Bluetooth audio codecs: aptX (HD), aptX, LDAC, AAC, SBC

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Home appliance stores offer a wide range of Bluetooth headphones, which are very popular due to their functionality and comfortable use. Wired analogues are preferred only by true audiophiles who enjoy the velvety mids. In order not to make a mistake in choosing the most suitable model, it is recommended to improve your knowledge in the field of codecs in headphones.

What are wireless headphone codecs?

Codec is a word made up of two other words “CODE” and “DECODE”. This concept name is an abbreviation-acronym. A Bluetooth codec is a program that, according to a given algorithm, first encodes information, reducing its size, and then decodes it for further playback.

What is Bluetooth Audio Codec

Codecs work on the following principle: an audio file of any format or a streaming service is played on the smartphone. Using a codec, a smartphone or tablet first encodes streaming information and then sends the already encoded signal to the headphones. The headphones, in turn, using the same codec, decrypt the received data, convert it into an analog signal and play music.

Note! For everything to work as expected, your smartphone/tablet/PC needs to support the same codec as your Bluetooth headphones. Otherwise, the information stream will not be decoded.

Minus receiver

“WiSA is quickly becoming the new de facto standard in wireless immersive audio,” the association wrote in a press release. Now it’s difficult to say how quickly, but as a fact, this technology claims to be a new standard and may well be successful. After all, she proposes to replace the home theater set in the format “TV/projector + AV receiver + set of acoustics” with a compact combination of the type “TV/projector + set of active acoustics”. As a result, the user will get rid of a bulky AV receiver and a bundle of speaker cables.

All speakers, like the subwoofer, are, of course, active; they receive the signal from a small central WiSA unit via wireless communication (and we wrote above that there are already options built directly into the TV), the acoustics only require power. But for many people, plugging a plug into the nearest outlet is easier than pulling an acoustic cable across the room to an AV receiver located somewhere near the front wall.

In addition, not just a home theater - in an interview with Sound&Vision, WiSA Association President Tony Ostrom Fr.

Types of codecs for Bluetooth headphones: advantages and disadvantages

Many connoisseurs of quality and comfort are wondering what codecs are used in modern headphones. In reality there are many of them. They differ in the data transfer rate per minute (bitrate), the calculation algorithm for encoding/decorating streaming information. The compression algorithm itself is also different.

What are the best codecs for headphones today?

AptX HD
A.A.C.
AptX
LDAC
SBC

It is better to familiarize yourself with the operating features of each codec in more detail.

AptX HD

Headphones with aptX HD
AptX HD is the best and most advanced codec for Bluetooth headphones in the aptX version. Numerous experiments conducted in laboratory conditions have proven that the HD version is capable of transmitting sound with minimal delays and higher sound quality.

Many marketers speculate on this codec, saying that if wireless headphones are equipped with it, the sound will be incredible. In reality this is not the case, despite the fact that he is one of the best today. The AptX HD codec is capable of almost completely covering the human audible range, with a maximum limit of 19 kHz. These values are quite acceptable, since people over 25 years of age rarely detect sound vibrations above 18 kHz.

The maximum bitrate is 576 Kbps. During the compression process, the audio track is divided into 4 frequency bands and quantized into 24 bits. As for the background noise level, it is far from 24-bit audio, especially in the high frequency range. Distortion and various noises are present.

high bitrate (data transfer rate)
in most cases the sound quality is better when compared to AAC, SBC and aptX
wide dynamic range
wide frequency range

Not many wireless headphones support this codec

Alternatives to WiSA

Many large brands are creating their own ecosystems that support multi-channel audio in one way or another. Among those familiar to our readers are Sonos, HEOS, MusicCast. And here, of course, the main problem is proprietary formats, and if you bought Sonos, it will be difficult for you to add, for example, HEOS. There are also open platforms from computer corporations - Google Chromecast and Apple Airplay 2, which have also learned multiroom, but do not yet work fully in multichannel mode (and it is not a fact that they will be “taught” this).

WiSA technology in this environment comes across as a more specialized and fundamental approach. In addition, when choosing equipment for a future wireless home theater, WiSA one way or another leaves the choice to the consumer. The only condition is the presence of certified compatibility.

A.A.C.

AAC audio codec
AAC (Advanced Audio Coding) is a codec developed for Apple devices. It has a complex implementation and is based on psychoacoustics. If you use a pair of iPhone and AirPods, the sound will be at a very high level. This codec is also supported by some models of wireless headphones from Sony.

The AAC codec begins to cut off the frequency very early, around 14 kHz. Even older people can pick up such frequencies. The bitrate of this codec is the lowest and is only 252 Kbps. This indicates a noticeable compression of the sound.

If we talk about the quality of the connection, then the AAC codec has the highest quality. Considering the low bitrate, this seems quite logical and understandable.

AptX

Headphones with aptX
AptX is a very common codec characterized by good sound quality. The only codec that is probably even more common is the SBC codec. Almost all devices running Android OS are equipped with support for this codec. This allows you not to worry about the operation of the headphones even if you buy a new smartphone.

The frequency range of AptX is practically no different from its previous predecessor. It is possible to “cut off” only frequencies above 19 kHz. The maximum bitrate reaches 352 Kbps.

In terms of background noise, the AptX codec is really close to 16-bit audio. Especially if you take into account the average volume level and the average human hearing. The quality of the connection under average conditions is quite stable; seconds start to be lost at -80 dBm.

Who is behind WiSA

Research and attempts to create a standard for high-quality sound transmission in a recreation center have been going on for a long time. Judging by the latest news, we can say that the WiSA Ready platform, which is actively promoted by Summit Wireless Technologies, Inc and the WiSA (Wireless Speaker and Audio Association) association of the same name, has become a leader. Summit Wireless, formerly Summit Semiconductor, Inc., is headquartered in San Jose, California, with sales offices in Taiwan, China, Japan and Korea.

If you count the logos on the website, then about thirty declared members have already joined WiSA. In 2022, there will be up to 60 million WiSA Ready products on the market. Right now, WiSA is already available in select models of LG Electronics TVs (while setting the “protection” parameters in the software of the TV that supports this technology), Xbox consoles and active speakers from nine premium speaker manufacturers, in particular, the Klipsch Reference speakers demonstrated there . Work is underway to certify WiSA Ready for all new devices.

LDAC

LDAC Audio Codec
LDAC is a high-resolution Bluetooth codec that streams information in near-CD quality. The bitrate (data transfer rate) is higher when compared with other analogues. However, numerous experiments have shown that the sound quality is not far from aptX HD, the stability of operation is slightly worse.

The LDAC codec is able to “exist” in three different bitrates: 990 Kbps, 660 Kbps and 330 Kbps. As for the frequency range, it reaches 47 kHz, which approximately corresponds to the Hi Res mode. The background noise level in part of the range is quite consistent with 24 bits. However, there is a lot of noise at high frequencies.

The connection quality is at a high level LDAC. Gradual packet loss is observed at -80 dBm.

high sound quality
technical parameters are similar to 16-bit audio
wide dynamic and frequency range
maximum bitrate among Bluetooth codecs

Poor sound quality in connection priority mode
not very widespread yet
unstable connection at frequencies 660Kbit/s and 990Kbit/s

Possible problems and how to overcome them

To be fair, it is worth noting that since signal transmission in devices of this class is carried out in the gigahertz range, when placing speakers with WiSA receivers (as well as wireless Hi-Res audio products from other manufacturers), you may have to pay attention to their surroundings. In the interior, massive objects are undesirable (this probably does not apply to people and chairs, we are talking about metal and reinforced concrete) that block the direct line of sight between the receiver and the transmitter (transmitter and receiver) of the system. This “shading” can cause problems due to reduced radio reception levels.

However, this problem cannot arise a priori in the vast majority of rooms with home theaters. In addition, the WiSA Association has already stated that the system components have been tested to provide clear communication within a range of 30x30 feet (10x10 m), even in the presence of interference.

SBC

SBC Audio Codec
SBC is the most widely used codec in the world and is supported by all wireless headphones and smartphones by default. There are many shortcomings in its work, but it all began with it and it is already known which codec will become its improved receiver - AC3. Reputable publications say that this will be a real breakthrough in wireless sound transmission.

The SBC codec is capable of transmitting frequency ranges up to 19 kHz inclusive. At the upper limit, distortion is much greater when compared with codecs from the artX line. The maximum bitrate is 320 Kbps, the expected compression is 4.4:1.

As for the level of background noise, there is much more noise here compared to other types of codecs. Officially, the SBC bitrate is not limited, but no device supports the SBC codec above 328 Kbps.

supported by all Bluetooth devices without exception
has a reliable connection
Sounds better than AAC on some devices

noises
uneven bitrate distribution

Does AirPods Max support lossless format?

It’s not clear why, but AirPods Max, which can be connected to an iPhone via a wire via the Lightning connector, also do not support lossless tracks. No, they are capable of processing 24-bit songs at frequencies up to 48 kHz, but due to technical limitations, the sound is not quite what it should be when playing lossless tracks.

AirPods Max do not support lossless even when connected to an iPhone via wire

What this limitation is is not at all clear. However, it is clear that such sound cannot be classified as lossless. Rumor has it that the whole point is that Apple began developing AirPods Max much earlier than it decided to add Lossless to Apple Music. However, from a product promotion point of view, this makes no sense at all, given that the AirPods Max are high-end headphones that have such an annoying limitation.

Do Bluetooth headphone codecs affect sound quality?

Codecs really affect sound quality. However, these changes may be so minor that ordinary users simply will not notice it.

All of the previously listed codecs compress information with losses. Losses, as we know, can be useful and useless. Same with codecs. A person is able to detect sounds in the range from 20 Hz to 20 kHz. The susceptibility of the upper limit depends on the individual characteristics of the body and the age of the person. So, codecs remove all audio information above a certain frequency.