Unless you have a) an iPhone and b) Apple’s AirPods, there’s a chance you may have found your experience with Bluetooth true wireless stereo (TWS) earbuds lacking. In low-end earbuds, one might find any number of annoyances: poor audio; unstable left/right syncing; short and unequal battery life; and a limited user interface. CEVA hopes to solve these problems with its Bluebud wireless audio platform. Bluebud aims to standardize DSP-enabled Bluetooth audio IP for the fast-growing markets around TWS earbuds, hearables, wireless speakers, gaming headsets, smart watches, and other wearables.
Bluebud is a self-contained, turnkey hardware/software solution that will enable makers of TWS and Bluetooth audio SoCs to get products quickly to market by being ready to just drop into their designs. The platform also allows for differentiation of end products by means of support for host-level application software that can run on the CEVA-BX1 audio processor or an optional host CPU.
The platform combines CEVA’s RivieraWaves Bluetooth 5.2 IP, with both Classic Audio and LE Audio, and the CEVA-BX1 audio processor, together with all the required peripherals for wireless audio, in a compact low-power design with a footprint of less than 0.5 mm2 on a 22-nm process. The single-core architecture reduces the overall latency from RF to audio output down to less than 20 ms, ensuring impeccable audio/video sync for movies and gaming. The design also incorporates an advanced power-management unit supporting idle and sleep power-down modes through sophisticated clock and voltage scaling, inherent in the fully integrated Bluetooth audio platform.
Furthermore, the onboard CEVA-BX1 DSP along with the SenslinQ DSP software framework enables semiconductor and OEM users to seamlessly integrate differentiating value-add software from CEVA, its ecosystem partners, or custom software, onto the Bluebud platform. CEVA’s optional software available for Bluebud includes ClearVox multi-microphone noise reduction and acoustic echo cancellation; WhisPro voice trigger and commands; and MotionEngine Hear for user control via tap and double tap, head tracking, in-ear detection, and activity classification. For lite AI inferencing workloads, Bluebud allows users to run TinyML models such as a wake-word engine to summon your voice assistant or detect sound events for contextual awareness, using native support for the TensorFlow Lite Micro neural network framework.
The TWS Challenge
TWS is the key element of wireless earbuds, a situation in which there is one source, but two sinks. The challenge is that TWS is not natively supported by the Bluetooth Classic standard. Bluetooth Classic supports only point-to-point streaming. Phones, tablets, and laptops support only one audio connection at a time, so proprietary techniques are required to support TWS devices.
While there are several techniques for streaming TWS audio using Bluetooth Classic (forwarding, sniffing, and dual stream), the Bluetooth SIG directly addressed the TWS use case in Bluetooth LE Audio, which is natively supported with dual streaming in parallel. The approach CEVA takes in the Bluebud platform is what they’re calling optimized relay, which can be thought of as optimized forwarding. One earbud is connected directly to the audio source using an A2DP stereo link. The second earbud is connected to the first with a Bluetooth LE mono link. As a result, packets are smaller, and the scheme uses less power while providing a stable connection and high audio quality.
Other features of the Bluebud platform include:
- Support for Bluetooth 5.2 with both Classic Audio and LE Audio, software upgradeable to next Bluetooth version
- Complete Classic Audio software stack, required for Bluetooth audio streaming
- A2DP profile for music streaming, including SBC, AAC and MP3 codecs
- HFP profile for voice call, including CVSD and mSBC codecs
- Complete LE Audio software stack, for audio streaming over Bluetooth low energy
- Audio profiles for voice call and music streaming, including LC3 codec
- Robust true wireless stereo connectivity for both voice calls and music streaming with low jitter and low latency between left and right channels
- Seamless bud-to-bud role switching to maximize battery life
- Easy and fast pairing with multi-source support, allowing buds to be connected to several devices and instantly switch between them when required
The Bluebud platform is available for licensing by end of Q1 2021.
CEVA, www.ceva-dsp.com