First there were truly wireless earbuds, then high quality stereo in those earbuds – True Wireless Stereo (TWS). That market is now showing spectacular growth. Apple alone shipped 1M AirPods in 2016. Overall 109M TWS earbuds shipped in 2019 and 1.2B are forecasted to ship in 2024. This growth, now at 70% CAGR, is even faster than the smartphone market was growing 10 years ago. Apple is playing a part in that growth, though now a much smaller part as TWS OEMs rapidly gain traction.
(Source: CEVA)
Opening walled gardens
Bluetooth Classic transmits over just one channel, using a profile called A2DP for stereo. One earbud receives the signal, say the left earbud, splits it into L and R channels and forwarded the R channel to the right earbud. Due to that, initial TWS earbuds worked in captive phone/earbud combinations to tackle the high latencies that can compromise the stereo quality noticeably. And that inter-earbud transmission drains tiny batteries much faster.
Proprietary solutions used proprietary techniques to mitigate these problems, sometimes requiring the same Bluetooth chipset in phone and earbuds. Non-captive OEMs followed with their own methods to do the same thing, without need for chipset help. That market has taken off like a rocket.
Then the Bluetooth SIG issued LE Audio with the 5.2 Bluetooth release. This directly supports the host (a phone for example) transmitting L and R channels simultaneously, each to the appropriate earbud. Latency problems between channels are further reduced, as is power burned in transmitting between earbuds. A standards-based solution which will simplify life for everyone, OEMs and users alike.
The challenge is that products using LE-Audio are not yet released. And even when they are, uptake will take time. Even then, there’ll be a long tail of late adopters. Manufacturers don’t want to build products they can only sell to early adopters. They want to sell great earbuds with the best possible TWS solution, whether their customers have upgraded to LE Audio or are still on Classic-Audio. And which will seamlessly switch over when those customers switch.
An all-in-one audio solution
This means that both BT Classic Audio and LE Audio need to be supported. A solution that will deliver an optimized stereo experience with synchronized L and R channels. Providing minimum jitter/latency between left and right earbuds, for voice calls and music streaming. All running on audio-optimized DSP.
There’s another consideration for truly high-quality voice communication – noise suppression and acoustic echo cancellation. To suppress ambient noise that could compromise the conversation experience. The very best earbuds now support multiple microphones for noise reduction, used to detect and eliminate ambient noise. For example, the ClearVox software suite from CEVA uses this input to filter out noise, for an enhanced experience. The product developer just has to provide the extra microphones.
It is now possible to get these capabilities, plus a complete Bluetooth stack alongside, running on the same DSP, meaning that a design team doesn’t need all this expertise in-house. One option is CEVA’s Bluebud, a product providing an embedded processor platform (CEVA-BX1) with both Classic Audio and LE Audio options and a comprehensive set of audio and voice codecs. Plus a complete Bluetooth stack, all running on the same DSP IP. This forms a turnkey package to support the TWS needs of both classes of users.
Elia Shenberger