to make sure your Bluetooth audio device supports AAC as that will provide a premium experience across different devices. If you want to buy wireless headphones for gaming, then make sure your device and headset support aptX-LL.

Understanding Bluetooth codecs can be a bit confusing and super complex. But getting the concept behind each codecs will help you know the codecs that are supported on your devices. So, you can enjoy a full wireless audio experience.

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