For great sound, LE Audio is all you need!

Since version 4.0, Bluetooth technology has developed in two different directions. Spurred on by the Internet of Things, Bluetooth Low Energy (BLE) emerged later in the game and rapidly gained popularity, becoming the standard specification for many IoT-based innovative applications such as wearables. On the other hand, Classic Bluetooth (BT) is still very much the mainstream technology for conventional uses such as audio and high-speed data transmission.

 

In the past four to five years, however, Classic Bluetooth has ushered in a new wave of growth in the realm of audio broadcasting, mainly due to Apple AirPods. This hit product fueled an entire new product category – the true wireless stereo (TWS) headset. According to Counterpoint's market research data, the global TWS headset market will grow by 33% year-on-year in 2021, reaching 310 million units.

 

 

 

However, as more and more companies begin utilizing TWS, the full depth of the "hole" that Classic Bluetooth has dug for TWS is becoming increasingly evident. In many ways, the original Classic Bluetooth audio broadcast standard has failed to adapt to the development requirements of TWS. This failure is due to two main reasons.

 

Firstly, it is a victim of poor coding technology. Classic Bluetooth uses SBC encoding technology which was previously serviceable for the simple use of transmitting phone voice. However, as audio applications with high user experience requirements such as music playback appeared, its weaknesses of low efficiency and poor sound quality become glaringly apparent. Hence for many people Bluetooth headsets have no true audio quality to speak of and can really only be used to “hear a sound.” There are of course ways to improve sound quality, but this requires the help of other proprietary encoding solutions, such as AC3 and AptX encoding. As this approach requires both manufacturers and users to pay additional hardware costs and technical licensing fees, it is clearly not the best solution.

 

Secondly, it is difficult to achieve binaural synchronization. Classic Bluetooth can only support a single point-to-point audio stream on the A2DP profile, while TWS works by broadcasting audio to two separate headsets. Consequently the traditional solution is to first broadcast audio to the headset (main speaker) on one side, then connect to the headset (secondary speaker) on the other side through the main speaker. However, the TWS scheme of main and secondary speakers has obvious weaknesses. Firstly, as the main speaker is used as a signal relay, it will inevitably consume more power and age faster, which will in turn lead to differences in the battery life and service life of the headphones on both sides. Secondly, audio coming out of the earphones on both sides is not synchronized, and audio latency between the screen image and sound on a mobile phone is too high. This is of course a fatal flaw for users watching videos or playing games.

 

To solve the problem of binaural audio synchronization, various TWS manufacturers are actively looking for new approaches. While Apple has solved this problem on AirPods with a proprietary monitoring solution, the strict patent barriers it has built have discouraged other latecomers to the field. In recent years, many other binaural connection solutions have also made significant progress, but these protocols and implementation solutions are all of different “origins” and will inevitably lead to challenging compatibility issues. For instance, the Qualcomm TWS+ solution only supports Snapdragon 845 and above mobile phone platforms.

 

As you can see, all of the above efforts to “dig ourselves out of the hole” are just band-aid measures in a vain attempt to patch the original Bluetooth standard. Fundamental changes must be made to the Bluetooth standard to help classic Bluetooth audio transmission “dig itself out of the hole” that it is currently in.

 

 

SIG is obviously well aware of this demand. When it launched the Bluetooth 5.2 standard version in early 2020, it went in for the kill by introducing LE Audio technology. As its name suggests, the technology provides audio broadcast through BLE connection (rather than classic Bluetooth), and, leveraging BLE’s advantage of low power consumption, extensively enhances the wireless audio experience for users.

 

If the development of Bluetooth technology can be said to have gone in two different directions due to differences in the application scenarios of BLE and classic Bluetooth, LE Audio has now enabled the two lines to intersect. It is now poised to take over the market that Classic Bluetooth previously occupied. Hence industry professionals are predicting that this will be "one of the largest development achievements in Bluetooth history."

 

So what exactly is the magic of this highly anticipated LE Audio technology? Upon close scrutiny, its advantages are mainly due to the three new technologies on which it is based.

 

 

 

This new high-quality, low-power audio encoder has the characteristics of providing high-quality audio under low-rate conditions while at the same time supporting a wide range of sampling rates, bit rates, and frame rates. This enables developers to flexibly adjust and optimize the product to provide users with the best audio experience.

 

The following figure compares LC3 with the classic SBC encoder. The vertical axis shows the audio impairment scale after encoding and compression based on the ITU-R BS.1116-3 specification with 5 indicating no difference from the original audio source, 4 indicating a significant but acceptable difference, and 3 indicating a particularly significant difference. As demonstrated, LC3 has obvious advantages, providing a good audio experience even if the bit rate is reduced by 50%.

 

It is not an exaggeration to say that LC3 has enabled Bluetooth audio to match the HiFi experience while also offering low power consumption.

 

 

 

This technology can be said to have been tailored to solve the issue of TWS audio synchronization by realizing multiple and independent audio streaming synchronization between a source device (the smart phone) and single or multiple sink devices (the earphones). In other words, through multi-stream audio technology, we can now send audio streams to two TWS headsets at the same time, providing a better personal audio experience and streamlining the switching between multiple audio source devices. What’s more, Multi-Steam Audio is an open standard. No wonder people have been foreseeing the "end of the AirPods monopoly" since the technology was first unveiled.

 

 

If we consider the first two new technologies to have been introduced for the purpose of using LE Audio to solve the real problems that TWS has encountered, then broadcast audio technology is here to open our minds to the future of LE Audio.

 

What exactly, though, is Broadcast Audio? It’s a technology that enables a single audio source device to broadcast one or more audio streams to an unlimited number of audio receiving devices, otherwise known as "audio sharing." This kind of sharing can be between individuals or locations, with a wide and flexible variety of application scenarios. Some plausible applications include:

 

 

If you pursue this train of thought, the possibilities of Broadcast Audio are mind-blowingly endless.

 

 

Already, various developments based on LE Audio are under way. For instance, it is expected that the upcoming 2022 version of the Android system will support LE Audio, while related chip research and development is also in full swing. We also anticipate that in the early years after LE Audio’s entry into the market, dual-mode chips that support both LE Audio and classic Bluetooth audio will be the norm. Subsequently, as LE Audio’s penetration rate rises and new application scenarios continue to arise, single-mode LE Audio chips will emerge and gradual gain a significant portion of the market.

 

In the future, if you happen to hear high-quality audio from Bluetooth headsets or other wireless audio devices, chances are it’s all due to LE Audio.