LC3

LC3 Codec

LC3 (Low Complexity Communication Codec) is the mandatory audio codec for LE Audio, standardized by the Bluetooth SIG in collaboration with Fraunhofer IIS and Ericsson. It delivers high-quality audio at low bitrates with modest computational requirements, making it suitable for battery-powered hearing aids, earbuds, and IoT audio devices.

Technical Characteristics

LC3 operates at frame durations of 7.5 ms or 10 ms with configurable bitrates from 16 kbps to 320 kbps per channel. At 160 kbps stereo, LC3 achieves perceptual quality equivalent to SBC at 345 kbps -- nearly a 2x bitrate reduction. This efficiency directly translates to lower TX Power duty cycles, shorter radio-on time, and extended battery life.

The codec supports sampling rates of 8, 16, 24, 32, 44.1, and 48 kHz, covering the full range from narrowband voice to high-fidelity music. Its algorithmic latency (codec delay) is 5 ms at the 7.5 ms frame duration, enabling real-time conversational audio suitable for hearing aids and hands-free calling.

LC3 vs SBC

While LC3 requires somewhat higher CPU cycles than SBC, modern BLE SoCs include hardware-accelerated DSP units that handle LC3 encoding and decoding without impacting the application processor. The nRF5340 dedicates its network core to audio processing, while the application core handles GATT and user logic.

Implementation Considerations

LC3 is licensed royalty-free for Bluetooth implementations. Vendors can integrate the reference implementation from the Bluetooth SIG or use optimized libraries from Fraunhofer. When designing an Auracast." data-category="LE Audio">LE Audio product, the choice of frame duration affects latency: 7.5 ms frames suit interactive applications (gaming, hearing aids), while 10 ms frames maximize efficiency for music streaming.