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LC3 (codec)
LC3 (codec)
LC3 (codec)
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LC3
Type of formatAudio
Extended toLC3plus
StandardBluetooth 5.2 LE
LC3plus
Type of formatAudio
StandardETSI TS 103 634

LC3 (Low Complexity Communication Codec) is an audio codec specified by the Bluetooth Special Interest Group (SIG) for the LE Audio audio protocol introduced about the time of Bluetooth 5.2.[1] It's developed by Fraunhofer IIS and Ericsson as the successor of the SBC codec.[2] Mono only LC3-SWB is also supported over Bluetooth Classic HFP 1.9, improving on mSBC. It is possible to send 4 LC3 streams to LE audio earbuds, like Samsung's Buds2 Pro.

Codec

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LC3 provides higher audio quality and better packet loss concealment than SBC, G.722 and Opus, according to subjective testing by the Bluetooth Special Interest Group and ETSI.[3][4][5] The conclusion regarding Opus is disputed as the test only included speech audio, but the comparison was made to version 1.1.4 of the reference Opus encoder, using complexity level 0 at 32 kbps and relying on CELT (general audio) instead of the FEC-capable SILK (speech); the test also did not take into account the newer version 1.2 of the Opus encoder released in 2017, where significant improvements were made to low bitrate streams.[5]

Supported systems:

LC3plus

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LC3plus High Resolution mode is a codec defined by ETSI and is not compatible with the LC3 defined by Bluetooth SIG.[16]: 3  It's included in the 2019 DECT standard.[17]

On November 9, 2022, the Japan Audio Society (JAS) released a statement certifying LC3plus with the "Hi-Res AUDIO WIRELESS" logo.[18] LC3plus is the 4th codec to receive this, alongside SCL6 (formerly known as MQair), LDAC and LHDC codecs.

The ETSI implementation of LC3plus is source-available software, subject to a ETSI Intellectual Property Rights Policy and the usual patent restrictions.[19]

Fraunhofer defines a way to use LC3plus over A2DP.

See also

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References

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LC3 (codec)

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The Low Complexity Communication Codec (LC3) is an audio codec developed by Fraunhofer IIS and , standardized by the (SIG) as the mandatory codec for (LE) Audio, enabling efficient transmission of high-quality speech and music over wireless connections with reduced bitrate, , and power consumption compared to legacy codecs like SBC. Introduced in 2020 as part of the LE Audio specification, LC3 addresses the limitations of previous audio technologies by supporting sampling rates from 8 kHz to 48 kHz, bit depths of 16, 24, or 32 bits, and configurable frame durations of 7.5 ms or 10 ms, allowing for low-latency applications such as real-time communication and hearing assistance. It achieves quality (up to 8 kHz bandwidth) at bitrates as low as 32 kbps for voice and super-wideband audio quality (up to 16 kHz bandwidth) at 64 kbps, with 96 kbps suitable for music, outperforming SBC in subjective listening tests ( scores >4.0 for "excellent" quality) while requiring approximately 50% less bitrate for equivalent performance. LC3's design emphasizes low complexity, with encoder operations consuming about 3–4 times the MIPS of SBC but enabling smaller, more power-efficient devices through its optimized algorithmic structure, including basic packet loss concealment to handle transmission errors in wireless environments. Key applications include voice calls via VoLTE headsets, multi-stream audio (Auracast), and personal hearing aids, where it supports unlimited channels and high-resolution streaming up to 96 kHz via the optional LC3plus extension. LC3 was qualified by the SIG in 2021. As of 2025, it is supported in a growing number of devices, including true earbuds and hearing aids, facilitating widespread adoption for enhanced and audio experiences.

Introduction

Definition and Purpose

LC3, or Low Complexity Communication Codec, is a transform-based audio compression developed for efficient encoding of speech and signals. It serves as a core component of the (LE) Audio standard, providing a standardized method for compressing audio data to facilitate transmission over wireless connections. The primary purpose of LC3 is to enable high-quality audio delivery while minimizing power consumption and computational complexity, making it suitable for low-power devices such as wireless earbuds and hearing aids. By achieving superior audio fidelity at reduced data rates compared to legacy codecs, LC3 supports versatile design tradeoffs that balance quality, latency, and energy efficiency in ecosystems. As the mandatory codec for LE Audio, it replaces the Subband Coding (SBC) codec used in classic audio profiles, thereby enhancing overall performance for applications like multi-stream audio and broadcast transmission. LC3 employs a block-based structure to process audio in fixed frames, allowing for modular encoding and decoding that integrates seamlessly with 5.2 and subsequent standards. This architecture includes optional mechanisms for handling , ensuring robust audio playback in imperfect environments.

Key Features

LC3 is engineered with low computational complexity, enabling efficient implementation on resource-constrained devices such as wearables and earbuds, which minimizes power consumption and processing demands. This design leverages a block-based transform approach that reduces the overall and operational overhead, making it particularly suitable for battery-powered audio accessories. The codec supports super-wideband audio with a bandwidth of up to 16 kHz (at 32 kHz sampling rate), facilitating natural and immersive sound reproduction that extends beyond traditional limitations. This capability ensures high-fidelity speech and music transmission, enhancing in applications requiring clear, detailed audio. LC3 incorporates robust error resilience through integrated packet loss concealment techniques, which mitigate the impact of data corruption or loss in transmissions. These mechanisms allow for seamless audio playback even in challenging network environments, maintaining quality without audible artifacts. Bitrate is a core advantage, permitting dynamic adaptation to fluctuating network conditions while preserving audio integrity across a broad range of rates. This flexibility supports efficient data usage in bandwidth-limited scenarios without compromising perceptual quality. Additionally, LC3 offers low-latency modes tailored for real-time applications, such as voice calls and , ensuring synchronized audio delivery with minimal delay. These features position LC3 as a foundational element in LE Audio, enabling advanced wireless audio ecosystems.

Development and Standardization

Historical Background

The development of the LC3 (Low Complexity Communication Codec) began as part of the Bluetooth Special Interest Group's (SIG) LE Audio working group initiatives around 2017–2018, aimed at improving audio efficiency and for low-energy applications. These efforts sought to address limitations in existing audio transmission, such as high power consumption and suboptimal at low , by introducing a new optimized for (LE). An early milestone occurred in January 2020, when released the industry's first implementation of the LC3 codec for its ARC processors, enabling testing and integration in power-sensitive audio and voice applications. This implementation, based on preliminary work, demonstrated the codec's potential for low-complexity encoding while meeting SIG requirements. The LC3 technical specification was officially released by the SIG on September 15, 2020, marking the codec's formal adoption as the mandatory audio codec for LE Audio profiles. The full set of LE Audio specifications, incorporating LC3, was completed by the Bluetooth SIG on July 12, 2022, finalizing the standard for broader implementation. Adoption has continued to accelerate thereafter, with notable integration into in 2022, which added native support for LE Audio and the LC3 codec; by 2025, support has expanded to (as of August 2025) and numerous consumer devices, enhancing wireless audio experiences on compatible platforms. Contributions from Fraunhofer IIS played a key role in the codec's design, focusing on high-quality performance at reduced bit rates.

Involved Organizations

The development of the LC3 codec was primarily led by Fraunhofer IIS, which designed the core algorithm leveraging its extensive expertise in audio compression technologies. Fraunhofer IIS collaborated closely with on this effort, combining their strengths in audio coding and wireless communications to create a codec optimized for low-bitrate, high-quality transmission. The specification for LC3 was developed through collaborative input from members of the (SIG), including , , and other industry leaders such as and , who contributed to refining the LE Audio protocol in which LC3 is integrated. The SIG ultimately standardized LC3 as the mandatory for LE Audio, ensuring across devices and profiles. Open-source initiatives have further supported LC3 adoption, notably Google's liblc3 library, an efficient implementation released for integration into Android ecosystems and compliant with SIG requirements. While LC3 itself is governed by the SIG, the European Telecommunications Standards Institute (ETSI) has contributed to extensions like LC3plus through its own standardization processes, focusing on enhanced features for broader wireless applications.

Technical Specifications

Audio Parameters

LC3 operates with configurable audio parameters that enable flexibility across different use cases, from low-bitrate speech transmission to high-quality music streaming. These parameters include sampling rates, bitrates, frame durations, bandwidth modes, and bit depth handling, all designed to optimize performance within constrained environments like communication. The codec supports sampling rates of 8 kHz, 16 kHz, 24 kHz, 32 kHz, 44.1 kHz, and 48 kHz, allowing adaptation to telephony up to fullband music reproduction. Bitrates range from 16 kbps to 320 kbps per channel, with support for both mono and channels to suit varying bandwidth availability and quality requirements. Frame durations can be set to 7.5 ms or 10 ms, providing options to balance low latency for real-time applications against higher compression efficiency for data-limited scenarios. In terms of bandwidth coverage, LC3 accommodates (up to 4 kHz for basic voice), (up to 8 kHz for clearer speech), super-wideband (up to 16 kHz for enhanced audio), and fullband (up to 20 kHz for near-CD quality). For bit depth, the codec accepts input of 16, 24, or 32 bits per sample, while the output is adapted to the specific transmission and needs to maintain efficiency without unnecessary overhead. These parameters collectively determine the trade-offs in audio and delay, influencing overall performance in practical deployments.
ParameterSupported ValuesPurpose
Sampling Rates8, 16, 24, 32, 44.1, 48 kHzAdapt to voice (low rates) or music (high rates) applications
Bitrates16–320 kbps (per channel, mono/)Scale quality from basic communication to high- streaming
Frame Durations7.5, 10 msTrade latency for compression in real-time vs. bandwidth-constrained scenarios
Bandwidth Modes (≤4 kHz), (≤8 kHz), Super-wideband (≤16 kHz), Fullband (≤20 kHz)Cover to immersive audio experiences
Bit Depth16, 24, 32 bits (input; adapted output)Handle high-dynamic-range sources while optimizing transmission

Encoding and Decoding Process

The LC3 encoding process begins with preprocessing of the input to prepare it for efficient compression. This involves applying a to remove low-frequency noise, typically using a second-order (IIR) filter with a 50 Hz , followed by downsampling if necessary. Transient detection is also performed to identify rapid signal changes, such as attacks, over short frame durations (e.g., 10 ms for higher sampling rates), enabling adaptive processing based on spectral shape and frame energy analysis. The preprocessed signal is then transformed into the using the (MDCT), specifically a low-delay variant that converts time-domain samples into coefficients. This step applies a windowing function and computes the transform coefficients via the formula X(k)=2N∑n=0N−1w(n)⋅x(n)⋅cos⁡[π(n+N+12)(k+12)/N]X(k) = \sqrt{\frac{2}{N}} \sum_{n=0}^{N-1} w(n) \cdot x(n) \cdot \cos\left[ \pi \left( n + \frac{N+1}{2} \right) \left( k + \frac{1}{2} \right) / N \right]
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