“Bluetooth technology has been divided into two branches since version 4.0: Bluetooth low energy BLE, as a rising star, borrowed the east wind of the Internet of Things, and developed so much that it has become the standard for many innovative applications of the Internet of Things such as wearables; and the classic Bluetooth (BT) stuck to the traditional base of Bluetooth technology, audio and high-speed data transmission, and lived tepidly.
Bluetooth technology has been divided into two branches since version 4.0: Bluetooth low energy BLE, as a rising star, borrowed the east wind of the Internet of Things, and developed so much that it has become the standard for many innovative applications of the Internet of Things such as wearables; and the classic Bluetooth (BT) stuck to the traditional base of Bluetooth technology, audio and high-speed data transmission, and lived tepidly.
In the past four to five years, Classic Bluetooth has ushered in a new wave of growth in the audio transmission field. This is mainly due to Apple’s AirPods. This successful product has prospered a new TWS true wireless stereo headset product category. 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.
The dilemma of TWS
However, as more and more people enter the field of TWS, everyone has become more and more aware of how deep the “pit” left by classic Bluetooth for TWS – in many respects, the original classic Bluetooth audio transmission standard It has been unable to meet the development requirements of TWS, and there are two main slots:
One is the limitation of coding technology. Classic Bluetooth uses SBC encoding technology, and it is okay to transmit a phone voice in the initial stage. However, in the face of audio applications with high user experience requirements such as music playback, its weaknesses of low efficiency and poor sound quality are exposed, so the sound quality of Bluetooth headsets is in people’s minds. In traditional cognition, it is just “listening to a sound”. There is no way to improve sound quality. This requires the help of other proprietary encoding solutions, such as AC3 and AptX encoding, but manufacturers and users have to pay additional hardware costs and technical licensing fees for this, which is obviously not the best Plan.
Second, it is too difficult to synchronize both ears. Classic Bluetooth can only support a single point-to-point audio stream on the A2DP profile, while TWS needs to transmit the audio to two separate headsets. For this reason, the traditional solution is to first transmit the audio to the headset (host) on one side. Then connect to the headset (secondary phone) on the other side through this host. However, the TWS solution of this main and auxiliary machine has obvious weaknesses: First, the main machine is used as a signal relay, and the power consumption will be higher and the aging will be faster, which will cause differences in the battery life and service life of the headphones on both sides; second, the two sides The headset audio is out of sync, and the phone’s picture-to-audio delay is too large-this is undoubtedly a fatal flaw for the video party and the game party.
In order to solve the problem of unsynchronized binaural audio, various TWS manufacturers are also actively thinking of ways. Apple has solved this problem well on AirPods through a proprietary monitoring solution, but the strict patent barriers it has built have discouraged other latecomers. In recent years, many binaural connection solutions have also made great progress, but these protocols and implementation solutions are not “family” after all, and compatibility issues are unavoidable to make people headache-for example, the Qualcomm TWS+ solution only supports Snapdragon 845 and above. Mobile platform.
It can be seen that all the above “filling holes” efforts are just repairs to the original Bluetooth standard, which is hard to say perfect. To solve the ring, you must be the person who is the ringer to solve the problem fundamentally. Fill in the “pits” of the classic Bluetooth audio transmission. You also need to work hard on the Bluetooth standard.
LE Audio standard arrives
SIG is clearly aware of this demand, so in the Bluetooth 5.2 standard version launched in early 2020, it finally released a big move-the introduction of LE Audio technology. From the name of this technology, it can be seen that it is to provide audio transmission through BLE connection (rather than classic Bluetooth), and on the basis of adhering to the low power consumption of BLE, it can comprehensively enhance the user’s wireless audio experience.
If we talk about the development of Bluetooth technology before, BLE and classic Bluetooth are like two parallel lines due to the difference in application scenarios. Now LE Audio makes the two intersect, and there is a high probability of moving the “cheese” of classic Bluetooth audio transmission. . Therefore, some people in the industry commented that this will be “one of the largest development work results in Bluetooth history.”
So what is the magic of this highly anticipated LE Audio technology? Observe carefully, this is mainly due to its three newly added skills.
Figure 1: Three key technologies used in LE Audio (Source: SIG)
First, the low-complexity communication codec (LC3)
This new high-quality, low-power audio encoder has the characteristics of providing high-quality sound under low-rate conditions. It also supports a wide range of sample rates, bit rates and frame rates. Developers can flexibly adjust as needed Optimize the product to provide users with the best audio experience.
The following figure compares the LC3 and 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-5 means no difference from the original audio source, 4 Indicates that there is a significant difference but acceptable, and 3 indicates that there is a particularly significant difference. It can be seen that the advantages of LC3 are very obvious, even if the bit rate is reduced by 50%, it can still provide a good audio experience.
It is not an exaggeration to say that LC3 gives Bluetooth audio the capital to match the HiFi experience under the premise of low power consumption.
Figure 2: Comparison of LC3 and SBC audio coding schemes (Source: SIG)
Second, Multi-Steam Audio technology
It can be said that this technology is tailored to solve the problem of TWS audio non-synchronization. It can realize multiple and independent synchronization between a single source device (Source Device) of a smartphone and a single or multiple audio sink devices (Sink Device). Audio streaming. In other words, the multi-stream audio technology can send audio streams to two headphones of TWS at the same time, providing a better stereo experience, and making the switching between multiple audio source devices smoother, and this is an open technical standard ! No wonder that once the technology was announced, the prophecy of “ending the AirPods monopoly” was endless.
Third, Broadcast Audio technology
If the introduction of the first two new technologies is to use LE Audio to solve the real problems encountered by TWS, then the broadcast audio technology is to open up greater imagination for the future of LE Audio.
Based on broadcast audio technology, a single audio source device can broadcast one or more audio streams to an unlimited number of audio receiving devices. A popular understanding is “audio sharing”. And this kind of sharing can be based on individual or location, and the application scenarios are wide and flexible. Some applications that we can directly imagine include:
• Personal music sharing: Let multiple friends enjoy the music on one mobile phone (or audio source device) at the same time.
• Public auxiliary listening: In theaters or museums, many users have heard Bluetooth headsets to listen to drama dialogues or explanations of exhibits.
• Public TV/teaching: Fitness coaches use Bluetooth headsets to teach target students, or square dance music does not need to be loudly released, but is transmitted to every “aunt” through headsets.
• Multi-language announcements: Use multiple audio streams to achieve multi-language simultaneous interpretation in international conferences or multi-language broadcasts on airplanes.
If this line of thought continues to expand, the brains of subsequent broadcast audio technology will be even bigger.
Figure 3: Bluetooth audio applications will continue to grow in the future (Source: SIG)
At present, various forces have developed the layout around LE Audio. It is expected that the new version of Android system will support LE Audio in 2022, and related chip research and development work is also in full swing. It is expected that in the early years of LE Audio’s entry into the market, dual-mode chips that support both LE Audio and classic Bluetooth audio will become the mainstream. With the increase in LE Audio’s penetration rate and the expansion of new application scenarios, single-mode LE Audio chips will also become mainstream. Will appear one after another.
In short, in the future, more and more good sounds from Bluetooth headsets or other wireless audio devices will be labeled LE Audio.
Avnet is the world’s leading technology distributor and solution provider, and has been upholding its original aspirations for the past century to meet the ever-changing needs of customers. From conception to design, and from prototype creation to production, Avnet can support customers at every stage of the product life cycle. Avnet is at the center of the entire technology value chain. This unique position allows Avnet to accelerate the design and supply speed in the product development process, thereby helping customers achieve revenue as soon as possible. For decades, Avnet has been committed to helping customers and suppliers around the world realize technological changes.